Abstract
ObjectiveTo report grade ≥2 overall late rectal and urinary toxicities in patients (pts) with prostate cancer treated by intensity-modulated radiotherapy (IMRT) at 3 dose-levels. Identify predictors of radiation toxicity and report biochemical progression free survival (bPFS).MethodsA total of 277 pts were treated with 70Gy (10.8%), 74Gy (63.9%) and 80 Gy (25.3%) using IMRT without pelvic irradiation were analyzed. Short or long-course androgen deprivation therapy (ADT) was allowed in 46.1% of pts. The toxicity was described using the Common Terminology Criteria for Adverse Events (CTCAE) v4.0 scale. Cox regression models addressed demographics, disease and dosimetry characteristics as potential predictors of late grade ≥2 toxicity after adjusting for other modifying factors.ResultsThe median follow-up was 77 months (range 15; 150). There was no grade ≥4 toxicity. The 5-year cumulative rate of grade ≥2 late rectal and urinary toxicities was 6.3% (95% CI = 3.8%; 10.3%) and 25.3% (95% CI = 19.8%; 31.8%) respectively. In multivariate analysis, only the dose (80Gy vs 74 and 70Gy) was found to increase the risk of rectal toxicity (HR = 2.96 [1.07; 8.20]). For pts receiving 74 Gy, International Prostate Symptom Score (IPSS) at baseline ≥8 (HR = 2.40 [1.08; 5.35]) and dose ≥73Gy delivered in more than 2% of bladder (D2%) were found to be predictors of bladder toxicity (HR = 3.29 [1.36; 7.98]). The 5–year biochemical relapse free survival was 81.0% [74.5%; 86.0%] in the entire population, 97.5% [83.5%; 99.6%] in the low risk group, 84.9% [76.7%; 90.3%] in the intermediate risk group and 66.4% [51.8%; 77.4%] in the high-risk group. D’Amico low (HR = 0.09 [0.01; 0.69]) and intermediate risk groups (HR = 0.50 [0.28; 0.88]) as well as PSA nadir ≥0.2 ng/ml (HR = 1.79 [1.01; 3.21]) were predictive of biochemical relapse.ConclusionsThe rate of late rectal toxicity increased with higher doses, while Dmax ≥74Gy, D2% ≥ 73Gy for bladder wall and baseline IPSS ≥8 increased late urinary toxicity.
Highlights
External beam radiation therapy is commonly used to treat with curative intent prostate cancer
The 5-year cumulative rate of grade ≥2 late rectal and urinary toxicities was 6.3% and 25.3% respectively
The rate of late rectal toxicity increased with higher doses, while Maximum dose (Dmax) ≥74Gy, D2% ≥ 73Gy for bladder wall and baseline International Prostate Symptom Score (IPSS) ≥8 increased late urinary toxicity
Summary
External beam radiation therapy is commonly used to treat with curative intent prostate cancer. During the past two decades, 7 randomized trials and one metaanalysis have shown improvements of 10 to 20% in biological progression-free survival rates (bPFS) and Nowadays, the use of modern intensity-modulated radiotherapy (IMRT) has shown to significantly reduce acute toxicity rates compared with what has been observed with 3D-CRT, and biochemical control rates are promising [13]. Jolnerovski et al Radiation Oncology (2017) 12:99 and biochemical outcome is still lacking even if earlier studies of prostate IMRT are beginning to report longer follow-up. The primary objective of our study was to report outcomes, including grade ≥2 overall late rectal and urinary toxicity and biochemical control rates in pts treated with IMRT to 70Gy, 74Gy and 80Gy. We aimed to identify potential clinical as well as dosimetric predictors of late toxicity in pts receiving moderate dose IMRT (74Gy-group)
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