Genitourinary Cancer

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SU_33_2334 - Does Body Mass Index affect Physician and Patient-Reported Toxicity after High Dose Rate Prostate Brachytherapy?

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Does Body Mass Index affect Physician and Patient-Reported Toxicity after High Dose Rate Prostate Brachytherapy?
K. Stang1, A. A. Harris1, B. Martin2, C. Hentz1, A. Farooq3, K. Baldea3, R. Flanigan3, M. M. Harkenrider1, and A. A. Solanki1; 1Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 2Clinical Research Office, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 3Department of Urology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL

Purpose/Objective(s): Some series suggest potentially worse toxicity in patients with a higher body mass index (BMI) with radical prostatectomy (RP) and external beam radiotherapy (EBRT). In the setting of low-dose-rate brachytherapy (BT) data are mixed regarding the association of BMI with toxicity. There are limited data studying the impact of BMI on toxicity following high-dose-rate (HDR) BT. We investigated the effect of BMI on acute toxicity after HDR BT.

Materials/Methods: We performed a retrospective cohort study of men with prostate cancer undergoing HDR BT at our institution as part of a prospectively maintained database. Patients received 13.5 Gy x 2 as monotherapy and 13.5-15 Gy x 1 as a boost. The International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index Composite Short Form (EPIC-26) were used to assess urinary, bowel, and sexual function at baseline and at each follow-up visit. The Common Terminology Criteria for Adverse Events v4.0 criteria were used to assess genitourinary (GU) and gastrointestinal (GI) toxicity. Baseline demographic and clinical characteristic data were compared between men with BMI <25, 25-30, 30-35, >35 using Pearson chi-square and Kruskal-Wallis tests. Patient-reported toxicities were compared using Generalized Estimating Equations with an independent weight matrix to determine significance and account for the correlation between patients’ multiple observations. Physician reported toxicities were assessed using a generalized linear mixed effects model.

Results: 119 men met selection criteria. The median follow-up was 7.6 months. 87 (73%) men underwent monotherapy and 32 (27%) underwent HDR as a boost. 20 men had a BMI <25, 52 men 25-30, 27 men 30-35, and 20 men ≥35. The BMI ≥35 group had a trend towards younger age (p=.06) and a higher PSA (p=.09), but no difference in prostate volume (p=.67), Gleason score (p=.23) or T-stage (p=.81). All men had worsened IPSS scores at 1 month (p<.001) and 9 months (p=.02), but not at 3, 6, and 12 months. Men had a decline in EPIC-26 urinary incontinence and irritation/obstruction scores at 1 month (p=.03 and p=.01), but not thereafter. There were no significant changes in bowel domain scores over time (p=.35), but there was a decline in the sexual domain (p<.001). After adjusting for age, monotherapy vs. boost, and prostate volume, BMI was not associated with changes in IPSS (p=.62), EPIC-26 urinary incontinence (p=.13), urinary irritative /obstruction (p=.27), bowel (p=.85), or sexual (p=.35). There was no difference in grade ≥2 GU toxicity (p=.69), and too few ≥2 GI toxicity events for analysis.

Conclusion: In this study, BMI was not significantly associated with acute patient-reported or physician-reported toxicity outcomes after HDR BT. These results demonstrate that BMI should not limit performance of HDR brachytherapy. Longer follow-up will be required to compare late toxicity and disease control.

Author Disclosure: K. Stang: None. A.A. Harris: None. B. Martin: None. M.M. Harkenrider: Radiation oncology program director and Trustee; Chicago Radiological Society. A.A. Solanki: None.

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