Dosimetric comparison of partial and whole breast external beam irradiation in the treatment of early stage breast cancer
Publication
, Journal Article
Kim, Y; Parda, DS; Trombetta, MG; Colonias, A; Werts, ED; Miller, L; Miften, M
Published in: Medical Physics
A dosimetric comparison was performed on external‐beam three‐dimensional conformal partial breast irradiation (PBI) and whole breast irradiation (WBI) plans for patients enrolled in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B‐39/Radiation Therapy Oncology Group (RTOG) 0413 protocol at our institution. Twenty‐four consecutive patients were treated with either PBI (12 patients) or WBI (12 patients). In the PBI arm, the lumpectomy cavity was treated to a total dose of 38.5 Gy at 3.85 Gy per fraction twice daily using a four‐field noncoplanar beam setup. A minimum 6 h interval was required between fractions. In the WBI arm, the whole breast including the entirety of the lumpectomy cavity was treated to a total dose of 50.4 Gy at 1.8 Gy per fraction daily using opposed tangential beams. The lumpectomy cavity volume, planning target volume for evaluation (PTV_EVAL), and critical structure volumes were contoured for both the PBI and WBI patients. Dosimetric parameters, dose volume histograms (DVHs), and generalized equivalent uniform dose (gEUD) for target and critical structures were compared. Dosimetric results show the PBI plans, compared to the WBI plans, have smaller hot spots in the PTV_EVAL (maximum dose: versus ) and reduced dose to the ipsilateral breast (: versus and : versus ), contralateral breast (: versus ), ipsilateral lung (: versus ), and thyroid (maximum dose: versus ) with values . However, similar dose coverage of the PTV_EVAL ( for PBI and for WBI, on average) was observed and the dose difference for other critical structures was clinically insignificant in both arms. The gEUD data analysis showed the reduction of dose to the ipsilateral breast and lung, contralateral breast and thyroid. In addition, preliminary dermatologic adverse event assessment data suggested reduced skin toxicity for patients treated with the PBI technique.
