RESUMEN
BACKGROUND: In 2017, the Food and Drug Administration approved pembrolizumab for treatment of any mismatch repair-deficient (dMMR) tumor making MMR immunohistochemistry (IHC) testing beneficial for all tumor types. For the first time, MMR IHC was not performed exclusively to screen for Lynch syndrome (LS). METHODS: In this study, all MMR IHC reports issued between 2017 and 2021 at an academic hospital were reviewed and completion of genetic testing was determined through chart review. Colorectal cancers (CRCs), endometrial cancers (ECs), and noncancerous lesions were excluded. RESULTS: Between 2017 and 2021, MMR IHC was completed in 1939 patients with a malignancy other than CRC or EC. Absent or weak staining for at least one MMR protein was detected in 115 (5.9%) patients and 59 (51%) of those completed germline genetic testing. Overall, the identification rate of LS in this cohort was 0.72%, which is similar to the rate in our previously reported CRC and EC universal screening cohort. A diagnosis of LS was most commonly made in patients with dMMR brain (18.75%) and small intestinal cancers (10.20%). Five additional patients were found to carry a pathogenic variant in a non-LS gene. CONCLUSIONS: Pan-cancer MMR testing for pembrolizumab consideration can identify LS cases at a rate similar to universal CRC and EC screening programs. A persistent challenge is subsequent uptake of genetic testing. MMR testing should be prioritized in brain and small intestinal tumors, and multigene panel testing is recommended in patients with dMMR, as unexpected pathogenic variants in non-LS genes were found as frequently as LS gene variants.
RESUMEN
This study evaluated the impact of mainstreamed genetic testing (MGT) on the timing and uptake of testing in an academic breast surgeon's practice. Before September 2019 (pre-MGT phase), a breast surgery practice at Massachusetts General Hospital followed a traditional model of a pre-test consultation with a genetic counselor (GC) following a referral. After September 2019 (post-MGT phase), the same practice offered patients genetic testing in a single clinical encounter with a breast surgeon. We evaluated the waiting time between referral and GC visit in the pre-MGT phase and compared the uptake and positivity rates between both phases. In the pre-MGT phase (204 patients), the median waiting time for GC visit was seven days for patients with a newly diagnosed cancer, 211 days for patients with a personal history of cancer, and 224 days for non-cancer patients who had a family history. A total of 105 (51.5%) patients completed a GC appointment. In the post-MGT phase (202 patients), a significantly higher proportion of patients (88.1%, p < 0.001) consented to genetic testing, while the proportion of patients who tested positive was lower (pathogenic variant: 11.9% vs. 20.0%; variant of uncertain significance: 19.9% vs. 28.0%; p = 0.047). Implementing MGT can reduce the number of clinical visits, significantly shorten patients' wait time to test initiation, and increase the completion of genetic testing. Successful integration of this model relied on the genetic expertise of the breast surgeon involved and the support of the GC team.