Prostate cancer reports from ASTRO, no. 2

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.

Most of the prostate cancer data presented in today’s scientific sessions were from retrospective reviews and the afternoon genitourinary session was focused on biomarkers and predictors of outcome in prostate cancer.

Dr. Katz presented a prostate cancer calculator (the “CaP Calculator”) which uses data from multiple clinical studies to estimate a patient’s risk of extracapsular extension, seminal vesicle invasion, and lymph node involvement. It also estimates PSA outcome after radiation treatment. This tool has been created for use by clinicians and, once validated, may be a useful reference for guiding discussion between physicians and patients.

In the poster discussion session, Dr. Mark presented data on 254 patients with organ-confined prostate cancer (of any Gleason score and any PSA) treated with interstitial high dose rate (HDR) brachytherapy alone. With a median follow-up of 90 months, biochemical disease-free survival was 89 percent overall (95 percent in low-risk patients; 90 percent in intermediate-risk patients; and 68 percent in high-risk patients). Toxicities from treatment were favorable with a 5.9 percent incidence of urethral strictures and a 3.5 percent incidence of stress urinary incontinence. Long-term follow-up and data from randomized clinical trials will help to further validate the use of HDR in prostate cancer.

In the same session, Dr. Deutsch presented a comparison (non-randomized) of 630 patients treated with radiation for prostate cancer: 470 were treated with ultra-high dose external beam radiotherapy and 160 with HDR brachytherapy in combination with external beam radiotherapy. HDR therapy was associated with improvement in prostate cancer control. However, this data need to be validated in a randomized trial.

Also in the poster session, Dr. Hsu presented preliminary results from RTOG 0321, which is a phase II clinical trial of HDR in combination with external beam radiation treatment. A total of 129 patients with prostate cancer were treated on this protocol and initial toxicity results were presented today. The estimated rate of significant late toxicity (Grade 3 or higher) at 18 months was reported to be 2.6 percent, and longer follow up is necessary for efficacy data.

Biomarkers were the key topic at this afternoon’s scientific session. Data from multiple studies implicated various markers (Ki-67, p53, MDM2, bcl-2, bax, p-16, Cox-2, EGFR, MMP7, c-Met, protein kinase A) as predictors of local and distant failure and prognosticators in prostate cancer. The data presented was interesting but requires validation prior to any possible clinical use.

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