Dosimetric and radiobiological comparation of 3DCRT, IMRT and VMAT techniques for postmastectomy radiotherapy in left breast cancer patients with positive lymph nodes

Abstract

Abstract Background/Purpose: To compare dosimetric and radiobiological parameters among 3DCRT, IMRT, and VMAT techniques to determine the optimal approach for postmastectomy radiotherapy (PMRT) in left breast cancer patients with positive lymph nodes. Methods: Three treatment plans for 37 patients with left-sided breast cancer and positive lymph nodes, post-modified radical mastectomy, were developed using 3DCRT, IMRT, and VMAT. A prescribed dose of 50 Gy in 25 fractions was set, ensuring 95% coverage of the PTV volume by 50 Gy. Dosimetric parameters for the target volume and critical organs, alongside the normal tissue complication probability (NTCP) and excess absolute risk (EAR) for specific organs, were evaluated for each technique. Results: The 3DCRT technique showed unsatisfactory target consistency and uniformity, with average CI and HI values of 0.50 and 0.15, respectively. IMRT achieved better results with CI and HI values of 0.68 and 0.12, respectively, while VMAT showed the best performance with 0.78 and 0.11, respectively. VMAT also outperformed in dosimetric parameters for the heart (V25Gy and Dmean), LAD (Dmax and Dmean), and ipsilateral lung (V20Gy, V30Gy, and Dmean), with significant statistical differences (p < 0.05). NTCP values for VMAT were significantly lower than the other two techniques, whereas 3DCRT showed the highest toxicity risk. For contralateral tissues, VMAT had higher dosimetric parameters in the contralateral lung (V5Gy and Dmean) and contralateral breast (V5Gy and Dmean) than 3DCRT and IMRT, with significant differences (p < 0.05). The estimated EAR for contralateral breast carcinoma induction was 15.31, 31.58, and 71.32 (per 10,000 patients per year) for 3DCRT, IMRT, and VMAT, respectively. For the contralateral lung, these figures were 13.94, 19.07, and 31.21, respectively. Conclusions: VMAT offers reduced cardiac and pulmonary toxicities in PMRT for left breast cancer patients with positive lymph nodes but increases the risk of low-dose radiation and secondary cancer in contralateral structures. VMAT may be more suitable for patients with cardiopulmonary concerns or older age, while younger, healthy individuals require careful clinical evaluation to balance risks.