Optimization of Craniospinal Irradiation for Pediatric Medulloblastoma Using VMAT and IMRT.

PURPOSE: Intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) provide highly conformal target radiation doses, but also expose large volumes of healthy tissue to low-dose radiation. With improving survival, more children with medulloblastoma (MB) are at risk of late adverse effects of radiotherapy, including secondary cancers. We evaluated the characteristics of IMRT and VMAT craniospinal irradiation treatment plans in children with standard-risk MB to compare radiation dose delivery to target organs and organs at risk (OAR). PATIENTS AND METHODS: Each of 10 children with standard-risk MB underwent both IMRT and VMAT treatment planning. Dose calculations used inverse planning optimization with a craniospinal dose of 23.4 Gy followed by a posterior fossa boost to 55.8 Gy. Clinical and planning target volumes were demarcated on axial computed tomography images. Dose distributions to target organs and OAR for each planning technique were measured and compared with published dose-volume toxicity data for pediatric patients. RESULTS: All patients completed treatment planning for both techniques. Analyses and comparisons of dose distributions and dose-volume histograms for the planned target volumes, and dose delivery to the OAR for each technique demonstrated the following: (1) VMAT had a modest, but significantly better, planning target volume-dose coverage and homogeneity compared with IMRT; (2) there were different OAR dose-sparing profiles for IMRT versus VMAT; and (3) neither IMRT nor VMAT demonstrated dose reductions to the published pediatric dose limits for the eyes, the lens, the cochlea, the pituitary, and the brain. CONCLUSIONS: The use of both IMRT and VMAT provides good target tissue coverage and sparing of the adjacent tissue for MB. Both techniques resulted in OAR dose delivery within published pediatric dose guidelines, except those mentioned above. Pediatric patients with standard-risk MB remain at risk for late endocrinologic, sensory (auditory and visual), and brain functional impairments.

Knowledge- and Experience-Based Perceptions of Radiation Therapists during the COVID-19 Outbreak.

Objective: To assess the perceived risks and impact of the COVID-19 outbreak on radiation therapists in Saudi Arabia. Methods: A questionnaire was distributed to all radiation therapists in the country. The questionnaire contained questions about demographic characteristics, the extent of the pandemic's impact on hospital resources, risk perception, work-life, leadership, and immediate supervision. The questionnaire's reliability was assessed using Cronbach's alpha; >0.7 was considered adequate. Results: Out of the 127 registered radiation therapists, 77 (60.6%) responded; 49 (63.6%) females; and 28 (36.4%) males. The mean age was 36.8 ± 12.5 years. Nine (12%) of the participants had a past experience with pandemics or epidemics. Further, 46 (59.7%) respondents correctly identified the mode of transmission of COVID-19. Approximately, 69% of the respondents perceived COVID-19 as more than a minor risk to their families and 63% to themselves. COVID-19 had an overall negative impact on work at the personal and organizational levels. However, there was a positive attitude toward organizational management during the pandemic in general; positive responses ranged from 66.2% to 82.4%. Ninety-two percent considered protective resources and 70% considered the availability of supportive staff to be adequate. Demographic characteristics were not significantly associated with the perceived risk. Conclusions: Despite the high perception of risk and negative impact on their work, radiation therapists conveyed a positive overall perception regarding resource availability, supervision, and leadership. Efforts should be made to improve their knowledge and appreciate their efforts.

Outcomes of Saudi Arabian Patients With Nasopharyngeal Cancer Treated With Primarily Neoadjuvant Chemotherapy Followed by Concurrent Chemoradiotherapy.

PURPOSE: Nasopharyngeal cancer (NPC) is the most common head and neck cancer in Saudi Arabia. This study reports the locoregional disease control and survival outcomes in patients with NPC treated in King Abdulaziz University Hospital. METHODS: Patients treated for NPC between June 2007 and October 2014 were retrospectively reviewed. Demographic information, clinicopathologic variables, and chemotherapy data were collected and analyzed. Cumulative survival and disease control rates were calculated by Kaplan-Meier product-limit actuarial method. RESULTS: Thirty-nine patients with NPC were reviewed. Thirty-five (90%) patients received definitive radiotherapy (RT) and four (10%) had palliative RT. Mean prescribed dose for definitive RT was 68 Gy (range, 60 to 70.2 Gy), delivered with mean doses per fraction of 1.9 Gy (range, 1.8 to 2.1 Gy). After a median follow-up of 15 months (range, 1 to 84 months), 22 (63%) patients who underwent definitive RT were disease free and 13 (37%) were still with disease. During this period, seven (18%) patients died of the disease; five (13%) of them received definitive RT. After 2 years' follow-up, the actuarial estimate rates were: 85.7% for local control, 91.4% for nodal control, and 85.7% for distant control. CONCLUSION: Our study showed a disease with clinical behavior similar to what has been observed in East and Southeast Asia. Further it explored the neoadjuvant chemotherapy approach in treating NPC with results that are comparable to literature. However, little is known about the molecular pathogenesis of this disease in this region, and further research integrating clinical and molecular biomarkers is required.

Single versus multichannel applicator in high-dose-rate vaginal brachytherapy optimized by inverse treatment planning.

PURPOSE: To retrospectively compare the potential dosimetric advantages of a multichannel vaginal applicator vs. a single channel one in intracavitary vaginal high-dose-rate (HDR) brachytherapy after hysterectomy, and evaluate the dosimetric advantage of fractional re-planning. MATERIAL AND METHODS: We randomly selected 12 patients with endometrial carcinoma, who received adjuvant vaginal cuff HDR brachytherapy using a multichannel applicator. For each brachytherapy fraction, two inverse treatment plans (for central channel and multichannel loadings) were performed and compared. The advantage of fractional re-planning was also investigated. RESULTS: Dose-volume-histogram (DVH) analysis showed limited, but statistically significant difference (p = 0.007) regarding clinical-target-volume dose coverage between single and multichannel approaches. For the organs-at-risk rectum and bladder, the use of multichannel applicator demonstrated a noticeable dose reduction, when compared to single channel, but statistically significant for rectum only (p = 0.0001). For D2cc of rectum, an average fractional dose of 6.1 ± 0.7 Gy resulted for single channel vs. 5.1 ± 0.6 Gy for multichannel. For D2cc of bladder, an average fractional dose of 5 ± 0.9 Gy occurred for single channel vs. 4.9 ± 0.8 Gy for multichannel. The dosimetric benefit of fractional re-planning was demonstrated: DVH analysis showed large, but not statistically significant differences between first fraction plan and fractional re-planning, due to large inter-fraction variations for rectum and bladder positioning and filling. CONCLUSIONS: Vaginal HDR brachytherapy using a multichannel vaginal applicator and inverse planning provides dosimetric advantages over single channel cylinder, by reducing the dose to organs at risk without compromising the target volume coverage, but at the expense of an increased vaginal mucosa dose. Due to large inter-fraction dose variations, we recommend individual fraction treatment plan optimization.