Outcomes and toxicities in patients with intermediate-risk prostate cancer treated with brachytherapy alone or brachytherapy and supplemental external beam radiation therapy

Abstract

Objective: To evaluate the cancer control outcomes and long-term treatment-related morbidity of brachytherapy as well as combination brachytherapy and external beam radiation therapy (EBRT) in patients with intermediate-risk prostate cancer.

Materials and methods: A retrospective review was conducted in a prospectively collected database of patients with intermediate-risk prostate cancer who were treated either with brachytherapy or brachytherapy and EBRT, with or without androgen deprivation therapy (ADT), in the period 1990-2014. Urinary and erectile dysfunction symptoms were measured using the International Prostate Symptom Score (IPSS), the Mount Sinai erectile function scale and the Sexual Health Inventory for Men (SHIM). Cancer control endpoints included biochemical failure and development of distant metastases. All statistical analyses were carried out using the Statistical Package for Social Science (SPSS). Survival curves were calculated using Kaplan-Meier actuarial methods and compared using log-rank tests. Cox regression multivariate analyses were used to test the effect of multiple variables on treatment outcomes.

Results: A total of 902 patients were identified, with a median follow-up of 91 months. Of these, 390 received brachytherapy and 512 received combination therapy with EBRT. In patients with one intermediate-risk factor, the addition of EBRT did not significantly affect freedom from biochemical failure or distant metastases. Among patients with two or three intermediate-risk factors, added EBRT did not improve freedom from biochemical failure. Significant differences in late toxicity between patients treated with brachytherapy vs combination brachytherapy and EBRT were identified including urge incontinence (P < 0.001), haematuria (P < 0.001), dysuria (P < 0.001), and change in quality-of-life IPSS (P = 0.002). These symptoms were reported by patients at any point during treatment follow-up. Analysis of patients who were potent before treatment using actuarial methods showed that patients receiving combination therapy more frequently experienced loss of potency, as measured by the Mount Sinai erectile function scale (P = 0.040).

Conclusion: Brachytherapy monotherapy results in equal biochemical and distant control in both patients with one and more than one intermediate-risk features. While no significant benefit was shown, we believe that the addition of EBRT may prevent recurrence in patients with multiple intermediate-risk features and should be considered.

Keywords: brachytherapy; external beam radiation therapy; intermediate risk; prostate cancer; toxicity.