A Practical Workflow for Magnetic Resonance-Guided Stereotactic Body Radiation Therapy to the Pancreas.

The increased adoption of stereotactic body radiation therapy has allowed for delivery of higher doses, potentially associated with better outcomes but at the risk of higher toxicity. The intimate association of radiosensitive organs at risk (eg, stomach, duodenum, bowel) has historically limited the delivery of ablative doses to the pancreas. The advent of magnetic resonance-guided radiation therapy with improved soft-tissue contrast allows for gated delivery without an internal target volume and online adaptive replanning to maximize the therapeutic ratio. Patient selection requires additional resources, including increased patient on-table time, physician time, and physics support. Within our center's workflow, integrating an educational video at consultation as well as optimizing biofeedback mechanisms have significantly improved the experience for our patients.

Impact of sarcopenia on outcomes of locally advanced esophageal cancer patients treated with neoadjuvant chemoradiation followed by surgery.

BACKGROUND: Sarcopenia is an independent predictor of clinical outcomes in multiple gastrointestinal cancers. Total psoas area (TPA), as measured on a single cross-sectional CT image at the L4 vertebral body level, has been correlated with sarcopenia. We sought to evaluate whether TPA was predictive of acute grade ≥3 toxicity, pathologic response, and overall survival in patients with locally advanced esophageal cancer receiving tri-modality therapy. METHODS: An institutional database of esophageal cancer patients treated with neoadjuvant chemoradiation followed by surgery was queried. Of 77 patients treated from 2008 to 2012 with intensity modulated radiation therapy (IMRT) and image guided radiation therapy (IGRT), 56 patients were eligible based on having CT imaging that included the L4 vertebral body. The L4 vertebra was identified on axial CT and the psoas muscle was manually contoured bilaterally to determine the skeletal muscle index. Sarcopenia was defined by the presence of the psoas area less than the median of the cohort. Acute toxicity was defined as within 3 months of radiotherapy based on Common Terminology Criteria for Adverse Events. ROC curve, logistic regression, and Kaplan Meier estimates were used when appropriate. RESULTS: Sarcopenia was associated with increased acute grade ≥3 toxicity from chemoradiation by ROC analysis using a cut off of 841.5 mm2/m2 (P=0.003, AUC 0.709, sensitivity 60.9%, specificity 78.8%) and logistic regression (P=0.002). Patients with TPA <841.5 mm2/m2 were 5.78 times more likely to develop grade 3 or higher toxicity (P=0.004). Sarcopenia did not predict a difference in overall survival (P=0.217) and was not significant for pathologic complete response or favorable pathologic response (TRG 0/1). CONCLUSIONS: In our cohort of patients, sarcopenia was associated with a significant increase in acute grade ≥3 toxicity with chemoradiation, suggesting a potential role for neoadjuvant patient selection strategies. There was no difference in pathologic response or overall survival.

Re-planning for compensator-based IMRT with original compensators.

Compared with multileaf collimator (MLC)-based intensity-modulated radiotherapy (IMRT) for moving targets, compensator-based IMRT has advantages such as shorter beam-on time, fewer monitor units with potentially decreased secondary carcinogenesis risk, better optimization-to-deliverable dose conversion, and often better dose conformity. Some of the disadvantages include additional time for the compensators to be built and delivered, as well as extra cost. Patients undergoing treatment of abdominal cancers often experience weight loss. It would be necessary to account for this change in weight with a new plan and a second set of compensators. However, this would result in treatment delays and added costs. We have developed a method to re-plan the patient using the same set of compensators. Because the weight changes seen with the treatment of abdominal cancers are usually relatively small, a new 4D computed tomography (CT) acquired in the treatment position with markers on the original isocenter tattoos can be registered to the original planning scan. The contours of target volumes from the original scans are copied to the new scan after fusion. The original compensator set can be used together with a few field-in-field (FiF) beams defined by the MLC (or beams with cerrobend blocks for accelerators not equipped with a MLC). The weights of the beams with compensators are reduced so that the FiF or blocked beams can be optimized to mirror the original plan and dose distribution. Seven abdominal cancer cases are presented using this technique. The new plan on the new planning CT images usually has the same dosimetric quality as the original. The target coverage and dose uniformity are improved compared with the plan without FiF/block modification. Techniques combining additional FiF or blocked beams with the original compensators optimize the treatment plans when patients lose weight and save time and cost compared with generating plans with a new set of compensators.