Investigate Change Cardiac Perfusion Pattern Following By Hypo-fractionated and Conventional Radiation Therapy Schedule in Patients with Left-Sided Breast Cancer

Introduction: Radiation-induced cardiovascular damage is a potential side effect of radiation therapy in patients with left-sided breast cancer. This prospective study compares the severity and reversibility of perfusion and functional abnormalities before, and six months after, 3D-Conformal radiation therapy treatment in left-side breast cancer patients with conventional and hypofractionated schedule radiation therapy by stress/rest gated myocardial perfusion imaging.   Materials and Methods: Stress/rest gated myocardial perfusion imaging with Tc-99m MIBI was performed in 36 patients with left-sided breast cancer before, and six months after, completion of radiation therapy schedules. Results: Myocardial perfusion defects were detected in 82.6% and 76.90% of patients with conventional and hypofractionated radiation therapy schedule, which were prominently located in anteroseptal (60.9% vs. 69.2%), anterior (52.2% vs. 61.5%), anterolateral (47.8% vs. 23.1%), apex (34.8% vs. 38.5%), lateral (21.7% vs. 7.7%) and inferior (8.7%Vs 0.0%) walls, respectively. Frequency of mild, moderate and severe perfusion defects in the radiation therapy schedules were 39.1% vs. 15.4%, 21.7% vs. 38.5% and 21.7% vs. 23.1%, respectively. Myocardial perfusion defects were reversible, partial reversible or fixed in 26.09% vs. 30.8%, 34.78% vs. 30.8% and 21.74% vs. 15.04% patients, respectively. A statistically significant increase was found in the summed stress score, summed difference score and summed rest score of patients treated with conventional and hypofractionated radiation therapy schedule at six months after treatment, compared to the baseline study. Also, between the dosimetric parameters and semi-quantitative SPECT data of patients, a significant correlation was observed. Conclusion: Radiation-induced cardiovascular damage is a common finding six months after radiation therapy. Cardiac complications show no statistically significant differences between the two radiation therapy schedules. Both stress and resting gated MPI are required for assessment of changes in myocardial perfusion in patients with left-sided BC