Morbidity and prostate-specific antigen control of external beam radiation therapy plus low-dose-rate brachytherapy boost for low, intermediate, and high-risk prostate cancer.

PURPOSE: Dose escalation has been shown beneficial in prostate cancer. Brachytherapy (BT) provides an opportunity for dose escalation beyond what can be safely delivered using only teletherapy methods. The purpose of this study was to determine cancer control and morbidity of external beam radiation therapy (EBRT) plus low-dose-rate (LDR) BT boost in patients with prostate cancer treated at Duke University Health System.

METHODS: Between June 1997 and August 2007, 199 patients were consecutively treated at our facility with 46Gy EBRT followed by 100Gy palladium-103 ((103)Pd) or 120Gy iodine-125 ((125)I) LDR prostate implant. Treatment characteristics and followup data were retrospectively analyzed. Intermediate risk was defined as T2b-c, Gleason score 7 (GS 7), or prostate-specific antigen (PSA) of 10.1-19.9ng/mL. High risk was defined as GS 8-10, PSA>20, T3+, or two intermediate risk factors. The Radiation Therapy Oncology Group toxicity scale was used to report morbidity for gastrointestinal (GI) and genitourinary (GU) effects. PSA recurrence was defined as nadir+2ng/mL.

RESULTS: Median followup was 4.2 years for all patients, 4.8 years for high-risk patients. Risk categories were as follows: 20% low risk, 47% intermediate risk, and 33% high risk. Forty five percent of patients received adjuvant androgen deprivation therapy (ADT). The median length of time since end of ADT to last followup was 2.7 years in all patients, 2.0 years for high-risk patients. Five-year biochemical relapse-free survival was 87% for all, 81% for high-risk patients. PSA control was similar at 92% for all and 86% for high-risk patients. Five-year actuarial risk of any and Grade 3 late GI morbidity was 38% and 7% respectively, and any and Grade 3 late GU morbidity was 21% and 3%, respectively. There were no significant differences in risk of Grade 2+GI or GU morbidity with choice of isotope.

CONCLUSIONS: EBRT plus LDR BT has acceptable morbidity and, with 5-year followup, provides excellent cancer control even in high-risk patients.