Survival benefit of cancer-directed surgery and the role of adjuvant therapy in malignant major salivary gland cancers: a propensity score matched retrospective analysis

Background The primary objective of this study was to assess the benefit of cancer-directed surgery (CDS) on both overall survival (OS) and cancer-specific survival (CSS) of patients with malignant major salivary gland cancers (MMSGCs). The secondary objective was to explore the benefits of adjuvant therapy on the survival outcomes of these patients. Methods Patients diagnosed with MMSGC were extracted from the SEER database and subsequently categorized into two cohorts: CDS and non-CDS. Propensity score matching (PSM) was used to mitigate confounding variables. The survival benefit associated with CDS was evaluated using Kaplan-Meier analysis, log-rank tests, and Cox proportional hazard models. Furthermore, the impact of adjuvant radiotherapy and chemotherapy was explored within the CDS subgroup. Results A total of 7,029 patients with MMSGC were included. PSM was performed and resulted in a matched cohort between both groups, including 595 patients in each group. Multivariable Cox proportional hazard indicated that patients who received CDS had better OS (HR: 0.45, 95% CI [0.39 to 0.52], P < 0.001) and CSS (HR: 0.46, 95% CI [0.40 to 0.52], P < 0.001). The 5- and 10-year OS for the CDS group was 42% (95% CI, 38 - 46%), and 25% (95% CI, 21 - 29%) consecutively, while the 5- and 10-year OS for the non-CDS group was 20% (95% CI, 17 - 24%), and 12% (95% CI, 9.7 - 16%) consecutively. Moreover, patients with younger age, localized tumors, and lower TNM stage could benefit more from CDS. Radiotherapy as adjuvant therapy was found to be beneficial (HR: 0.69, 95% CI [0.55-0.85], p < 0.001), while chemotherapy could not significantly benefit these patients. Conclusion CDS improved the OS and CSS survival in MMSGC patients. Specific patient subgroups seemed to have a superior benefit from CDS. Adjuvant radiotherapy could help enhance the survival outcomes of these patients while chemotherapy could not.