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Journal of Clinical Oncology, Vol 25, No 6 (February 20), 2007: pp. 669-674 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2006.06.8197 Double-Blinded Randomized Study of High-Dose Calcitriol Plus Docetaxel Compared With Placebo Plus Docetaxel in Androgen-Independent Prostate Cancer: A Report From the ASCENT Investigators
From the Division of Hematology and Medical Oncology, Oregon Health & Science University, Portland, OR; Columbia Presbyterian Medical Center, New York, NY; University of Pittsburgh, Pavillion Hellman Cancer Center, Pittsburgh, PA; Sharp HealthCare; San Diego Cancer Center, Vista; Kaiser Permanente Medical Center, Vallejo; Novacea Inc, South San Francisco, CA; Georgia Cancer Specialists, Tucker, GA; Oncology Hematology Care, Cincinnati; The Cleveland Clinic Foundation, Cleveland, OH; The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD; Seattle Cancer Care Alliance, Seattle, WA; University of Arizona Cancer Center, Tucson, AZ; Cross Cancer Institute, Edmonton; Tom Baker Cancer Centre, Calgary, Alberta; and the University of British Columbia Cancer Agency, Vancouver Centre, Vancouver, British Columbia, Canada Address reprint requests to Tomasz M. Beer, MD, Department of Medicine, Oregon Health & Science University, Mail Code CR-145, 3181 SW Sam Jackson Park Rd, Portland, OR 97239; e-mail: beert{at}ohsu.edu
PURPOSE: To compare the safety and activity of DN-101, a new high-dose oral formulation of calcitriol designed for cancer therapy, and docetaxel with placebo and docetaxel. PATIENTS AND METHODS: Patients with progressive metastatic androgen-independent prostate cancer and adequate organ function received weekly docetaxel 36 mg/m2 intravenously for 3 weeks of a 4-week cycle combined with either 45 µg DN-101 or placebo taken orally 1 day before docetaxel. The primary end point was prostate-specific antigen (PSA) response within 6 months of enrollment, defined as a 50% reduction confirmed at least 4 weeks later. RESULTS: Two hundred fifty patients were randomly assigned. Baseline characteristics were similar in both arms. Within 6 months, PSA responses were seen in 58% in DN-101 patients and 49% in placebo patients (P = .16). Overall, PSA response rates were 63% (DN-101) and 52% (placebo), P = .07. Patients in the DN-101 group had a hazard ratio for death of 0.67 (P = .04) in a multivariate analysis that included baseline hemoglobin and performance status. Median survival has not been reached for the DN-101 arm and is estimated to be 24.5 months using the hazard ratio, compared with 16.4 months for placebo. Grade 3/4 adverse events occurred in 58% of DN-101 patients and in 70% of placebo-treated patients (P = .07). Most common grade 3/4 toxicities for DN-101 versus placebo were neutropenia (10% v 8%), fatigue (8% v 16%), infection (8% v 13%), and hyperglycemia (6% v 12%). CONCLUSION: This study suggests that DN-101 treatment was associated with improved survival, but this will require confirmation because survival was not a primary end point. The addition of weekly DN-101 did not increase the toxicity of weekly docetaxel.
Calcitriol (1,25-dihydroxycholecalciferol, 1,25(OH)2D3) is the natural ligand for the vitamin D receptor (VDR). This compound, as well as synthetic VDR ligands, has been extensively examined using in vitro and in vivo models of adenocarcinoma of the prostate1-7 and many other neoplasms. These studies have indicated significant antitumor activity through inhibition of proliferation, induction of apoptosis, and reduction in tumor invasiveness and angiogenesis. The antineoplastic activity of VDR ligands is synergistic or additive with the activity of several classes of agents including cytotoxic chemotherapy drugs, such as paclitaxel,8 docetaxel,9 platinum compounds,10 and mitoxantrone.11 The antineoplastic activity of calcitriol occurs at concentrations of calcitriol that substantially exceed the physiologic range, and are achievable with intermittent, but not continuous dosing of calcitriol in humans.12-18 Docetaxel-containing chemotherapy was recently shown to prolong survival and has become the standard of care in metastatic androgen-independent prostate cancer (AIPC).19,20 Calcitriol was first combined with docetaxel in a phase II trial reported by investigators at Oregon Health & Science University (Portland, OR).21 Prostate-specific antigen (PSA) decline of 50% or greater was seen in 81% of patients. In order to overcome the limitations of previous calcitriol formulations (nonlinear, variable pharmacokinetics and the very large number of capsules required at one time), Novacea Inc (South San Francisco, CA) developed DN-101, a high concentration formulation of calcitriol specifically designed for use in cancer treatment.22 AIPC Study of Calcitriol Enhancing Taxotere (ASCENT) is a double-blind randomized phase II study to further evaluate the efficacy and safety of DN-101 (high-dose calcitriol) plus weekly docetaxel compared with placebo plus weekly docetaxel in AIPC.
