Vol. 10, 6111– 6118, September 15, 2004
`
`Clinical Cancer Research
`
`6111
`
`Phase II Study of the Proteasome Inhibitor Bortezomib (PS-341) in
`Patients with Metastatic Neuroendocrine Tumors
`
`Manisha H. Shah,1 Donn Young,2
`Hedy L. Kindler,3 Iain Webb,4 Barbara Kleiber,1
`John Wright,5 and Michael Grever1
`1Division of Hematology-Oncology, Department of Internal Medicine,
`and 2Center for Biostatistics, The Ohio State University, Columbus,
`Ohio; 3Department of Medicine, University of Chicago, Chicago,
`Illinois; 4Millennium Pharmaceuticals, Inc., Cambridge,
`Massachusetts; and 5Cancer Therapy Evaluation Program, Bethesda,
`Maryland
`
`ABSTRACT
`Purpose: This phase II study was undertaken to assess
`objective response, toxicity, tumor marker response, and
`pharmacodynamics of bortezomib in patients with meta-
`static neuroendocrine (carcinoid and islet cell) tumors.
`Experimental Design: A total of 16 patients with meas-
`urable metastatic carcinoid (n ⴝ 12) or islet cell (n ⴝ 4)
`tumors received i.v. bolus of single agent bortezomib at a
`dose of 1.5 mg/m2 on days 1, 4, 8, and 11 every 21 days.
`Tumor response was assessed at 12-week intervals using
`Response Evaluation Criteria in Solid Tumors (RECIST)
`criteria. All patients were chemotherapy naı¨ve and had
`Eastern Cooperative Oncology Group performance status of
`0 to 1.
`Results: No patient achieved a partial or a complete
`remission. The patients received total of 264 doses of therapy
`with a median of 15 doses per patient. Grade 4 toxicities
`were not observed. The most common grade 3 adverse
`events included peripheral sensory neuropathy (37%), diar-
`rhea (25%), vomiting (18%), and ileus (18%). Six of 10
`patients who experienced grade 2 to 3 peripheral sensory
`neuropathy also had grade 2 to 3 dizziness (n ⴝ 2), ortho-
`static hypotension (n ⴝ 2), syncope (n ⴝ 1), ileus (n ⴝ 2), or
`abdominal cramps (n ⴝ 1). Changes in tumor marker levels
`did not correlate with tumor response. The mean percentage
`of 20S proteasome inhibition achieved in whole blood at 1
`and 24 hours after bortezomib administration was 68 and
`30%, respectively.
`Conclusions: Despite achieving the surrogate biologic
`end point, single-agent bortezomib did not induce any ob-
`
`Received 3/2/04; revised 4/27/04; accepted 5/5/04.
`Grant support: NIH Grant CA63185.
`The costs of publication of this article were defrayed in part by the
`payment of page charges. This article must therefore be hereby marked
`advertisement in accordance with 18 U.S.C. Section 1734 solely to
`indicate this fact.
`Requests for reprints: Manisha H. Shah, The Ohio State University,
`A438 Starling-Loving Hall, 320 West Tenth Avenue, Columbus,
`OH 43210. Phone:
`(614) 293-8629; Fax:
`(614) 293-3112; E-mail:
`shah-2@medctr.osu.edu.
`©2004 American Association for Cancer Research.
`
`jective responses in patients with metastatic carcinoid or
`islet cell tumors. Additional investigation is warranted to
`clarify the possible association of autonomic neuropathy
`with bortezomib.
`
`INTRODUCTION
`Because of the pivotal role of the proteasome in controlling
`key cellular processes, the proteasome has emerged as an at-
`tractive novel target for the development of anticancer therapy
`(1). The 26S proteasome is an ATP-dependent multicatalytic
`protease that is central to the ubiquitin-proteasome-degradative
`pathway. The 26S proteasome acts as a housekeeper to eliminate
`damaged or misfolded proteins. In addition, many regulatory
`proteins governing the cell cycle, transcription factor activation,
`apoptosis, and cell trafficking, are the substrates for proteasome-
`mediated degradation (1). The proteasome plays a significant
`role in degradation of cyclin-dependent kinase inhibitors (p21,
`p27; refs. 2, 3) and tumor suppressor (p53; ref. 4) proteins that
`are required for cell cycle arrest. The proteasome is also re-
`quired for activation of transcription factor nuclear factor-␬B
`by degradation of its inhibitory protein inhibitor of nuclear
`factor-␬B (5). Nuclear factor-␬B is necessary, in part, to main-
`tain cell viability through transcription of inhibitors of apoptosis
`in response to stress or cytotoxic agents. Nuclear factor-␬B has
`also been implicated in controlling gene expression of endothe-
`lial cell surface adhesion molecules such as intercellular adhe-
`sion molecule 1, vascular cell adhesion molecule, and E-selectin
`(6), which are involved in tumor metastasis and angiogenesis.
