Dosimetric evaluation of cardiac and left anterior descending artery dose in patients with left-sided breast cancer treated by different techniques of hypofractionated adjuvant radiotherapy after breast conservative surgery

The aims: to dosimetrically evaluate the dose to the heart and left anterior descending artery in left-sided early breast cases using different techniques. Materials and methods: Prospective observational/analytical study done in cases of left-sided BCS referred for adjuvant RT in 54 patients. Patients who underwent left-sided BCS (breast conservative surgery), patients aged between 18- and 75 years performance status ECOG 0-2, histological confirmed DCIS, Invasive Breast Cancer-Stage 1, 2, 3, patients without any evidence of metastatic disease Irrespective of hormonal receptor and HER-2 neu status are included in the study. Results: All the 3 parameters for LAD showed the highest doses with 3DCRT and lowest with VMAT. Thus our study favoured VMAT (p<0.01) as the planning technique to achieve the least doses of LAD. However, for the heart, there was no statistically significant difference between 3DCRT and IMRT (p=0.349) for the average mean dose (Gy). On the other hand, there was a statistically significant difference between 3DCRT Vs VMAT and IMRT Vs VMAT (95 % CI, p<0.01), again favouring VMAT as the choice of planning technique. The average heart max dose(Gy) and average heart V20(%) showed statistically significant benefits with VMAT (p<0.01). There was a statistically significant benefit (p<0.000) with VMAT for both LV parameters. At the same time, there was a statistically significant benefit in terms of ipsilateral lung dose with VMAT(p<0.000), the dose to the right lung, right breast and favoured 3DCRT (p<0.01). PTV95 % (Gy) by 3DCRT, IMRT, and VMAT in our study is 41.01, 41.96, and 41.76, respectively. Though the difference between the 3 techniques seems meagre, there was a statistically significant difference (p<0.012) favouring IMRT. Conclusion: We conclude that using the VMAT technique in radiotherapy for left-sided breast cancer can significantly reduce radiation doses to the heart and LAD, potentially reducing cardiac risk. For all patients, the cardiac doses are considerably decreased for all dose levels without compromising the dose coverage to PTV, which is an advantage over IMRT and 3DCRT