Introduction: The feasibility and success rate of repeat biopsy for epidermal growth factor receptor (EGFR) mutation-positive lung cancers that have progressed on tyrosine kinase inhibitors (TKIs) are varied and merits further assessment.
Materials and methods: EGFR mutation-positive lung cancers were offered repeat biopsy upon progression on TKIs. Two groups of patients, first one on a clinical trial and second one from a database, were included for analysis. The feasibility to perform a repeat biopsy was analyzed in the first group. Success rate of biopsy and tissue adequacy for molecular testing was analyzed in both groups. Descriptive statistics were used for analyzing the demography, EGFR mutation type, tissue adequacy, and molecular profile at repeat biopsy. Kolmogorov-Smirnov test was used to assess normality of data. Two sample t-tests were used for comparison of proportions.
Results: The feasibility of undergoing repeat biopsy was 77% (95% confidence interval [CI] of 69.4%-83.5%) in the first group (114/148 patients). Feasibility was not analyzed in the second group of patients. Out of 196 patients who underwent a repeat biopsy, 154 patients (78.6%; 95% CI: 72.2%-84.1%) had tumor tissue adequate for performing molecular testing. 27/196 (13.8%) patients did not have any evidence of malignancy on repeat biopsy whereas 15/196 (7.6%) patients had scanty tissue on repeat biopsy prohibiting molecular testing. Six patients (3.06%; 95% CI: 1.1%-6.5%) had small cell transformation. T790M mutation was detected in 12 out of the 42 patients (28.6%; 95% CI: 15.7-44.6) in whom EGFR testing was performed on repeat biopsy specimen.
Conclusion: Repeat biopsy was able to provide adequate tissue acquisition in only two-thirds of the patients. Liquid biopsy represents an important tool to bridge this gap.