`Furthermore, the proteasome is implicated in in vivo angiogen-
`esis, a phenomenon essential for tumor growth and metastasis
`(7).
`
`Bortezomib [Velcade (Millennium Pharmaceuticals, Inc.,
`Cambridge, MA), previously known as PS-341] is a dipeptidyl
`boronic acid that is a specific, potent and reversible inhibitor of
`the 26S proteasome. Preclinical work revealed significant anti-
`tumor activity of bortezomib in vitro and in vivo. In the cell line
`screen of the National Cancer Institute, bortezomib demon-
`strated a unique pattern of growth inhibitory and cytotoxic
`activity against a broad range of solid tumors (8). Bortezomib
`also significantly reduced tumor volumes in several murine and
`human tumor xenograft models including the Lewis lung,
`HT-29 human colon, PC-3 human prostate, squamous cell car-
`cinoma, and pancreatic cancer (9 –13). The initial dose and
`schedule of bortezomib for phase I clinical trials was chosen
`based on the acute and multiple dose toxicity studies performed
`on rodents and primates (14). Preclinical studies in animals
`showed that bortezomib was rapidly removed from the vascular
`compartment and distributed widely, quickly approaching the
`limits of detection. Therefore, a sensitive, accurate and repro-
`ducible ex vivo 20S proteasome inhibition assay to monitor
`bortezomib activity in whole blood was developed (15). Several
`phase I and/or II clinical trials done to date showed that the
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`6112 Bortezomib in Metastatic Neuroendocrine Tumors
`
`target proteasome inhibition of ⬃70% can be achieved in cancer
`patients with a reasonable safety profile. Moreover, complete
`responses, partial responses, or minor responses were observed
`in the variety of solid tumors and hematologic malignancies
`(16 –20). Bortezomib was recently approved by the Food and
`Drug Administration for its use in the patients with refractory or
`relapsed multiple myeloma.
`Carcinoid and islet cell tumors are generally classified at
`the less-aggressive end of the spectrum of neuroendocrine tu-
`mors. They are thought to derive from enterochromaffin cells,
`which are distributed throughout the gastrointestinal and respi-
`ratory system. Although plasma chromogranin A and 24-hour
`urine for 5-hydroxy indole acetic acid are known prognostic
`markers for survival in patients with carcinoid tumors, the role
`of other tumor markers is not well described (21, 22). Although
`local or locoregional carcinoid or islet cell tumors are surgically
`manageable, metastatic disease is present in ⬃50% of patients at
`the time of diagnosis, and the overall 5-year survival for patients
`with distant metastasis is only 22%. Somatostatin analogues,
`IFN-␣ or hepatic artery chemoembolization provide good pal-
`liation of the symptoms of carcinoid syndrome associated with
`such tumors. However, no systemic therapy has been shown to
`consistently elicit tumor responses and prolong survival. The
`ineffectiveness of systemic chemotherapy in metastatic neu-
`roendocrine tumors may relate to their unique biological fea-
`tures such as slow growth pattern or hypervascularity.
`Preclinical in vitro and in vivo work suggests that bort-
`ezomib has antitumor activity in a broad spectrum of solid
`tumors, including the PC-12 neuroendocrine (pheochromocy-
`toma) tumor cell line (23). Although primarily targeting the
`proteasome pathway, bortezomib has been shown to affect key
`proteins involved in cell cycle regulation, angiogenesis, and
`apoptosis. On the basis of this and the unique antitumor mech-
`anisms of bortezomib, we hypothesize that it may have clinical
`activity in metastatic carcinoid and islet cell tumors. We thus
`conducted a phase II clinical trial in patients with metastatic
`carcinoid and islet cell tumors. On the basis of toxicity and
`pharmacodynamic data available from initial phase I clinical
`trials in solid tumor and hematologic malignancies, the dose of
`1.5 mg/m2 administered as an i.v. bolus on days 1, 4, 8, and 11
`every 21 days was considered optimal for our trial. We report
`the results of the first prospective phase II study of bortezomib
`in patients with metastatic neuroendocrine tumors.