Eligibility Men with histopathologically or cytologically proven metastatic adenocarcinoma of the prostate with evidence of progression (the development of new metastatic lesions or rising PSA23) despite standard hormonal management (orchiectomy, gonadotropin-releasing hormone agonist or antagonist including withdrawal of antiandrogens, if applicable; 6 weeks for bicalutamide, 4 weeks for flutamide or nilutamide) were eligible. Other eligibility criteria were: serum PSA 5.0 ng/mL, serum testosterone level 50 ng/dL, Eastern Cooperative Oncology Group performance status 2, life expectancy 3 months, age 18 years, patient agreement to use adequate contraception, and patient ability to give informed consent. Patients were excluded if they had an active malignancy within 5 years (except nonmelanoma skin cancer), significant active medical illness that would preclude protocol treatment, a history of hypercalcemia or vitamin D toxicity, or hospitalization for treatment of angina, myocardial infarction, or congestive heart failure in the previous 12 months. Patients were also excluded for kidney stones (calcium salt) within 5 years, hypersensitivity to calcitriol or drugs formulated with polysorbate-80, grade 2 or higher peripheral neuropathy, neutrophil count less than 1,500/mm3, platelet count lower than 100,000/mm3, serum creatinine more than upper limit of normal (ULN), serum calcium more than ULN (for patients with an albumin lower than 3.0, a corrected calcium = serum calcium + [0.8][3.5 serum albumin] was used), conjugated bilirubin more than ULN, alkaline phosphatase more than 4 x ULN (patients with known bone involvement and a normal conjugated bilirubin, ALT, and AST were not excluded), ALT or AST more than 2.0 x ULN when alkaline phosphatase is less than 2.5 x ULN, ALT or AST more than 1.5 x ULN when alkaline phosphatase is more than 2.5 x ULN. In addition, patients were excluded for prior investigational therapy or use of calcitriol within 30 days, prior chemotherapy for prostate cancer except for adjuvant therapy more than 12 months before enrollment, prior chemotherapy with docetaxel, treatment with radiotherapy within 4 weeks or treatment with other radiopharmaceuticals within 8 weeks. The study was approved by institutional review boards at all participating institutions.
Study End Points and Statistical Design The primary analysis for efficacy was on the intention to treat population and toxicity was evaluated in the as-treated population. These two populations were identical.
A sample size of at least 116 patients per treatment group was expected to provide 85% power to detect a 20% absolute increase in the PSA response rate (from 45% to 65%) with a two-sided significance level of .045 based on a two-group comparison using an uncorrected The initial analysis plan underwent two modifications. The first modification was made before any analysis and called for a change in the primary end point from PSA response overall to PSA response achieved within 6 months of enrollment and for elimination of a planned interim analysis of the primary end point. The second modification to the analysis plan was made after the analysis of the primary end point and an interim analysis of secondary end points and prior to the prespecified final analysis of survival. This modification specified that the final analysis of survival was to be performed using multivariate Cox regression including the known prognostic factors of baseline hemoglobin and performance status as covariates. The modified analysis plan also included a sensitivity analysis of survival data with unadjusted log-rank test.
Pretreatment Evaluation
Random Assignment DN-101 (45 µg) or placebo was administered orally on day 1 followed by docetaxel 36 mg/m2 intravenously on day 2 along with dexamethasone (4 mg orally 12 hours before, 1 hour before, and 12 hours after docetaxel administration). This regimen was administered weekly for 3 consecutive weeks of a 4-week cycle. For each patient, the first dose of docetaxel (week 1, cycle 1 only) was attenuated (27 mg/m2) to collect additional safety data for the combination of DN-101 with docetaxel.
