Comparison of two radiation techniques for the breast boost in patients undergoing neoadjuvant treatment for breast cancer

• Published in: British journal of radiology Vol. 89; no. 1066; p. 20160264
• Main Authors: De Santis, Maria C, Nardone, Luigia, Diletto, Barbara, Canna, Roberta, Dispinzieri, Michela, Marino, Lorenza, Lozza, Laura, Valentini, Vincenzo
• Format: Journal Article
• Language: English
• Published: England The British Institute of Radiology 01.10.2016
• Subjects: Adult; Aged; Antineoplastic Combined Chemotherapy Protocols - therapeutic use; Breast Neoplasms - drug therapy; Breast Neoplasms - radiotherapy; Breast Neoplasms - surgery; Dose Fractionation; Female; Heart - radiation effects; Humans; Mastectomy, Segmental; Middle Aged; Neoadjuvant Therapy; Neoplasm Grading; Neoplasm Staging; Radiometry; Radiotherapy and Oncology; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Retrospective Studies; Tomography, X-Ray Computed; Treatment Outcome
• ISSN: 0007-1285; 1748-880X
• DOI: 10.1259/bjr.20160264

After breast conservative surgery (BCS) and whole-breast radiotherapy (WBRT), the use of boost irradiation is recommended especially in patients at high risk. However, the standard technique and the definition of the boost volume have not been well defined. We retrospectively compared an anticipated pre-operative photon boost on the tumour, administered with low-dose fractionated radiotherapy, and neoadjuvant chemotherapy with two different sequential boost techniques, administered after BCS and standard adjuvant WBRT: (1) a standard photon beam (2) and an electron beam technique on the tumour bed of the same patients. The plans were analyzed for the dosimetric coverage of the CT-delineated irradiated volume. The minimal dose received by 95% of the target volume (D95), the minimal dose received by 90% of the target volume (D90) and geographic misses were evaluated. 15 patients were evaluated. The sequential photon and electron boost techniques resulted in inferior target volume coverage compared with the anticipated boost technique, with a median D95 of 96.3% (range 94.7-99.6%) and 0.8% (range 0-30%) and a median D90 of 99.1% (range 90.2-100%) and 54.7% (range 0-84.8%), respectively. We observed a geographic miss in 26.6% of sequential electron plans. The results of the anticipated boost technique were better: 99.4% (range 96.5-100%) and 97.1% (range 86.2-99%) for median D90 and median D95, respectively, and no geographic miss was observed. We observed a dose reduction to the heart, with left-sided breast irradiation, using the anticipated pre-operative boost technique, when analyzed for all dose-volume parameters. When compared with the sequential electron plans, the pre-operative photon technique showed a higher median ipsilateral lung Dmax. Our data show that an anticipated pre-operative photon boost results in a better coverage with respect to the standard sequential boost while also saving the organs at risk and consequently fewer side effects. This is the first dosimetric study that evaluated the association between an anticipated boost and neoadjuvant chemotherapy treatment.