`
`PATIENTS AND METHODS
`Patient Selection. Eligibility criteria included histologi-
`cally confirmed well-differentiated neuroendocrine carcinoma;
`metastatic and measurable disease; no more than one prior
`systemic chemotherapy regimen; no IFN-␣, systemic chemo-
`therapy, or radiation therapy within the past 4 weeks; no hepatic
`artery chemoembolization within the past 12 weeks; age ⱖ 18
`years; Eastern Cooperative Oncology Group performance status
`0 to 2; life expectancy ⱖ 6 months; and adequate organ func-
`tions: total bilirubin ⱕ 1.5 mg/dL, aspartate aminotransferase/
`alanine aminotransferase ⱕ 2.5⫻ upper limit of normal, abso-
`lute neutrophil count ⱖ 1500/␮L, platelet count ⱖ 100,000/␮L,
`and serum creatinine of ⱕ1.5 mg/dL. The standard dose (10 to
`40 mg every 3 to 4 weeks) of intramuscular long-acting oct-
`
`reotide [Sandostatin LAR (Novartis Pharmaceuticals Co., East
`Hanover, NJ)] was permitted for the control of carcinoid syn-
`drome symptoms provided that the dose was stable for 3 months
`before study entry. Exclusion criteria were pregnancy, breast-
`feeding, and uncontrolled intercurrent illness.
`Study Design. Bortezomib was administered as an i.v.
`bolus at a dose of 1.5 mg/m2 on days 1, 4, 8, and 11 every 21
`days. Antiemetic therapy or growth factor support was not used
`on a prophylactic basis. Therapy was given for a total of 24
`weeks unless patients met one of the following criteria: progres-
`sive disease; unacceptable adverse event; off of study drug for
`⬎2 weeks; or patient withdrawal from the study. Patients were
`maintained at the full dose of 1.5 mg/m2 unless patients had
`grade 3 or 4 adverse event. In case of grade 3 or 4 adverse event,
`treatment was withheld for 1 week. Upon reevaluation, patients
`who showed a partial (improvement to grade 1 or 2 adverse
`event) or a full resolution were started on bortezomib at the
`reduced dose of 1.0 mg/m2 that was escalated to 1.3 mg/m2 after
`1 week and to 1.5 mg/m2 after the second week as tolerated. The
`patients with persistent grade 3 or 4 adverse event were taken
`off of the protocol.
`History, physical examination, complete blood count, and
`serum chemistry were obtained within 14 days before initiation
`of therapy and within 2 to 4 weeks after the last dose of
`bortezomib (posttreatment). Baseline tumor measurements were
`performed with computed tomography scan within 4 weeks
`before initiation of therapy and repeated every 12 weeks during
`study and at the posttreatment visit. In addition, patients had a
`history and physical examination performed every 6 weeks and
`had complete blood count, serum chemistries, and adverse event
`evaluation performed once a week during their treatment weeks
`(week 1, 2, 4, 5, and so on). Objective response was assessed
`according to Response Evaluation Criteria in Solid Tumors
`(RECIST) criteria, and toxicity was assessed according to Na-
`tional Cancer Institute Common Toxicity Criteria, version 2.0
`(24).6
`Tumor Marker Studies. Serum tumor markers (pancre-
`astatin, gastrin, calcitonin, pancreatic polypeptide, vasoactive
`intestinal peptide, neurotensin, substance-P, gastrin-releasing
`peptide, glucagon, somatostatin, and serotonin) and 24-hour
`urine for 5-hydroxy indole acetic acid were obtained within 14
`days before initiation of therapy every 12 weeks during therapy
`and within 2 to 4 weeks posttreatment.
`Pharmacodynamic Studies. We used an ex vivo 20S
`proteasome inhibition assay to monitor bortezomib activity in
`whole blood using the previously described method (15). This
`fluorogenic kinetic assay consisted of measuring proteasome
`activity at chymotryptic and tryptic sites within the 20S core of
`the proteasome and determining the degree of inhibition con-
`ferred by bortezomib. Using the ratio of these chymotryptic:
`tryptic activities and the catalytic mechanism of the proteasome,
`percentage of inhibition was calculated compared with predose
`whole blood obtained from the same patient.
`Blood samples were collected at 0 hour (just before admin-
`istration of bortezomib), 1 hour, and 24 hours after bortezomib
`
`6 Internet address: http://ctep.info.nih.gov/reporting/ctc.html.
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`Clinical Cancer Research
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`6113
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`on days 1 and 4 of the first course of therapy. For each time
`point, 8-mL of blood were collected in one heparinized green
`top tube, immediately placed on ice, and then frozen at ⫺70°C.
