Brain CT for Diagnosis of Intracranial Disease in Ambulatory Cancer Patients: Assessment of the Diagnostic Value of Scanning Without Contrast Prior to With Contrast.

Background and purpose: Brain imaging with MRI or CT is standard in screening for intracranial disease among ambulatory cancer patients. Although MRI offers greater sensitivity, CT is frequently employed due to its accessibility, affordability, and faster acquisition time. However, the necessity of routinely performing a non-contrast CT with the contrast-enhanced study is unknown. This study evaluates the clinical and economic utility of the non-contrast portion of the brain CT examination.

Materials and methods: A board-certified neuroradiologist reviewed 737 brain CT reports from outpatients at MD Anderson Cancer Center who underwent contrast and non-contrast CT for cancer staging (October 2014 to March 2016) to assess if significant findings were identified only on non-contrast CT. A GPT-3 model was then fine-tuned to extract reports with a high likelihood of unique and significant non-contrast findings from 1,980 additional brain CT reports (January 2017 to April 2022). These reports were manually reviewed by two neuroradiologists, with adjudication by a third reviewer if needed. The incremental cost-effectiveness ratio of non-contrast CT inclusion was then calculated based on Medicare reimbursement and the 95% confidence interval of the proportion of all reports in which non-contrast CT was necessary for identifying significant findings RESULTS: Seven of 737 reports in the initial dataset revealed significant findings unique to the non-contrast CT, all of which were hemorrhage. The GPT-3 model identified 145 additional reports with a high unique non-contrast CT finding likelihood for manual review from the second dataset of 1,980 reports. 19 of these reports were found to have unique and significant non-contrast CT findings. In total, 0.96% (95% CI: 0.63% -1.40%) of reports had significant findings identified only on non-contrast CT. The incremental cost-effectiveness ratio for identification of a single significant finding on non-contrast CT missed on the contrast-enhanced study was $1,855 to $4,122.

Conclusions: In brain CT for ambulatory screening for intracranial disease in cancer patients, non-contrast CT offers limited additional diagnostic value compared to contrast-enhanced CT alone. Considering the associated financial cost, workload, and patient radiation exposure associated with performing a non-contrast CT, contrast-enhanced brain CT alone is sufficient for cancer staging in asymptomatic cancer patients.

Abbreviations: GPT-3＝ Generative Pretrained Transformers 3.