Prostate cancer reports from ASTRO: no. 1

Prostate cancer reports from the 50th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), being held in Boston, are kindly provided by Eyad Abu-Isa, MD, a resident in radiation oncology at the University of Michigan.

This afternoon, new and updated data from three large Phase III clinical trials were presented at the ASTRO plenary session and clinical updates section.

In the plenary session, as a late-breaking study, Dr. Anders Widmark presented data from “A Randomized Trial Comparing Anti-Androgens With or Without Radiotherapy in the Treatment of Locally Advanced Prostate Cancer: Survival and QOL Outcome.” This study was a Phase III clinical trial of 880 patients, all treated with lifelong antiandrogen therapy. Patients had locally advanced features based on tumor staging and WHO grading and had no evidence of positive lymph nodes or distant disease. Patinets were randomized to receive or not receive radiation treatment starting 3 months after initiation of antiandrogen therapy. This is a critically important study because all prior trials involving radiation and antiandrogen therapy have had radiotherapy in both arms of the trials.

Results showed that addition of radiation treatment decreased the rate of prostate cancer-specific mortality by a factor of 50 percent (24 vs. 12 percent), increased overall survival by an absolute value of 10 percent, and decreased PSA recurrence rates by a factor of ~3. There were, however, increases in urinary symptoms, bowel symptoms, and sexual side effects in the patients who received radiation treatment. At 4 years, overall quality of life was similar with the exception of decreased sexual function in the radiation arm. This study presents solid evidence in support of the use of radiation treatment with antiandrogen therapy in patients with locally advanced prostate cancer and is the first Phase III trial to show improvement in local and distant disease as well as improved overall survival with the addition of radiation treatment in this patient population. It does not answer the question of the optimal duration of antiandrogen therapy, however.

In the clinical trials update session, Dr. Michel Bolla presented the 10-year results of his key Phase III EORTC study evaluating use long-term adjuvant androgen deprivation in combination with radiotherapy in patients with locally advanced prostate cancer. A total of 415 patients with locally advanced prostate cancer were treated with radiation and randomized to 3 years of androgen deprivation (long-term androgen deprivation) or placebo. The 10-year update of this study continues to show that addition of long-term androgen deprivation to radiation in patients with locally advanced disease improves overall survival (58.1 vs. 39.8 percent), improves prostate cancer-specific survival, and decreases the risk of progression both locally and distantly. Recently, there has been increased concern for cardiovascular toxicity in patients treated with androgen deprivation. In this study, there was no significant difference in risk of cardiovascular-related deaths in either arm.

Also in the clinical trials update session, Dr. Gregory Swanson presented an update of SWOG 8794, with a median follow-up of 11.5 years. In this study, 473 patients after prostatectomy with high-risk features for recurrence (positive surgical margins, extracapsular extension, or invasion into the seminal vesicles) were randomized to receive radiation treatment (adjuvant radiation) vs. observation. Patients receiving adjuvant radiation had improvement in overall survival (47 vs. 37 percent). Adjuvant radiation also decreased the risk of metastasis, decreased the rate of biochemical and local failures, and decreased the need for antiandrogen therapy. Global quality of life evaluation showed increased genitourinary toxicities at 6 months and 2 years, but this difference disappeared at 2 years. As expected, patients in the adjuvant radiation arm showed higher rates of urinary strictures, urinary incontinence, and radiation proctitis. This study presents convincing evidence in support of use of adjuvant post-prostatectomy radiation in patients with high-risk features for recurrence.

In summary, the data presented from these three well-performed Phase III studies will help guide the treatment decisions in patients with prostate cancer. For patients with locally advanced prostate cancer, Dr. Widmark’s data show a clear survival advantage with addition of radiation to antiandrogen therapy and Dr. Bolla’s data show a survival advantage with addition of long-term antiandrogen therapy to radiation. In patients with high-risk features post-prostatectomy, Dr. Swanson’s data shows a survival benefit with use of adjuvant radiotherapy.

2 Responses

  1. Phenomenal post! Thank you very much Dr. Abu-Isa.

  2. Good to find that trials now support what many of us have believed as appropriate treatment for localized advanced PC. However, extending antiandrogen therapy for 3 years is questionable, since such constant therapy without intermittent relief would likely result in little chance of testosterone recovery at conclusion.

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