Cardiac dosimetry using a 3D conformal technique for adjuvant breast radiotherapy

Background: Radiation-induced cardiac toxicity is influenced by specific dose-volume parameters, including mean heart dose (MHD), volume of the heart receiving ≥ 25 Gy (V25), and the dose to the left anterior descending artery (LADA). Aim: To evaluate the cardiac radiation dose parameters in patients receiving postmastectomy radiotherapy using three-dimensional conformal radiotherapy (3DCRT). Setting: Department of Radiation Oncology, Steve Biko Academic Hospital. Methods: A retrospective analysis was performed on treatment plans of 62 consecutive breast cancer patients who received adjuvant chest wall radiotherapy at Department of Radiation Oncology, Steve Biko Academic Hospital, which was selected for analysis. Dose-volume histograms were used to assess MHD and volume receiving 25 Gy (V25). The maximum point dose to the LADA was estimated from axial planning CT images. Fifty-seven patients received 50 Gy in 25 fractions; most received a supraclavicular field (SCF) and/or a scar boost. Analysis focused on the 27 left-sided cases. Results: Among left-sided patients, 24 (88.9%) had an MHD > 2 Gy, and 13 (48.1%) had V25 exceeding 10%. The maximum LADA dose exceeded 6.7 Gy in 24 patients (88.9%). All right-sided patients remained within these constraints. There was a strong correlation between MHD, V25, and LADA dose (Spearman p > 0.8, p < 0.001). Inclusion of SCFs or boost did not significantly affect cardiac dose parameters. Conclusion: Conventional 3DCRT techniques frequently exceed recommended cardiac dose constraints in left-sided chest wall radiotherapy. Contribution: These findings underscore the need for advanced techniques, such as deep inspiratory breath hold, to reduce cardiac exposure and long-term cardiovascular risk.