Clinical efficacy of Stereotactic Body Radiation Therapy (SBRT) for adrenal gland metastases: A multi-center retrospective study from China

To evaluate the efficacy and safety of CyberKnife Stereotactic Body Radiation Therapy (SBRT) in the treatment of adrenal gland metastases (AGM), we designed a large-scale multicenter retrospective study to report the safety and efficacy of SBRT for inoperable AGM. In this study, 75 (61 males, 14 females) patients with 84 AGM and Karnofsky performance score ≥70 were treated by SBRT from October 2006 to January 2017. Of these, the purpose of treatment were controlling all known metastatic sites for 21 patients while 54 for palliation of bulky adrenal metastases. The efficacy and safety of SBRT were evaluated during follow-up. Potential factors predictive of local control (LC) and overall survival (OS) were identified by univariate and multivariate analysis. Median follow-up time was 12.7 months (range 1.8–96.4). The complete response (CR), partial response (PR), stable disease (SD) and progressive disease (PD) rates were 23.8%, 23.8%, 31.0% and 21.4%, respectively. The 0.5, 1, and 2-year LC rates were 93.6%, 83.8%, and 62.1%, respectively; OS rates on the same follow-up intervals were 93.7%, 62.5%, and 49.6%, respectively, and the corresponding PFS rates were 48.5%, 33.9%, and 16.0%, respectively. The treatment was well tolerated with 2 patients reporting grade-3 diarrhea and fatigue, respectively. Multivariate analysis showed that simultaneous treatment of SBRT for other metastatic lesions, the number of AGM, initiation of systemic therapy, and the maximum diameter of AGM were predictive of LC rates. Moreover, patients with AGM < 5 cm had a superior OS compared with those with AGM ≥ 5 cm (28.0 months vs. 17.6 months, P = 0.032). SBRT is an effective therapeutic option for treatment of AGM with high LC rates with minimal toxicity.