Cardiac doses with deep inspiration breath hold in breast cancer radiotherapy: direct comparison between WBI, PBI, and interstitial APBI.

Background: The optimal radiotherapy technique for cardiac sparing in left-sided early breast cancer (EBC) is not clear. In this context, the aim of our dosimetric study was to compare cardiac and lung doses according to the type of radiotherapy - whole breast irradiation (WBI), external partial breast irradiation (PBI), and multicatheter interstitial brachytherapy-accelerated partial breast irradiation (MIB-APBI). The dosimetric results with the WBI and PBI were calculated with and without DIBH. Materials and methods: Dosimetric study of 23 patients treated with WBI, PBI, with and without DIBH, or MIB-APBI. The prescribed dose was 40 Gy in 15 fractions for WBI and PBI and 34 Gy in 10 fractions (bid) for MIB-APBI. Doses to the organs-at-risk (OAR) - heart, left anterior descending coronary artery (LAD), left ventricle (LV), and left lung - were recalculated to the equivalent dose in 2-Gy fractions (EQD2). Results: The addition of DIBH significantly reduced EQD2 doses to all OARs (except for the left lung maximal dose) in WBI and PBI. MHD values were 0.72 Gy for DIBH-WBI, 1.01 Gy for MIB-APBI and 0.24 Gy for DIBH-PBI. There were no significant differences in cardiac doses between WBI with DIBH and PBI without DIBH. DIBH-PBI resulted in significantly lower mean doses to all OARs (except for maximum lung dose) compared to MIB-APBI. Conclusions: These results show that the use of DIBH significantly reduces cardiac doses in patients with left EBC. Partial irradiation techniques (PBI, MIB-APBI) significantly reduced cardiac doses due to the smaller clinical target volume. The best results were obtained with DIBH-PBI.

Cardiac doses of accelerated partial breast irradiation with perioperative multicatheter interstitial brachytherapy.

PURPOSE: To quantify mean heart dose (MHD) and doses to the left anterior descending artery (LAD) and left ventricle (LV) in a retrospective series of patients who underwent perioperative accelerated partial breast irradiation with multicatheter interstitial brachytherapy (MIB-APBI). METHODS: Sixty-eight patients with low-risk left breast cancer were treated with MIB-APBI at our institution between 2012 and 2017. Interstitial tubes were inserted during the tumorectomy and sentinel node biopsy and APBI was started 6 days later. The prescribed dose was 34 Gy in 10 fractions (twice a day) to the clinical target volume (CTV). The heart, LAD, and LV were contoured and the distance between each structure and the CTV was measured. The MHD, mean and maximum LAD doses (LAD mean/max), and mean LV doses (LV mean) were calculated and corrected to biologically equivalent doses in 2­Gy fractionation (EQD2). We also evaluated the impact of the distance between the cardiac structures and the CTV and of the volume receiving the prescribed dose (V100) and high-dose volume (V150) on heart dosimetry. RESULTS: Mean EQD2 for MHD, LAD mean/max, and mean LV were 0.9 ± 0.4 Gy (range 0.3-2.2), 1.6 ± 1.1 Gy (range, 0.4-5.6), 2.6 ± 1.9 Gy (range, 0.7-9.2), and 1.3 ± 0.6 Gy (range, 0.5-3.4), respectively. MHD, LAD mean/max, and LV mean significantly correlated with the distance between the CTV and these structures, but all doses were below the recommended limits (German Society of Radiation Oncology; DEGRO). The MHD and LV mean were significantly dependent on V100. CONCLUSION: Perioperative MIB-APBI resulted in low cardiac doses in our study. This finding provides further support for the value of this technique in well-selected patients with early-stage left breast cancer.

Accelerated partial breast irradiation with perioperative multicatheter interstitial brachytherapy-A feasibility study.

PURPOSE: To assess the feasibility of high-dose-rate perioperative multicatheter interstitial brachytherapy to deliver accelerated partial breast irradiation (APBI) in selected patients with early breast cancer. METHODS AND MATERIALS: Perioperative multicatheter interstitial brachytherapy for APBI has been used at our department since 2012 for patients with low-risk breast cancer. Interstitial catheters were inserted perioperatively via hollow needles immediately following tumorectomy with sentinel node biopsy. APBI started on Day 6 after surgery. The prescribed dose was 34 Gy (10 fractions of 3.4 Gy bid). Hormonal therapy was prescribed in all cases. RESULTS: Between June 2012 and December 2017, 125 patients were scheduled for APBI. Of these, APBI was not performed in 12 patients (9.6%) due to adverse prognostic factors identified on the definitive biopsy. We observed wound dehiscence in 2/113 cases (1.8%), inflammatory complications requiring antibiotics in 7/113 cases (6.2%), transient Grade I radiodermatitis in 6/113 patients (4.4%), and seroma which resolved spontaneously in 3/113 patients (2.7%). With median followup of 39 months (range 3.3-75.3) no relapses were observed. No late complications in Radiation Therapy Oncology Group Grade 3 or higher were documented. Cosmetic outcome in patients with followup > 2 years was excellent or good in 92%. CONCLUSION: Our preliminary results show that the perioperative multicatheter interstitial high-dose-rate brachytherapy for APBI in selected patients with early breast cancer is feasible. This treatment schedule reduces treatment duration, spares the patients of repeated anesthesia, and enables precise application of the afterloading tubes under direct visual control.