Prolongation of Total Treatment Time Because of Infrequently Missed Days of Treatment Is Not Associated With Inferior Biochemical Outcome After Dose-Escalated Radiation Therapy for Prostate Cancer

Abstract

Prolongation of treatment time with radiation therapy (RT) is associated with inferior disease control for many rapidly proliferating tumors, but it is uncertain whether the same effect is seen in prostate cancer. 596 patients underwent with curative-intent RT for adenocarcinoma of the prostate. By National Comprehensive Cancer Network criteria, men were classified as having low-risk (30%), medium-risk (40%), or high-risk (30%) disease. The median RT dose was 72 Gy. Androgen-deprivation therapy (ADT) was used in 45%. The idealized treatment time was defined as the total elapsed time (including weekends) to complete treatment if started on a Monday. Missed days of treatment, defined as the number of days beyond the idealized treatment time, was recorded for all patients. Missed days were added to the end of therapy resulting in a longer treatment time. Analysis was conducted for missed days and other standard prognostic variables against freedom from biochemical failure (FFBF). The median number of missed days was 2 (range, -3 to 22). With a median follow-up of 51 months, men with 5 or more missed days had similar 4-year FFBF rates (79% vs. 83% in men with <5 missed days, p = 0.0809), especially in the subset of men receiving 74 Gy or greater (89% for both groups, p = 0.8008). Analysis of missed days was performed for the subsets of dose, ADT, and risk category. Men without ADT had a lower FFBF rate with more missed days (p = 0.0030), but this association was not seen in men treated to a dose of 74 Gy or greater (p = 0.7425). On multivariate analysis, dose (p = 0.0010), T stage (p = 0.0145), and prostate-specific antigen level (p < 0.0001) were associated with FFBF, but Gleason score (p = 0.1351) and missed days (p = 0.3767) were not. Slight prolongation of treatment time (e.g., ≤7 days) was not associated with inferior FFBF, especially in men receiving an RT dose of 74 Gy or greater.