The Tumor Fraction Estimated by Rapid On-Site Evaluation Is Useful for Assessing the Suitability of Biopsy Specimens for Multiplex Genetic Testing.

Introduction: Multiplex genetic testing (MGT) has become the mainstream method for genetic mutation testing in the field of lung cancer treatment, but the suitability criteria for MGT biopsy specimens are stringent. Although rapid on-site evaluation (ROSE) is considered a useful method for obtaining the suitable biopsy specimens for MGT, no direct comparisons of ROSE and MGT are available. In this study, we first evaluated the accuracy of MGT and ROSE in our hospital. Then, we explored the potential utility of the cytological findings of ROSE for indicating the adequacy of biopsy specimens for MGT.

Methods: These analyses were performed retrospectively using the data of 74 patients with lung cancer who underwent ROSE at our hospital in 2020-2022.

Results: Regarding the accuracy of MGT, the success rate was 97.9% and the frequency of epidermal growth factor receptor mutation in adenocarcinoma cases was 34.6%. The results of ROSE were then compared with histological diagnoses. The sensitivity and positive predictive value were 95.9% and 100.0%, respectively. To analyze the utility of the ROSE results for determining the adequacy of biopsy specimens for MGT, we determined the tumor fraction in the ROSE preparations (ROSE-T%) and the tumor fraction (B-T%)/tumor cell number (B-TN) in the biopsy specimens. When the threshold of the ROSE-T% was set at 80%, there were statistically significant biases of the B-T% ≥20%/B-TN ≥300 cases between the ROSE-T% ≥80% and <80% groups.

Conclusion: This is the first report to suggest the utility of ROSE-T% in assessing the suitability of biopsy specimens for MGT. This predictive ability may add further value to ROSE and help reduce the time required for diagnostic testing, and thereby the patient burden.