Programmed Death Ligand 1 Immunohistochemistry in Triple-Negative Breast Cancer: Evaluation of Inter-Pathologist Concordance and Inter-Assay Variability

New Approach in the Interpretation of Complex Triple-negative Breast Cancer Immunohistochemistry Specimens Processed With VENTANA PD-L1 (SP142) Assay

Triple-negative breast cancer (TNBC) is challenging to treat because of its lack of specific molecular targets. The IMMUNOPEG study aimed to evaluate a novel structured method for interpreting TNBC immunohistochemistry specimens processed with VENTANA PD-L1 (SP142) assay. The study involved 10 pathologists who evaluated 50 different immunohistochemistry specimens of TNBC with programmed death ligand 1 (PD-L1) expression considered challenging and that were previously evaluated by the scientific committee, using the NAVIFY Digital Pathology platform. Initially, the overall percent agreement (OPA) was 74%, with a negative percent agreement (NPA) of 68.2% for samples classified as negative, and a positive percent agreement (PPA) of 94.5% for positive samples. After training on the method, the OPA improved significantly to 81.6%, with the NPA increasing to 80.5% and the PPA decreasing to 85.5%. The mean percentage of the tumor area occupied by PD-L1-stained immune cells decreased from 2.5% to 1.6% post-training, approaching to the scientific committee's consensus of 1.029%. The study found that the pathologists' confidence in their assessments increased significantly when using the structured method, which was found to be easy to use by 9 out of 10 pathologists. All pathologists agreed that the structured method was useful for assessing PD-L1 expression. The study suggests that this method has potential value in interpreting challenging cases of PD-L1 immunohistochemistry (IHC) in TNBC. Further refinement and a training protocol may be necessary to enhance the method's efficiency. The potential for generalizing this structured method to other IHC procedures and pathologies warrants additional research.

Concordance of PD-L1 Expression in Metastatic Triple-negative Breast Cancer Between the 22C3 and E1L3N Antibodies Using Combined Positive Scoring

For patients with metastatic triple-negative breast cancer (TNBC), treatment with pembrolizumab is dependent on the accurate determination of programmed death ligand 1 (PD-L1) expression using immunohistochemistry (IHC). This study evaluated the interobserver concordance in assessing PD-L1 expression on TNBC samples using the commercial 22C3 IHC assay and an in-house assay based on the E1L3N antibody. Concordance between the 22C3 and the E1L3N IHC assays was evaluated on TNBC samples read by a commercial laboratory and a Brigham and Women's Hospital breast pathologist (BWH reader). Each slide was given a PD-L1 combined positive score (CPS) and was considered PD-L1 positive or negative based on the CPS cutoff of 10. Interobserver concordance for the assays was also evaluated on a subset of samples between 2 and 3 independent readers. On 71 samples, 2 independent readers (1 BWH reader and commercial laboratory) using E1L3N and 22C3, respectively, reached agreement on PD-L1 status (positive/negative) on 64 samples (90.1%). Using 22C3, 2 independent readers reached agreement on PD-L1 status on 30 of 36 samples (83.3%), and 3 independent readers reached agreement on 16 of 27 samples (59.3%). Using E1L3N, 2 BWH readers reached agreement on PD-L1 status on 18 of 27 samples (66.7%). Three BWH readers reached an agreement on 2 of 12 of the most challenging samples (16.7%). In conclusion, concordance between E1L3N and 22C3 testing using CPS for PD-L1 in metastatic TNBC was >90%. However, certain cases were challenging to agree upon using current threshold criteria, highlighting the need for more standardized evidence-based methods to assess PD-L1 expression.

