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Radiation Oncology • Neuro-Oncology
When treating resected brain metastases with post-op SRS, what dose, fractionation and PTV margin do you use for large (>3 cm) cavities?
Two randomized trials which included single-fraction post-op SRS as an arm reported high 1-year local failure. In Alliance N107C (12-20 Gy, 2 mm PTV margin) and an MDACC trial (12-16 Gy, 1 mm PTV margin), 1 year local failure rates were 44% and 28%, respectively. Even higher risk of local failure might be expected in the subset with >3 cm cavities, since tumor size correlated with recurrence (and also lower SRS dose). For intact brain mets, a large retrospective (Minitti et al, IJROBP 2016) comparison of 15-16 Gy x1 vs 9 Gy x3 using 1-2 mm PTV margins for mets >3 cm found that hypofractionated therapy significantly reduced local failure (46% vs 27%, p = 0.02). Should this approach be adopted in the post-op setting?
Answer from: Radiation Oncologist at Academic Institution
I would refer you to Scott Soltys' work:https://www.ncbi.nlm.nih.gov/pubmed/22652105https://www.ncbi.nlm.nih.gov/pubmed/17881139This is also useful:https://www.ncbi.nlm.nih.gov/pubmed/24331659
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Answer from: Radiation Oncologist at Community Practice
I think it's a reasonable approach (fractionation). It is certainly one we use at our institution. Having said that, this is only based on retrospective reports. It will be interesting to see the manuscripts of the MDACC and Alliance trials as the reported local control rates were lower than expecte...