Stereotactic ablative radiation therapy for extracranial metastases from malignant melanoma: An international multi-institutional analysis.

OBJECTIVE

To report on local control (LC), toxicity, and overall survival (OS) following stereotactic ablative radiation therapy (SABR) for extracranial metastases from malignant melanoma.

METHODS

The RSSearch Patient Registry was searched for patients with extracranial melanoma metastases treated with SABR. LC was defined as the time from completion of SABR to the date of last radiographic follow-up with either stability or decrease in size of the treated metastasis or the date at which lesion growth was radiographically confirmed per RECIST criteria. Kaplan-Meier analyses were utilized to evaluate potential prognostic factors on univariate analyses (UVA) with log-rank tests followed by use of a Cox proportional hazards multivariate (MVA) model.

RESULTS

There were 45 patients with 52 extracranial melanoma metastases treated with SABR. One- and 2-year LC rates were both 85.3% (95% CI: 67.9-93.7%) following SABR. On UVA, BED10 < 60 Gy was associated with poorer 1-year and 2-year LC (96% vs. 61.9%), which remained significant on MVA (hazard ratio [HR] = 7.06; p = 0.03). On UVA, pulmonary vs. non-pulmonary metastases were correlated with 1-year OS (84.5% vs. 57.4%; p = 0.05) and non-spinal vs. spinal metastases (74.3% vs. 56.3%; p = 0.02), though neither were significant on MVA. The incidence of treatment-related toxicity was 18.9%, all Grade 1-2.

CONCLUSION

We recommend dose/fractionation schedules that meet or exceed BED10 ≥ 60 Gy when treating extracranial melanoma metastases with SABR.