Rectal Dose–Volume Histogram Parameters Are Associated With Long-Term Patient-Reported Gastrointestinal Quality of Life After Conventional and High-Dose Radiation for Prostate Cancer: A Subgroup Analysis of a Randomized Trial

Abstract

We examined whether rectal dose-volume histogram (DVH) parameters were associated with long-term patient-reported gastrointestinal (GI) quality of life (QOL) after conventional (70.2 GyE) or high-dose (79.2 GyE) radiation for prostate cancer. Of 64 men with localized prostate cancer alive with a minimum 7-year follow-up after treatment as part of a randomized trial with either 70.2 GyE or 79.2 GyE of external beam radiation at Massachusetts General Hospital, 56 men (88%) returned a QOL questionnaire, and 50 of those men had DVH information. The DVH parameters of the anterior rectal wall were correlated with patient-reported long-term GI QOL using Pearson correlation and t tests. There was a trend toward an association between increased long-term GI dysfunction and higher V60 (p=0.07), V65 (p = 0.06), V70 (p = 0.09), and V75 (p = 0.09). When dichotomized by their medians, a V60 > 54% (p = 0.04), V70 > 44% (p = 0.06), and V75 > 39% (p = 0.06) were associated with increased long-term GI dysfunction. There was no difference in long-term GI dysfunction between men on the conventional vs. high-dose arms (p = 0.49). Dose-volume histogram parameters of the anterior rectal wall were associated with long-term patient-reported GI QOL after prostate radiation, whereas the dose prescribed to the prostate was not, suggesting that DVH constraints, rather than total prescribed dose, may have the greatest impact on long-term bowel dysfunction, and therefore that continued dose escalation may be feasible if appropriate dose-volume constraints are met.