Evaluation of effect of inverse and field-in-field IMRT planning for left-sided anterior descending coronary artery doses in left-sided breast cancer patients

Abstract

OBJECTIVE The aim of the study is to evaluate radiation doses of left-sided whole-breast irradiation on left-sided anterior descending coronary artery (LAD) among various radiotherapy treatment planning techniques for 45 left-sided breast cancer patients. METHODS Three different radiotherapy techniques, field-in-field, 4-field inverse IMRT, and 5-field IMRT, were undertaken. For inverse IMRT, the fields were special for each patient. We used 2 opposed tangential beams in the field-in-field technique, and for the other two techniques, the beams were obtained by 10° refraction. RESULTS The 5-field IMRT technique is not useful for decreasing the LADmax dose. We figured out that in the field-in-field technique, 18 of our 45 patients received doses greater than 10 Gy to LAD. We also found that using the 4-field inverse IMRT technique, LAD and lung doses could be reduced. CONCLUSION The mean LADmax dose was smaller than 10 Gy for all techniques except the field-in-field technique. There was no significant difference between 4-field inverse IMRT and field-in-field techniques. However, if LAD is located deeper than 2.5 cm, the LADmax dose could increase; this could further be decreased to under 10 Gy using the 4-field inverse IMRT technique.