Margins in major salivary gland surgery: clinical and pathological criteria for defining margins and their implications on the choice of multimodal therapies. A systematic review.

OBJECTIVE

Major salivary gland malignancies (MSGM) are a rare and heterogeneous group of tumours accounting for 1-5% of all head and neck cancers. When feasible, surgical removal with negative margins is the preferred treatment, reserving adjuvant radiotherapy for adverse clinicopathological features such as high-grade, advanced-stage, extranodal extension, lympho-vascular invasion, perineural invasion, and positive margins. This systematic review aims to evaluate the current literature on the definition of negative and close margins for MSGM, their impact on loco-regional recurrence (LRR), disease-free (DFS), and overall survival (OS), and their implications in the choice of multimodal therapies.

METHODS

An online search of articles published between 2004 and 2024 was carried out using PubMed via a PICO search strategy for qualitative questions and written following the PRISMA statement guidelines. The following parameters were evaluated: definition of free and close margins, and their impact on local control.

RESULTS

The initial search yielded 158 articles. Following the application of inclusion and exclusion criteria, 30 full-text publications were reviewed. All studies were retrospective. A total of 15,985 patients who underwent surgery were considered. Margin involvement ranged widely among the studies from 14.3% to 65.4%. Five out of 30 studies reported no data about association between margins and LRR, DFS, and OS. Twenty of 25 studies reported a significant correlation between positive margins and oncological outcomes regardless of the histological types, while 5 focused on high-stage cancers or more aggressive histotypes and described no association between margin status and oncological outcomes. Nine of 30 studies described close margins in the absence of a univocal definition of threshold for close vs. negative margins. Most studies did not report a significant correlation between close margins and oncological outcomes.

CONCLUSIONS

Surgical resection achieving negative margins is recommended for MSGM. Positive margin is widely considered an adverse clinicopathological feature and performing adjuvant radiotherapy has documented survival benefits. A consensus involving a definition of close margin is missing, although further treatment is not recommended, preferring a watch-and-wait approach in presence of close margins.