What is the next step in management following surgical resection of a primary adenoid cystic carcinoma of the lung?

Primary lung adenoid cystic carcinoma is quite rare, and limited data exist to guide treatment. Often these tumors arise centrally or in the trachea, but can occur in the lung parenchyma. It is important to ascertain whether the tumor is truly of primary lung origin vs a metastasis, so ENT evaluation should be sought. Surgery is the optimal treatment for localized disease. Adjuvant radiation therapy can be offered in cases of R1 resection/positive margins but I am unaware of any prospective data to support this. There are several retrospective studies of outcomes, one of the largest of which compared the outcomes of tracheal ACC vs squamous cell carcinoma https://www.ncbi.nlm.nih.gov/pubmed/15560996). As always with other rare or complicate...