Breath Hold Breast Radiotherapy In The Era of Precision Medicine: Appropriate Selection for Left Descending Artery Sparing

Abstract Background and purpose To identify anatomical and/or preplanning characteristics correlated with left descending artery (LAD) dose and therefore provide guidance in the selection of patients with left-breast cancer that could benefit the most from the use of deep inspiration breath hold radiotherapy (DIBH-RT). Materials and methods We retrospectively identified patients with left-sided breast cancer who underwent whole breast radiotherapy in DIBH and extracted data from treatment plans in free-breathing (FB) and DIBH. The following anatomical parameters were obtained from the planning CTs in FB: lung volume, heart volume, breast separation, minimum distance from LAD to tangent open field. Receiving operating characteristics was also performed to define the cut-off point of parameters to use in LAD dosimetry prediction. Areas under the curve (AUCs) were calculated for all variables. Post-test probability has been calculated to evaluate advantage for parameters combination. Results One hundred ninety-seven patients were identified. The strongest predictor at FB CT scan of LAD maximum dose > 10 Gy and a LAD mean dose > 4 Gy was the minimum distance of LAD from tangent open fields. Adding consecutively other preplanning anatomic parameters, the positive predictive value (PPV) to identify patients at risk of higher dose to LAD was > 90%. Conclusions The dosimetric benefit of DIBH is valid for all patients and DIBH should be preferred for all left sided patients; however we can identify a subgroup of patients who benefit the least from DIBH. This is the group with favorable anatomy: limited breast separation, well expanded lungs, LAD distant from open tangent fields.