Treatment on ASCENT continued until disease progression (either by PSA measurements or tumor assessments by imaging), unacceptable toxicity, or patient request. Patients enrolled in ASCENT who reached a confirmed PSA
Concomitant Medications
On Study Evaluations
Patients Two hundred fifty patients were randomly assigned at 48 sites between September 2002 and January 2004. At the time of this data analysis the median duration of follow-up was 18.3 months, 229 patients (92%) have completed study treatment and 122 patients (49%) have died. All randomly assigned patients were treated and all patients are included in the analyses presented here. The baseline characteristics of patients are summarized in Table 1. Briefly, the two groups were well matched with respect to age, performance status, extent of disease, serum PSA, and serum lactate dehydrogenase. There were no statistically significant differences between the two groups in any of these categories.
Response to Therapy PSA decline (> 50% confirmed 4 weeks later) within 6 months of enrollment, the primary end point, was reached in 49% of placebo-treated patients and 58% of DN-101-treated patients (P = .16). At any time while on study, this end point was achieved in 52% of placebo-treated patients and 63% of DN-101-treated patients (P = .07). Median time to PSA response was 5.3 months in placebo-treated patients and 2.9 months in DN-101-treated patients (P = .06). Median duration of PSA progression-free survival was 7.6 months for placebo-treated patients and 7.9 months for DN-101-treated patients (P = .7). Measurable disease meeting RECIST criteria was present in 59 of placebo-treated patients (47%) and 48 of DN-101 treated patients (38%). Tumor response in this group of patients was seen in 14 (24%) and 14 (29%) of placebo and DN-101-treated patients, respectively (P = .51). Median duration of tumor progression-free survival and median duration of clinical progression-free survival could not be reliably assessed due to the lack of regularly scheduled tumor imaging for those patients (57%) who entered the study without measurable tumor lesions meeting RECIST criteria as target lesions and because many of the patients with measurable disease were removed from the study due to increases in PSA without evidence for objective disease progression.
Skeletal Morbidity-Free Survival
Overall Survival The secondary end point of overall survival is shown in Figure 2. After adjustment for baseline characteristics of hemoglobin and Eastern Cooperative Oncology Group performance status, overall survival showed a promising improvement in the DN-101 group over the placebo group with a HR of 0.67 (95% CI, 0.45 to 0.97; P = .04). While the median survival in the placebo was 16.4 months, it has not been reached in the DN-101 group, but is estimated to be 24.5 months using the adjusted HR. Likewise, in a sensitivity analysis, the unadjusted HR similarly favored DN-101 (HR, 0.70; 95% CI 0.48 to 1.028; P = .07).
Toxicity All adverse events are reported regardless of perceived relationship to treatment. Overall, no increase in toxicity was seen with the addition of DN-101 to docetaxel. There were reductions in the frequency of several classes of adverse events observed in the DN-101-treated group. The incidence of any grade 3 or 4 adverse events was 70% in placebo treated patients and 58% in DN-101 treated patients (P = .065). Adverse effects leading to discontinuation of therapy were seen in 28% of placebo-treated patients and 22% of DN-101-treated patients. Serious adverse events, generally those requiring hospitalization, were observed in 41% of placebo-treated patients and 27% of DN-101-treated patients (P = .023). Grade 3 or 4 hematologic toxicity was uncommon and no patients in either arm were diagnosed with neutropenic fever. Among the grade 3 or 4 nonhematologic toxicities, the most common were fatigue (16% placebo; 8% DN-101), infection (13% placebo; 8% DN-101), and hyperglycemia (12% placebo; 6% DN-101). Adverse event frequencies are summarized in Table 2. Toxicities that might be expected with administration of supraphysiologic doses of calcitriol were uncommon with weekly administration of DN-101 except for mild hypercalcemia. There were no grade 3 or 4 creatinine elevations, hypercalcemia, or renal calculi. Six percent of placebo-treated patients and 7% of DN-101-treated patients had grade 1 to 2 creatinine elevation, 8% of placebo-treated patients and 33% of DN-101-treated patients had transient hypercalcemia. All the hypercalcemia episodes observed in the DN-101 arm were grade 1 and required no intervention, and did not result in dose reduction or delay in therapy. In the placebo arm, there was one episode of grade 3 hypercalcemia and all other episodes of hypercalcemia were grade 1 and were self-limited. No patients on placebo and one patient on DN-101 experienced symptomatic renal calculi.
