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Journal of Clinical Oncology, Vol 23, No 4 (February 1), 2005: pp. 927-928 © 2005 American Society of Clinical Oncology. DOI: 10.1200/JCO.2005.05.352
In Reply:Gynecology Oncology Group, Buffalo, NY
Fox Chase Cancer Center, Philadelphia, PA Ovarian cancer is a relatively rare disease, and patients are infrequently diagnosed with early stages of the disease. Among those with high-risk stage I disease, the probability of disease recurrence within 10 years is approximately 27%, and for those with stage II disease, 44%.1 Most of the women, who are diagnosed with stage I or II ovarian cancer that is completely resected, will die of causes unrelated to this cancer. When GOG-951 was initiated, intraperitoneal (IP) 32P was a common treatment approach for early-stage ovarian cancer. Three randomized trials have compared 32P with platinum-based treatment. The first study, conducted by the Norwegian Radium Hospital, randomly assigned the treatments for 340 patients (including 27 with stage III disease), and with a 5.2-year median follow-up period, observed 77 recurrences.2 The second randomized study, conducted by an Italian cooperative group (Gruppo Interregionale Cooperativo di Oncologia Ginecologica [GICOG]), involved 152 patients with early-stage disease, and with a 6.3-year median follow-up period, observed 38 recurrences.3 Finally, the Gynecologic Oncology Group (GOG) enrolled 229 eligible patients, and with a median 10-year follow-up period, observed 70 recurrences. Only the GICOG trial, which was the smallest of these studies, detected a statistically significant difference in recurrence rates between treatment groups, and none of them demonstrated a significant benefit in overall survival. Nevertheless, the authors from these three studies concur that 32P is not preferable to platinum-based treatment for the treatment of early-stage ovarian cancer. Rather than evaluating treatment options specifically in the early-stage patient population, some investigators have chosen to include them into larger trials in which the accrual is dominated by patients with more advanced, incompletely resected disease. Although those trials often have very low statistical power to detect clinically relevant heterogeneity of the treatment effects across patient subgroups defined by their stage of disease or extent of debulking, the conclusions are tacitly extended to these small subgroups of patients. Whether this approach is preferable to enrolling only patients from the more restricted population is based in part on the treatment's presumed mechanism of action. Since IP 32P was expected to primarily exhibit local control of the disease, each of the previously mentioned studies evaluated the 32P in patients diagnosed with early-stage, completely resected disease. Regardless of how these patients are studied, statistical power is often a concern in patients with such an uncommon form of this disease. As mentioned in our report, those deaths that occurred before recurrence are not treated as censored events in the calculation of cumulative probability of recurrence. While individuals who are alive and recurrence-free remain at risk for recurring, those who die before recurrence are no longer at risk of subsequently recurring. A reference to the procedures used to estimate the cumulative probability of recurrence is provided in the last paragraph of the Statistical Methods section. Indeed, focusing on only one specific type of failure when patients are truly at risk for several competing types of failure can sometimes be misleading. However, this is one reason that the frequency of non-disease-related deaths for each treatment group was included in the report. Since death before recurrence occurred in only 7% of these patients and the difference between the two treatment groups is 0.5%, the potential for distortion is very limited. Authors' Disclosures of Potential Conflicts of Interest The following authors or their immediate family members have indicatd 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. Leadership Position: Robert C. Young, Bristol-Myers Squibb Oncology. For a detailed description of these 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 of Information for Contributors found in the front of every issue. REFERENCES
1. Young RC, Brady MF, Nieberg RK, et al: Adjuvant treatment for early ovarian cancer: A randomized phase III trial of intraperitoneal 32P or intravenous cyclophosphamide and cisplatin—A Gynecology Oncology Group study. J Clin Oncol 21:4350-4355, 2003 2. Vergote IB, Vergote-De Vos LN, Abeler VM, et al: Randomized trial comparing cisplatin with radioactive phosphorus or whole-abdominal irradiation as adjuvant treatment of ovarian cancer. Cancer 69:741-749, 1992[CrossRef][Medline]
3. Bolis G, Colombo N, Percorelli S, et al: Adjuvant treatment for early epithelial ovarian cancer: Results of two randomised clinical trials comparing cisplatin to no further treatment or chromic phosphate (32P)—G.I.C.O.G.: Gruppo Interregionale Collaborativo in Ginecologia Oncologica. Ann Oncol 6:887-893, 1995
Related Correspondence
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Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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