Early and late side effects, dosimetric parameters and quality of life after proton beam therapy and IMRT for prostate cancer: a matched-pair analysis.

Purpose: To compare early and late toxicities, dosimetric parameters and quality of life (QoL) between conventionally fractionated proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) in prostate cancer (PCA) patients. Methods: Eighty-eight patients with localized PCA treated between 2013 and 2017 with either definitive PBT (31) or IMRT (57) were matched using propensity score matching on PCA risk group, transurethral resection of the prostate, prostate volume, diabetes mellitus and administration of anticoagulants resulting in 29 matched pairs. Early and late genitourinary (GU) and gastrointestinal (GI) toxicities according to Common Terminology Criteria for Adverse Events (CTCAE) and QoL based on EORTC-QLQ-C30/PR25 questionnaires were collected prospectively until 12 months after radiotherapy (RT). Associations between toxicities and dose-volume parameters in corresponding organs at risk (OARs) were modeled by logistic regression. Results: There were no significant differences in GI and GU toxicities between both treatment groups except for late urinary urgency, which was significantly lower after PBT (IMRT: 25.0%, PBT: 0%, p  = .047). Late GU toxicities and obstruction grade ≥2 were significantly associated with the relative volume of the anterior bladder wall receiving 70 Gy and the entire bladder receiving 60 Gy, respectively. The majority of patients in both groups reported high functioning and low symptom scores for the QoL questionnaires before and after RT. No or little changes were observed for most items between baseline and 3 or 12 months after RT, respectively. Global health status increased more at 12 months after IMRT ( p  = .040) compared to PBT, while the change of constipation was significantly better at 3 months after PBT compared to IMRT ( p  = .034). Conclusions: Overall, IMRT and PBT were well tolerated. Despite the superiority of PBT in early constipation and IMRT in late global health status compared to baseline, overall QoL and the risks of early and late GU and GI toxicities were similar for conventionally fractionated IMRT and PBT.