Abstract
PurposeTo assess acute gastrointestinal (GI) and genitourinary (GU) toxicities of intensity-modulated proton therapy (IMPT) targeting the prostate/seminal vesicles and pelvic lymph nodes for prostate cancer.Materials and MethodsA prospective study (ClinicalTrials.gov: NCT02874014), evaluating moderately hypofractionated IMPT for high-risk or unfavorable intermediate-risk prostate cancer, accrued a target sample size of 56 patients. The prostate/seminal vesicles and pelvic lymph nodes were treated simultaneously with 6750 and 4500 centigray radiobiologic equivalent (cGyRBE), respectively, in 25 daily fractions. All received androgen-deprivation therapy. Acute GI and GU toxicities were prospectively assessed from 7 GI and 9 GU categories of the Common Terminology Criteria for Adverse Events (version 4), at baseline, weekly during radiotherapy, and 3-month after radiotherapy. Fisher exact tests were used for comparisons of categorical data.ResultsMedian age was 75 years. Median follow-up was 25 months. Fifty-five patients were available for acute toxicity assessment. Sixty-two percent and 2%, respectively, experienced acute grade 1 and 2 GI toxicity. Grade 2 GI toxicity was proctitis. Sixty-five percent and 35%, respectively, had acute grade 1 and 2 GU toxicity. The 3 most frequent grade 2 GU toxicities were urinary frequency, urgency, and obstructive symptoms. None had acute grade ≥ 3 GI or GU toxicity. The presence of baseline GI and GU symptoms was associated with a greater likelihood of experiencing acute GI and GU toxicity, respectively. Of 45 patients with baseline GU symptoms, 44% experienced acute grade 2 GU toxicity, compared with only 10% among 10 with no baseline GU symptoms (P = 0.07). Although acute grade 1 and 2 GI and GU toxicities were common during radiotherapy, most resolved at 3 months after radiotherapy.ConclusionA moderately hypofractionated IMPT targeting the prostate/seminal vesicles and regional pelvic lymph nodes was well tolerated with no acute grade ≥ 3 GI or GU toxicity. Patients with baseline GU symptoms had a higher rate of acute grade 2 GU toxicity.
Highlights
External beam radiotherapy (RT) has been a mainstay for the treatment of high-risk, clinically localized prostate carcinoma (PC)
Most large randomized trials demonstrating the benefit of RT or of adding androgen-deprivation therapy (ADT) to RT for high-risk PC have encompassed the regional pelvic nodes as part of clinical target volumes (CTVs) of RT [1,2,3,4,5,6]
intensity-modulated RT (IMRT) provides a conformal dose distribution to CTVs, it is achieved by spreading out the integral dose over a large volume of healthy tissues with a considerable dose to organs at risk (OARs)
Summary
External beam radiotherapy (RT) has been a mainstay for the treatment of high-risk, clinically localized prostate carcinoma (PC). This dosimetric advantage of IMPT can be amplified, when CTVs expand over a large anatomical area that poses a larger volume of nearby OARs to unnecessary radiation exposure Such an example is pelvic nodal irradiation; in which, IMPT can provide substantial sparing of nontargeted pelvic organs, such as the bladder, rectum, large bowel, and small bowel, in comparison with IMRT. This dose reduction to OARs can translate into a decrease in gastrointestinal (GI) and genitourinary (GU) toxicity
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