166P A mono-institutional experience of field-in-field 3D-CRT planning in breast radiotherapy with FAST and FAST-forward protocols

The benefits of hypofractionated radiotherapy with FAST and FAST-forward protocols could be compromised by soft tissue reactions cardiac toxicity caused dose inhomogeneity inaccurate heart sparing. This study aims to evaluate the dosimetric results whole-breast field-in-field 3D conformal (3D-CRT) technique. A mono-institutional consecutive cohort 122 early-stage invasive breast cancer patients was treated using 3D-CRT. Thirty-nine were 28.5 Gy in 5 fractions once a week (FAST protocol) eighty-three 26 (FAST-forward protocol). Different parameters evaluated assess target coverage, conformity homogeneity hot spots unspecified tissues. To dimensions, nipple-to-pectoral muscle distance (NPD) maximum mediolateral thickness (MLT) along tangential fields measured. Evaluated OARs ipsilateral lung their respective constraints as required clinical protocols. median NPD MLT 4.65 cm [1.70-9.30] 21.55 [11.26-32.30] respectively, CTV 380.50 cm3 [60.29-1255.13]. V95% 99.45% [95.19-100], 105% isodose volume 0.74 [0.00-48.02] whom 0.07 [0.00-5.22] first skin centimetre. led CI 0.53 [0.33-1.00] HI [0.03-0.19]. dose-volume always respected. V8Gy 7.32% [0.31-25.15]; for (left only), V1.5Gy 6.45% [0.00-25.12] V7Gy 0.34% [0.00-4.50]. Each plan achieved clinically acceptable coverage homogeneity, reduced superficial spots. These suggested that 3D-CRT can provide good quality RT plans, advantages an efficient cost-effective delivery follow-up will give further critical feedback on treatment outcomes toxicities.