Dosimetric comparison between 3d-crt, IMRT and VMAT radiotherapy plans in left breast cancer with DIBH

Abstract

Purpose: To compare dose parameters of 3D-Conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and Volumetric-modulated arc radiotherapy (VMAT) to evaluate the best treatment option for left Breast cancer with Deep Inspiration Breath Hold (DIBH).

Materials and methods: Twenty left breast cancer were surgeried and indicated radiotherapy with DIBH in the Radiotherapy Department-Vinmec International Hospital Times City from January 2018 to March 2020. For each patient, 3DCRT, IMRT and VMAT plans were generated on Eclipse planning system version 13.0 (Varian, USA). The planning target volume (PTV) was assigned a dose of 50Gy/25 fraction and was normalized at the same level. Dosimetric comparisons between 3DCRT, IMRT and VMAT plans were analyzed to evaluate indicators: V95, CI, HI, dose to OARs, MU, treatment time.

Results: The volume of PTV receive 95% dose description on VMAT (99.8±0.2%) and IMRT plans (99.7±0.1%) better than 3DCRT plans (99.1±0.5%, p <0.01). VMAT plans have CI (0.998±0.01), HI (0.094±0.02) better than 3DCRT (CI=0.991±0.01; HI =0.116±0.02) and IMRT plans (CI=0.997±0.01; HI=0.110±0.02) (p<0.01).

The mean dose to the lungs and the left lung in VMAT plans are the lowest (p<0.05). The dose of V5Gy, V10Gy in 3DCRT plans to the lungs and left lung are lower IMRT and VMAT plans, but higher in V20Gy, V30Gy and V40Gy (p <0.05).

Similar, the mean dose to heart and right breast in 3DCRT plans are lower, but at higher in V20Gy, V30Gy, and V40Gy when comparing with IMRT and VMAT plans (p <0.01). VMAT plans have dose to the coronary are smallest (Dmax=18.5±2.6Gy, p<0.01) compare with 3DCRT (46.5±2.5Gy) and IMRT plans (23±2.4Gy). Dose to the spinal cord and the humerous head no significant difference (p>0.05). The number of MU in the IMRT plans are largest (2115±239, p<0.01) in three types of plan (3DCRT=550±45; VMAT=565±71). The treatment time of 3DCRT (3.3±0.2 minutes) and VMAT plans (3.4±0.1minutes) are lower than IMRT plans (6.1 ± 0.5 minutes) (p <0.01).

Conclusions: VMAT plans provides better comminity index, homogeneity index, dose distribution to target volume and high dose reductions in healthy organs are better than 3D-CRT and IMRT plans. VMAT and 3D-CRT plans have treatment time and number of MUs lower than IMRT plans.