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From gaps to compliance: a 12-year retrospective cohort study of trends in mismatch repair protein testing and Lynch syndrome identification in colorectal cancer in Central Switzerland

  • 0Institute of Pathology, Cantonal Hospital Lucerne, Lucerne, Switzerland.
Swiss Medical Weekly +

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August 14, 2025

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August 14, 2025

View abstract on PubMed

Summary

This summary is machine-generated.

Colorectal cancer diagnostics in Central Switzerland show significant improvement, with near-complete adherence to mismatch repair protein and molecular testing guidelines by 2022. Early study years revealed testing gaps, particularly for rectal cancers, potentially missing Lynch syndrome cases.

Area Of Science

  • Oncology
  • Genetics
  • Cancer Diagnostics

Background

  • Colorectal cancer (CRC) diagnosis and Lynch syndrome screening are critical for patient management.
  • Mismatch repair (MMR) protein testing and molecular analysis (BRAF, KRAS, NRAS) are key for identifying microsatellite instability (MSI) and Lynch syndrome.
  • Adherence to guidelines, such as those from the Swiss Academy for Quality in Medicine (SAQM), is crucial for effective CRC diagnostics.

Purpose Of The Study

  • To evaluate the implementation and trends of MMR protein and gene mutation testing in CRC in Central Switzerland (2011-2022).
  • To assess adherence to SAQM guidelines for CRC molecular testing.
  • To identify gaps in testing practices that may hinder the diagnosis of Lynch syndrome or MSI.

Main Methods

  • Retrospective analysis of 2673 histologically confirmed CRC cases from the Central Switzerland Cancer Registry (2011-2022).
  • Data included demographic, molecular, and immunohistochemical profiles.
  • Statistical analyses utilized R (v4.3.1) with packages like tidyverse, employing Shapiro-Wilk tests, Wilcoxon rank-sum tests, chi-square/Fisher's exact tests, and Poisson/binomial regression models for trend analysis.

Main Results

  • MMR protein testing rates increased from 58% in 2011 to over 99% by 2022.
  • 14% of tested tumors showed MMR deficiency; 73% of MLH1-deficient cases underwent BRAF testing.
  • 6% of tested tumors were Lynch-suspected; potential missed cases due to incomplete testing were estimated.
  • Tumor incidence and Lynch-suspected proportions remained stable; no regional hotspots identified.

Conclusions

  • Significant progress in CRC diagnostics in Central Switzerland, achieving near-complete guideline compliance for MMR and molecular testing by 2022.
  • High adherence supports personalized surveillance and treatment, improving patient care.
  • Gaps in early years, especially for rectal cancers and incomplete molecular follow-up, may have led to missed MSI and Lynch syndrome diagnoses, impacting treatment and surveillance.