Biomarker concordance between primary colorectal cancer and ovarian metastases: a Dutch cohort study

Purpose The genetic characteristics and mismatch repair (MMR) status of the primary tumor and corresponding metastases in colorectal cancer (CRC) are generally considered to be highly concordant. This implies that either the primary or metastatic tumor can be used for testing gene mutation and MMR status. However, whether this is also true for CRC and their ovarian metastases is currently unknown. Ovarian metastases generally show a poorer response to systemic therapy compared to other metastatic sites. Differences in biomarker status between primary CRC and ovarian metastases could possibly explain this difference in therapy response. Methods The study cohort was selected from CRC patients treated in two Dutch hospitals. Eligible patients with CRC and ovarian metastasis who were surgically treated between 2011 and 2018 were included. CRC and corresponding ovarian metastatic tissues were paired. Gene mutation status was established using next-generation sequencing, while the MMR status was established using either immunohistochemistry or microsatellite instability analysis. Results Matched samples of CRC and ovarian metastasis from 26 patients were available for analysis. A biomarker concordance of 100% was detected. Conclusion Complete biomarker concordance was found between MMR proficient CRC and their matching ovarian metastasis. Biomarker testing of MMR proficient CRC tissue appears to be sufficient, and additional testing of metastatic ovarian tissue is not necessary. Differences in therapy response between ovarian metastases and other metastases from CRC are thus unlikely to be caused by differences in the genetic status.