## 3 Results  
### Risk of Second Primary Cancers  
The dose constraints for the OARs, as described in Section 2.3, were met in all 3D-CRT, IMRT, and VMAT plans. The mean value of the D\({}_{\text{av}}\) of the lungs, left breast, right breast, esophagus, and thyroid gland from 3D-CRT plans was 10.87 \(\pm\) 3.10 Gy, 12.50 \(\pm\) 3.78 Gy, 13.01 \(\pm\) 4.35 Gy, 18.46 \(\pm\) 5.33 Gy, and 4.29 \(\pm\) 4.80 Gy, respectively. The corresponding values from IMRT plans were equal to 10.67 \(\pm\) 2.80 Gy, 8.76 \(\pm\) 2.53 Gy, 8.71 \(\pm\) 3.54 Gy, 13.34 \(\pm\) 5.89 Gy, and 4.12 \(\pm\) 4.94 Gy, respectively, while those associated with VMAT were 10.46 \(\pm\) 3.05 Gy, 12.37 \(\pm\) 4.58 Gy, 12.87 \(\pm\) 4.56 Gy, 14.25 \(\pm\) 5.02 Gy, and 4.06 \(\pm\) 4.66 Gy, respectively. The mean OED values for the lungs, left breast, right breast, esophagus, and thyroid are presented in Table 2. The above OEDs varied from 0.69 Gy to 4.26 Gy by the organ under examination and the applied radiotherapy technique. The patient-specific LARs for developing second primary cancers in the surrounding OARs are presented in Figure 1. The range of probabilities for the appearance of second lung, left breast, right breast, esophageal, and thyroid malignancies was 1.88-6.85%, 0.44-5.53%, 0.38-5.53%, 0.12-0.48%, and 0.005-0.16%, respectively. The mean LAR values, as derived from the risk assessments of all study participants, for the three radiotherapy techniques employed for the management of thymroma are presented in Table 3. These mean risk values for left breast, right breast, esophageal, and thyroid cancer induction estimated by IMRT or VMAT plans were lower than those associated with 3D-CRT. The differences between the LARs estimated by the three irradiation techniques are summarized in Table 4. The lifetime risks for developing malignancies in the left and right breasts, esophagus, and thyroid as estimated by the 3D-CRT plans were significantly different from those derived from IMRT plans (\(p\) = 0.001-0.008). Statistical \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & \multicolumn{4}{c}{**Organ-At-Risk**} \\ \hline  & **Lung** & **Female Breast** & **Esophagus** & **Thyroid** \\ \hline a (1/Gy) & 0.042 & 0.044 & 0.46 & 0.0318 \\ a/ \(\beta\) (Gy) & 3 & 3 & 3 & 3 \\ R & 0.83 & 0.15 & 0.46 & - \\ \(\beta_{\circ}\) (10\({}^{-4}\) PY Gy) & 8.0 & 8.2 & 3.2 & 0.4 \\ \(\gamma_{\text{e}}\) (years) & 0.0002 & \(-\)0.037 & \(-\)0.002 & \(-\)0.046 \\ \(\gamma_{\text{a}}\) (years) & 4.23 & 1.7 & 1.9 & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Model parameters used for the assessment of the organ-specific second cancer risk [22; 24]. significances of the differences were observed between the LARs for esophageal and thyroid cancer related to 3D-CRT and VMAT (\(p\) = 0.003-0.031). The patient-specific bilateral breast cancer risks from IMRT and VMAT plans were also significantly different (left breast: \(p\) = 0.022; right breast: \(p\) = 0.005). Insignificant differences were observed between the lung cancer risks estimated by the three techniques (\(p\)\(\geq\) 0.06). The LARs for developing left and right breast cancers from 3D-CRT did not differ significantly from the risks related to VMAT (\(p\)\(\geq\) 0.411). The above insignificant results were also found for esophageal and thyroid cancer risks derived from IMRT and VMAT plans (\(p\)\(\geq\) 0.548). Figure 1: Patient-specific lifetime attributable risk (LAR) for developing (**a**) lung cancer, (**b**) left breast cancer, (**c**) right breast cancer, (**d**) esophageal cancer, and (**e**) thyroid cancer following 3D-CRT, IMRT, and VMAT for thymoma. The lines represent the mean LAR values. Figure 3: Patient-specific relative risk (RR) for developing chronic heart failure following 3D-CRT, IMRT, and VMAT for thymoma. The lines represent the mean RR values.