`Batched samples were shipped on dry ice to Millennium Phar-
`maceuticals, Inc., for performing an assay. On the basis of the
`preclinical efficacy and toxicity studies, a target level of ⬃70%
`proteasome inhibition was considered optimal.
`Statistical Considerations. For this phase II study, the
`minimax two-stage design of Simon was chosen, resulting in a
`trial with a decision to proceed to the second stage based on
`efficacy seen in the first 16 patients. Bortezomib was to be
`considered ineffective or uninteresting if the true response prob-
`ability was ⬍10% (p0). The regimen was to be worthy of further
`study if the true response probability or target response rate was
`ⱖ30% (p1). These figures resulted in a two-stage design of 16
`and 25 patients, with an ␣ of 0.10 and ␤ of 0.10. If one or no
`responses were seen in the first 16 patients, the study was to be
`terminated early, and this regimen was deemed ineffective for
`this patient population. If two or more patients respond in the
`first 16, an additional 9 patients were to be treated for a total
`of 25.
`The primary end point was to assess the objective response
`(partial remission or complete remission) of bortezomib in met-
`astatic carcinoid and islet cell tumors. Stable disease was not
`considered an objective response to therapy given the relatively
`slow-growing nature of these cancers and due to a single-arm
`study design. Patients who had stable disease were taken off
`from the protocol at 24 weeks of therapy. Secondary end points
`were to assess the toxicity of bortezomib in patients with met-
`astatic neuroendocrine tumors, to assess tumor marker response,
`and to evaluate pharmacodynamics of bortezomib by ex vivo
`20S proteasome inhibition assay.
`
`RESULTS
`Patients. After obtaining informed consent, 16 patients
`with metastatic neuroendocrine tumor were enrolled on to the
`Institutional Review Board-approved phase II study at The Ohio
`State University (n ⫽ 14) and at University of Chicago (n ⫽ 2)
`between May 2001 and December 2001. Patient characteristics
`are outlined in Table 1. A majority of patients (n ⫽ 12; 75%)
`had carcinoid tumors, whereas the rest (n ⫽ 4, 25%) had islet
`cell tumors. Of the four patients with islet cell tumors, one
`patient had symptoms of diarrhea related to carcinoid syndrome,
`whereas the rest of the patients had no symptoms associated
`with abnormally high hormone production (pancreatic polypep-
`tide, gastrin, glucagon, or calcitonin) related to their islet cell
`tumors.
`Treatment Administered.
`If the best response achieved
`was stable disease, treatment with bortezomib was continued for
`up to 24 weeks (32 doses). All 16 patients received median of 15
`doses (range, 1 to 32 doses), with a median cumulative total
`dose of 21.8 (range, 1.5 to 48) mg/m2. Of the total 264 doses
`given in the study, 42 doses in seven patients were given at the
`reduced doses per protocol guidelines because of grade 3 ad-
`verse events [neutropenia (n ⫽ 2), peripheral neuropathy (n ⫽
`2), ileus (n ⫽ 2), and thrombocytopenia (n ⫽ 1)] or recurrent
`grade 2 vomiting. The median duration of therapy for all pa-
`tients was 12 weeks (range, 0.5 to 24 weeks) and only 4 of 16
`
`Table 1 Patient characteristics
`
`Characteristic
`
`Total patients
`Age (y)
`Median
`Range
`Sex
`Female
`Male
`Eastern Cooperative Oncology Group
`performance status
`0
`1
`Type of neuroendocrine tumor
`Carcinoid tumor
`Islet cell tumor
`Primary sites
`Pancreas
`Ileocecal
`Colon
`Stomach
`Lung
`Unknown
`Metastatic sites
`Liver alone
`Liver and lymph nodes
`Liver, lymph nodes, and bone
`Carcinoid syndrome/concurrent octreotide therapy
`Present
`Absent
`Prior treatment
`Debulking or palliative surgery
`Hepatic artery chemoembolization
`Systemic chemotherapy
`Baseline elevation of serum tumor markers
`Pancreastatin
`Glucagon
`Neurotensin
`Gastrin
`Pancreatic polypeptide
`Calcitonin
`
`No.
