## 4 Discussion  
The comparative analysis between high-dose-rate (HDR) interventional radiotherapy (IRT) using \({}^{192}\)Ir and Volumetric Modulated Arc Therapy (VMAT) and electron beams in this retrospective study revealed significant insights into dose distribution and coverage efficiency in non-melanoma skin cancer (NMSC) treatments. There are no major differences in the side effects that have been observed when comparing IRT to EBRT [8], making IRT a valid alternative to surgery for managing NMSC [9]. On the other hand, IRT's reliance on image guidance and intensity modulation could offer significant advantages [10], which has sparked renewed clinical interest [11]. Despite this potential, dosimetric comparisons for NMSC are less robust. For instance, IRT has been shown to provide better target coverage than electron beam therapy in a series of 10 patients with head-and-neck NMSC [12]. Comparisons between IRT and Volumetric Modulated Arc Therapy (VMAT) are limited to a small series. In a study of 7 patients, it was noted that for extensive lesions, both approaches are feasible, but VMAT delivers lower doses to OARs [13]. Another study involving 14 patients found that VMAT provides equal target coverage with lower doses to OARs [14]. However, this advantage of VMAT over IRT decreases for smaller targets [15]. Hypofractionation, which is particularly beneficial for elderly and frail patients, could be employed for treating smaller volumes [16]. Both external beam therapy and IRT typically yield very satisfactory results for skin NMSC [17]. Traditionally, the maximum thickness of lesions that could be treated was considered to be 5 mm, but recent advances in clinical practice using intensity-modulated techniques in IRT now allow for the treatment of tumors thicker than 5 mm [18]. Another important consideration is IRT's capability to treat curved surfaces by modulating dose distribution [19]. Since the dose to OARs is a critical factor in comparing dosimetric outcomes, it is essential to carefully consider this aspect [20]. When delivering IRT treatments to skin targets near sensitive OARs, such as in the case of eyell lesions, it is important to note that both target coverage and the dose to the eye can be significantly affected by the use of a bolus [21]. Our comparative analysis between high-dose-rate (HDR) interventional radiotherapy (IRT) using \({}^{192}\)Ir and Volumetric Modulated Arc Therapy (VMAT) and electron beams in this retrospective study revealed significant insights into dose distribution and coverage efficiency in non-melanoma skin cancer (NMSC) treatments. The dosimetric analysis, particularly through a graph illustrating the comparison among IRT, VMAT, and electron beam therapy, indicated a superior clinical target volume (CTV) coverage by IRT. The analysis highlighted that IRT delivers a significantly higher mean dose compared to other techniques, emphasizing its capability to provide a more intense and focused treatment to the targeted lesion. This aspect is particularly advantageous in treating complex cases where precision is paramount. Additionally, the consistency in minimum dose levels between IRT and VMAT across the treatment plans, as observed in the figures, suggests that both techniques are capable of reaching the prescribed threshold dose. However, the mean dose remains higher with IRT, further supporting its efficacy in delivering concentrated therapy to targeted lesions without escalation to surrounding areas. Electron-based therapies, on the other hand, were found to be infeasible for patients with significantly large CTVs. The extensive volume requiring irradiation in such cases makes electron therapy impractical, thereby validating the adaptability and superiority of IRT in handling complex and extensive cases effectively. Moreover, even when electron therapy is feasible, the quality of the plan is generally inferior to that of IRT and VMAT, as evidenced by the lower V\({}_{95\%}\)CTV values and the less consistent dose distribution.