Salvage brachytherapy for locally recurrent prostate cancer after definitive external beam radiation therapy

Abstract

To determine the efficacy and toxicity profile of salvage brachytherapy for locally recurrent prostate cancer after definitive external beam radiation therapy. Fewer than 100 such cases in the post-PSA era have been described in the literature. Twelve consecutive patients received salvage brachytherapy for locally recurrent prostate cancer after prior definitive external beam radiation therapy that delivered between 70-74 Gy. Histologic confirmation of local prostate cancer recurrence was required as was absence of radiographic evidence of distant metastases. A total of three months of LHRH agonist therapy was administered prior to ultrasound-guided 125I or 103Pd permanent interstitial brachytherapy and prescribed doses were 75% of standard doses for monotherapy brachytherapy. Subsequent biochemical recurrence was defined by the ASTRO consensus definition. Pre- and post-implant IPSS urinary symptom scores were recorded and serial post-implant PSA levels were obtained. With a median follow-up of 34 months (12–52) 10 of the 12 patients remain free of biochemical recurrence. Prior to the original external beam radiation therapy, the median presenting PSA and Gleason scores were 3.85 (1.8–11.5) and 6 (4–7), respectively. After external beam therapy, the median PSA nadir was 0.7, the median time to PSA recurrence was 63 months (24.5–102), and the median PSA doubling time was 184 days (145–857). After salvage brachytherapy, two biochemical recurrences were observed at 18 and 52 months, respectively. At one month post-implant, the median IPSS score increase was 10.5 (3–25), but this declined to 6 (1–16) by last follow-up and in general continued to improve with time. One patient experienced long-term urinary incontinence secondary to urethral scar formation, but there were no documented procedure-related rectal toxicities in any patient. With a median follow-up of nearly three years, salvage brachytherapy reestablished biochemical control in a group of originally favorable risk patients failing external beam radiation therapy. Importantly, rectal toxicities were absent and post-brachytherapy, urinary symptom scores, while initially elevated, continued to improve with time. Finally, the frequency of urinary incontinence was very low, comparing favorably with rates reported after salvage prostatectomy