Exploratory Analyses of Toxicity
ASCENT is the first placebo-controlled randomized study to test targeting the VDR for prostate cancer treatment. The addition of DN-101 to weekly docetaxel did not produce a statistically significant improvement in the PSA response rate. Overall the response rate was 63% in DN-101-treated patients and 52% for placebo-treated patients (P = .07). In contemplating the meaning of these PSA response data, it is worthwhile to consider the limitations of the PSA response as a predictor of a survival benefit that have come to light since ASCENT was designed. Southwest Oncology Group 9916 investigators showed that a 50% reduction in PSA did not satisfy the Prentice criteria for surrogacy.26 TAX327 investigators reported that the PSA response rate explained approximately half of the observed survival differences.19,27 ASCENT results are consistent with these observations in so far as the apparent survival advantage seen with DN-101 is more impressive than the PSA response rates might lead one to expect. The addition of DN-101 to docetaxel was associated with a reduction in the risk of death by approximately one third. If confirmed in a phase III trial, this represents a large difference in this disease where randomized studies of 3-weekly docetaxel-based chemotherapy, using mitoxantrone and prednisone as control therapy, reported HRs for death of 0.8 and 0.76.19,20 The addition of weekly DN-101 to weekly docetaxel was not associated with any apparent increase in toxicity. This encouraging finding is consistent with the previously reported phase II results from Oregon Health & Science University.21 The lack of toxicity attributable to DN-101 means that treatment assignment was in fact blinded to patients and caregivers and therefore increases our confidence in the observations made within ASCENT. In an exploratory safety analysis, the number of serious gastrointestinal events was reduced in the DN-101 arm (2.4%) as compared with the placebo arm (9.6%; P = .02). Previous epidemiologic investigations have established that serum concentrations of vitamin D are inversely correlated with the proliferation of the colonic epithelium as determined by the crypt index in rectal biopsies of healthy human subjects.28 Similar studies in animal models showed that higher levels of vitamin D metabolites are associated with reduced proliferation of gastrointestinal epithelial cells.29 Therefore, one mechanism by which DN-101 might reduce the gastrointestinal toxicity of docetaxel would be to induce temporary cell cycle arrest in the rapidly proliferating cells of the gastrointestinal tract, rendering them less sensitive to the cytotoxic effects of docetaxel chemotherapy. This hypothesis should be tested prospectively in future studies of DN-101. The trends favoring DN-101 over placebo with regard to skeletal morbidity-free survival are consistent with the hypothesis that more effective antineoplastic therapy may result in delay of skeletal-related events. It is also possible that the observed trends reflect direct effects of DN-101 on bone metastases. These hypotheses should also be tested prospectively in future studies. In summary, the survival difference between the two groups, the other efficacy results, and the safety profile of DN-101 seen in ASCENT are compelling for further evaluation of this combination in AIPC. These results have led to the initiation of a phase III study (ASCENT-2) that compares the weekly DN-101 plus weekly docetaxel regimen described here to the standard 3-weekly regimen of docetaxel therapy.
Although all authors completed the disclosure declaration, the following authors or their immediate family members indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors. Employment: W. David Henner, Novacea Inc; Alan Arroyo, Novacea Inc; Fong W. Clow, Novacea Inc Leadership: N/A Consultant: Tomasz M. Beer, Novacea Inc; Daniel P. Petrylak, Novacea Inc, sanofi-aventis; Gurkamal S. Chatta, sanofi-aventis, Novacea Inc; Michael A. Carducci, Novacea Inc; Frederick R. Ahmann, sanofi-aventis; Kim N. Chi, Novacea Inc Stock: Tomasz M. Beer, Novacea Inc; W. David Henner, Novacea Inc; Alan Arroyo, Novacea Inc; Fong W. Clow, Novacea Inc Honoraria: Daniel P. Petrylak, Novacea, Inc, sanofi-aventis; Gurkamal S. Chatta, sanofi-aventis; Michael A. Carducci, sanofi-aventis; Robert Dreicer, sanofi-aventis; Frederick R. Ahmann, sanofi-aventis Research Funds: Peter M. Venner, Novacea Inc; Daniel P. Petrylak, Novacea Inc; Charles H. Redfern, Novacea Inc Testimony: N/A Other: N/A
