Size of boost field may need re-evaluating in breast conservation therapy
MedWire News: Patients who receive chemotherapy (CTX) before whole-breast radiation receive radiotherapy (RT) to a smaller volume of tissue than those who do not due to contraction of the lumpectomy cavity, research suggests.
The finding is counterintuitive, since neo-adjuvant CTX patients are at higher risk for local recurrence than patients who do not receive CTX, the team says.
Jonathan Strauss (Rush University Medical Center, Chicago, Illinois, USA) and colleagues analyzed the clinical variables and treatment planning volumes for patients who received whole-breast radiotherapy (RT), as part of breast-conserving treatment, at a single institution between July 2006, and December 2007.
Of the 93 patients identified, 29 received CTX before RT and 64 did not. Patients given CTX were more likely to have higher T and N disease stage than those who did not, and a longer interval between definitive breast surgery and RT.
Strauss et al report in the International Journal of Radiation Oncology Biology Physics that the lumpectomy specimens of women receiving CTX trended toward being significantly larger than those of women not receiving CTX, at 113.4 cm3 vs 74.6 cm3.
Despite this, the volume of the lumpectomy cavity measured on computed tomography was smaller in patients receiving CTX, at 9.1 cm3 vs 16.8 cm3 , as was the volume of the planning target volume, at 56.6 cm3 vs 79.9 cm3.
Strauss et al comment: “In this series of 93 patients, the volume of the lumpectomy cavity, the volume of the surrounding breast tissue included in the planning target volume, and the boost volume as a proportion of total breast volume was significantly smaller in patients who did receive adjuvant CTX as compared with those who did not receive adjuvant CTX preceding whole-breast radiotherapy.”
They conclude: “Given that the patients receiving CTX more often had high-risk features for local failure, this finding is counterintuitive and supports re-evaluation of the optimal size of the boost field.”
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By James Taylor