PurposeThis study aimed to develop prediction models for severe oral mucositis (OM) (grade ≥ 3) from head and neck cancer (HNC) radiotherapy (RT) using machine learning (ML) techniques and different types of features, including clinical, dose-volume metric, and radiomic features.Materials and MethodsRetrospective data of 148 HNC RT patients were collected and randomly divided into 80% training and 20% test datasets. Sixteen combinations of feature selection and classification algorithms were used for modeling with different combinations of feature types. The model performance was evaluated using a confusion matrix and the area under the receiver operating characteristic curve (AUROC). The difference in the error rates obtained from any pair of modeling approaches were evaluated with McNemar’s test.ResultsThe best-performing model was based on the random forest classifier and minimum redundancy maximum relevance feature selection algorithm, achieving the accuracy of 0.930 (95% confidence interval [CI], 0.926 to 0.933) and AUROC of 0.901 (95% CI, 0.897 to 0.905). For this model, D45% of the oral cavity, subsite, V75Gy of the parotid glands and total dose to the target were found to be the most important features. All modeling approaches achieved the accuracy and AUROC of at least 0.756 and 0.722 and the error rates obtained by all modeling approaches were insignificantly different.ConclusionThe inclusion of clinical and dose-volumetric features were most promising for ML-based prediction of severe OM, although information obtained prior to dose calculation (clinical or radiomic) may also be used exclusively with insignificantly different error rates.

PurposeLymphocytopenia is a known side effect of radiation exposure to the bone marrow. However, the hematological impact of irradiating the bowel bag—a highly vascularized region containing numerous mesenteric lymph nodes—remains poorly understood. This study aimed to examine whether radiation to the bowel bag leads to a decrease in absolute lymphocyte count (ALC) during pelvic radiotherapy.Materials and MethodsWe retrospectively analyzed 168 patients with prostate, bladder, gynecologic, and gastrointestinal cancers who received whole pelvic radiotherapy (45–60 Gy) without concurrent chemotherapy between October 2016 and November 2022. Dose-volume parameters (V5, V10, V15, V20, and V30) representing the percentage of bowel bag volume receiving ≥x Gy were calculated. The primary endpoint was grade 3 lymphocytopenia (ALC 200–500/μL) measured at 3 weeks post-treatment initiation. Logistic regression analysis evaluated associations between bowel bag dosimetric parameters and severe lymphocytopenia.ResultsThe overall lymphocytopenia rate was 92.3%, with 23.8% developing grade 3 toxicity. Logistic regression analysis demonstrated that higher radiation doses to the bowel bag at V5, V10, and V15 significantly increased the risk of grade 3 lymphocytopenia (odds ratios, 3.0 to 5.9, all p < 0.01).ConclusionRadiation dose to the bowel bag independently predicts severe lymphocytopenia during pelvic radiotherapy. These findings suggest that dose constraints to the bowel bag should be considered alongside bone marrow sparing techniques to preserve hematopoietic function. Prospective validation and development of bowel bag dose-volume guidelines are warranted.

PurposeThis study investigates patterns of postmastectomy radiation therapy (PMRT) use in patients with pT1–2N1 breast cancer treated with mastectomy in Korea over 2 decades.Materials and MethodsData from 700 patients treated at 16 institutions across three decades (1990, 2000, and 2010) were retrospectively reviewed.ResultsOverall, 10.0% of patients received PMRT, with utilization rates of 7.4%, 8.8%, and 11.1% in 1990, 2000, and 2010, respectively. The use of PMRT varied substantially among the hospitals (0%–87.5%). The two-dimensional radiotherapy was used in 1990, but the adoption of tangential beam three-dimensional conformal radiotherapy increased in subsequent decades. Axillary irradiation was performed in all patients in 1990 but was omitted in some cases starting in the 2000s (performed in 72.7% of cases in 2000, 84.1% in 2010). The inclusion of axillary levels, internal mammary nodes, and supraclavicular nodes decreased over time. The 10-year overall survival (OS) and recurrence-free survival (RFS) rates for all patients were 81.3% and 76.3%, respectively. Locoregional recurrence rates were significantly lower in the PMRT group (1.4%) compared to the no-PMRT group (8.1%, p=0.043). However, no significant differences were observed in 10-year OS, RFS, or distant metastasis–free survival rates between the two groups.ConclusionPMRT was performed in approximately 10% of patients with pT1–2N1 breast cancer after mastectomy, with minimal changes in utilization rates over two decades. The use and extent of regional nodal irradiation has declined over time. Further research is needed to reflect the latest patterns of practice.

