Dosimetry of intensity-modulated radiation therapy and volumetric-modulated arc therapy techniques after modified radical mastectomy for breast cancer and hypofractionated intensity-modulated radiotherapy

Objective: The aim of this study was to compare the advantages and disadvantages of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with left-sided breast cancer who underwent hypofractionated IMRT after a modified radical mastectomy.Materials and Methods: Twenty patients who required adjuvant radiotherapy after modified radical mastectomy were randomly selected, and a specified dose of 43.5 Gy/15 F was used to plan for IMRT or VMAT. Dose-volume histograms (DVHs) were utilized to evaluate the dose distribution of the planning target volumes (PTVs) and organs at risk (OARs).Results: VMAT demonstrated a greater and more uniform dose distribution of PTVs and lower number of monitor units. No significant differences were found in V-5 of the affected lung and heart between the two techniques (P > 0.05). The V-10, V-20, V-30, and D-mean of the affected lung and V-10, V-20, V-30, V-40, D-mean, and D-max of the whole heart were better in the VMAT than in the IMRT (P < 0.05). The D-mean and D-max of the left anterior descending (LAD) branch of the coronary artery of the heart were better in the VMAT (P < 0.05), and the use of the VMAT effectively reduced the cardiopulmonary dose. A significant advantage of V-30 and D-mean was also found in VMAT (P < 0.05).Conclusion: These findings indicate that VMAT has higher clinical significance than IMRT, because it improved the dose distribution in the target area, reduced the cardiopulmonary dose, protected the OARs (e.g. thyroid), and shortened the treatment duration.