Artificial Intelligence in Predicting Microsatellite Instability and KRAS, BRAF Mutations from Whole-Slide Images in Colorectal Cancer: A Systematic Review

Mismatch repair deficiency (d-MMR)/microsatellite instability (MSI), KRAS, and BRAF mutational status are crucial for treating advanced colorectal cancer patients. Traditional methods like immunohistochemistry or polymerase chain reaction (PCR) can be challenged by artificial intelligence (AI) based on whole slide images (WSI) to predict tumor status. In this systematic review, we evaluated the role of AI in predicting MSI status, KRAS, and BRAF mutations in colorectal cancer. Studies published in PubMed up to June 2023 were included (n = 17), and we reported the risk of bias and the performance for each study. Some studies were impacted by the reduced number of slides included in the data set and the lack of external validation cohorts. Deep learning models for the d-MMR/MSI status showed a good performance in training cohorts (mean AUC = 0.89, [0.74-0.97]) but slightly less than expected in the validation cohort when available (mean AUC = 0.82, [0.63-0.98]). Contrary to the MSI status, the prediction of KRAS and BRAF mutations was less explored with a less robust methodology. The performance was lower, with a maximum of 0.77 in the training cohort, 0.58 in the validation cohort for KRAS, and 0.82 AUC in the training cohort for BRAF.

Discordance in PD-L1 expression using 22C3 and SP142 assays between primary and metastatic triple-negative breast cancer

AIMS

SP142 and 22C3 assays are approved companion diagnostic assays for anti-PD-1/PD-L1 therapy selection in metastatic triple-negative breast cancer (TNBC). The discordance in PD-L1 status between primary and metastatic tumors in the same patient has been poorly characterized. Here, we examined the concordance of PD-L1 status between the two assays and between primary tumors and metastases for each assay.

METHODS

We retrospectively evaluated tumor samples from 160 patients with TNBC, including 45 patients with paired primary and metastatic tumors. PD-L1 status was assessed using SP142 and 22C3 assays, to determine the immune cell (IC) score, tumor cell (TC) score (SP142 and 22C3), and combined proportion score (CPS: 22C3).

RESULTS

The concordance of PD-L1 positivity at diagnostic cutoffs for SP142 (IC ≥ 1) and 22C3 (CPS ≥ 10) was substantial (κ = 0.80) in primary tumors and moderate (κ = 0.60) in metastatic tumors. In comparison, between primary and metastatic tumors, the concordance with 22C3 was moderate (κ = 0.50), whereas that with SP142 was poor (κ = -0.03). Among patients who were PD-L1 negative for both assays in primary tumors, 7/30 (23.3%) were PD-L1 positive for both or either 22C3 or SP142 in the metastatic tumors.

CONCLUSIONS

The inter-assay concordance of PD-L1 positivity at diagnostic cutoffs was substantial in primary tumors and moderate in metastatic tumors. Discordance between PD-L1 status in primary and metastatic tumors was frequently observed, especially with SP142. Some patients with a PD-L1-negative status in primary tumors may still be candidates for immunotherapy, depending on the PD-L1 status in their metastatic tumors.

Triple-negative breast cancer: from none to multiple therapeutic targets in two decades

Triple-negative breast cancers (TNBCs) are more likely to occur in younger patients and have a poor prognosis. They are highly heterogeneous tumors consisting of different molecular subtypes. The only common characteristic among them is the absence of targets for endocrine therapy and human epidermal growth factor receptor 2 (HER2) blockade. In the past two decades, there has been an increased understanding of these tumors from a molecular perspective, leading to their stratification according to new therapeutic strategies. TNBC has ushered breast carcinomas into the era of immunotherapy. The higher frequency of germline BRCA mutations in these tumors enables targeting this repair defect by drugs like PARP inhibitors, resulting in synthetic lethality in neoplastic cells. Additionally, we have the identification of new molecules to which this generation of smart drugs, such as antibody-drug conjugates (ADCs), are directed. In this review, we will discuss the trajectory of this knowledge in a systematic manner, presenting the molecular bases, therapeutic possibilities, and biomarkers.

Comparison of SP142 and 22C3 PD-L1 assays in a population-based cohort of triple-negative breast cancer patients in the context of their clinically established scoring algorithms

BACKGROUND

Immunohistochemical (IHC) PD-L1 expression is commonly employed as predictive biomarker for checkpoint inhibitors in triple-negative breast cancer (TNBC). However, IHC evaluation methods are non-uniform and further studies are needed to optimize clinical utility.

