Deep inspiration breath-hold versus free breathing: Dosimetry and cardiac protection in postoperative left-sided breast cancer (breast-conserving surgery or mastectomy)

Purpose To compare irradiation dose distribution and cardiac protection effects between DIBH and FB radiotherapy in postoperative patients with left-sided breast cancer. Methods Retrospective study included 230 left-sided breast cancer patients who received postoperative adjuvant radiotherapy, with 103 treated using DIBH and 127 using FB. Dosimetric parameters for the heart, LAD, ipsilateral lung, and contralateral breast were extracted from dose-volume histograms. Acute radiation toxicities were graded according to CTCAE version 5.0. Cardiac biomarkers, including cTnI and NT-proBNP, were measured at baseline and 6 months post-radiotherapy. Results Compared with FB, DIBH significantly reduced heart mean dose, maximum dose, and all V5–V40 parameters (all P < 0.001), LAD mean and maximum doses (both P < 0.001), and ipsilateral lung mean dose, V20, and V30 (P = 0.002--0.009), while ipsilateral lung volume was significantly larger (P < 0.001) (Reductions in lung V5 and V10, though statistically significant, are of debated clinical relevance). At 6 months, the DIBH group showed lower cTnI (P < 0.001) and NT-proBNP levels (P = 0.004), with a lower proportion of subclinical cardiac injury (P = 0.034). Target coverage and short-term clinical outcomes (including local-regional recurrence, symptomatic radiation pneumonitis, and early cardiac events) were comparable (all P > 0.05). Conclusion DIBH radiotherapy reduces cardiac and pulmonary doses, attenuates elevations in cardiac biomarkers, and maintains comparable target coverage and short-term clinical outcomes compared with FB in postoperative left-sided breast cancer patients.