Research Fellow MD Anderson Cancer Center Houston, Texas, United States
Introduction: Cancer patients with metastatic disease are living longer given significant improvement in the efficacy of systemic therapies. These improvements, however, have not consistently translated into better disease control within the brain. To achieve local disease control in patients with < 4 brain metastases, stereotactic radiosurgery (SRS) is recommended for lesions 3cm in diameter or less. It remains unclear, however, what the optimal size cut-off for achieving durable local disease control following SRS for brain metastasis. In this study, we assessed the local disease control rates for SRS treated metastatic brain lesions in 0.5cm increments in patients presenting with < 4 brain metastasis.
Methods: Following institutional review board (IRB) approval, we reviewed 1679 metastatic brain lesions (1088 patients) treated with SRS at MD Anderson Cancer Center between 1996-2019. The most common primaries were non-small cell lung cancer (n=388 lesions, 23%), melanoma (n=368 lesions, 22%) and renal cell (n=237 lesions, 14%). Local recurrence was documented for each lesion based on the RANO-BM criteria. The rate of local disease control (%) were documented for lesions in 0.5cm increments till >/=2cm diameter.
Results: Following SRS, 270 out of 1679 treated lesions recurred locally (16%). The 1-, 2-year local control rates for all lesions treated were: ≤0.59cm (92%,87%), 0.6-1.09cm (85%,83%), 1.1-1.5cm (80%,72%), 1.6-1.9cm (65%, 51%), >/=2cm (62%,53%). Post-2009 (new SRS modality), we find improvement in the local control rates for all treated lesions. Post-2009, however, the 1-,2-year local control rates for lesions 1.6-1.9cm and >/=2cm were 75%,56% and 62%,56% respectively (p < 0.001 compared to lesions < 1.6cm. Log-Rank test).
Conclusion : Following SRS for brain metastasis, the local control rates at 1-and 2-years diminish significantly for lesions >/=1.6cm with approximately 56% of lesions failing within 2 years. To achieve durable local disease control for surgically accessible brain metastasis that are >/=1.6cm in diameter, upfront surgical resection should be considered.
