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

Abstract

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 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.