Replacement of the tumor bed following oncoplastic breast-conserving surgery with immediate latissimus dorsi mini-flap

The aim of the present study was to evaluate the geographic variability of the tumor bed following oncoplastic breast-conserving surgery (OP-BCS), and to assess its relevance for radiotherapy planning. In this prospective study, pre- and postoperative computerized tomography (CT) scans of 22 patients with early-stage breast cancer were fused. The preoperative gross tumor volume or excisional biopsy cavity were contoured under the guidance of preoperative radiological images. Postoperative lumpectomy cavities were contoured under the guidance of surgical clips. The conformity index (CI) was calculated and defined on a scale between 0 and 1, where 0 indicated no overlap and 1 indicated 100% concordance. Associations between CI and the number of clips, time interval between surgery and CT scans, pathological tumor size and age were assessed using independent sample testing. The median CI was 0.07 (in five cases, 1, and in eight cases, 0). The lumpectomy cavity shifted from the primary location in 36.4% of the cases. Median shifts between the isocenters of pre- and postoperative volumes were measured as 1.02 cm (range, 0.4-4.43 cm) in the x, 1.07 cm (range, 0.05-5.67 cm) in the y, and 1.12 cm (range, 0-3.75 cm) in the z directions. Only the clip number was determined to be significantly associated with CI (P=0.017). Pre- and postoperative tumor bed volumes were fully superposed in five of the 22 cases. The present study has shown that the tumor bed is markedly replaced following OP-BCS with latissimus dorsi mini-flap (LDMF) reconstruction. Special care should therefore be taken when defining the lumpectomy cavity following OP-BCS with LDMF reconstruction.