Adherence to Mismatch Repair Testing Guidelines in PT1 Colorectal Carcinomas Diagnosed Before the age of 70 Years

Aims Mismatch repair (MMR) testing is recommended in the Netherlands for all patients under 70 years of age with newly diagnosed colorectal cancer (CRC) in order to identify Lynch syndrome. T1 CRC can be removed by local excision or oncological surgical resection. We evaluated the frequency of MMR testing in pT1 lesions within the Dutch CRC screening cohort.

Methods pT1 CRC diagnosed within the Dutch population-based screening program from 2016-2018 were identified through the Dutch pathology registry (PALGA). Pathology reports were evaluated, including registration of MMR testing (by immunohistochemistry and/or microsatellite instability PCR). Frequency of MMR testing was compared between pT1 tumors that were treated by local (endoscopic or transanal) excision and oncological surgical resections.

Results A total of 3.692 pT1 CRCs were diagnosed (median age 63 years, 61.4% males). MMR testing was performed in 83% and uptake increased over time (71% in 2016 to 92% in 2018, p<0.01). MMR testing was significantly more often performed in younger patients and in academic hospitals (Table 1). When pT1 CRC was treated by oncological surgical resection, MMR testing was performed in 89% of n=1.132 cases and was known prior to oncological resection in 51% of the cases. MMR testing occurred significantly less often in case of local excision (80% of n=2.560) compared to oncological surgical resection (p<0.01).

	MMR testing performed (n = 3.095)	MMR testing not performed (n = 642)	p-value
Gender
Male	1855 (60.8%)	411 (64.0%)	0.12
Female	1195 (39.2%)	231 (36.0%)
Age at diagnosis
≤ 60 years	982 (87.5%)	140 (12.5%)	<0.01
>61 years	2.068 (80.5%)	502 (19.5%)
Hospital
Academic	633 (90.2%)	69 (9.8%)	<0.01
Non-academic	2417 (80.8%)	573 (19.2%)

Conclusions MMR testing was performed in 83% of pT1 CRCs and uptake increased over time. To further increase MMR testing levels and adherence to guidelines, we suggest performing MMR testing on the first available endoscopic sample (either biopsy or local excision specimen) in order to increase uptake of testing.

Citation Ykema B, Nagtegaal I, Kuhlmann K et al. OP78 ADHERENCE TO MISMATCH REPAIR TESTING GUIDELINES IN PT1 COLORECTAL CARCINOMAS DIAGNOSED BEFORE THE AGE OF 70 YEARS. Endoscopy 2021; 53: S33.

Publication History

Article published online:
19 March 2021