Prognostic factors and survival after recurrence in major salivary gland carcinomas: a multicenter study

Introduction: Major salivary gland carcinomas (MSGCs) are rare, heterogeneous malignancies with high recurrence rates. Recurrent-metastatic (RM) MSGCs frequently represent a clinical challenge due to their unpredictable behavior and the absence of established prognostic markers for the disease course of relapsed disease. Materials and methods: This multicenter retrospective study, involving 10 tertiary centers worldwide, included patients affected by loco-regional and/or distant relapse after surgery with curative intent. The study aimed to analyze residual survival (recurrent-metastatic survival, RMS) and identify key prognostic factors to support personalized treatment strategies, especially for exclusive loco-regional and distant recurrences. Results: Among 212 patients, the median disease-free interval (DFI) after the initial treatment was 14 months, with a 1-year RMS of 58.1% (95% CI, 51.6–65.6%). Longer DFI (>30 months), adenoid cystic carcinoma histology, loco-regional recurrence rather than failure at distance, and absence of nodal metastasis (pN0) at initial diagnosis were significantly associated with a better residual overall survival. In patients with exclusive loco-regional recurrence, independent positive prognostic factors included DFI, salvage surgery, primary low-grade tumor, and lower pT classification. In contrast, for patients with exclusive distant metastasis, longer DFI (>30 months) and the type of intervention (metastasectomy for oligometastatic disease) were independent prognosticators. Conclusion: Disease-free interval is a key prognostic factor for the residual overall survival after a recurrence event. Primary tumor characteristics were associated with survival outcomes in the loco-regional recurrent setting, but not if the recurrence is at distance. Whenever feasible, salvage surgery for loco-regional recurrence and metastasectomy for oligometastatic disease may be considered in highly selected patients.