Dosimetric predictors of acute and late gastrointestinal toxicities in stereotactic online adaptive magnetic resonance-guided radiotherapy (SMART) for locally advanced pancreatic adenocarcinoma.

BACKGROUND AND PURPOSE: A retrospective evaluation of dosimetric predictors and leveraged dose-volume data for gastrointestinal (GI) toxicities for locally-advanced pancreatic cancer (LAPC) treated with daily stereotactic MRI-guided online-adaptive radiotherapy (SMART). MATERIALS AND METHODS: 147 patients with LAPC were treated with SMART at our institution between 2018 and 2021. Patients were evaluated using CTCAE V5.0 for RT-related acute (≤3 months) and late (>3 months) toxicities. Each organ at risk (OAR) was matched to a ≥ grade 2 (Gr2+) toxicity endpoint composite group. A least absolute shrinkage selector operator regression model was constructed by dose-volumes per OAR to account for OAR multicollinearity. A receiver operator curve (ROC) analysis was performed for the combined averages of significant toxicity groups to identify critical volumes per dose levels. RESULTS: 18 of 147 patients experienced Gr2+ GI toxicity. 17 Gr2+ duodenal toxicities were seen; the most significant predictor was a V33Gy odds ratio (OR) of 1.69 per cc (95 % CI 1.14-2.88). 17 Gr2+ small bowel (SB) toxicities were seen; the most significant predictor was a V33Gy OR of 1.60 per cc (95 % CI 1.01-2.53). The AUC was 0.72 for duodenum and SB. The optimal duodenal cut-point was 1.00 cc (true positive (TP): 17.8 %; true negative (TN); 94.9 %). The SB cut-point was 1.75 cc (TP: 16.7 %; TN: 94.3 %). No stomach or large bowel dose toxicity predictors were identified. CONCLUSIONS: For LAPC treated with SMART, the dose-volume threshold of V33Gy for duodenum and SB was associated with Gr2+ toxicities. These metrics can be utilized to guide future dose-volume constraints for patients undergoing upper abdominal SBRT.

Ablative radiotherapy for colorectal liver metastases and intrahepatic cholangiocarcinoma.

The role of radiation therapy in the management of liver cancers, both primary and metastatic, has changed drastically over the past several decades. Although conventional radiation was limited by technology, the advent of advanced image-guided radiotherapy and the rise in evidence for and popularity of stereotactic body radiotherapy have expanded the indications for radiation in these two distinct disease types. Magnetic resonance imaging-guided radiation therapy, daily online adaptive radiotherapy, and proton radiotherapy are some of many modern radiotherapy techniques that allow for increasingly efficacious treatment of intrahepatic disease while simultaneously allowing for increased normal tissue sparing, including sparing of the normal liver and the radiosensitive luminal gastrointestinal tract. Modern radiation therapy should be considered along with approaches such as surgical resection and radiofrequency ablation for the management of liver cancers of diverse histologies. Herein we describe the use of modern radiotherapy in two example settings, colorectal liver metastases and intrahepatic cholangiocarcinoma, and how external beam radiotherapy provides options within multidisciplinary discussions to elect optimal patient-specific treatments.

Spine-specific skeletal related events and mortality in non-small cell lung cancer patients: a single-institution analysis.

OBJECTIVE: The population prevalence of non-small cell lung cancer (NSCLC) continues to increase; however, data are limited regarding the incidence rate of skeletal related events (SREs) (i.e., surgery to the spinal column, radiation to the spinal column, radiofrequency ablation, kyphoplasty/vertebroplasty, spinal cord compression, or pathological vertebral body fractures) and their impact on overall mortality. In this study, the authors sought to estimate the incidence rates of SREs in NSCLC patients and to quantify their impact on overall mortality. METHODS: This was a single-institution retrospective study of patients diagnosed with NSCLC between 2002 and 2014. The incidence rates for bone metastasis and subsequent SREs (per 1000 person-years) by time since lung cancer diagnosis were calculated and analyses were stratified separately for each histological type. Incidence rates for mortality at 1, 2, and 3 years from diagnosis stratified by the presence of SREs were also calculated. Kaplan-Meier survival curves were constructed to describe crude survival ratios in patients with spine metastasis and SREs and those with spine metastasis but without SREs. These curves were used to estimate the 1- and 2-year survival rates for each cohort. RESULTS: We identified 320 patients with incident NSCLC (median follow-up 9.5 months). The mean ± SD age was 60.65 ± 11.26 years; 94.48% of patients were smokers and 60.12% had a family history of cancer. The majority of first-time SREs were pathological vertebral body compression fractures (77.00%), followed by radiation (35%), surgery (14%), and spinal cord compression (13.04%). Mortality rates were highest in NSCLC patients with spine metastasis who had at least 1 SRE. Stratifying by histological subtype, the incidence rate of mortality in patients with SRE was highest in the large cell cohort, 7.42 per 1000 person-years (95% CI 3.09-17.84 per 1000 person-years); followed by the squamous cell cohort, 2.49 per 1000 person-years (95% CI 1.87-3.32 per 1000 person-years); and lowest in the adenocarcinoma cohort, 1.68 per 1000 person-years (95% CI 1.46-1.94 per 1000 person-years). Surgery for decompression of neural structures and stabilization of the spinal column was required in 6% of patients. CONCLUSIONS: SREs in NSCLC patients with bone metastasis are associated with an increased incidence rate of mortality.