Abscopal Effect Following CT Guided Permanent Seed Brachytherapy for Metastatic Adenoid Cystic Carcinoma to Lung

This is the first report in the literature demonstrating the abscopal effect following clinical brachytherapy for human malignancy. The abscopal effect is tumor regression in untreated tumors due to some systemic agent generated by the irradiated tumor. Abscopal effect may be mediated by radiation induced production of T cell and other immunity factors by different cancer cell clones. Adenoid Cystic Carcinoma (ACC) is a rare salivary gland cancer with a propensity to metastasize to lung. There is no known cure and current systemic cytotoxic and immune therapies are not effective. We have previously reported on our CT guided permanent seed implant technique for intrathoracic sites for both ACC and non-small cell lung cancer (NSCLC). We present here a case of metastatic ACC to the lungs treated with brachytherapy with a dramatic regression of the implanted lesions and an equally dramatic regression of unimplanted lesions due to the abscopal effect.