Radiation Protection Dosimetry

Differential cardiovascular outcomes of radiotherapy in rectal, breast, and cervical cancer: insights from a SEER data analysis

Abstract Recent years have witnessed an increase in mortality and morbidity from chronic diseases unrelated to tumors in patients with malignant tumors. While radiation therapy reduces local tumor recurrence, it may elevate late mortality from cardiovascular diseases (CVD). The relationship between radiotherapy for cancer and CVD risk remains debated. This study analyzed the surveillance, epidemiology, and end results (SEER) Database from 1975 to 2014, focusing on long-term CVD observation periods of 1, 5, and 10 y. We tracked patients from cancer diagnosis to death or last follow-up, calculating hazard ratios (HRs) and 95% confidence intervals (CIs) for cardiovascular-specific survival (CVSS) using Fine-Gray binary competing risk regression analysis. Our analysis included 303 665 patients diagnosed with rectal (18 398), breast (276 263), and cervical (8004) cancers. Among these, 7098 (2.34%) died from CVDs. Rectal cancer patients undergoing radiotherapy, mainly in later stages, showed a reduced risk of CVD mortality (HR = 0.72, 95% CI: 0.61–0.84). Breast cancer patients treated with radiotherapy, who generally had smaller tumors, experienced significantly lower cardiovascular mortality (HR = 0.48, 95% CI: 0.46–0.51). Conversely, cervical cancer patients receiving radiotherapy had a higher rate of CVD mortality (HR = 2.14, 95% CI: 1.30–3.52). The AUC values for 3-y CVSS were 0.788, 0.837, and 0.821 for rectal, breast, and cervical cancers, respectively, indicating good predictive accuracy. The impact of tumor radiotherapy on CVD outcomes appears cancer-type specific, with cervical cancer radiotherapy increasing the risk of cardiovascular morbidity and mortality.

Dosimetric comparison of O-ring versus conventional C-arm linear accelerator for volumetric modulated arc therapy (VMAT) of head and neck cancer and carcinoma cervix patients

Abstract The objective of this study is dosimetric comparison between the O-ring Halcyon and C-arm Clinac iX linac for volumetric modulated arc therapy (VMAT) plans for head & neck (H&N) cancer and carcinoma cervix patients. Total 60 patients of H&N cancer and carcinoma cervix were enrolled prospectively from March 2021 to March 2023. VMAT plans with 6 MV photons for Halcyon and Clinac iX were generated and compared for each patient by dose volume histogram for planning target volume coverage and organ at risk (OAR) sparing. There were no differences in between both the linacs for PTV D2% and D98%, homogeneity index, conformity index, Dmax (maximum dose) and Dmean (mean dose) of OAR. Halcyon had significantly shorter treatment time compared to Clinac iX. Halcyon delivered higher integral dose and monitor units. O-ring Halcyon produces VMAT plans comparable to other C-arm linacs for H&N and carcinoma cervix patients.

Dosimetric impact of bladder volume on organs at risk during external beam radiotherapy of cervical cancer

Abstract This study aimed to investigate the effect of bladder volume on the dosimetry of pelvic organs at risk (OARs) in patients treated with external beam radiation therapy. Twenty patients with locally advanced cervical cancer were selected. Two computed tomography-simulation scans were obtained, one with an empty bladder followed by one with a full bladder. The acquired images were transferred to the treatment planning system. Target and OARs were contoured in both images, and treatment plans were performed for each computed tomography image. The delivered doses to target and OARs were determined using dose–volume histograms. The mean dose of the bowel bag in the empty and full bladder were 35.06 ± 4.13 (Gy) and 31.59 ± 3.86 (Gy), respectively. Furthermore, the V45 of the bowel bag in the empty bladder was 364.27 ± 154.39 (cc) and in the full bladder, it was 240.84 ± 129.66 (cc). The mean dose of the rectum in the empty and full bladder were 49.50 ± 1.95 (Gy) and 49.18 ± 1.03 (Gy), respectively. The rectal V50 (%) was 52.82 ± 21.84 (%) in the empty bladder and 45.49 ± 29.55 (%) in the full bladder. The mean dose and V45 of the bowel bag, also V50 of the rectum, had significantly decreased in the full bladder status (p-value < 0.05). The results showed that the bladder volume significantly affected the delivered dose to the bowel bag and rectum. The average bowel bag V45 and rectum V50 in the full bladder were significantly decreased. Bladder distention is an effective method to improve the dosimetric parameters of pelvic OARs.