Session Item

Radiation therapy for left breast cancer results in significant exposure to heart resulting in long term cardiac morbidity. This exposure can be reduced by performing Deep Inspiratory Breath Hold (DIBH) technique however no patient selection criteria or predictive parameters can identify patients on free breathing CT simulation, who will have significant benefit with this technique. This study intends to find some predictive parameters measured on free breathing simulation scan which can help to select such patients.

A total of 35 patients of left breast cancer post-surgery were recruited in the study. All patients underwent 2- 3 sessions of DIBH coaching followed by planning Computed Tomography (CT) scan in both free breathing (FB) phase and DIBH phase. Various anatomical parameters like Cardiac Contact Distance para-sagittal (CCDps), axial (CCDax), Heart Chest Distance (HCD) and D was measured on FB scan and were correlated with mean heart dose achieved in DIBH scan. Another parameter was the maximal heart distance (D)which was measured as the perpendicular distance to the farthest point on heart from a line drawn from left end of sternum to the anterior border of left latissimus dorsi at the level of the dome of right diaphragm.

Dose to normal structures namely heart and lung were drastically reduced for DIBH scan over FB scan. V5, V10, V20 of heart also followed similar reduction. Mean dose to heart in free breathing scan was 5.34 Gy while in DIBH scan was 2.79 Gy which was statistically significant with p value of <0.0001. V20 left lung was 21.3 % in FB Scan while it was 19.5 % in DIBH scan which was also statistically significant. Mean CCDax and CCDps on FB scan were 6.67 cm and 3.88 cm respectively while mean HCD and D (maximal heart distance) were 2.17 cm and 2.88 cm. Patients who had CCDax> 7 cm and CCDps> 3.5 cm had less benefit from doing DIBH technique, although CCD ax did not correlate significantly with these results. HCD on FB scan was inversely correlated with mean heart dose in DIBH scan with a cutoff value of 2.1 cm. Amongst all the parameters measured, CCDps and D had statistically significant positive correlation with the mean heart dose in DIBH phase while HCD had negative correlation which was statistically significant. The parameter ‘D’ which we assessed had positive correlation with all heart dosimetric parameters but statistically significant results were associated with mean heart dose and V20.

Cardiac parameters on FB scan like CCDps, HCD and D predicts the patients with usual cardiac risk who will benefit most with DIBH techniques setting an arbitrarily cutoff value. In our study, all patients were benefitted with the use of DIBH technique but the benefit was most pronounced with the cutoff values suggested above.