Initial results of a randomized phase III trial of high dose image guided radiation with or without androgen deprivation therapy for intermediate-risk prostate cancer

Abstract

Background: Prior randomized studies have shown a survival benefit using combined androgen deprivation therapy (ADT) and radiation therapy for intermediate-risk prostate cancer. However, these studies either used low doses of radiation (66.6 Gy to isocenter) or imaged guidance was not available. This study reports the initial differences for high dose image guided radiation with or without ADT.

Methods: From 2012 to 2014, 56 patients were treated with and 60 patients without 6 months of ADT (N = 116) in our phase III randomized trial for intermediate-risk prostate cancer. The primary endpoints of the current analysis are Expanded Prostate Cancer Index Composite (EPIC) scores, International Prostate Symptom Score (IPSS) scores, and bowel or urinary adverse events (AEs, graded using CTCAE v4) with and without ADT. Treatment consisted of 81 Gy in 45 treatments (tx) or 100 Gy Pd-103 implant followed by 45 Gy in 25 tx with or without ADT. Cone-beam fiducial-based guidance was done. Statistical analysis included Fisher's exact test, chi-square test, and ANCOVA.

Results: Median follow-up for both groups was 2.6 years. Acute or chronic urinary and acute or chronic bowel toxicities were similar with or without ADT (acute urinary: 16 vs 25 G0-1, 39 vs 35 G2 and 1 vs 0 G3, p = 0.17; chronic urinary: 40 vs 45 G1 and 16 vs 15 G2 toxicities, p = 0.68; acute bowel: 56 vs 59 G1 and 0 vs 1 G2 toxicities, p = 0.99; chronic bowel: 56 vs 59 G1 and 0 vs 1 G2 toxicities, p = 0.99). One patient had grade 3 urinary AE (1/116 or 0.8%). No patient had grade 3 bowel AE. With the use of ADT, a temporary decline in the EPIC sexual (p = 0.004) and hormonal scores (p = 0.02) were seen for the first 3 to 6 months after the completion of radiation, but the scores recovered by 12 months. Brachytherapy plus external beam radiation was compared to external beam radiation alone; brachytherapy EPIC urinary irritative scores were temporarily lower at 3 months, 76 vs. 84 (p = 0.006), had higher IPSS scores at 3 months, 15 vs 12 (p = 0.01), and had increased acute urinary AEs (p<0.001). No difference in failures were seen with or without ADT or associated with the use of brachytherapy.

Significance: Low toxicity and minimal temporary bother as measured by EPIC and IPSS were seen in both arms. ADT was well-tolerated and associated with temporary changes.

Keywords: Androgen deprivation; Brachytherapy; IMRT; Image guidance; Prostate cancer; Prostatic neoplasms; Radiotherapy; phase III; randomized.