Ornithine transcarbamylase (OTC) deficiency is a rare urea cycle disorder that impairs ammonia detoxification, increasing the risk of hyperammonemic crises under metabolic stress. While chemotherapy-related risks have been reported, data on the safety of ionizing radiation therapy (RT) in this population are limited. This case describes a 30-year-old woman with late-onset OTC deficiency diagnosed with right-sided ductal carcinoma in situ. She underwent segmental mastectomy followed by adjuvant 3D conformal RT (40 Gy in 15 fractions with a concomitant boost to 48 Gy). Her multidisciplinary care involved preoperative hydration, close nutritional monitoring, and serial ammonia measurements. She completed RT without treatment interruptions or signs of hyperammonemia. This case illustrates that breast RT can be delivered safely in patients with OTC deficiency with a multidisciplinary, preventative approach. To our knowledge, this is the first report describing RT planning and metabolic surveillance in this population.

PurposePalliative thoracic radiotherapy plays a crucial role in the management of patients with non–small cell lung cancer (NSCLC). Conventional dose-fractionation schemes often yield modest and short-lived tumor responses. This study aims to evaluate the efficacy and safety of a high-dose hypofractionated radiotherapy regimen of 40 Gy in 10 daily fractions in NSCLC. Materials and MethodsConsecutive NSCLC patients who underwent palliative thoracic radiotherapy using the 40 Gy in 10 daily fractions regimen between January 2017 and December 2022 were identified from institutional databases of two tertiary oncology centers. Treatment responses were assessed using the Response Evaluation Criteria in Solid Tumor criteria. Local tumor control rate was estimated using cumulative incidence function, considering death as a competing event. The rates of radiation pneumonitis and esophagitis were assessed.ResultsSixty-two eligible patients were included. Median age was 72.6 years, with 52 patients (83.4%) having Eastern Cooperative Oncology Group performance status of ≥2. Radiotherapy was given to 33 patients (53.2%) with locally advanced primary NSCLC and 29 patients (47.8%) with oligopersistent or oligoprogressive NSCLC. Fifty-three tumors (85.4%) were considered unsuitable for stereotactic radiotherapy by location or size. With a median follow-up of 4.1 years, the overall response rate was 69.3%. Local control rates at 1 and 3 years were 96.7% and 76.9%, respectively. Grade 1–2 radiation pneumonitis and esophagitis occurred in 46.7% and 8.1% of patients. One case of grade 3 esophagitis was observed. ConclusionThe 40 Gy in 10 daily fractions regimen demonstrates high local tumor control rate and a favorable safety profile, representing an effective and safe palliative option for NSCLC patients.

PurposeThis study aims to figure out prognostic factors affecting treatment outcomes for early-stage endometrial cancer patients undergoing adjuvant vaginal brachytherapy (VBT) and to develop a histopathological risk stratification model.Materials and MethodsWe retrospectively reviewed International Federation of Gynecology and Obstetrics stage I endometrioid endometrial cancer patients who underwent primary surgery followed by VBT from January 2010 to December 2022. The high dose rate VBT was prescribed in either 30 Gy in 6 fractions or 21 Gy in 3 fractions. In order to identify significant factors influencing locoregional recurrence-free survival (LRRFS), disease-free survival (DFS), and overall survival (OS). Patients were stratified into risk groups according to the identified prognostic factors.ResultsA total of 217 patients were reviewed with a median follow-up of 58.4 months. The recurrences were observed in 21 cases (9.7%). Distant metastasis accounted for most of the failure pattern (18/21 patients, 85.7%). The 5-year LRRFS, DFS, and OS rates were 94.5%, 91.2%, and 98.7%, respectively. Multivariate analysis revealed three statistically significant prognostic factors for DFS: high grade (hazard ratio [HR], 6.12; p = 0.010), tumor size ≥4 cm (HR, 6.48; p = 0.001), and depth of myometrial invasion ≥50% (HR, 4.97; p = 0.027). Risk stratification based on these factors demonstrated significant differences in DFS only between intermediate and high-risk groups (p = 0.002).ConclusionOur histopathological risk stratification model could successfully differentiate the high-risk group from others in early-stage endometrial cancer patients. This model provides crucial prognostic information and could be helpful, especially in resource-limited settings where molecular classification might not be readily available.

