For patients with breast cancer, tangential plans are considered the most common method for RT of BCS and mastectomy patients. Several studies have discussed the imposed radiation dose to OARs such as ipsilateral lung, heart, and LAD (
17-
20). However, to the best of our knowledge, there is limited data about the imposed radiation dose to other organs such as LAD and RCA for 3D-CRT, IMRT, and hypofractionated modalities for the discussed patients. In addition, it would seem that data about the evaluation of TCP and NTCP models using MATLAB and R programs for the target volumes and OARs among the mentioned method for BCS and mastectomy patients are scarce. Therefore, this study aimed at evaluating the imposed dose and TCP-NTCP models for the target volumes and OARs including ipsilateral lung, heart, LAD, and RCA using MATLAB and R programs with and without internal mammary nodes.
Based on our findings, the mean (± SD) imposed dose (with/without internal mammary fields) to ipsilateral lung, heart, LAD, and RCA for 3D-CRT were significantly higher compared to 6 and 9 fields IMRT inverse plans (P < 0.005) for both BCS and post-mastectomy patients.
Tables 2 and
3 illustrate that the mean (± SD) imposed radiation dose to the studied OARs for 6FIMRT was significantly lower than 3D-CRT (P < 0.005). In addition, the mean (± SD) dose of 6FIMRT for the discussed OARs was lower compared to 9FIMRT and hypofractionated IMRT, but it was not significant (P > 0.005). Furthermore, the V
20Gy for Ipsilateral lung and the V
25Gy for heart, LAD, and RCA of 6 and 9 fields and hypofractionated (with/without internal mammary fields) were significantly lower compared to 3D-CRT (P < 0.005) for both groups, while there were no significant differences for the V
20Gy of ipsilateral lung and the V
25Gy of heart, LAD, and RCA among 6 and 9 fields with hypofractionated RT (P > 0.005). Moreover, it was found that the mean (± SD) imposed dose to LAD was higher compared to heart and RCA for all studied modalities, while the imposed dose to RCA was lower than heart and LAD among the mentioned RT methods for BCS and post-mastectomy patients (
Tables 2 and
3), which is highly due to their different anatomical features. Furthermore, it is considered that the minimum dose of heart, LAD, and RCA were not significantly different for the 3D-CRT, IMRT, and hypofractionated RT (P > 0.005).
Our findings are in an agreement with the study of Taylor et al. who stated that the imposed RT dose to the anterior part of the heart including LAD is higher than the whole heart (
30). Recently, Gocer and Ozer have performed a dosimetric study on OARs of patients with breast cancer including heart, LAD, left circumflex coronary artery, right and left ventricles, using tangential beams of 3D-CRT. In their study, they concluded that the mean radiation dose to LAD was higher than the heart and its coronary arteries for patients with left-sided breast cancer (
20), which is in line with our study. In addition, in their study, they have reported that the highest maximum radiation dose was for the heart for patients with left-sided breast cancer (
20). Moreover, the results of our study are similar to Rudat et al. who mentioned that the tangential IMRT plans may significantly reduce the dose-volumes of the ipsilateral lung and heart compared to tangential 3D-CRT for post-mastectomy breast cancer patients (
10). Aznar et al. have focused on the imposed dose to heart, arch, and also whole LAD in respiration-adapted RT of left-sided breast cancers. In this study, they found that the radiation dose to arch and whole LAD was different for some of their patients, and, thus, it is demonstrated that the assessment of the dose to the whole heart as well as to the whole LAD is crucial for the stated patients (
17).
Based on
Table 2, the TCP of the stated target volumes (with/without internal mammary fields) for 9FIMRT and hypofractionated RT were higher than 6 fields and 3D-CRT, but they were not significant (P > 0.005). Whereas, the NTCP of the Ipsilateral lung for 6FIMRT was lower compared to the 9 fields and hypofractionated RT (P > 0.005). Also, the NTCP for 3D-CRT was significantly higher than other methods (P < 0.005). Li et al. have found that the TCP of conventional RT and IMRT is more than 90%, but the NTCP of the lung for IMRT is less than the conventional method (
31), which is similar to our results. Furthermore, our findings showed that the NTCP of the heart and its coronary arteries including LAD and RCA for 6FIMRT was lower compared to 3D-CRT, 9FIMRT, and hypofractionated methods. Moreover, our data showed that the hypofractionated RT may decrease the treatment time, which is in line with Li et al. who mentioned that their hypofractionated technique may reduce the RT time for their patients with breast cancer (
31).
According to the results of our study, 6FIMRT not only may provide suitable PTV dose coverage but also may impose lower complication probabilities to OARs compared to 9FIMRT, hypofractionated RT, and 3D-CRT. Nevertheless, the hypofractionated method may be a good alternative to reduce breast cancer treatment time.
5.1. Conclusions
In this study, the dose distribution and TCP-NTCP models of 3D-CRT, 6 and 9 fields IMRT inverse plans, and hypofractionated IMRT are evaluated for patients with left-sided breast cancer (BCS and mastectomy). Based on our findings, 6FIMRT inverse planning is well worth treating patients with left-sided breast cancer due to enough dose coverage for PTV, suitable TCP for target volumes, and lower NTCP for ipsilateral lung, heart, LAD, and also RCA compared to others. However, as a result of lower treatment time for the hypofractionated IMRT, using this modality is suggested.
According to our findings of the above-discussed methods, further research about the advantages and disadvantages of hypofractionated RT for BCS and post-mastectomy patients is proposed.