Evaluation of the international Ki67 working group cut point recommendations for early breast cancer: comparison with 21-gene assay results in a large integrated health care system.

PURPOSE: The International Ki67 Working Group (IKWG) has developed training for immunohistochemistry (IHC) scoring reproducibility and recommends cut points of ≤ 5% and ≥ 30% for prognosis in ER+, HER2-, stage I/II breast cancer. We examined scoring reproducibility following IKWG training and evaluated these cut points for selecting patients for further testing with the 21-gene Recurrence Score (RS) assay. METHODS: We included 307 women aged 50+ years with node-negative, ER+PR+HER2- breast cancer and with available RS results. Slides from the diagnostic biopsy were stained for Ki67 and scored using digital image analysis (IA). Two IHC pathologists underwent IKWG training and visually scored slides, blinded to each other and IA readings. Interobserver reproducibility was examined using intraclass correlation (ICC) and Kappa statistics. RESULTS: Depending on reader, 8.8-16.0% of our cohort had Ki67 ≤ 5% and 11.4-22.5% had scores ≥ 30%. The ICC for Ki67 scores by the two pathologists was 0.82 (95% CI 0.78-0.85); it was 0.79 (95% CI 0.74-0.83) for pathologist 1 and IA and 0.76 (95% CI 0.71-0.80) for pathologist 2 and IA. For Ki67 scores ≤ 5%, the percentages with RS < 26 were 92.6%, 91.8%, and 90.9% for pathologist 1, pathologist 2, and IA, respectively. For Ki67 scores ≥ 30%, the percentages with RS ≥ 26 were 41.5%, 51.4%, and 27.5%, respectively. CONCLUSION: The IKWG's Ki67 training resulted in moderate to strong reproducibility across readers but cut points had only moderate overlap with RS cut points, especially for Ki67 ≥ 30% and RS ≥ 26; thus, their clinical utility for a 21-gene assay testing pathway remains unclear.

Comparison of Universal Versus Age-Restricted Screening of Colorectal Tumors for Lynch Syndrome Using Mismatch Repair Immunohistochemistry: A Cohort Study.

Background: Guidelines recommend screening all patients with newly diagnosed colorectal cancer (CRC) for Lynch syndrome (LS). However, the efficiency of universal LS screening in elderly populations has not been well studied. Objective: To compare the performance of age-restricted and universal LS screening using reflex mismatch repair (MMR) immunohistochemistry (IHC) of CRC tumors. Design: Retrospective cohort study. Setting: A large, diverse, community-based health care system. Participants: 3891 persons with newly diagnosed CRC who had LS screening between 2011 and 2016. Measurements: Diagnostic yield of different LS screening strategies. Results: Sixty-three LS cases (diagnostic yield, 1.62%) were identified by universal screening, with only 5 (7.9%) detected after age 70 years and 1 (1.6%) detected after age 80 years. When all patients with CRC who had universal screening were used as the denominator, 58 LS cases (diagnostic yield, 1.49% [95% CI, 1.13% to 1.92%]) were identified in patients with CRC diagnosed at or before age 70 years, 60 LS cases (diagnostic yield, 1.54% [CI, 1.18% to 1.98%]) were identified in those with CRC diagnosed at or before age 75 years, and 62 LS cases (diagnostic yield, 1.59% [CI, 1.22% to 2.04%]) were identified in those with CRC diagnosed at or before age 80 years. Using 75 years as the upper age limit for screening missed 3 of 63 (4.8%) LS cases but resulted in 1053 (27.1%) fewer cases requiring tumor MMR IHC. Using 80 years as the upper age limit missed 1 of 63 (1.6%) LS cases and resulted in 668 (17.2%) fewer cases requiring tumor MMR IHC. Limitation: Persons who were eligible for but did not complete germline analysis were excluded from calculations of performance characteristics. Conclusion: The incremental diagnostic yield decreased substantially after age 70 to 75 years. Stopping reflex CRC screening for LS after age 80 years may be reasonable because of very low efficiency, particularly in resource-limited settings, but this merits further investigation. Studies evaluating the effect of diagnosing LS in elderly persons on their family members are needed. Primary Funding Source: Kaiser Permanente Northern California Division of Research.