Biomarkers in Breast Cancer: An Integrated Analysis of Comprehensive Genomic Profiling and PD-L1 Immunohistochemistry Biomarkers in 312 Patients with Breast Cancer
Authors: Huang Richard S.P. , Li Xinyan , Haberberger James , Sokol Ethan , Severson Eric , Duncan Daniel L. , Hemmerich Amanda , Edgerly Claire , Williams Erik , Elvin Julia , Vergilio Jo-Anne , Killian Jonathan Keith , Lin Douglas , Hiemenz Matthew , Xiao Jinpeng , McEwan Deborah , Holmes Oliver , Danziger Natalie , Erlich Rachel , Frampton Garrett , Cohen Michael B. , McGregor Kimberly , Reddy Prasanth , Cardeiro Dawn , Anhorn Rachel , Venstrom Jeffrey , Alexander Brian , Brown Charlotte , Pusztai Lajos , Ross Jeffrey S. , Ramkissoon Shakti H. 
Published: September 2020

Background

We examined the current biomarker landscape in breast cancer when programmed death-ligand 1 (PD-L1) testing is integrated with comprehensive genomic profiling (CGP).

Material and Methods

We analyzed data from samples of 312 consecutive patients with breast carcinoma tested with both CGP and PD-L1 (SP142) immunohistochemistry (IHC) during routine clinical care. These samples were stratified into hormone receptor positive (HR+)/human epidermal growth factor receptor negative (HER2−; n = 159), HER2-positive (n = 32), and triple-negative breast cancer (TNBC) cohorts (n = 121).

Results

We found that in the TNBC cohort, 43% (52/121) were immunocyte PD-L1–positive, and in the HR+/HER2− cohort, 30% (48/159) had PIK3CA companion diagnostics mutations, and hence were potentially eligible for atezolizumab plus nab-paclitaxel or alpelisib plus fulvestrant, respectively. Of the remaining 212 patients, 10.4% (22/212) had a BRCA1/2 mutation, which, if confirmed by germline testing, would allow olaparib plus talazoparib therapy. Of the remaining 190 patients, 169 (88.9%) were positive for another therapy-associated marker or a marker that would potentially qualify the patient for a clinical trial. In addition, we examined the relationship between immunocyte PD-L1 positivity and different tumor mutation burden (TMB) cutoffs and found that when a TMB cutoff of ≥9 mutations per Mb was applied (cutoff determined based on prior publication), 11.6% (14/121) patients were TMB ≥9 mutations/Mb and of these, TMB ≥9 mutations per Mb, 71.4% (10/14) were also positive for PD-L1 IHC.

Conclusion

Our integrated PD-L1 and CGP methodology identified 32% of the tested patients as potentially eligible for at least one of the two new Food and Drug Administration approved therapies, atezolizumab or alpelisib, and an additional 61.2% (191/312) had other biomarker-guided potential therapeutic options.

Implications for Practice

This integrated programmed death-ligand 1 immunohistochemistry and comprehensive genomic profiling methodology identified 32% of the tested patients as eligible for at least one of the two new Food and Drug Administration-approved therapies, atezolizumab or alpelisib, and an additional 61.2% (191/312) had other biomarker-guided potential therapeutic options. These findings suggest new research opportunities to evaluate the predictive utility of other commonly seen PIK3CA mutations in hormone receptor-positive breast cancers and to standardize tumor mutation burden cutoffs to evaluate its potentially predictive role in triple-negative breast cancer.