`16
`
`60
`26–72
`
`10
`6
`
`13
`3
`
`12
`4
`
`4
`7
`1
`1
`1
`2
`
`6
`6
`4
`
`6
`10
`
`11
`6
`0
`
`13
`5
`5
`4
`2
`2
`
`%
`
`62
`38
`
`81
`19
`
`75
`25
`
`25
`43
`6
`6
`6
`12
`
`37
`37
`25
`
`38
`62
`
`68
`38
`0
`
`81
`31
`31
`25
`12
`12
`
`patients (25%) completed 24 weeks of therapy. The reasons for
`leaving the study before 24 weeks of planned therapy in the 12
`patients included progressive disease (n ⫽ 3), persistent grade 3
`adverse events [peripheral neuropathy (n ⫽ 2), diarrhea (n ⫽ 1),
`fatigue (n ⫽ 1)], and patient withdrawal [grade 3 hypertension/
`atrial fibrillation (n ⫽ 1); grade 2 nausea (n ⫽ 1), vomiting (n ⫽
`1) or seizure (n ⫽ 1); and social reason (n ⫽ 1)] (Fig. 1).
`Objective Response. All 16 patients were considered
`evaluable for response in an intent-to-treat analysis. No pa-
`tients achieved a partial response or a complete response.
`Stable disease was noted in 11 of 16 patients (69%) at the
`median evaluation time of 12 weeks (range, 3 to 24 weeks)
`after the start of therapy. Five patients (31%) had progressive
`disease noted at weeks 0.5 (n ⫽ 1), 12 (n ⫽ 2), 16.5 (n ⫽ 1),
`and 24 (n ⫽ 1).
`Tumor Marker Response. Serum pancreastatin was
`consistently elevated at the prestudy evaluation in 13 patients,
`whereas other tumor markers (pancreatic polypeptide, gastrin,
`glucagon, calcitonin, or neurotensin) were elevated in only a
`few patients at baseline (Table 1). Tumor markers were evalu-
`able in 10 patients, and marker levels did not correlate with
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`6114 Bortezomib in Metastatic Neuroendocrine Tumors
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`Fig. 1 Treatment administered and reasons for off study. f indicates maximum doses planned,
`indicates individual patient and data label indicates
`the reason for off study (type of response). PD, progressive disease; SD, stable disease; HTN, hypertension, AF, atrial fibrillation.
`
`objective tumor response in most patients. Table 2 summarizes
`serum pancreastatin results in 10 evaluable patients. Of eight
`patients who showed stable disease, three patients had an 11 to
`24% reduction in serum pancreastatin, whereas five patients had
`an increase (median increase, 44%; range, 7 to 55%) in serum
`pancreastatin compared with the prestudy levels. Serum pancre-
`astatin was increased by 13 to 18% as compared with baseline
`in patients who showed progressive disease.
`
`Pharmacodynamic Studies. A pharmacodynamic assay
`was performed to correlate the degree of proteasome inhibition
`with tumor response or adverse events. The percentage of 20S
`proteasome inhibition was compared with the predose (0 hour)
`value obtained on the same day in each individual patient.
`Peripheral blood samples were evaluable in 15 of total 16
`patients on the study. The mean percentage of 20S proteasome
`inhibition achieved in whole blood at 1 and 24 hours after
`
`Table 2 Correlation of serum tumor marker response with objective response
`Serum pancreastatin (pg/mL) (normal value ⬍ 135 pg/mL)
`
`Subject
`Posttherapy
`Pretherapy
`no.
`755
`851
`105
`260
`346
`110
`1,200
`1,580
`113
`1,620
`1,520
`112
`1,420
`1,070
`108
`8,210
`12,500
`107
`853
`555
`104
`8,790
`5,650
`101
`389
`343
`106
`570
`484
`103
`Abbreviations: SD, stable disease; PD, progressive disease.
`
`% change with therapy
`⫺11
`⫺21
`⫺24
`7
`33
`44
`54
`55
`13
`18
`
`Best clinical response
`SD
`SD
`SD
`SD
`SD
`SD
`SD
`SD
`PD
`PD
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`6115
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`bortezomib. Moreover, one patient had neuropathy symptoms
`starting at 3 weeks after the last of bortezomib. Grade 3 neu-
`ropathy symptoms in this patient improved to grade 2 and to
`grade 1 at week 12 and at week 18 after the last of bortezomib,
`respectively, despite subsequent treatment with etoposide and
`cisplatin. Although peripheral neuropathy is a common side
`effect of cisplatin, it is usually cumulative and progressive
`during the course of cisplatin chemotherapy. Thus, spontaneous
`improvement of neuropathy from grade 3 to grade 1 in our
`patient during the six cycles of cisplatin-based chemotherapy
`indicates its likely attribution to bortezomib. Seven of 10 pa-
`tients had improvement up to grade 1 (n ⫽ 5) or grade 0 (n ⫽
`2) peripheral neuropathy at a median of 18 weeks (range, 2 to 76
`weeks) after the last dose of bortezomib.
