Stereotactic body radiotherapy for multisite extracranial oligometastases: final report of a dose escalation trial in patients with 1 to 5 sites of metastatic disease.

BACKGROUND

A subset of patients with metastatic cancer in limited organs may benefit from metastasis-directed therapy. The authors investigated whether patients with limited metastases could be safely treated with metastasis-directed radiotherapy.

METHODS

Patients with 1 to 5 metastatic cancer sites with a life expectancy of >3 months received escalating stereotactic body radiotherapy (SBRT) doses to all known cancer sites. Patients were followed radiographically with CT scans of the chest, abdomen, and pelvis and metabolically with fluorodeoxyglucose-positron emission tomography, 1 month after treatment, and then every 3 months. Acute toxicities were scored using the National Cancer Institute's Common Terminology Criteria for Adverse Events version 3.0, and late toxicities were scored using the Radiation Therapy Oncology Group late toxicity scoring system.

RESULTS

Sixty-one patients with 113 metastases were enrolled from November 2004 to November 2009 on a prospective radiation dose escalation study. Median follow-up was 20.9 months. Patients tolerated treatment well; the maximal tolerated dose was not reached in any cohort. Eleven patients (18.3%) have not progressed. One and 2-year progression-free survival are 33.3% (95% confidence interval [CI], 22.8-46.1) and 22.0% (95% CI, 12.8-34.4); 1-year and 2-year overall survival are 81.5% (95% CI, 71.1-91.1) and 56.7% (95% CI, 43.9-68.9). Seventy-two percent of patients whose tumors progressed did so in limited (1-3) metastatic sites.

CONCLUSIONS

Patients with 1 to 5 metastases can be safely treated to multiple body sites and may benefit from SBRT. Further investigation should focus on patient selection.