Personalized Radiation Attenuating Materials for Gastrointestinal Mucosal Protection.

Cancer patients undergoing therapeutic radiation routinely develop injury of the adjacent gastrointestinal (GI) tract mucosa due to treatment. To reduce radiation dose to critical GI structures including the rectum and oral mucosa, 3D-printed GI radioprotective devices composed of high-Z materials are generated from patient CT scans. In a radiation proctitis rat model, a significant reduction in crypt injury is demonstrated with the device compared to without (p < 0.0087). Optimal device placement for radiation attenuation is further confirmed in a swine model. Dosimetric modeling in oral cavity cancer patients demonstrates a 30% radiation dose reduction to the normal buccal mucosa and a 15.2% dose reduction in the rectum for prostate cancer patients with the radioprotectant material in place compared to without. Finally, it is found that the rectal radioprotectant device is more cost-effective compared to a hydrogel rectal spacer. Taken together, these data suggest that personalized radioprotectant devices may be used to reduce GI tissue injury in cancer patients undergoing therapeutic radiation.

Novel use of proton beam therapy for neoadjuvant treatment of radiation-associated squamous cell carcinoma of the esophagus.

Secondary esophageal cancers from prior thoracic radiation therapy are rare but challenging cases to deliver standard combined modality therapy as part of a curative approach. In patients with prior exposure to cardiopulmonary-toxic chemotherapy or radiotherapy, management requires meticulous multidisciplinary evaluation given the morbidity associated with surgery in the previously irradiated thorax and re-irradiation of the spinal cord, heart, and lungs. Oftentimes, suboptimal treatment regimens, either with compromised radiation coverage, attenuated chemotherapy doses, or exclusion of surgery, are required to avoid significant toxicity. The physical properties inherent to protons allow for optimal coverage of tumor while achieving remarkably low dose to surrounding normal tissue compared to standard photon treatment. Proton therapy has been studied across various disease sites and may facilitate treatment intensification for radiation-associated esophageal tumors. While no comparative studies have evaluated the efficacy and safety of protons versus photons for esophageal cancer, three cases of radiation-associated esophageal cancer presented in this series are exemplary to highlight the benefit of protons in this unique clinical circumstance. The technical considerations in planning, including passively scattered versus pencil-beam scanning technique, as well as the clinical course and tolerance to treatment, are discussed, which may guide consideration of this advanced treatment modality in this disease site.

Evaluation of radiation-induced cardiac toxicity in breast cancer patients treated with Trastuzumab-based chemotherapy.

PURPOSE: Patients with Her2-positive breast cancer treated with trastuzumab have higher rates of cardiotoxicity (CT). Left-breast radiation might increase the risk for CT from cardiac exposure to radiation. The goal of our study is to evaluate the contribution of radiotherapy (RT) in the development of CT in breast cancer patients receiving trastuzumab. METHODS: Two hundred and two patients were treated with RT and trastuzumab from 2000 to 2014. The RT plans for left-side disease were recalled from archives. The heart, each chamber, and left anterior descending artery (LAD) were independently contoured. New dose-volume histograms (DVH) were generated. Their serial left-ventricular ejection fractions (LVEF) were studied. CT for left and right side were compared using Fisher's exact test. The DVH data were correlated with the predefined cardiac events using actuarial Cox regression analysis. RESULTS: Compared to the right sided, the left-side cases showed statistically significant development of arrhythmia (14.2%) versus (< 1%) (p < 0.001). Cardiac ischemia was found in 10 patients in left and one patient in right side (p = 0.011). The equivalent uniform dose (EUD) to the left ventricle (LV), right ventricle (RV), and LAD was significantly associated with decrease in LVEF by > 10% (p = 0.037, p = 0.023 and p = 0.049, respectively). CONCLUSIONS: Among patients treated for left-sided lesions, there were no significant differences in EF decline. However, there was a higher rate of ischemia and arrhythmia compared to those with right-sided disease. The EUD index of LV, RV, and LAD could be considered as a parameter to describe the risk of radiation-induced CT.

A dosimetric comparison of proton and intensity modulated radiation therapy in pediatric rhabdomyosarcoma patients enrolled on a prospective phase II proton study.

BACKGROUND: Pediatric rhabdomyosarcoma (RMS) is highly curable, however, cure may come with significant radiation related toxicity in developing tissues. Proton therapy (PT) can spare excess dose to normal structures, potentially reducing the incidence of adverse effects. METHODS: Between 2005 and 2012, 54 patients were enrolled on a prospective multi-institutional phase II trial using PT in pediatric RMS. As part of the protocol, intensity modulated radiation therapy (IMRT) plans were generated for comparison with clinical PT plans. RESULTS: Target coverage was comparable between PT and IMRT plans with a mean CTV V95 of 100% for both modalities (p=0.82). However, mean integral dose was 1.8 times higher for IMRT (range 1.0-4.9). By site, mean integral dose for IMRT was 1.8 times higher for H&N (p<0.01) and GU (p=0.02), 2.0 times higher for trunk/extremity (p<0.01), and 3.5 times higher for orbit (p<0.01) compared to PT. Significant sparing was seen with PT in 26 of 30 critical structures assessed for orbital, head and neck, pelvic, and trunk/extremity patients. CONCLUSIONS: Proton radiation lowers integral dose and improves normal tissue sparing when compared to IMRT for pediatric RMS. Correlation with clinical outcomes is necessary once mature long-term toxicity data are available.