`
`DISCUSSION
`Given the broad spectrum of in vitro and in vivo antineo-
`plastic activity and safety of single-agent bortezomib, we stud-
`ied its efficacy in patients with metastatic neuroendocrine tu-
`mors. Despite achieving the surrogate biological end point of
`20S proteasome inhibition in peripheral blood mononuclear
`cells obtained from 15 patients, our study failed to show any
`objective tumor response in this patient population. Although
`stable disease was noted in 11 of 16 patients (69%) at the
`median evaluation time of 12 weeks (range, 3 to 24 weeks) after
`
`Table 3 Bortezomib-related adverse events reported in
`all 16 patients
`
`Adverse event
`Gastrointestinal
`Anorexia
`Nausea
`Vomiting
`Diarrhea
`Constipation
`Ileus
`Abdominal cramps
`Dehydration
`Dysgeusia
`Neurological
`Neuropathic pain
`Neuropathy-sensory
`Dizziness
`Syncope
`Seizure
`Constitutional
`Fatigue
`Weight loss
`Hematologic
`Neutropenia
`Thrombocytopenia
`Others
`Skin rash
`Mouth sores (cold sores)
`Infection without neutropenia
`Hyperglycemia
`Orthostatic hypotension
`Hypertension
`Atrial fibrillation
`Conjunctivitis
`
`Number (%)
`
`Grade 1
`
`Grade 2
`
`Grade 3
`
`4 (25)
`1 (6)
`1 (6)
`3 (18)
`1 (6)
`0
`0
`0
`3 (18)
`
`0
`0
`1 (6)
`0
`0
`
`7 (43)
`2 (12)
`
`0
`1 (6)
`
`2 (12)
`0
`1 (6)
`1 (6)
`0
`0
`0
`0
`
`5 (31)
`9 (56)
`3 (18)
`1 (6)
`4 (25)
`0
`0
`3 (18)
`1 (6)
`
`4 (25)
`4 (25)
`1 (6)
`0
`1 (6)
`
`5 (31)
`1 (6)
`
`1 (6)
`1 (6)
`
`2 (12)
`3 (18)
`2 (12)
`1 (6)
`2 (12)
`0
`0
`0
`
`0
`2 (12)
`3 (18)
`4 (25)
`0
`3 (18)
`2 (12)
`0
`0
`
`6 (37)
`6 (37)
`0
`1 (6)
`0
`
`1 (6)
`0
`
`2 (12)
`2 (12)
`
`0
`0
`0
`1 (6)
`0
`1 (6)
`1 (6)
`1 (6)
`
`Fig. 2 Pharmacodynamic assay for bortezomib (n ⫽ 15). Percentage of
`20S proteasome inhibition in whole blood at indicated time points
`during the first course of bortezomib (mean ⫾ SD). Percentage of 20S
`proteasome inhibition is compared with the predose value obtained on
`the same day in each individual patient.
`
`bortezomib administration on day 1 was 68 (SD ⫾6) and 30 (SD
`⫾6), respectively. Similar results were achieved on day 4 of
`bortezomib administration (Fig. 2). The target level of 20S
`proteasome inhibition was achieved in our study patients, and
`there was no correlation with type or degree of adverse events or
`clinical outcome.
`Adverse Events. Bortezomib was generally well toler-
`ated. There were no grade 4 adverse events or deaths related to
`the study. All of the drug-related adverse events reported in the
`16 study patients are outlined in Table 3. The worst grade
`experienced by individual patient was used to report the adverse
`events. Although the most common adverse event seen was
`nausea (74%), the most common grade 3 toxicities were periph-
`eral sensory neuropathy (37%), followed by diarrhea (25%). It is
`noteworthy that four patients (25%) developed viral-associated
`infections during the study period. Three of these patients had
`recurrent grade 2 cold sores, whereas one patient had grade 3
`conjunctivitis in absence of neutropenia. Three patients (18%)
`had ileus occur at the cumulative dose (mg/m2) of 6, 7.5, or
`10.5. All of these patients had prior laparotomy, two patients
`had active mesenteric carcinoid tumor, and one patient was on
`a stable dose of tincture of opium. Ileus resolved within 2 to 3
`days of hospitalization with conservative treatment, and patients
`subsequently received one, three, or eight doses of bortezomib
`without recurrent ileus. Of the two patients who experienced
`grade 3 abdominal cramps, one had ileus as noted above.
