Impact of adjuvant therapy on survival in patients with myoepithelial carcinoma: A systematic review and individual patient data analysis of 691 patients.

Introduction: Myoepithelial carcinoma (MEC) is an extremely rare low grade salivary gland neoplasm [1-4]. A surgical resection is considered as corner stone of therapy. Role of adjuvant therapy is not clear.

Methodology: We performed systematic review and individual patient data analysis of 691 patients to look into the impact of adjuvant therapy and different prognostic variable for MEC.

Results: Data of 691 individual patients were retrieved from 340 publications. Median age of presentation was 56 years (Range: 0-103 years) with a trend of increasing incidence for increase in age. Major salivary glands (36.4%) were the commonest sub-site followed by minor salivary glands, skin and soft tissue, and breast. Median PFS and OS of entire cohort was 48 months (95% CI: 30-65 months) and 167 months (95% CI: 82-251 months). In univariate analysis A R0 resection was associated with significantly better PFS and OS. Median PFS and OS were significantly worse for patients with tumour size >5 cm compared to smaller tumours and for patients with a mitotic index >10/10 high power field (hpf) compared to lower mitotic index. Adjuvant radiation was found to reduce loco-regional recurrence. Adjuvant radiation and chemotherapy both were associated with negative impact on survival in univariate analysis. This negative impact on survival was lost in multivariate analysis.

Conclusion: MEC appears to be a low grade malignancy with good survival outcome. A R0 resection should be the standard of care. Adjuvant radiation should be considered for patients with adverse risk features to improve loco-regional disease control.