# Impact of Treatment Package Time on Survival in Patients with Head and Neck Adenoid Cystic Carcinoma

## TL;DR

The study found that delays in starting treatment or waiting between surgery and radiation for adenoid cystic carcinoma did not affect survival, but longer radiation therapy duration was linked to worse outcomes.

## Contribution

This is the first study to analyze the impact of treatment timing on survival in adenoid cystic carcinoma using a large national database.

## Key findings

- Delays from diagnosis to surgery did not significantly affect survival in ACC patients.
- Longer radiation therapy duration was independently associated with worse overall survival.
- The interval between surgery and radiation start had no significant impact on survival.

## Abstract

Delays in treatment initiation and completion are associated with poor outcomes for head and neck squamous cell carcinomas. Adenoid cystic carcinoma (ACC) is a rare malignancy characterized by slow growth patterns, and thus it is unclear if delays have similar impacts on survival for this type of cancer. This study analyzed outcomes for 1449 patients with non-metastatic ACC treated with surgery and radiation between 2004 and 2019 in the National Cancer Database. After adjustment for relevant clinical and sociodemographic factors, time from diagnosis to surgery and time from surgery to the start of radiation were not associated with clinically meaningful differences in overall survival. In contrast, longer radiation duration was independently associated with worse survival. These results support prioritizing efficient, uninterrupted radiation schedules and addressing barriers that extend the course. Prospective studies are needed to confirm these findings and optimize treatment timing strategies for ACC patients.

Background/Objectives: Treatment delays have been shown to be associated with overall survival (OS) in head and neck squamous cell carcinomas (HNSCCs). Given the slow tumor growth kinetics of adenoid cystic carcinoma (ACC), it is unclear if delays have a similar impact in this tumor histology. Methods: We queried the National Cancer Database for patients diagnosed with non-metastatic ACC between the years 2004 and 2019 and treated with surgery followed by RT. A multivariable Cox regression model was used to examine the associations between the time from diagnosis to surgery, the duration of RT, and OS. Results: A total of 1449 patients were included for analysis. Increased time from diagnosis to surgery (HR: 1.02, 95% CI: 1.01–1.03, p < 0.001) and duration of RT (HR: 1.14, 95% CI: 1.04–1.25, p = 0.004) were associated with worse survival on UVA, while time from surgery to RT start was not (p = 0.647). Increased duration of RT (aHR: 1.13, 95% CI: 1.03–1.24, p = 0.012) remained significantly associated with OS on multivariable analysis, while time from diagnosis to surgery (aHR: 1.00, 95% CI: 0.98–1.02, p = 0.979) did not. Conclusions: Delays in treatment initiation and in the interval from surgery to radiation did not result in clinically significant differences in survival in this analysis, while prolonged duration of radiation therapy was significantly associated with worse survival. These findings are hypothesis-generating and suggest that treatment delays for ACC may have different effects on oncologic outcomes than those for HNSCC; however, prospective data is paramount to verify these results before strong conclusions can be made.