Dosimetric and Radiobiological Comparison of IMRT Versus 3DCRT Treatment Plans for Hypofractionated Left-Sided Breast 10 MV Photon Irradiation: A Single Center Study

Abstract

Objectives: This study aims to perform a dosimetric and radiobiological comparison between Three-Dimensional Conformal Radiotherapy (3DCRT) and Intensity-Modulated Radiotherapy (IMRT) for a hypofractionated regimen.

Methods: A retrospective analysis was conducted on fifty patients with left-sided, node-negative breast cancer after breast-conserving surgery. Treatment plans were generated for each patient using both 3DCRT (field-in-field technique) and IMRT (inverse-planned with 5 fields) techniques for a prescription dose of 40.05 Gy in 15 fractions. Plans were evaluated based on dosimetric parameters for planning target volume (PTV) coverage (Dmin, Dmean, V95%, V105%), conformity (CI), homogeneity (HI), and doses to OARs (heart, lungs, spinal cord). Radiobiological evaluation included calculating Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP).

Results: IMRT demonstrated significantly superior PTV coverage, with higher D_min (27.55 vs. 16.54 Gy, p<0.0001), V95% (99.81% vs. 87.55%, p<0.0001), and ideal conformity (CI=1.00 vs. 0.87, p<0.0001). However, IMRT resulted in a larger volume receiving 105% of the dose (V105%=44.68% vs. 11.70%, p<0.0001). For OARs, IMRT reduced the mean heart dose (3.40 vs. 2.51 Gy, p<0.0001) and ipsilateral lung V20Gy (17.42% vs. 18.21%, p=0.31), but increased low-dose exposure (e.g., heart V10Gy and lung V5Gy). IMRT demonstrated a superior TCP (96.2% compared to 93.1%, p<0.0001) and IMRT demonstrated a superior TCP (96.2% compared to 93.1%, p<0.0001) and markedly reduced NTCP for radiation pneumonitis (2.1% versus 19.2%, p<0.0001) and cardiac problems (0.10% versus 0.20%, p<0.0001). NTCP for radiation pneumonitis (2.1% versus 19.2%, p<0.0001) and cardiac problems (0.10% versus 0.20%, p<0.0001). IMRT required substantially more monitor units and longer beam-on time.

Conclusion: IMRT offers a dosimetrically and radiobiologically enhanced plan for hypofractionated radiation treatment of left-sided breast cancer, ensuring superior target coverage and a marked decrease in the anticipated risk of pulmonary and cardiac problems. Nonetheless, this strategy incurs the expense of heightened low-dose exposure to adjacent tissues and increased complexity in treatment administration. The selected approach must be tailored according to patient anatomy and specific risk profiles.