Evidence for efficacy without increased toxicity of hypofractionated radiotherapy for prostate carcinoma: early results of a Phase III randomized trial.

Purpose: We performed a randomized trial to compare the GI and urogenital toxicity of radiotherapy (RT) for localized (confined to the organ), early-stage (T1-T2N0M0, TNM classification) carcinoma of the prostate, using a conventional (64 Gy in 32 fractions within 6.5 weeks) vs. a hypofractionated (55 Gy in 20 fractions within 4 weeks) schedule and to determine the efficacy of the respective treatment schedules.

Methods And Materials: This report is based on an interim analysis of the first 120 consecutive patients in this Phase III trial after a median follow-up of 43.5 months (range 23-62). RT planning was based on two-dimensional CT data, and the treatment was delivered using a three- or four-field 6-23-MV photon technique. GI and urogenital toxicity (symptom questionnaires incorporating the subjective elements of the late effects of normal tissues-subjective, objective, management, analytic classification of late effects and the European Organization for Research and Treatment of Cancer sexual function questionnaire) were evaluated before RT and 1 month, 1 year, and 2 years after RT completion. The efficacy of RT was assessed clinically (digital rectal examination and radiologic imaging) and biochemically (prostate-specific antigen assay) at baseline, and every 3 months for 2 years after RT and every 6 months subsequently.

Results: RT, whether conventional or hypofractionated, resulted in an increase in all six symptom categories used to characterize GI toxicity and in four of five symptom categories used to document urinary morbidity 1 month after therapy completion. Sexual dysfunction (based on limited data), which existed in more than one-third of patients before RT, also increased to just more than one-half of patients 1 month after RT. The increase in urinary toxicity after RT was not sustained (diurnal urinary frequency had decreased significantly at 2 years). In contrast, all six symptom categories of GI toxicity remained increased 1 year after RT. Four of the six GI symptom categories (rectal pain, mucous discharge, urgency of defecation, and rectal bleeding) were still increased at 2 years compared with baseline. Except for a slightly greater percentage of patients experiencing mild rectal bleeding at 2 years among those who received hypofractionated RT, no differences were noted in toxicity between the conventional and hypofractionated RT schedule. The mean prostate-specific antigen level was 14.0 +/- 1.0 ng/mL at baseline and declined to a nadir of 1.3 +/- 0.2 ng/mL at a median of 16.8 months (range 0.8-28.3) after RT completion. However, it then rose in 17 patients (8 in the hypofractionated and 9 in the conventional treatment group). Only 8 of these 17 patients were found to have signs of clinical relapse (5 local, 1 regional lymph node, and 2 systemic [bony metastases]) after histopathologic and radiologic reassessment). The remaining 9 patients had biochemical relapse only (defined as three consecutive rises in prostate-specific antigen after nadir). The 4-year biochemical relapse-free survival rate was 85.8% for all patients and did not differ significantly between the two radiation dose schedules (86.2% for the hypofractionated and 85.5% for the conventional fractionation group).

Conclusion: RT for prostate carcinoma, using a three- or four-field 6-23-MV photon technique without posterior shielding of the lateral fields, is an underestimated cause of persistent GI morbidity. The incidence of clinically significant GI and urogenital toxicity after conventional and hypofractionated RT appears to be similar. Hypofractionated RT for carcinoma of the prostate seems just as effective as conventional RT after a median follow-up approaching 4 years.