Audit of routine immunohistochemistry testing for mismatch repair proteins at diagnosis of colorectal cancer under the age of 50

Abstract

In May 2007, the Victorian Cancer Oncology Hereditary Bowel Cancer Group (VCOG HBCG) released a position statement in regards to the identification of Hereditary Non-Polyposis Colorectal Cancer (HNPCC) by immunohistochemistry (IHC) testing. This was based on the consensus among clinical groups, that most families with HNPCC are not being identified and strategies to improve identification should be implemented. The VCOG HBCG recommendation was to test all colorectal cancers in patients under 50 years of age by IHC for MLH1, MSH2, MSH6, and PMS2 proteins, as part of the routine pathological assessment of cancers presenting in these patients, without direct consent. This recommendation was widely circulated to the clinical community from 2007. The primary purpose of this audit was to ascertain the frequency of IHC being performed for consecutive patients diagnosed with colorectal cancer under 50 years of age, at three Victorian hospitals since the publication of the VCOG HBCG position statement. The purpose of this audit was also to ascertain the number of cases where IHC Results: showed loss of expression, and which were referred to a Familial Cancer Centre (FCC) for further assessment. Methods: Lists of patients with colorectal cancer diagnosed under 50 years of age for the calendar years of 2007, 2008, and 2009 were extracted from each hospital database. Pathology reports for all patients were manually checked to assess whether IHC was performed. Those patients with IHC absent Results: were cross-checked with FCC databases to see whether they were referred for further evaluation. Results: Data from two of the three hospitals was available at time of abstract submission. Patients diagnosed with colorectal cancer under 50 years of age who had IHC testing: 29% (4/14) in 2007, 81% (17/ 21) in 2008, 74% (17/23) in 2009. Patients with IHC absent results referred to a FCC: 33% (1/3) in 2008, 100% (3/3) in 2009. Conclusion: There were differences between hospitals in the uptake of the recommendation to implement routine IHC for patients diagnosed with colorectal cancer under 50 years of age. Barriers and enablers were identified for initiating routine IHC testing at the hospitals. These include addressing concerns around consent and onus of consent acquisition if needed, confusion about whether the IHC testing is a genotypic or phenotypic test, translation of the findings to clinical practice, establishment and optimization of the IHC testing, and funding of IHC testing. The audit shows that addressing such concerns has increased the IHC activity for this cohort