PurposeThis study aimed to investigate treatment outcomes in patients with intermediate- and high-risk meningioma who underwent radiotherapy (RT) and identify prognostic factors for progression-free survival (PFS). In addition, failure patterns after RT were analyzed.Materials and MethodsWe retrospectively reviewed 61 patients with intermediate- and high-risk meningiomas, categorized according to the NRG Oncology/Radiation Therapy Oncology Group 0539 trial, who underwent surgery followed by adjuvant or salvage RT.ResultsWe included 12 and 49 patients with intermediate- and high-risk meningiomas, respectively. A total of 26 cases of tumor progression and 17 deaths after RT were identified. The 5-year PFS and overall survival of the entire cohort were 55.8% and 74.2%; intermediate-risk group, 80.2% and 100%; high-risk group, 48.7% and 67.1%, respectively. The World Health Organization (WHO) grade 3 (hazard ratio [HR], 16.7; 95% confidence interval [CI], 3.0 to 92.3; p = 0.001) and recurrent tumor (HR, 41.2; 95% CI, 3.6 to 473.6; p = 0.003) were identified as adverse prognostic factors for PFS in high-risk patients. Among the 15 patients who had recurrence after conventional fractionated radiotherapy (CFRT), 13 experienced local failure (LF) and two experienced distant failure.ConclusionRT with adjuvant or salvage intent showed favorable treatment outcomes in patients with intermediate- to high-risk meningioma. WHO grade 3 histology and recurrent tumors were identified as adverse prognostic factors for PFS in high-risk patients. LF was the dominant failure pattern after CFRT, accounting for 86.7% of all recurrences. These findings underscore the need for further studies on dose-escalated RT to enhance local control in patients with these adverse features.

PurposeThis study aimed to compare treatment outcomes between patients who received adjuvant radiotherapy (RT) and those who did not, in a cohort of patients with low-risk, early-stage breast cancer.Materials and MethodsPostmenopausal women with pT1N0/Nx, grade 1–2, hormone receptor-positive, human epidermal growth factor 2–negative, and Ki-67 ≤ 20% breast cancer who underwent breast-conserving surgery and adjuvant endocrine therapy between 2010 and 2020 were included. The decision on RT omission was based on physician assessment and patient preference. The primary outcome was cumulative incidence of disease recurrence. Secondary outcomes included locoregional recurrence, overall survival, and breast cancer-specific survival.ResultsOf the 742 patients, 707 received adjuvant RT (postoperative radiation therapy [PORT] group) and 35 did not (RT omission group). Baseline characteristics were generally similar; however, the RT omission group was older (median age, 76 years; range, 68 to 85 years) than the PORT group (median age, 62 years; range, 55 to 87 years). After a median follow-up of 60 months in the PORT group and 52 months in the RT omission group, the 5-year cumulative incidence of disease recurrence was 1.28% and 0%, respectively (Gray’s test, p = 0.305). Locoregional recurrence occurred in seven patients (1.0%) in the PORT group, whereas no locoregional recurrences were observed in the RT omission group. The results remained consistent after propensity score matching.ConclusionLow-risk, early-stage breast cancer patients exhibited comparable disease recurrence and survival rates regardless of the RT status. Our study underscores the necessity for further investigation into RT omission in carefully selected patients.

PurposeThis study aimed to investigate retrospectively the feasibility of reducing the standard postoperative radiation therapy (PORT) dose of 45–50 Gy for locally invasive thymoma to shorten treatment duration and minimize side effects, while preserving disease-specific survival (DSS) and progression-free survival (PFS).Materials and MethodsBetween January 2016 and June 2022, 150 locally advanced thymoma patients underwent surgery followed by intensity-modulated radiation therapy, with a median follow-up of 40.8 months; the standard regimen was 45–50 Gy in 25 fractions (median biological effective dose [BED] 60 Gy), compared to a de-escalation regimen of 30–35 Gy in 10 fractions (median BED 47.25 Gy), with PFS as the primary endpoint, and overall survival (OS), DSS, and toxicity as secondary endpoints.ResultsNo significant differences were found between standard and de-escalation groups in 3-year PFS (p = 0.406), with both groups achieving 100% 3-year DSS; two deaths in the de-escalation group were due to double primary cancers. All locoregional recurrences occurred outside the radiation field. Factors including age, initial tumor size, myasthenia gravis, and pathological type showed no correlation with PFS or OS. No grade II toxicities occurred in the de-escalation group, whereas the standard group had three cases of grade II toxicity, specifically radiation pneumonitis.ConclusionRadiation dose de-escalation in locally advanced thymoma patients undergoing PORT showed comparable survival outcomes with reduced toxicity and shorter treatment duration, but requires longer follow-up to confirm efficacy and safety.