Incidence and characteristics of mismatch repair (MMR) protein deficient colorectal cancer (CRC) in a community hospital based cancer center in rural central Nebraska.

Abstract

e22591 Background: MMR protein deficient (dMMR) CRC has distinctive clinical and pathologic features that can be either sporadic or genetic. Immunohistochemistry (IHC) 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 IHC testing and genetic consultation referrals in the diagnostic evaluation and management of CRC patients (pts) in a community hospital-based cancer center in rural central Nebraska. Methods: All pathologically confirmed CRC pts` data, diagnosed between January 2017 and December 2023 at Morrison Cancer Center, were evaluated. Data on age, gender, tumor location, stage, tumor IHC 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: A total of 272 pts (F/M 137/135), median age 71(range:38-96), non-metastatic 215/272 (75%) and metastatic 57/272(25%) were evaluated. 205/272(75%) pts had MMR IHC testing, 86/272 (32%) had BRAF (600E) IHC testing. 42/272(15%) had dMMR and 163/272(60%) had pMMR while 67/272(25%) pts did not have MMR testing. 107/272(39%) referred for genetic consultation (GC), 33/272 (12%) followed through with GC appointment. 4/272(1.4%) were diagnosed with Lynch Syndrome. Metastatic pts were more likely to have dMMR status than non-metastatic pts [4/47 (8.5%) vs 38/158 (2.4%)], p = 0.023. More pts with dMMR status than pMMR status had BRAF mutation [22/28 (78%) vs 6/28 (21%)], p = 0.0001. GC referrals and Lynch syndrome were more likely in dMMR CRC group, p = 0.0009, and p = 0.002. Conclusions: We present a real world community hospital based cancer center data from rural central Nebraska. Utilization rates for MMR and BRAF IHC testing were 75% and 32%, respectively. Comparison of patient characteristics based on the MMR status revealed statistically significant associations in metastatic vs non-metastatic disease, positive or negative BRAF mutation, GC referral and Lynch syndrome status. Future studies comparing community based cancer center data to tertiary cancer center data would be valuable. dMMR 42/272 pMMR 163/272 P Age (Median) 76 70 Gender Female Male 22 (52%)20 (48%) 79 (49%)84 (51%) 0.7 Tumor Site Right Colon Left Colon Rectum 28 (67%)11 (26%)3 (7%) 83 (51%)46 (28%)34 (21%) 0.07 Tumor Stage Metastatic Non-metastatic 4 (10%)38 (91%) 43 (26%)120 (74%) 0.02 BRAF mutation BRAF (-) BRAF (+) 11 (33%)22 (67%) 47 (89%)6 (11%) 0.0001 GC Referral No referral 16 (49%)17 (52%) 17 (17%)81 (83%) 0.0009 Lynch syndrome Yes No 4 (16%)21 (84%) 0 (0%)87 (100%) 0.0020