Conception and design: Tomasz M. Beer Administrative support: Alan Arroyo Provision of study materials or patients: Christopher W. Ryan, Peter M. Venner, Daniel P. Petrylak, Gurkamal S. Chatta, J. Dean Ruether, Charles H. Redfern, Louis Fehrenbacher, Mansoor N. Saleh, David M. Waterhouse, Michael A. Carducci, Daniel Vicario, Robert Dreicer, Celestia S. Higano, Frederick R. Ahmann, Kim N. Chi Collection and assembly of data: Christopher W. Ryan, Peter M. Venner, Daniel P. Petrylak, Gurkamal S. Chatta, J. Dean Ruether, Charles H. Redfern, Louis Fehrenbacher, Mansoor N. Saleh, David M. Waterhouse, Michael A. Carducci, Daniel Vicario, Robert Dreicer, Celestia S. Higano, Frederick R. Ahmann, Kim N. Chi, W. David Henner, Alan Arroyo Data analysis and interpretation: Tomasz M. Beer, W. David Henner, Fong W. Clow Manuscript writing: Tomasz M. Beer, Christopher W. Ryan, W. David Henner Final approval of manuscript: Tomasz M. Beer, Christopher W. Ryan, Peter M. Venner, Daniel P. Petrylak, Gurkamal S. Chatta, J. Dean Ruether, Charles H. Redfern, Louis Fehrenbacher, Mansoor N. Saleh, David M. Waterhouse, Michael A. Carducci, Daniel Vicario, Robert Dreicer, Celestia S. Higano, Frederick R. Ahmann, Kim N. Chi, W. David Henner, Alan Arroyo, Fong W. Clow
We thank John Curd, MD, for advice and insights related to analyses of skeletal outcomes. For information regarding participating investigators not included among the authors, please see Appendix Table A1 (online only).
Supported by Novacea Inc and sanofi-aventis. Presented in part at the Annual Meeting of the American Society of Clinical Oncology, May 13-17, 2005, Orlando, FL; and at the European Cancer Conference (ECCO 13), October 30-November 3, 2005, Paris, France. Oregon Health & Science University (OHSU) and Tomasz M. Beer have a significant financial interest in Novacea Inc, a company that may have a commercial interest in the results of this research and technology. This potential conflict was reviewed and a management plan approved by the OHSU conflict of interest in research committee and the integrity program oversight council was implemented. Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.
1. Skowronski RJ, Peehl DM, Feldman D: Vitamin D and prostate cancer: 1,25 dihydroxyvitamin D3 receptors and actions in human prostate cancer cell lines. Endocrinology 132:1952-1960, 1993 2. Peehl DM, Skowronski RJ, Leung GK, et al: Antiproliferative effects of 1,25-dihydroxyvitamin D3 on primary cultures of human prostatic cells. Cancer Res 54:805-810, 1994 3. Schwartz GG, Oeler TA, Uskokovic MR, et al: Human prostate cancer cells: Inhibition of proliferation by vitamin D analogs. Anticancer Res 14:1077-1081, 1994[Medline] 4. Skowronski RJ, Peehl DM, Feldman D: Actions of vitamin D3, analogs on human prostate cancer cell lines: Comparison with 1,25-dihydroxyvitamin D3. Endocrinology 136:20-26, 1995[Abstract] 5. Hedlund TE, Moffatt KA, Miller GJ: Vitamin D receptor expression is required for growth modulation by 1 alpha,25-dihydroxyvitamin D3 in the human prostatic carcinoma cell line ALVA-31. J Steroid Biochem Mol Biol 58:277-288, 1996[CrossRef][Medline] 6. Zhuang SH, Schwartz GG, Cameron D, et al: Vitamin D receptor content and transcriptional activity do not fully predict antiproliferative effects of vitamin D in human prostate cancer cell lines. Mol Cell Endocrinol 126:83-90, 1997[CrossRef][Medline] 7. Getzenberg RH, Light BW, Lapco PE, et al: Vitamin D inhibition of prostate adenocarcinoma growth and metastasis in the Dunning rat prostate model system. Urology 50:999-1006, 1997[CrossRef][Medline] 8. Hershberger PA, Yu WD, Modzelewski RA, et al: Calcitriol (1,25-dihydroxycholecalciferol) enhances paclitaxel antitumor activity in vitro and in vivo and accelerates paclitaxel-induced apoptosis. Clin Cancer Res 7:1043-1051, 2001 9. Beer TM, Hough