The 5-Year Outcomes of Moderately Hypofractionated Radiation Therapy for Localized Prostate Cancer

Abstract

Reports of a lower alpha-beta ratio of prostate cancer than that of surrounding normal tissues suggested that hypofractionated radiotherapy using fewer and larger fractional doses could be more effective than conventional radiotherapy. The aim of this study is to evaluate therapeutic outcomes and toxicities of hypofractionated radiotherapy for localized prostate cancer. This is retrospective review of 195 patients with localized prostate cancer who underwent intensity-modulated radiotherapy consisting of 66 Gy delivered in fractions of 3 Gy every other weekday between May 2005 and December 2011. The proportion of risk classifications according to D’Amico classifications, low-risk was 27 patients (13.8%), intermediate-risk was 70 patients (35.9%), and high-risk was 98 patients (50.3%). Patients received androgen deprivation therapy according to our institutional criteria based on perceived low-, intermediate-, or high-risk of their diseases. Biochemical failure was defined as prostate-specific antigen nadir plus 2.0 ng/mL. As for toxicities, the patient-reported outcomes (PROs) were assessed using the expanded prostate cancer index composite at six points such as before radiotherapy (baseline), and 1 month, 3 months, 6 months, 12 months and 24 months after radiotherapy. In addition, the clinician-reported outcomes were assessed based on the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer Toxicity criteria. Over a median follow-up of 69 months (range, 9 to 138 months), 13 of 195 patients experienced biochemical failure within a median of 40 months (range, 14 to 95 months). The 5-year overall survival rate was 97.7%, and the 5-year no biological evidence of disease rate was 95.0%. By the risk classifications, the 5-year bNED rates were 100%, 96.3% and 90.6% for those with low-, intermediate- and high-risk diseases, respectively. PROs showed that there was a significant difference among the average values of the general urinary and bowel domains. The average score of these domains significantly decreased at 1 month after completion of radiotherapy, and then returned to the baseline level at 3 months after radiotherapy. Acute genitourinary (GU) toxicities were graded 0-1 in 168 patients and two in 27 patients; none was graded three or higher. Late GU toxicities were graded 0-1 in 190 patients and two in 5 patients; none was graded three or higher. Gastrointestinal (GI) toxicities were graded 0-1 in 193 patients and two in 2 patients; none was graded three or higher. Using of this protocol of moderately hypofractionated radiotherapy (a total dose of 66 Gy/22 fraction for 7 weeks) yielded satisfactory clinical outcomes with significant reduction of toxicity profiles including PROs, although follow-up period is not long enough to allow a definitive conclusion.