ABSTRACT
Background: Axillary radiation and surgery have provided equivalent local control in early breast cancer patients. It is believed that tangential field (TF) radiation that was used to treat the breast coincidently delivered radiation treatment to the lower axilla and eradicated the disease. In the era of CT-based three dimensional- (3D) radiotherapy planning, however concerns have been raised about the adequacy of coverage of the axillary levels in the tangential fields. In this study, author evaluated the coverage of the axillary nodal levels I and II using high conventional tangential fields in patients with or without axillary dissection.Methods: A prospective study was conducted which included 18 cases for a period of one year, radiation therapy was planned to the chest wall or whole breast by using the high conventional tangential field using 2D radiation portals. Central lung distance (CLD) and the distance of superior border was measured form the head of the humerus and were recorded. CECT chest was done in the same position alike during conventional simulation. All the images were shifted to the treatment planning system. The Contouring of Axillary lymph nodes level I and II was done on Oncentra contouring software.Results: The coverage of the axillary nodes was not related to central lung distance (CLD). However, some with CLD of 1cm had more coverage of the level I nodes than with CLD of 2 cm and the maximum CLD in the field was 2.5 cm. Of the 18 patients in the study, 13 patients had <2 cm distance from the humeral head and all the axillary level II LN covered in the field. Whereas 5 patients having distance >2 cm did not have adequate coverage of level II axillary LN’s.Conclusions: The distance of the cranial border of the tangent portal from the head of the humerus shows a relationship with coverage of level II nodes cranially. As the distance decreases the coverage of level II nodes cranially keeps increasing. In majority of the patients a distance of 2 cm or less than 2 cm ensured good coverage of level II nodes cranially. Similarly, no correlation was found between volumetric coverage of the axillary nodes with central lung distance.
ABSTRACT
Objective To investigate the impacts of planning target volume (VPTV),maximal heart distance (MHD),central lung distance (CLD),and cardiothoracic ratio (CTR) on intensity-modulated radiotherapy (IMRT) after breast-conserving surgery for breast cancer.Methods Forty-eight patients with breast cancer (31 with left-sided breast cancer and 17 with right-sided breast cancer) who received whole-breast IMRT after breast-conserving surgery in our hospital from 2016 to 2017 were enrolled as subjects.The prescribed radiation dose tor PTV was 50 Gy in 25 fractions.In IMRT planning for each patient,the objective function was optimized using physical parameters and the equivalent uniform dose.The relationship of influencing factors with dose-volume histogram,conformal index (CI),and homogeneity index (HI) for organ at risk was predicted using univariate and multivariate linear regression analyses.Results CTR and VPTV were independent influencing factors for CI in patients with left-sided breast cancer (R2=0.56,P=0.04;R2 =0.56,P=0.00).CLD was an independent influencing factor for HI in patients with left-sided breast cancer (R2=0.17,P=0.023).VPTV was an independent influencing factor for CI in patients with right-sided breast cancer (R2 =0.48,P=0.00).MHD and CTR were predictors for VHeart30 of the heart.MHD and CLD were predictors for DmaxHeart of the heart.The prediction formulae for left-sided breast cancer were CI=0.38+0.32CTR and HI=1.06+0.02CLD.CI was 0.48 at the right side.At the left side,Vlung20=12.68+3.18CLD,Vlung10=18.78+4.3CLD,Vlung5=26.2+5.2CLD,and Dmeanlung=686.7+210.ICLD.For the heart,VHeart30=-13.65+30.5CTR+1.9MHD and DmaxHeart =5 140.1 +248.9MHD-195.6CLD.There was no correlation of patient's heart volume with MHD,VHeart10,VHeart5,DmeanHeart,or DmaxHeart.There was no correlation of whole lung volume with CLD,Vlung20,Vlung10,Vlung5,or Dmeanlung.The mean values of CI and HI were 0.63± 0.06 (0.46-0.72) and 1.09± 0.02 (1.07-1.14-) in radiotherapy plans for left-sided breast cancer,and 0.65± 0.08 (0.4-8-0.76) and 1.09± 0.04 (1.03-1.18) in radiotherapy plans for right-sided breast cancer,respectively.Conclusions CTR,CLD,and MHD can predict the rationality of each parameter in IMRT planning for left-sided breast cancer rather than right-sided breast cancer.The obtained formulae can help physicians choose the optimal setting mode for radiation field and improve the quality of treatment plans.