Abstract: Objective To analyze the efficacy of the 3D printing compensation film in the postoperation radiotherapy for breast cancer patients after immediate breast reconstruction. Methods A total of 11 patients who underwent immediate breast reconstruction after modified radical mastectomy in Hunan Cancer Hospital from November 2021 to May 2022 were selected. The same sequence was used to perform CT positioning scanning after covering the 3D printing compensation film and the commercial compensation film, and the air gap, target area and organs at risk were delineated. Two intensity modulated radiation therapy (IMRT) plans were designed with the same parameters (Plan A: 3D printing compensation film; Plan B: commercial compensation film). The differences between the two plans were analyzed with respect to air gap, homogeneity index (HI), new conformity index (nCI), the mean dose (Dmean), V5, V20, V30 of the lung on the affected side lung, the cardiac dose V30 and the healthy side breast Dmean. Results  The air gap volume of Plan A was smaller than that of Plan B ［(8.029±2.542) cm3 vs (20.048±4.372) cm³, t=-5.300, P<0.001］. Compared with those of Plan B, the HI ［(0.134±0.008) % vs (0.161±0.016) %, t=-2.246, P=0.049］, the healthy breast Dmean ［(159.909±17.925) cGy vs (173.364±19.248) cGy, t=-2.343, P=0.041］ and the lung on the affected side lung V20 ［(25.782±0.876) % vs (26.373±0.836) %,t=-2.334, P=0.042) of Plan A were decreased, and the nCI was increased ［0.79% (IQR: 0.77%-0.83%) vs 0.78% (IQR: 0.75%-0.81%), Z=-2.316, P=0.021］, but there was no significant difference in cardiac dose V30, and the affected side lung Dmean, V5 and V30 (all P>0.05). Conclusions In patients with immediate breast reconstruction after radiotherapy for breast cancer, the 3D printing compensation film has advantages over the commercial compensation film with respect to fitness to skin, dose distribution and uniformity in the target area, improving the epidermal dose while reducing the dose of exposure to organs at risk, and has certain potential value in clinical application.

Key words: Breast cancer, Immediate breast reconstruction, Radiotherapy, Compensation film, 3D printing, Air gap