Mismatch Repair/Microsatellite Instability Testing and Genetic Consult Referral Practice Patterns for Colorectal Cancer in a Community Hospital Based Cancer Center in Rural Central Nebraska.
Authors: Ternent Christina , Wedel Whitney , Tun Soe Min , Fiala Shari , Peterson Tonya , Reily Bronson , Simpson Charles Kelly , Horn Adam , Lintel Nicholas , Springer Carlene , Robbins Leslie , Sitki Copur Mehmet ,   Medical Director of Oncology,Medical Oncology/Hematology Professor, University of Nebraska Medical Center, Adjunct Faculty,Omaha, Mary Lanning Healthcare,Morrison Cancer Center
Published: December 2024

Background : MMR protein deficient colorectal cancer (CRC)
has distinctive clinical and pathologic features which can
be either sporadic or inherited. Mismatch Repair (MMR),
Microsatellite Instability (MSI) testing of CRC tumor tissue
for absent MMR proteins and BRAF (V600E) mutation has
become a routine practice in most tertiary cancer centers. We
sought to examine the utilization of MMR and BRAF testing
and genetic consultation referral pattern in the diagnostic
evaluation and management of CRC patients in a community
hospital-based cancer center in rural central Nebraska.
Methods : All pathologically confirmed CRC patients
diagnosed between January 2018 and December 2023 at
Morrison Cancer Center in central rural Nebraska were
evaluated. Data on age, gender, tumor location, stage, tumor
testing for MMR, BRAF (V600E) and genetic consultation
referrals were collected and analyzed. The independent
sample t-test, and Fisher’s exact tests were used to look at
the association of patient characteristics based on the MMR
status.
Results: Among a total of 272 patients (137 female, 135 male,
median age 71), seventy-nine percent (215/272)were nonmetastatic and twenty-one percent (57/272)) were metastatic
CRC. Overall, 75% (205/272) of patients had MMR/MSI testing
done and 32% (86/272) had BRAF V600E testing performed.
Fifteen percent (42/272) of all CRC patients had deficient MMR
(dMMR) and 60% (163/272) had proficient MMR (pMMR) while
67/272 (25%) patients did not have MMR testing. Thirty-nine
percent (107/272) of all CRC patients were referred for genetic
consultation but only 12% (33/272) of them followed through
with their appointment. Four patients (4/272,1.4%) were
diagnosed with Lynch Syndrome. Among 205 patients who
had MMR/MSI testing, metastatic CRC patients were more
likely to have dMMR status than non-metastatic CRC patients
[4/47 (8.5%) vs 38/158 (2.4%)], p=0.023. More patients with
dMMR status than pMMR status had BRAF mutation [22/28
(78%) vs 6/28 (21%)], p=0.0001. Genetic consultation referrals
and Lynch syndrome were more likely in dMMR CRC group
than pMMR group.
Conclusions: We present a real world rural community
hospital based cancer center data from central Nebraska. Our
data provides a glimpse of universal molecular testing and
genetic consultation referral practice pattern for CRC patients
in a rural community-based cancer center. Efforts to enhance
the accessibility and integration of universal molecular testing
and genetic counseling services into routine cancer care at
the rural community oncology settings are crucial to ensure
equitable cancer care for all patients, regardless of their
geographic location.