## 4 Discussion  
BC RT treatments are typically delivered using two different fractionation schedules: SF and HF. Clinical trial results report 10-year local recurrence rates of 4.3% for HF and 5.5% for SF [39]. For this reason, HF is the preferred approach, although SF is still used in specific clinical conditions. In this study, the difference in RT-induced lung cancer risk for BC was evaluated for both fractionation schemes using [PERSON]'s model. The risk was estimated for 58 Sicilian women aged between 30 and 70 years, all treated with a 3D-CRT SF approach between 2015 and 2021. Risk factor calculations were performed using a custom-developed Eclipse(tm) script. This tool enables immediate visualization of relevant risk metrics. It significantly reduces the time compared to the standard workflow of exporting the DVH file and applying [PERSON]'s model post hoc. The results obtained in this work, alongside those from the literature, are reported in Tables 1 and 2, respectively. For the SF approach, _EAR_ values ranged from 23 to 42 (per 10,000 PY) and _LAR_ values from 31 to 455 (per 10,000 P). For the HF approach, _EAR_ values ranged from 20 to 37 (per 10,000 PY) and LAR values from 27 to 400 (per 10,000 P). [PERSON] et al. [35] reported _LAR_ values ranging from 359 to 494 (1/10,000 P) for the Intensity-Modulated Radiation Therapy (IMRT) SF approach, and from 316 to 437 (1/10,000 P) for the IMRT HF approach. [PERSON] et al. [40] found _EAR_ values between 23 and 55 (1/10,000 PY) and _LAR_ values between 275 and 654 (1/10,000 P) for 3D-CRT SF. For Volumetric Modulated Arc Therapy (VMAT), they reported _EAR_ values between 58 and 64 and _LAR_ values between 410 and 770. These studies commonly applied [PERSON]'s model for risk assessment but differ in terms of treatment technique and, in some cases, prescription dose. Only one of them, i.e., [PERSON] et al. [40], evaluated RT-induced lung cancer risk for 3D-CRT SF in breast cancer patients, with prescription doses of either 50 Gy in 25 fractions of 2.0 Gy or 50.4 Gy in 28 fractions of 1.8 Gy. The smaller patient sample analyzed by [PERSON] et al. (n = 10) may partly explain the narrower range of results compared to our study, which included a larger cohort of 58 patients. Any comparison with the findings of [PERSON] et al. should consider these differences, as well as the fact that they assumed an age\({}_{\text{a}}\) of 70 years. For the same _OAR_, the risk of radiation-induced cancer also depends on the treatment technique employed. For instance, IMRT typically results in higher doses to the contralateral breast compared to 3D-CRT. [PERSON] et al. [38] extended their analysis to this _OAR_, reporting _OED_ values of up to 0.99 Gy for SF and 0.86 Gy for HF. The corresponding patient-specific _RR_ ranged from 1.04 to 1.10 for SF, and from 1.03 to 1.09 for HF. [PERSON] et al. [40] conducted a study comparing multiple RT techniques--3D-CRT, VMAT, and Pencil Beam \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Paper**} & \multirow{2}{*}{**Prescription Dose**} & \multirow{2}{*}{**Treatment Type**} & **EAR** & **LAR** & **age\({}_{\text{a}}\)** \\  & & & **(1/10,000 PY)** & **(1/10,000 P)** & **(Y)** \\ \hline [PERSON] et al. [35] & 50 Gy at 2 Gy/fraction & IMRT & / & 359–494 & 75 \\ [PERSON] et al. [35] & 42.56 Gy at 2.66 Gy/fraction & IMRT & / & 316–437 & 75 \\  & 50 Gy at & & 46 & 458 & \\ [PERSON] et al. [40] & 2 Gy/fraction or 50.4 Gy at & & (23–55) & (275–654) & 70 \\  & 1.8 Gy/fraction & & & (23–55) & (275–654) & \\  & 50 Gy at & & & & \\ [PERSON] et al. [40] & 2 Gy/fraction or 50.4 Gy at & VMAT & & 61 & 656 & \\  & 1.8 Gy/fraction & & (58–64) & (410–770) & 70 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Excess Absolute Risk (EAR) and Lifetime Attributable Risk (LAR) values for lung carcinogenesis risk after RT treatment [35; 40]. Scanning (PBS).