Assessment of Bilateral Breast Cancer 3-DCRT Effective Planning Methods According to Isocenter Placement

Objective: This study aims to evaluate and compare single-isocenter versus dual-isocenter 3D-CRT techniques to optimize planning efficiency and dosimetric outcomes, particularly in high-volume or resource-limited clinical settings. Methods: A retrospective study of 30 patients with bilateral breast carcinoma and nodal involvement was conducted. For each patient, two 3D-CRT treatment plans were generated: single-isocenter and dual-isocenter. Both used 12–16 fields with subfields and a prescription of 40.1 Gy in 15 fractions. Dosimetric parameters included PTV/CTV coverage (V95%, V90%), dose homogeneity, and organ-at-risk (OAR) sparing for lungs and heart, evaluated against RTOG guidelines. Statistical analysis was performed using descriptive statistics and ANOVA, with p<0.05 considered significant. Results: The single-isocenter technique provided superior target coverage (V95%: 96.4% left PTV, 95.1% right PTV) compared with dual-isocenter (93.4% and 93.8%). Nodal coverage was comparable across techniques. Both techniques satisfied OAR constraints: lung V20 was 24.1 Gy. 22.8 Gy, and heart V25 were 4% vs. 2% for single- and dual-isocenter plans, respectively. Single-isocenter plans showed a trend toward superior PTV coverage compared to dual-isocenter plans; however, this difference was not statistically significant (left breast: p = 0.357, right breast: p = 0.255). Conclusion: Single-isocenter 3D-CRT for bilateral breast cancer improves target coverage, eliminates junctional uncertainties, and streamlines treatment delivery. Its efficiency and practicality make it a valuable solution for high-volume and resource-constrained settings, enabling high-quality care without compromising dosimetric standards.