Refining adjuvant radiation therapy decision using a nomogram in major salivary gland carcinoma

Major salivary gland carcinoma (SGC) comprises diverse histologies with multiple interrelated risk factors, making it difficult to determine which patients truly benefit from post-operative radiotherapy (PORT). We developed a nomogram to predict the risk of locoregional failure (LRF) and model postoperative risk estimates under different PORT scenarios.

Major SGC patients treated with curative-intent surgery between 2000 and 2021 across five tertiary cancer centers were identified. Prognostic factors (p < 0.05) from multivariable analysis and clinicopathologically relevant characteristics were utilized to construct a nomogram estimating five-year LRF risk. Subsequently, we modeled the five-year LRF and overall survival (OS) risks for each nomogram point-value, with and without PORT.

A total of 1175 patients were included in the analysis. The median follow-up was 5.3 years. The nomogram for prediction of five-year LRF risk comprised six statistically significant negative prognostic factors (lymphovascular invasion [100 points], WHO high-risk pathology [84], involved resection margins [61], parotid primary tumor [69], pathologic T3-4 category [44], and the non-utilization of PORT [57]), and two relevant factors (pathologic nodal involvement [34] and perineural invasion [7]). The corrected C-index was 0.77. We estimated the values of five-year LRF and OS depending on the PORT. For example, a patient with 271 points had a five-year LRF risk of 20% without PORT versus 11% with PORT, and a five-year OS of 65% versus 79%, respectively.

This nomogram provides individualized estimates of LRF after surgery for major SGC and offers model-based risk estimates under different PORT scenarios. It may serve as a practical tool to guide personalized adjuvant treatment decisions.