Functional Outcomes With Dose-Escalated, Conventionally Dosed, or Without Nodal Irradiation in Prostate Cancer

Abstract

Despite the potential for improved local control, there is little data on long term quality of life (QoL) outcomes using dose escalated nodal radiotherapy (RT) in prostate cancer with conventional fractionation. We compare QOL following RT with conventional, dose-escalated, or no nodal irradiation.From 2009 to 2017, 445 patients with low-risk to high-risk prostate cancer recorded baseline scores using the Expanded Prostate Cancer Index Composite (EPIC), prior to definitive or post-prostatectomy (PP) radiation. Each subsequently completed a new EPIC 18-36 months after intensity modulated RT. Absolute change in each domain summary and subscale score was recorded as well as if the change met minimally important difference (MID) criteria. All baseline comparisons were done using bivariate analysis methods. Multivariate analysis (MVA) was performed using a generalized linear model to assess changes in each domain summary and sub-scale score. MVA was performed with a proportional odds model to assess MID changes. Variables were age, RT setting (definitive or PP), pre-treatment score, and nodal dose. P-value significance was set to < 0.05.Prescribed nodal dose was 0 Gy, 45-51 Gy, and ≥54 Gy in 31%, 8%, and 61% of patients, respectively. Radiation was given PP in 37% of patients. PP patients had significantly worse baseline urinary function, incontinence, and overall scores. In each MVA, PP was associated with greater decreases of urinary function, incontinence, and overall scores following RT. Prior prostatectomy was not associated with a significant difference in the bowel, hormonal, or sexual domains. Including all RT settings, median changes reported in urinary function, bother, incontinence, and overall scores were: for 54 Gy, -4.1, 0.0, -6.3, and -2.4; for 45-51 Gy, 0.0, -3.6, 0.0, and -0.7; for 0 Gy 0.0, 0.0, 0.0, and 0.0. MVA showed that nodal irradiation to ≥ 54 Gy was significantly correlated with greater decreases of urinary function, bother, incontinence, and overall score in one or both models. Nodal irradiation to ≥ 54 Gy was not found to be significantly correlated with changes in the bowel, hormonal, or sexual domains. Nodal irradiation to 45 Gy was not significantly associated with any domain or subscale change.Compared to no nodal irradiation, escalated nodal irradiation to ≥54 Gy was associated with a small but significantly worse urinary QOL while 45 Gy was not. Escalated nodal irradiation to ≥54 Gy was not associated with worse bowel QOL. Prior prostatectomy was associated with a greater decrease in urinary QOL following RT. Clinical judgement should be used to balance the benefits and toxicities of nodal irradiation in prostate cancer.