Response of Oligometastatic Non–Small Cell Lung Cancer to the Adrenal Gland Treated with Stereotactic Body Radiosurgery

Abstract

Stereotactic body radiation therapy (SBRT) delivers high-dose hypofractionated radiation precisely to a particular site of cancer. The results of SBRT on local control for patients with oligometastatic Non-Small Cell Lung Cancer (NSCLC) with adrenal metastases were analyzed in this prospective study. Data from all consecutive patients with oligometastatic NSCLC to the adrenal gland were prospectively evaluated. Twenty-six adrenal metastases from NSCLC (19 adenocarcinoma, 4 squamous cell carcinoma, 2 bronchogenic carcinoma and 1 large cell carcinoma) were treated in 23 individuals. Age at treatment ranged from 42 – 77 years (mean 62) with 13 men and 10 women. Two patients had bilateral adrenal metastases. Tumor volumes ranged from 2.7 – 168 cc (mean 44.2 cc) and were treated with 500 – 900cGy per fraction, in 5 – 8 fractions, to a cumulative dose of 2,500 – 4,500cGy (mode 4,000cGy). Cancers were followed with MRI, CT and PET scans. Tumor control was defined as cessation of growth, shrinkage, or disappearance of the treated cancer. At analysis, follow-up ranged from 1 – 53 months (mean 10 months). There was an overall 88% control rate for NSCLC. Univariate logistic regression of tumor response showed that histology, age, total dose, pre-treatment volume, and gender were not significant predictors of local control. One patient with progression of both their adrenal metastases initially had tumor regression, but progressed as their primary disease subsequently grew. Another patient with tumor growth following SBRT underwent re-irradiation which continued to provide tumor control at last follow-up (30 months). The treatments were generally well tolerated without significant adverse events. In our experience, SBRT for oligometastatic NSCLC in the adrenal gland provides a safe, non-invasive treatment modality with a high rate of local tumor control. Patients with oligometastatic lung cancer treated to adrenal gland metastases continue to be evaluated for longer follow-up in order to determine if controlling the extrathoracic disease translates to a progression free and overall survival benefit.