Comparative toxicity outcomes of proton-beam therapy versus intensity-modulated radiotherapy for prostate cancer in the postoperative setting

Patricia Mae G. Santos, Andrew R. Barsky, Wei-Ting Hwang, Curtiland Deville, Xingmei Wang, Stefan Both, Justin E. Bekelman, John P. Christodouleas, Neha Vapiwala*

*Corresponding author for this work

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    Abstract

    Background Despite increasing utilization of proton-beam therapy (PBT) in the postprostatectomy setting, no data exist regarding toxicity outcomes relative to intensity-modulated radiotherapy (IMRT). The authors compared acute and late genitourinary (GU) and gastrointestinal (GI) toxicity outcomes in patients with prostate cancer (PC) who received treatment with postprostatectomy IMRT versus PBT. Methods With institutional review board approval, patients with PC who received adjuvant or salvage IMRT or PBT (70.2 gray with an endorectal balloon) after prostatectomy from 2009 through 2017 were reviewed. Factors including combined IMRT and PBT and/or concurrent malignancies prompted exclusion. A case-matched cohort analysis was performed using nearest-neighbor 3-to-1 matching by age and GU/GI disorder history. Logistic and Cox regressions were used to identify univariate and multivariate associations between toxicities and cohort/dosimetric characteristics. Toxicity-free survival (TFS) was assessed using the Kaplan-Meier method. Results Three hundred seven men (mean +/- SD age, 59.7 +/- 6.3 years; IMRT, n = 237; PBT, n = 70) were identified, generating 70 matched pairs. The median follow-up was 48.6 and 46.1 months for the IMRT and PBT groups, respectively. Although PBT was superior at reducing low-range (volumes receiving 10% to 40% of the dose, respectively) bladder and rectal doses (all P = .05). Five-year grade >= 2 GU and grade >= 1 GI TFS was 61.1% and 73.7% for IMRT, respectively, and 70.7% and 75.3% for PBT, respectively; and 5-year grade >= 3 GU and GI TFS was >95% for both groups (all P >= .05). Conclusions Postprostatectomy PBT minimized low-range bladder and rectal doses relative to IMRT; however, treatment modality was not associated with clinician-reported GU/GI toxicities. Future prospective investigation and ongoing follow-up will determine whether dosimetric differences between IMRT and PBT confer clinically meaningful differences in long-term outcomes.

    Original languageEnglish
    Pages (from-to)4278-4293
    Number of pages16
    JournalCancer
    Volume125
    Issue number23
    Early online date10-Sep-2019
    DOIs
    Publication statusPublished - 2019

    Keywords

    • adjuvant radiation
    • gastrointestinal toxicity
    • genitourinary toxicity
    • intensity-modulated radiation therapy
    • postoperative radiation
    • prostate cancer
    • proton therapy
    • salvage radiation
    • CONFORMAL RADIATION-THERAPY
    • LATE URINARY TOXICITY
    • RADICAL PROSTATECTOMY
    • ADJUVANT RADIOTHERAPY
    • PHOTON RADIATION
    • HYPOFRACTIONATED RADIOTHERAPY
    • SALVAGE RADIOTHERAPY
    • DISEASE-CONTROL
    • FRACTURE RISK
    • VOLUME

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