Prospective Cohort of Permanent Seed Implantation Prostate Brachytherapy for Intermediate Risk Prostate Cancer: Patient Reported Outcomes and Comparison of Toxicity Profiles between 125-iodine, 131-cesium and 103-palladium

Pierre Blanchard, MD, PhD, Thomas J. Pugh, MD, David A. Swanson, MD, Usama X. Mahmood, MD, Hsiang-Chun Chang, MSc, Xuemei Wang, MSc, William J. Graber, MD, Rajat J. Kudchadker, PhD, Teresa Bruno, CMD, Maria C. Occena, RN, Toweilla G. Henry, RN, Steven J. Frank, MD MD Anderson Cancer Center, Houston, TX, USA.
PP06 Presentation Time: 9:45 AM

Purpose

Different radioactive isotopes can be used for permanent seed implantation of the prostate, but their differences in side effect profile are unknown. We have conducted a prospective cohort of intermediate risk cancer patients in which 125-Iodine, 131-Cesium and 103-Palladium were used each in a third of the patients. We report the patient reported outcomes overall and the differences between the three isotopes.

This prospective single center cohort aimed at evaluating the efficacy and toxicity of prostate brachytherapy in intermediate risk prostate cancer patients. Eligible patients had a non-pretreated prostate cancer with intermediate risk prostate cancer as determined by one of the following combinations: Gleason < 7 and PSA 10-15; Gleason 7 and PSA must be < 10. T stage had to be ≤ T2b. Hormonal therapy was not allowed. All patients provided written informed consent. Follow-up was scheduled every 4 months for the first year, every 6 months up to 5 years and yearly afterwards. At each time point physician reported outcomes were measured, and patient filled the Expanded Prostate Cancer Index Composite (EPIC), the American Urology Association Symptom Index (AUA-SI), the SF-12, and a questionnaire on the use of sexual medical devices.

From August 2006 to August 2013, 300 intermediate risk patients were included. Three cohorts were treated successively with 125-Iodine (n=98, prescribed dose=145 Gy), 103-Palladium (n=102, prescribed dose=125 Gy) and 131-Cesium (n=100, prescribed dose=115 Gy). Median age was 64.9 (range: 44.2, 86.3). The median follow-up of the last cohort was 2.6 years, results are only presented up to two years following treatment. Rate of EPIC completion at baseline, one and two years were respectively 11.2%/4.1%/4.3% for the I-125 cohort, 14%/11.6%/13.2% for the Pd-103 cohort and 12%/11.1%/22.8% for the Cs-131 cohort. On the overall population, all quality of life domains show an initial drop at three months post treatment. While bowel and hormonal scores quickly return to baseline values (respective p-values for clinically meaningful difference at one/two years of 0.49/0.48 and 0.99/0.99), urinary and sexual impairment in quality of life never fully return to baseline, the difference being clinically meaningful for the urinary domain (with respective p-values for clinically meaningful difference at one/two years for sexual and urinary summary scores of 0.98/0.79 and <0.001/<0.001). When comparing between isotopes, there were no differences in terms of bowel and hormonal scores at baseline, but I-125 patients had a poorer sexual function and Pd-103 patients a better urinary score at baseline. At twelve months post implant, the decrease from baseline in bowel score was statistically and clinically significantly higher for Cs-131 patients (p=0.03), but no significant difference was observed in hormonal (p=0.33), sexual (p=0.14) or urinary (p=0.07) scores or between the three isotope groups. Compared to baseline, the decrease in bowel, hormonal, sexual or urinary scores at two years post implant were not different according to the isotope used. Both at one and two years, the decreases in EPIC scores were always numerically larger in patients treated with Cs-131, intermediate with I-125 and smaller with Pd-103. Out of the patients who had erections firm enough for intercourse at baseline, 90% of I-125 patients, 66% of Pd-103 patients and 35% of Cs-131 patients remained potent at two years post implant.

This prospective analysis patient reported outcomes following prostate brachytherapy shows long lasting and clinically significant decrements in urinary and sexual domains. Comparison of the different isotopes shows a favorable toxicity profile favoring Pd-103.