1075 - Patient Reported Outcomes after Chemoradiation with IMPT vs. IMRT for Patients with Anal Canal Squamous Cell Carcinoma

M. Shuja¹, S. N. Shah¹, W. S. Harmsen², H. J. Gunn³, M. G. Haddock¹, C. M. Callaghan¹, J. B. Ashman⁴, T. T. W. Sio⁴, W. G. Rule⁴, Z. Jin⁵, H. Xie⁵, N. P. McKenna⁶, A. L. D. DAngelo⁶, K. L. Mathis⁶, D. W. Larson⁶, C. L. Hallemeier¹, K. W. Merrell¹, and K. R. Jethwa¹; ¹Department of Radiation Oncology, Mayo Clinic, Rochester, MN, ²Department of Biostatistics and Health Sciences Research, Mayo Clinic, Rochester, MN, ³Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN, ⁴Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, ⁵Division of Medical Oncology, Mayo Clinic, Rochester, MN, ⁶Division of Colon & Rectal Surgery, Mayo Clinic, Rochester, MN

Purpose/Objective(s): Chemoradiation (CRT) for patients with anal canal squamous cell carcinoma (ACSCC) is associated with significant toxicity that impacts quality of life (QoL) and function. There are limited data comparing patient reported outcomes (PROs) with intensity modulated proton (IMPT) versus photon (IMRT) therapy. Our aim was to analyze differences between the IMPT and IMRT cohorts. Materials/

Methods: This was an IRB approved retrospective cohort study including patients with ACSCC treated with CRT between 2015-2024. PROs were prospectively collected at baseline, end of-CRT, 3-months and 1-2 years after CRT utilizing the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Colorectal Cancer Module 29 (EORTC QLQ CR29). The analysis focused on the overall score, and secondarily on bowel, urinary, and sexual symptom or functional scales. The defecation or stoma problems scale incorporates flatulence, fecal incontinence or leakage, sore skin around anus or stoma, stool frequency, or embarrassment by defecation patterns or stoma. Comparisons of the change from baseline at each timepoint between the IMPT vs IMRT cohorts were made using the Wilcoxon rank sum test.
Results: We analyzed 177 consecutive patients with ACSCC. 129 (73%) received IMRT and 48 (27%) received IMPT. The median age was 64 years (range 38-88) and 77% were female. T stage was cT3-4 in 34% of patients and 58% were N+. There were no significant differences between cohorts. The median dose was 54 Gy (IQR 50.4-54.6) in 28 (IQR 27-30) fractions and 98% received concurrent chemotherapy. PROs in table 1. There were no significant differences in change from baseline between IMPT vs IMRT cohorts in overall score, stool frequency, defecation or stoma problems, urinary, or sexual scales at any timepoint, although, each modality was associated with worsening post CRT. There was improvement of defecation or stoma problems and urinary scales from 3 months to 1-2 years, but the detrimental impact on overall score and sexual scales persisted. IMPT was associated with increased change from baseline of the blood and mucus in stool scale across all time points.
Conclusion: IMPT and IMRT for ACSCC have relatively comparable impact on patient reported QoL and function with considerable impact post-CRT and persisting detriment by 1-2 years. These data emphasize the need for rigorous symptom surveillance and supportive care intervention for this patient cohort.

Scale	Baseline (N=177)		Post-CRT (N=99)		3-months (N=104)		1-2 years (N=96)
	IMRT	IMPT	IMRT	IMPT	IMRT	IMPT	IMRT	IMPT
Overall	22	21	12	14	2	4	18	20
Defecation and stoma problems	21	20	17	19	4	10	4	9
Blood and mucus in stool	29	18*	-4	18**	-18	4**	-10	2*
Urinary frequency	33	38	15	4	1	0	-2	-4
Dysuria	4	4	39	42	0	0	0	0
Dyspareunia (women)	11	12	8	12	12	7	11	22
Impotence (men)	44	55	0	17	12	-27	22	13
Reported as baseline absolute score and mean change from baseline at follow-up timepoints Higher numbers indicate worse symptoms or function *p=0.05 **p < 0.01