Prognostic importance of the lymphovascular invasion in head and neck adenoid cystic carcinoma: A systematic review and meta-analysis

The presence of lymphovascular invasion is considered a prognostic determinant for different human neoplasms and is frequently taken into account by surgeons and oncologists to determine patients' treatment. However, the exact frequency of this microscopic event and its prognostic impact for patients affected by adenoid cystic carcinoma (AdCC) remains unclear. Therefore, the aim of this study was to carry out a systematic review and meta-analysis to address the prevalence and the prognostic potential of lymphovascular invasion in head and neck AdCC. A literature search on PubMed, Scopus, ClinicalTrials. gov, Web of Science and ProQuest databases was undertaken in January 2019. The primary outcomes of interest were overall survival (OS) and disease-free survival (DFS). The relative frequency of lymphovascular invasion and its possible association with other clin-icopathological parameters were addressed. A total of 22 studies and 2117 patients were included in this study. The frequency of lymphovascular invasion ranged from 5.2% to 72.5%. Lymphovascular invasion was associated with an increased likelihood of lymph node metastasis (OR=2.58; 95% CI 1.61-4.12; p=0.0001) and death (OR=3.09; 95% CI 1.82-5.26; p=0.0001), solid/higher-grade AdCC were more likely to present lymphovascular invasion (OR=5.51; 95% CI 1.87-16-21; p=0.002) and patients with this microscopic finding had a significantly lower OS (HR=8.30; 95% CI 1.68-40.91; p=0.009) and DFS (HR=3.76; 95% CI 1.13-12.53; p=0.03). In conclusion, lymphovascular invasion seems to be a significant predictor of poor prognosis for head and neck AdCC patients.