NYU Langone Health- Radiation Oncology New York, NY
K. M. Banson1, G. L. Fuligni2, C. Oh3, J. D. Domogauer4, K. L. Du5, C. Hill6, A. Mahadevan7, J. Xiao8, and F. Shaikh1; 1NYU Radiation Oncology, New York, NY, 2NYU Grossman School of Medicine, New York, NY, 3Biostatistics, Department of Population Health, NYU Langone Health, New York, NY, 4NYU Langone Health, New York, NY, 5Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, 6Department of Radiation Oncology, New York University Grossman School of Medicine, New York, NY, 7NYU Langone Health Laura and Isaac Perlmutter Cancer Center, New York, NY, 8New York University Grossman School of Medicine, Department of Radiation Oncology, New York, NY
Purpose/Objective(s): Ongoing prospective trials are investigating radiation de-escalation to both tumor and elective nodes for early stage node negative anal cancer. In anticipation of these trials’ results, we aimed to characterize dose response by studying patterns of failures in a modern cohort of patients treated with concurrent chemoradiation (CRT). Materials/
Methods: In this single institution retrospective study, patients with clinical T1-4 N0 anal squamous cell carcinoma (ASCC) who received CRT from 2012-2023 were included. Local recurrence free survival (LRFS), progression free survival (PFS) and overall survival (OS) were evaluated using the Kaplan-Meier method. Multivariable Cox regression analysis was used to identify associations between covariates and endpoints. ROC analysis and areas under the curves (AUCs) were used to identify the sensitivity and specificity of EQD2 for tumor and node parameter cut-off points for the prediction of recurrences. Results: 124 patients with node negative ASCC were included with a median follow up of 33.3 months (IQR 10, 74.2). There were 31 (25%), 72 (58%), 11 (9.7%) and 10 (8.1%) patients who had stage I, IIA, IIB and IIIB disease respectively. Majority were men (58%) and white (65%). Thirty-one (25%) patients were HIV+. 73% of patients received staging PET scans. 98% of patients were treated with IMRT with a median EQD2 (a/b 10) to tumor 51.3 Gy (IQR 49.6, 53.1) and to elective node 35.4 Gy (IQR 35.4, 44.3) in a median of 29 fractions (IQR 28, 30). 90% of patients received concurrent mitomycin and 5-fluorouracil/capecitabine. Seven patients did not receive chemotherapy. Eleven (8.9%) patients discontinued radiation prematurely due to toxicity. At 3 years, the LRFS, PFS and OS were 85% (95% CI 79%, 93%), 84% (95% CI 77%,92%), 97% (95% CI 93%, 100%) respectively. On multivariable analysis, age, sex, HIV status, EQD2 dose to tumor and nodes were not predictors of LRFS, PFS and OS. No covariate was associated with OS. There were 12 patients who locally recurred of which 8 recurred in the primary site only; 2 recurred in the primary site and with distant metastasis (DM); only 2 patients recurred in the nodes. There were 5 patients who developed DM. There were 6 deaths. AUCs analysis of dose to the nodes as well as primary site did not demonstrate a threshold cut-off dose that predicted PFS or OS. Conclusion: In node negative anal cancer, recurrence in the elective nodes is low, supporting further investigation into ENI de-escalation. The highest risk of local failure was associated with advanced T stage suggesting dose de-escalation may be safe in select T1-T2 tumors.
