Plastic surgery for breast conservation therapy: how to define the volume of the tumor bed for the boost?

PURPOSE: To describe the procedure of definition of the boost volume using pre- and post-operative computed tomography (CT) and surgical clips in the tumor bed after oncoplastic surgical procedure.

PATIENTS AND METHODS: Thirty-one consecutive breast cancer patients who underwent simple lumpectomy or oncoplastic surgery were studied. All of them underwent pre- and post-operative CT scan in treatment position to evaluate the planning target volume (PTV) boost volume and define the primary tumor (gross tumor volume (GTV)) and tumor bed zones (CTV), with an overall margin of 5 mm in lateral and 10 mm in craniocaudal directions, corresponding to localization and setup uncertainties.

RESULTS: Thirteem patients underwent simple lumpectomy and 18 oncoplastic surgery. The volumetric analysis showed that the intersection between GTV and CTV clips was significantly higher in patients with three and more clips (28.4% vs 3.14%; p < 0.001). In the case of patients with oncoplastic surgery, more than three clips were needed to define the tumor bed volume with accuracy. The number of clips was directly related to the exact definition of the boost volume.

CONCLUSIONS: The use of more than three clips allows better definition of the PTV boost volume after oncoplastic surgical procedure.