`A drug-related grade 2 to 3 peripheral sensory neuropathy
`manifested by pain, tingling, and numbness occurred in 10
`patients (62%). In general, tingling and numbness were more
`intense in the feet and legs than in the hands, whereas neuro-
`pathic pain was mainly localized to legs and feet. All of these
`patients required narcotics and gabapentin for pain control. The
`median cumulative dose at the onset of neuropathy was 13.3
`(range, 1.5 to 28.5) mg/m2 (Table 4). Five of these patients had
`worsening of neuropathy during the off-study period at a median
`of 3.5 weeks (range, 3 to 9 weeks) after the last dose of
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`6116 Bortezomib in Metastatic Neuroendocrine Tumors
`
`Table 4 Analysis of bortezomib-associated neurotoxicity
`
`Subject
`no.
`101
`
`Total cumulative
`dose (mg/m2)
`17.4
`
`Worst grade
`of PSN
`3
`
`Grade of PSN
`at recovery
`1
`
`3
`
`1
`
`3
`
`1
`
`1
`
`102
`
`27.3
`
`103
`
`104
`
`105
`
`21.1
`
`10.5
`
`15
`
`106
`
`22.5
`
`107
`
`24
`
`108
`
`109
`110
`
`48
`
`36
`39.3
`
`3
`
`3
`
`3
`
`3
`
`3
`
`2
`
`2
`
`2
`2
`
`Cumulative total dose at
`the onset of PSN
`16.1 mg/m2: grade 2
`17.4 mg/m2: grade 3
`10.5 mg/m2: grade 1
`
`13.5 mg/m2: grade 2
`21.3 mg/m2: grade 3
`10.5 mg/m2: grade 1
`
`Status of PSN during
`off study period
`Wk after the last
`dose of bortezomib:
`grade of PSN
`Wk 7: grade 2
`Wk 12: grade 1
`Wk 8: grade 3
`
`Wk 3–5: grade 3
`
`18.1 mg/m2: grade 2
`6 mg/m2: grade 2
`
`Wk 24: grade 1
`Wk 3–102: grade 3
`
`1.5 mg/m2: grade 1
`
`Wk 6–34: grade 3
`
`12 mg/m2: grade 2
`
`No symptoms during
`study
`
`Wk 56: grade 2
`Wk 76: grade 1
`Wk 3 (d 7, 1st cycle
`VP/cis): grade 3
`Wk 12 (4th cycle
`VP/cis): grade 2
`Wk 18 (6th cycle
`VP/cis): grade 1
`Wk 23–27: grade 1
`Wk 2: grade 1
`
`Wk 4–12: grade 2
`Wk 16: grade 1 T/N
`Wk 16: grade 0 pain
`Wk 2–30: grade 0
`
`Wk 9–20: grade 2
`Wk 12: grade 1
`
`1 T/N
`
`10.5 mg/m2: grade 1
`
`0 pain
`
`0
`
`2
`0
`
`21 mg/m2: grade 1
`27 mg/m2: grade 2
`28.5 mg/m2: grade 1
`27 mg/m2: grade 1
`
`Symptoms possibly related to
`autonomic neuropathy
`(Cumulative dose of
`bortezomib at onset)
`
`Grade 2 orthostatic
`hypotension (18 mg/m2)
`
`Grade 1 dizziness, grade 3
`ileus (10.5 mg/m2)
`
`Grade 3 ileus (6 mg/m2)
`
`Grade 2 dizziness
`(12 mg/m2)
`
`Grade 2 orthostatic
`hypotension, grade 3
`syncope (21 mg/m2)
`
`Grade 3 abdominal cramps
`(3 mg/m2)
`
`Grade 3 ileus (7.5 mg/m2)
`
`Wk 24: grade 0
`Lost to follow up
`0
`8.5
`111
`Abbreviations: VP, VP-16; cis, cisplatin; PSN, peripheral sensory neuropathy; T/N, tingling/numbness.
`
`28.5 mg/m2: grade 2
`
`the start of therapy, our study was not designed to evaluate
`progression-free survival. Given the slow growing nature of
`these tumors, we cannot attribute stable disease to the antitumor
`effect of bortezomib in our single-arm study. Given that protea-
`some inhibition in tumor tissue was not evaluated in our study,
`it is conceivable that the ineffectiveness of bortezomib may
`relate to an insufficient level or duration of 26S proteasome
`inhibition in the tumors. Although bortezomib affects the nu-
`clear factor-␬B pathway, cyclin-dependent kinase inhibitors
`(e.g., p21, p27), or tumor suppressor (e.g., p53) proteins, it is
`possible that redundant pathways exist for tumor progression
`and survival of metastatic neuroendocrine tumors.
