Brachytherapy Improves 10-Year Rates of Freedom from Biochemical Failure

Chicago—Researchers in California conducted a study to compare 10-year treatment outcomes of radical prostatectomy versus external beam radiation therapy (EBRT) versus brachytherapy for patients with intermediate risk prostate cancer. Barry W. Goy, MD, and colleagues reported results of the retrospective analysis during a poster session at the ASCO 2018 Annual Meeting in a poster titled Ten Year Treatment Outcomes of Radical Prostatectomy vs External Beam Radiation Therapy vs Brachytherapy for 1503 patients with Intermediate Risk Prostate Cancer.

The analysis utilized propensity score matching on 1503 patients who underwent treatment from 2004 to 2007. Of the 1503 patients included in the analysis, 819 underwent radical prostatectomy, 574 underwent EBRT to a median dose of 75.3 Gy, and 110 underwent brachytherapy using idodine-125. The researchers defined biochemical failure using the American Urological Association definition of prostate specific antigen (PSA) failure for the patients in the radical prostatectomy group, and the American Society of Therapeutic Radiology and Oncology (ASTRO)–Phoenix definition for patients in the EBRT and brachytherapy groups.

Median follow-up was 10.0 years for the radical prostatectomy group, 9.6 years for the EBRT group, and 9.8 years for the brachytherapy group. In the radical prostatectomy group, 76.3% had Gleason score 7, as did 72.8% of the EBRT group and 57.3% of the brachytherapy group (P=.0001). Median initial PSA levels for the radical prostatectomy group, EBRT group, and brachytherapy group were 7.4, 9.4, and 8.3, respectively (P<.0001).

Neoadjuvant androgen deprivation therapy was administered to 58.9% of the EBRT patients, 12.7% of the brachytherapy patients, and 0.6% of the patients undergoing radical prostatectomy (P<.0001). Supplemental external radiation was administered to only 14% of the brachytherapy group.

Rates of 10-year freedom from biochemical failure were 82.0% for brachytherapy, 58.0% for radical prostatectomy and 58.8% for EBRT (P<.0001). In subset analyses of unfavorable intermediate risk prostate cancer patients, the rates of freedom from biochemical failure were 81.6% for brachytherapy, 55.8% for radical prostatectomy, and 51.0% for EBRT (P<.0001). The 10-year freedom from salvage therapy rates were 89.5% for brachytherapy, 64.0% for radical prostatectomy, and 73.4% for EBRT (P<.0001).

Following adjustment for age, there were no significant differences among the three groups in metastases-free survival, prostate cancer-specific survival, or overall survival.

In multivariable analyses between pairwise groups with brachytherapy balanced by stabilized inverse probability of treatment weights, brachytherapy remained an independent predictor for improved freedom from biochemical failure (P=.049 for brachytherapy vs EBRT, and P<.0001 for brachytherapy vs radical prostatectomy).

“Brachytherapy using iodine-125 is a reasonable treatment option for intermediate risk prostate cancer patients. Although brachytherapy showed improved freedom from biochemical failure after propensity score matching, this did not impact overall survival,” the researchers said.

Source: Goy BM, Burchette RJ, Soper MS, Chang TC, Cosmatos HA. Ten year treatment outcomes of radical prostatectomy vs external beam radiation therapy vs brachytherapy for 1503 patients with intermediate risk prostate cancer. Abstract of a poster presented at the American Society of Clinical Oncology 2018 Annual Meeting, June 2, 2018, Chicago, Illinois.