KM, Garzotto M, et al: Weekly high-dose calcitriol and docetaxel in advanced prostate cancer. Semin Oncol 28:49-55, 2001[Medline] 10. Moffatt KA, Johannes WU, Miller GJ: 1 11. Ahmed S, Johnson CS, Rueger RM, et al: Calcitriol (1,25-dihydroxycholecalciferol) potentiates activity of mitoxantrone/dexamethasone in an androgen independent prostate cancer model. J Urol 168:756-761, 2002[CrossRef][Medline] 12. Osborn JL, Schwartz GG, Smith DC, et al: Phase II trial of oral 1,25-dihydroxy D (calcitriol) in hormone refractory prostate cancer. Urol Oncol 1:195-198, 1995[CrossRef] 13. Gross C, Stamey T, Hancock S, et al: Treatment of early recurrent prostate cancer with 1,25-dihydroxyvitamin D3 (calcitriol). J Urol 159:2035-2039, 1998[CrossRef][Medline] 14. Smith DC, Johnson CS, Freeman CC, et al: A phase I trial of calcitriol in patients with advanced malignancy. Clin Cancer Res 5:1339-1345, 1999 15. Beer TM, Munar M, Henner WD: A phase I trial of pulse calcitriol in patients with refractory malignancies: Pulse dosing permits substantial dose escalation. Cancer 91:2431-2439, 2001[CrossRef][Medline] 16. Beer TM, Lemmon D, Lowe BA, et al: High-dose weekly PO calcitriol in patients with a rising PSA after prostatectomy or radiation for prostate carcinoma. Cancer 97:1217-1224, 2003[CrossRef][Medline] 17. Muindi JR, Peng Y, Potter DM, et al: Pharmacokinetics of high-dose oral calcitriol: Results from a phase I trial of calcitriol and paclitaxel. Clin Pharmacol Ther 72:648-659, 2002[CrossRef][Medline] 18. Morris MJ, Smaletz O, Solit D, et al: High-dose calcitriol, zoledronate, and dexamethasone for the treatment of progressive prostate carcinoma. Cancer 100:1868-1875, 2004[CrossRef][Medline] 19. Tannock IF, de Wit R, Berry WR, et al: Docetaxel plus prednisone or mitoxantrone plus prednisone for advanced prostate cancer. N Engl J Med 351:1502-1512, 2004 20. Petrylak DP, Tangen CM, Hussian HM, et al: Docetaxel and estramustine compared with mitoxantrone and prednisone for advance refractory prostate cancer. N Engl J Med 351:1513-1520, 2004 21. Beer TM, Eilers KM, Garzotto M, et al: Weekly high-dose calcitriol and docetaxel in metastatic androgen-independent prostate cancer. J Clin Oncol 21:123-128, 2003 22. Beer T, Javle M, Lam G, et al: Pharmacokinetics and tolerability of a single dose of DN-101, A new formulation of calcitriol, in patients with cancer. Clin Cancer Res 11:7794-7799, 2005 23. Bubley GJ, Carducci M, Dahut W, et al: Eligibility and response guidelines for phase II clinical trials in androgen-independent prostate cancer: Recommendations for the Prostate-Specific Antigen Working Group. J Clin Oncol 17:3461-3467, 1999 24. Therasse P, Arbuck SG, Eisenhauer EA, et al: New guidelines to evaluate the response to treatment in solid tumors: European Organization for Research and Treatment of Cancer, National Cancer Institute of the United States, National Cancer Institute of Canada. J Natl Cancer Inst 92:205-216, 2002[CrossRef] 25. Beer TM, Garzotto M, Henner WD, et al: Intermittent chemotherapy in metastatic androgen-independent prostate cancer. Br J Cancer 89:968-970, 2003[CrossRef][Medline] 26. Prentice RL: Surrogate endpoints in clinical trials: Definition and operational criteria. Stat Med 8:431-440, 1989[Medline] 27. Roessner M, de Wit R, Tannock F, et al: Prostate-specific antigen (PSA) response as a surrogate endpoint for overall survival (OS): Analysis of the TAX 327 study comparing docetaxel plus prednisone with mitoxantrone plus prednisone in advanced prostate cancer on behalf of the TAX 327 investigators. J Clin Oncol 23:395s, 2004 (abstr 4554) 28. Holt PR, Arber N, Halmos B, et al: Colonic epithelial cell proliferation decreases with increasing levels of serum 25-hydroxy vitamin D. Cancer Epi Biomarkers and Prevention 11:113-119, 2002 29. Cantorna MT, Munsick C, Berniss C, et al: 1,25 Dihydroxycholecalciferol prevents and ameliorates symptoms of experimental murine inflammatory bowel disease. J Nutr 130:2648-2652, 2000 Submitted April 3, 2006; accepted November 28, 2006.
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Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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