## 3 Results
### Genitourinary Toxicity  
The occurrence of GU toxicities during RT for pelvic region cancers has an impact on both patient tolerance to treatment and accuracy of dose delivery. On the one hand, urinary symptoms impact patients' QoL, restricting their ability to perform daily activities [89]. On the other hand, RT-induced incontinence complicates the maintenance of adequate bladder filling during treatment, resulting in the need for re-optimization for adequate target coverage [131]. In response to these challenges, multiple studies have focused on establishing validated dosimetric constraints to predict the onset of GU toxicity in PCa RT. A retrospective study from the University Medical center of Seoul in 2014 analyzed acute and late toxicities in 70 patients with localized PCa treated with hypoffractionated helical tomotherapy [115]. RT protocol included doses of 75 Gray (Gy) in 2.5 Gy per fraction to the prostate gland, 63 Gy in 2.1 Gy per fraction to the seminal vesicles, and 54 Gy in 1.8 Gy per fraction to the pelvic lymph nodes. The findings revealed that acute gastrointestinal (GI) toxicity occurred in 51.4% of patients at grade 0, 42.9% at grade 1, and 5.7% at grade 2, while acute genitourinary (GU) toxicity was noted in 7.1% at grade 0, 64.3% at grade 1, and 28.6% at grade 2. Significant predictive factors for severe toxicities included maximum rectal dose and bladder V40 and V50. The analysis showed a significant correlation between bladder toxicity onset and values of bladder V40 \(>\) 17.3% and V50 \(>\) 10.2%, where Vx is the volume of tissue receiving at least x Gy. The results from [PERSON] et al. [115] were similar to the outcomes reported in the study by [PERSON] et al. (2021) [126]. The authors analyzed a cohort of 175 patients and found a significant correlation between bladder G \(\geq\) 2 late toxicity and a bladder Vdose of 51 Gy. [PERSON] et al. (2014) conducted a prospective study to investigate the occurrence of acute bladder toxicity following pelvic RT and identified potential dosimetric predictors [116]. Acute bladder toxicity was assessed weekly using the Common Terminology Criteria for Adverse Events (CTCAE version 4.0). The reported symptoms were also rated according to the International Prostate Symptom Score (IPSS) and the Operactive Bladder Symptom Score (OABSS) to provide a comparative analysis of different toxicity metrics. The study involved the delineation of the bladder wall, solid bladder, and trigone on CT scan planes, followed by analysis of dose-volume histograms to identify the most reliable predictors. A total of 92 patients were included in the analysis, and 27 patients (29%) showed CTCAE G2 acute bladder toxicity, with notcuria as the most prevalent symptom. V20 for both the bladder wall and the whole bladder had a higher predictive value for bladder toxicity. The IPSS was found to be more aligned with CTCAE than OABSS for toxicity reporting [116]. A prospective trial conducted by [PERSON] et al. (2015) developed an alternative predictive tool for bladder toxicity [118]. The bladder dose-surface histograms (DSHw) were weekly reported as dosimetric descriptors in 262 PCa patients treated with RT (120 conventional fractionation, 142 hypofraction). The authors found that GU toxicity in terms of increased risk of frequency, intermittency, urgency, and notcuria was significantly associated with DSHw values. DSH is an RT evaluation tool that quantifies the distribution of radiation dose across the surface of the bladder. Unlike traditional dose-volume histograms (DVH), which assess the dose delivered to the entire volume of an organ, the DSH specifically focuses on the dose distribution along the organ's surface. [PERSON] et al. (2016) retrospectively analyzed the relationship between GU toxicity and clinical dosimetric parameters in 86 PCa patients treated with conformal RT [120]. They found a strong association between high doses (>77 Gy) in the bladder and late GU toxicity. Similar results were reported in a study by [PERSON] et al.