METHODS

We compared the concordance, prognostic value and gene expression between PD-L1 IHC expression by SP142 immune cell (IC) score and 22C3 combined positive score (CPS; companion IHC diagnostic assays for atezolizumab and pembrolizumab, respectively) in a population-based cohort of 232 early-stage TNBC patients.

RESULTS

The expression rates of PD-L1 for SP142 IC ≥ 1%, 22C3 CPS ≥ 10, 22C3 CPS ≥ 1 and 22C3 IC ≥ 1% were 50.9%, 27.2%, 53.9% and 41.8%, respectively. The analytical concordance (kappa values) between SP142 IC+ and these three different 22C3 scorings were 73.7% (0.48, weak agreement), 81.5% (0.63) and 86.6% (0.73), respectively. The SP142 assay was better at identifying 22C3 positive tumors than the 22C3 assay was at detecting SP142 positive tumors. PD-L1 (CD274) gene expression (mRNA) showed a strong positive association with all two-categorical IHC scorings of the PD-L1 expression, irrespective of antibody and cut-off (Spearman Rho ranged from 0.59 to 0.62; all p-values < 0.001). PD-L1 IHC positivity and abundance of tumor infiltrating lymphocytes were of positive prognostic value in univariable regression analyses in patients treated with (neo)adjuvant chemotherapy, where it was strongest for 22C3 CPS ≥ 10 and distant relapse-free interval (HR = 0.18, p = 0.019). However, PD-L1 status was not independently prognostic when adjusting for abundance of tumor infiltrating lymphocytes in multivariable analyses.

CONCLUSION

Our findings support that the SP142 and 22C3 IHC assays, with their respective clinically applied scoring algorithms, are not analytically equivalent where they identify partially non-overlapping subpopulations of TNBC patients and cannot be substituted with one another regarding PD-L1 detection. Trial registration The Swedish Cancerome Analysis Network - Breast (SCAN-B) study, retrospectively registered 2nd Dec 2014 at ClinicalTrials.gov; ID NCT02306096.

Reproducibility in PD-L1 Immunohistochemistry Quantification through the Tumor Proportion Score and the Combined Positive Score: Could Dual Immunostaining Help Pathologists?

We studied the pathologists' agreements in quantifying PD-L1 expression through the tumor proportion score (TPS) and the combined positive score (CPS) using single PD-L1 immunohistochemistry (S-IHC) and double immunohistochemistry (D-IHC) combining PD-L1 staining and tumor cell markers. S-IHC and D-IHC were applied to 15 cancer samples to generate 60 digital IHC slides (30 whole slides images and 30 regions of interest of 1 mm²) for PD-L1 expression quantification using both TPS and CPS, twice by four pathologists. Agreements were estimated calculating intraclass correlation coefficients (ICC). Both S-IHC and D-IHC slides analyses resulted in excellent (for TPS, ICC > 0.9) to good (for CPS, ICC > 0.75) inter- and intra-pathologist agreements with slightly higher ICC with D-IHC than with S-IHC. S-IHC resulted in higher TPS and CPS than D-IHC (+5.6 and +6.1 mean differences, respectively). High reproducibility in the quantification of PD-L1 expression is attainable using S-IHC and D-IHC.

Inter- and Intra-Observer Agreement of PD-L1 SP142 Scoring in Breast Carcinoma-A Large Multi-Institutional International Study

The assessment of PD-L1 expression in TNBC is a prerequisite for selecting patients for immunotherapy. The accurate assessment of PD-L1 is pivotal, but the data suggest poor reproducibility. A total of 100 core biopsies were stained using the VENTANA Roche SP142 assay, scanned and scored by 12 pathologists. Absolute agreement, consensus scoring, Cohen's Kappa and intraclass correlation coefficient (ICC) were assessed. A second scoring round after a washout period to assess intra-observer agreement was carried out. Absolute agreement occurred in 52% and 60% of cases in the first and second round, respectively. Overall agreement was substantial (Kappa 0.654-0.655) and higher for expert pathologists, particularly on scoring TNBC (6.00 vs. 0.568 in the second round). The intra-observer agreement was substantial to almost perfect (Kappa: 0.667-0.956), regardless of PD-L1 scoring experience. The expert scorers were more concordant in evaluating staining percentage compared with the non-experienced scorers (R² = 0.920 vs. 0.890). Discordance predominantly occurred in low-expressing cases around the 1% value. Some technical reasons contributed to the discordance. The study shows reassuringly strong inter- and intra-observer concordance among pathologists in PD-L1 scoring. A proportion of low-expressors remain challenging to assess, and these would benefit from addressing the technical issues, testing a different sample and/or referring for expert opinions.

