Mismatch Repair/Microsatellite Instability Testing Practices among US Physicians Treating Patients with Advanced/Metastatic Colorectal Cancer

Abstract

The study objective was to assess US physicians' Mismatch Repair/Microsatellite Instability (MMR/MSI) testing practices for metastatic colorectal cancer (mCRC) patients. A non-interventional, cross-sectional online survey was conducted among 151 physicians (91 oncologists, 15 surgeons and 45 pathologists) treating mCRC patients in the US. Eligible physicians were US-based with at least 5 years of experience treating CRC patients, had at least one mCRC patient in their routine care in the past 6 months, and had ordered at least one MMR/MSI test for CRC in the past 6 months. Descriptive and logistic regression analyses were performed. Awareness of specific MMR/MSI testing guidelines was high (n = 127, 84.1%). Of those, 93.7% (119/127) physicians had awareness of specific published guidelines with majority 67.2% (80/119) being aware of National Comprehensive Cancer Network (NCCN) guidelines. Universal testing for all CRC patients was performed by 68.9% (104/151) physicians, while 29.8% (45/151) selectively order the test for some CRC patients. Key barriers for testing included insufficient tissue sample (48.3%, 73/151), patient declined to have the test done (35.8%, 54/151) and insurance cost concerns for patients (31.1%, 47/151), while 27.2% (41/151) reported no barriers. The survey demonstrated high awareness and compliance with MMR/MSI testing guidelines although universal testing rates seem to be suboptimal.

Keywords: colorectal cancer; mismatch repair/microsatellite instability testing; survey.

Figure 1

Reasons and barriers for ordering MMR/MSI testing—% of physicians agreeing with each statement. * Multiple selections were allowed. Thus, total percentage will not add up to 100%. ** Answer included: eligibility for certain therapies, and compliance with guidelines. *** Answer included: Patients do not go to third line.

Figure 2

Physician discussion with patients—% of physicians agreeing with each statement. * Multiple selections were allowed. Thus, total percentage will not add up to 100%. ** Referral to genetic counselling.