`Bortezomib was generally well tolerated at the dose and
`schedule used in our study. Similar to previously reported
`studies, the most common adverse events in this study in-
`cluded gastrointestinal, neurologic, constitutional, and hema-
`tologic. However, we observed a higher (37 versus 12%)
`
`incidence of grade 3 peripheral sensory neuropathy in our
`chemo-naı¨ve patients compared with the phase II trial of
`bortezomib in multiple myeloma (16). It is unclear if grade 3
`pain in limb reported in 7% of their study patients was
`neuropathic pain. Given that 86% of patients in the reported
`myeloma study had prior thalidomide (and likely Vinca al-
`kaloids), it is possible that an attribution of neuropathy to
`bortezomib might have been difficult. Although the median
`duration of therapy administered in both studies was roughly
`similar (12 versus 15 weeks), the dose of bortezomib was
`higher (1.5 versus 1.3 mg/m2/dose) in our study. Thus, it is
`possible that the higher dose may account for the higher
`incidence of neuropathy seen in our study. A recently re-
`ported phase II study used a dose and schedule similar to our
`study and reported only 9% grade 3 peripheral neuropathy
`but 47% incidence for all grades of neuropathy (25). Al-
`though we did not evaluate predisposing factors for neurop-
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`Clinical Cancer Research
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`6117
`
`athy in a prospective manner, no obvious risk factors (such as
`diabetes mellitus, concomitant or prior neurotoxic medica-
`tions, or B12 deficiency) were found in our patients. Periph-
`eral sensory neuropathy was generally dose related, cumula-
`tive, and reversible up to less than or equal to grade 1 (Table
`4). The median time in improvement or resolution of neu-
`ropathy was 18 weeks (range, 2 to 76 weeks) after the last
`dose of bortezomib. However, patients were not required to
`follow-up at the specific intervals during the off-study pe-
`riod. The clinical pattern seen in our patients with peripheral
`neuropathy was most consistent with small-fiber painful sen-
`sory neuropathy where A-␦ (small myelinated) and nocicep-
`tive C (unmyelinated) nerve fibers are affected. With the
`striking association of peripheral neuropathy with bort-
`ezomib, it is possible that the ileus, abdominal cramps, syn-
`cope, dizziness, and orthostatic hypotension seen in seven of
`our patients (43%) could be a result of bortezomib-related
`autonomic neuropathy. Six of seven patients who developed
`such symptoms also developed grade 2 to 3 peripheral neu-
`ropathy during the course of their therapy. Although existing
`predisposing factors (e.g., prior laparotomy, narcotic use, or
`active bowel carcinoid tumor) could explain the occurrence
`of ileus in three of our patients (18%), possible association of
`ileus with bortezomib cannot be excluded. Interestingly,
`there were eight patients on the study who had prior laparot-
`omy for tumor debulking who did not develop ileus. The high
`incidence of nausea and vomiting seen our study suggests
`that patients might benefit from prophylactic antiemetic ther-
`apy. Although the given patient population could have diar-
`rhea because of carcinoid syndrome, the baseline symptoms
`were taken into consideration in grading diarrhea, and no
`simultaneous worsening of other carcinoid syndrome symp-
`toms was seen. Hematologic toxicity was of short duration
`alleviating the need for transfusion or growth factor support.
`We also question whether bortezomib administration might
`be associated with viral reactivation given that 25% of our
`patients had either cold sores or conjunctivitis in the absence
`of neutropenia. Of note, we did not observe any of the
`electrolyte abnormalities seen in phase I studies.
`In conclusion, single-agent bortezomib does not have ac-
`tivity in patients with metastatic neuroendocrine tumors. Bort-
`ezomib is safe at the schedule and dose used in our study, with
`the most significant clinical adverse event being a peripheral
`sensory neuropathy. The detailed evaluation of bortezomib-
`associated neurotoxicity, including autonomic neuropathy and
`value of prophylactic strategies, merits future investigation.
`These studies will be particularly helpful because this agent may
`be used with other neurotoxic agents in the future. Furthermore,
`with growing preclinical data demonstrating synergism between
`bortezomib and cytotoxic chemotherapy (26 –30), future studies
`should evaluate bortezomib in combination with chemotherapy
`in solid tumors but caution should be taken in combining chem-
`otherapy that may have overlapping gastrointestinal or neuro-
`logic toxicity.
`
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