3-D conformal photon boost in the treatment of early stage breast cancer: four year follow up results.

In the treatment of early stage breast cancer, breast conserving surgery (BCS) followed by whole breast irradiation (WBI) is the standard treatment. The impact of the tumor bed boost following WBI is well-defined, but there are various delivery methods. In this study we demonstrate our 4 year experience with the 3-D conformal boost technique. Between January 2004 and June 2005, 77 early stage (Stage I-II) breast cancer patients were treated in our institute with whole breast irradiation (WBI, 50.4 Gy in 28 fractions) after breast conserving surgery. Following WBI, 3-D conformal photon boost was delivered (10-16 Gy in five to eight fractions) for all patients. The clinical outcome was retrospectively recorded in terms of survival and local control. The side effect profile (fibrosis, fat necrosis and cosmetic outcome) was also recorded and studied. In our patient group the mean follow up time was 46.8 months (median: 52, range: 17-71, SD: 14.4) The 4-year probability of local tumor control was 96% (crude rate: 74/77-96.1%), the 4-year probability of overall survival was 96% (crude rate: 74/77-96.1%) in this patient group. In case of the distant metastasis free survival the probability was 89, 5% (crude rate: 70/77-90, 1%). Probability of disease specific survival was 98% (crude rate: 76/77-98. 7%). Local relapse occurred in three cases (3.9%). In ten cases (12.9%) asymptomatic grade I-II breast fibrosis, in eight cases (10.4%) asymptomatic breast fat necrosis were registered. For 14 patients (18.2%) asymptomatic lung fibrosis was recorded on the control CT scans. In term of the relapse free survival, the close resection margin and the nodal positivity resulted in significant difference in favor of the clear resection margin group and the node negative group. In this study the 3-D conformal photon boost resulted in good local control and side effect profile. The presence of tumor bed clips resulted in significantly lower boost PTV volumes, but no correlation was found between the irradiated boost volume and the breast fibrosis. In the relapse free survival analysis, nodal negativity and clear margin status resulted in significantly better RFS.