Long-term outcomes of endoscopic resection and tailored adjuvant radiotherapy for sinonasal intestinal-type adenocarcinoma: a historical single-center cohort study in 200 patients

Quentin-Alexandre Parys Matthias De Witte Esther Hauben Paul M. Clement Robert Hermans Thomas Decramer Johannes Van Loon Sandra Nuyts Mark Jorissen Vincent Vander Poorten Laura Van Gerven ^*

• University Hospitals Leuven, Leuven, Belgium

Sinonasal intestinal-type adenocarcinoma (ITAC) is a rare disease entity. In contrast to most previous studies, this cohort study consists of a substantial number of uniformly treated patients undergoing endoscopic surgery and adjuvant radiotherapy and provides updated insights into survival outcomes and tumor and treatment-related prognostic factors.We retrospectively analyzed the medical records of 200 patients primarily treated for ITAC between 1992 and 2022 in our tertiary referral center. Descriptive statistics were applied using Kaplan-Meier method. Cox models were used for univariable and multivariable data analysis.The 5-year overall survival (OS), disease-specific survival (DSS), and local recurrence-free survival (LRFS) rates were 71.4%, 85.1%, and 55.2% respectively. At 10 years, the numbers decreased to 48.2%, 76.2%, and 32.2% respectively. Significant differences were found in OS and DSS between T-groups. Poorly differentiated tumors had decreased DSS compared to well-differentiated tumors (HR: 3.38 [95% CI: 1.20-9.51], p=.0209). Signetcell differentiation was associated with the poorest survival among poorly differentiated tumors although not reaching significance. In 34.0% of patients, there was local recurrence, with half of the cases detected within the first two years of follow-up but over 10% of recurrence occurring after 10 years. Positive surgical margins (HR: 2.95 [95% CI: 1.29-6.74], p=.0106), local recurrence (HR: 12.28 [95% CI: 5.59-26.99], p<.0001), and distant metastasis (HR: 41.17 [95% CI: 21.58-78.55], p<.0001) negatively affected DSS. Distant metastasis occurred more frequently in poorly differentiated tumors (25.6%) compared to moderately differentiated (9.5%) and well-differentiated tumors (2.5%) (p=.002).This extensive study focusing on sinonasal ITAC primarily managed through endoscopic resection and radiotherapy, demonstrates that T-classification and tumor differentiation are independent prognostic factors influencing survival. Furthermore, local recurrence, distant metastasis, and positive surgical margins negatively affect OS and DSS.