Long-term treatment of metastatic adenoid cystic carcinoma with sequential brachytherapy and stereotactic body radiotherapy

Adenoid cystic carcinoma is a malignancy that is difficult to treat and often metastasizes to the lung. Systemic chemotherapies are not effective for this tumor type, thus local therapies are frequently used. Here, we report a case demonstrating the use of extensive ablative interventions in controlling the progression of metastatic adenoid cystic carcinoma. A patient with adenoid cystic carcinoma developed numerous metastases to his lungs and liver. Local ablative therapies including interstitial brachytherapy and SBRT were used to treat approximately 80 different metastases over the course of a decade. Over 850 brachytherapy seeds were implanted in this patient, and the tumor control and patient outcome were good. As of the most recent follow-up in March 2024, the patient has survived for approximately 12 years since his diagnosis of adenoid cystic carcinoma. To our knowledge, this case represents the most brachytherapy treatments reported in a single patient. It highlights the utility of interstitial brachytherapy and SBRT in treating extensive lung and liver metastases.