3262 - Clinical Outcomes of Rectal Wall Infiltration Following Hydrogel Spacer Placement: A Single-Institution Retrospective Study
Presenter(s)
Z. El Kouzi1, E. Chang2, M. K. Rooney1, G. M. Rauch3, V. Surabhi4, A. Surabhi5, O. Mohamad6, P. T. Tran1, C. J. Hassanzadeh1, C. Tang1, H. Mok7, S. Choi1, S. E. McGuire1, K. E. Hoffman1, Q. N. Nguyen3, S. Lee4, and S. J. Frank2; 1Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Houston, TX, 4University of Texas MD Anderson, Houston, TX, 5Lawrence E. Elkins HS, Houston, TX, 6American University of Beirut Medical Center, Beirut, Lebanon, 7Department of Genitourinary Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s):
Gastrointestinal toxicity remains a clinically significant adverse effect of radiation therapy for prostate cancer. The use of rectal spacer reduces the risk of rectal toxicity; however, the procedure can be complicated with rectal wall infiltration which might contribute further toxicity. This study aimed to evaluate the association between rectal wall infiltration and gastrointestinal toxicity.Materials/Methods:
We retrospectively gathered individual patient data, including demographics, initial disease characteristics, treatment details, and gastrointestinal (GI) toxicities. Rectal wall changes were evaluated on MRI using a standardized four-point scoring system: 0, no rectal wall signal abnormality; 1, rectal wall edema or signal change without definite infiltration; 2, partial infiltration of the rectal wall; and 3, full-thickness rectal wall infiltration. We evaluated the direct relation between the presence of rectal toxicity and rectal infiltration using Chi Squared testing. We further evaluated the factors associated with GI toxicity using a logistic regression model.Results:
A total of 316 patients who received hydrogel spacers between 2022 and 2025 were included. Of those, 111 (35.1%) had favorable intermediate risk, while 75 (23.7%) had unfavorable intermediate risk and 125 (39.5%) had high and very high risk prostate cancer. Pelvic irradiation was delivered in 94 patients (29.7%). Most patients received external beam radiation therapy (EBRT) alone (277, 87.6%), while 39 (12.4%) received EBRT with a brachytherapy boost. Gastrointestinal (GI) toxicity was observed in 20 patients (6.3%), including 18 (5.6%) grade 1 and 2 (0.6%) grade 2 events. Among patients with grade 1 rectal edema (n = 23), only 1 (4.4%) developed grade 1 gastrointestinal (GI) toxicity. Similarly, among those with grade 2 rectal infiltration (n = 21), only 1 (4.8%) experienced grade 1 GI toxicity. We did not observe GI toxicity among patients with grade 3 rectal infiltration (n=2). There was no significant association between rectal spacer infiltration and GI toxicity (OR 0.64, 95% CI 0.07–2.82; p=0.74). On univariate logistic regression, pelvic irradiation was associated with increased GI toxicity (OR 2.52, 95% CI 1.20–6.37; p=0.04). The use of brachytherapy showed a nonsignificant trend (OR 2.75, 95% CI 0.51–7.64; p=0.06), while spacer infiltration was not associated with toxicity (OR 0.67, 95% CI 0.10–2.43; p=0.60). On multivariate logistic regression, we were unable to identify any significant variables that predicted for GI toxicity.Conclusion:
Grade 1-2 rectal wall infiltration after hydrogel spacer placement was not associated with increased clinically relevant gastrointestinal toxicity requiring holding radiation treatment. We recommend MRI-grading of rectal infiltration to further assess holding radiation treatments for grade 3 or higher rectal wall infiltration.