Chemotherapy May Improve Survival in Men with Advanced Prostate Cancer on ADT

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SAN FRANCISCO—Chemotherapy is associated with a significantly decreased risk of death from prostate cancer (PCa) among elderly men with Stage IV prostate cancer treated with androgen deprivation therapy (ADT), new findings suggest.

In a propensity score (PS) matched cohort of 2,084 such patients age 66 years and older at the time of diagnosis, men who received chemotherapy had a significant 23% reduced risk of death from prostate cancer after adjusting for potential confounders, according to data presented here at the Genitourinary Cancers Symposium. Chemotherapy did not decrease the risk of death from causes other than prostate cancer.

Michael Grabner, PhD, a postdoctoral fellow at the University of Maryland School of Pharmacy in Baltimore, and colleagues also looked at subsamples of patients with and without metastatic disease. In a PS matched cohort within the non-metastatic group, chemotherapy did not affect the risk of death from prostate cancer. In men with metastatic cancer, however, chemotherapy was associated with a significant 20% reduced risk of prostate cancer mortality in a PS matched group.

The investigators analyzed data from Stage IV prostate cancer patients diagnosed between 2000 and 2005 as identified in the Surveillance, Epidemiology, and End Results (SEER)-Medicare data set with claims from 1999-2007. To be included in the study, patients need to have received ADT (luteinizing hormone-releasing hormone or orchiectomy) and had to be enrolled continuously in Medicare Parts A and B for the 12 months immediate prior to and including the month of diagnosis.

“Our findings suggest that survival benefits of chemotherapy in advanced-stage prostate cancer patients are restricted to those with metastatic (M1) disease,” Dr. Grabner told Renal & Urology News. “No survival benefits are apparent in those with non-metastatic (M0) disease. It may seem surprising that chemotherapy was used in non-metastatic patients at all, but results from the SEER-Medicare data set of real-world patients do suggest that similar fractions of M0 and M1 patients received chemotherapy (20-25%), presumably because there are few other treatment options for these patients.”

In addition, the results underscore that a clear distinction needs to be made between Stage IV and metastatic patients. “These two terms are often used interchangeably in colloquial use, yet treatment outcomes may vary considerably,” he noted, adding that it is important to raise awareness of these issues among patients and caregivers.

With respect to study limitations, Dr. Grabner's group noted that the results for the Medicare patients are not necessarily generalizable to other groups, such as younger and privately-insured older patients. Moreover, information on the presence of hormone-refractory PCa was not available, so they were limited to using data on the receipt of ADT. 

The symposium is sponsored by the American Society of Clinical Oncology, the American Society for Radiation Oncology, and the Society of Urologic Oncology.

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