The impact of dose-escalated radiotherapy plus androgen deprivation for prostate cancer using 2 linked nomograms

Randomized trials have demonstrated that escalated-dose external-beam radiotherapy (EDRT) is better than standard-dose radiotherapy (SDRT) for patients with prostate cancer and that adding androgen-deprivation therapy (ADT) to SDRT is better than SDRT alone; however, no trials have compared EDRT versus SDRT plus ADT or EDRT versus EDRT plus ADT. The authors designed a model to estimate the results of various doses of radiotherapy (RT) combined with various durations of ADT.

From 1989 to 2007, 3215 men consecutively received definitive EDRT with or without ADT. In total, 2012 patients had complete records available for creating the nomogram. The duration of ADT varied for patients who received no RT (n = 1562), ≤6 months of RT (n = 145), from >6 months to <24 months of RT (n = 140), and ≥24 months of RT (n = 165) with a median follow-up of 65.7 months, 66.2 months, 60.1 months, and 63 months, respectively. The model included the following covariates: palpation T-category, biopsy Gleason score, the percentage of tumor cells with a Gleason pattern of 4 or 5, the percentage of tumor tissue, initial pretreatment prostate-specific antigen (PSA) level, ADT duration, and RT dose. Two nomograms, for outcomes with and without ADT, were created from a single competing-risks model. Biochemical failure was defined as a rise in serum PSA of 2 ng/mL over the post-treatment PSA nadir.

According to the results from analyzing representative intermediate-risk to high-risk patient parameters, the gains from increasing the RT dose from 70 Gray (Gy) to 80 Gy were far less than the gains from adding ≥3 months of ADT.

The nomograms provided unique patient-specific estimates of the effects of various doses and durations of RT and ADT. The results indicated that adding ADT to treatment for intermediate-risk and high-risk prostate cancer is far more beneficial than a modest RT dose escalation.