PD-L1 testing by immunohistochemistry in immuno-oncology

Immunotherapy, based on immune checkpoint inhibitors targeting the Programmed cell death ligand 1 (PD-L1) and/or Programmed Death Receptor 1 (PD-1), has substantially improved the outcomes of patients with various cancers. However, only ~30% of patients benefit from immune checkpoint inhibitors. Tumor PD-L1 expression, assessed by immunohistochemistry, is the most widely validated and used predictive biomarker to guide the selection of patients for immune checkpoint inhibitors. PD-L1 assessment may be challenging due to the necessity for different companion diagnostic assays for required specific immune checkpoint inhibitors and a relatively high level of inter-assay variability in terms of performance and cutoff levels. In this review, we discuss the role of PD-L1 immunohistochemistry as a predictive test in immunotherapy (immuno-oncology), highlight the complexity of the PD-L1 testing landscape, discuss various preanalytical, analytical and clinical issues that are associated with PD-L1 assays, and provide some insights into optimization of PD-L1 as a predictive biomarker in immuno-oncology.

Clinicopathological and Prognostic Significance of Programmed Death Ligand-1 SP142 Expression in 132 Patients With Triple-negative Breast Cancer

BACKGROUND/AIM

The prognostic value of programmed death ligand-1 (PD-L1) expression in triple-negative breast cancer (TNBC) has not been sufficiently investigated. In this study, we examined whether PD-L1 expression status is associated with clinicopathological features and outcomes of patients with TNBC.

PATIENTS AND METHODS

Immunostaining for PD-L1 SP142 was performed on tissue microarrays containing 132 TNBC samples. High PD-L1 expression was defined as ≥10% of the tumor area occupied by PD-L1-expressing cells.

RESULTS

Thirty-five (26.5%) patients showed high PD-L1 SP142 expression on immune cells (ICs). High IC PD-L1 expression was significantly correlated with smaller tumor size (p=0.030), absence of lymphovascular invasion (p=0.024), and fewer lymph node metastases (p=0.002). Multivariate survival analysis revealed that high IC PD-L1 expression independently predicted better disease-free survival (DFS) of TNBC patients.

CONCLUSION

High PD-L1 SP142 expression on ICs was significantly associated with favorable clinicopathological parameters and better outcomes in patients with TNBC. Our observations suggest that high IC PD-L1 expression can be used as an independent prognostic marker for predicting better DFS in patients with TNBC.

Clinical Outcomes and Immune Markers by Race in a Phase I/II Clinical Trial of Durvalumab Concomitant with Neoadjuvant Chemotherapy in Early-Stage TNBC

PURPOSE

The incidence of triple-negative breast cancer (TNBC) is higher among Black or African American (AA) women, yet they are underrepresented in clinical trials. To evaluate safety and efficacy of durvalumab concurrent with neoadjuvant chemotherapy for stage I-III TNBC by race, we enrolled additional AA patients to a Phase I/II clinical trial.

PATIENTS AND METHODS

Our study population included 67 patients. The primary efficacy endpoint was pathologic complete response (pCR; ypT0/is, N0) rate. χ2 tests were used to evaluate associations between race and baseline characteristics. Cox proportional hazards models were used to assess association between race and overall survival (OS) and event-free survival (EFS). Multivariate logistic regression analyses were used to evaluate associations between race and pCR, immune-related adverse events (irAE) and recurrence.

RESULTS

Twenty-one patients (31%) self-identified as AA. No significant associations between race and baseline tumor stage (P = 0.40), PD-L1 status (0.92), and stromal tumor-infiltrating lymphocyte (sTIL) count (P = 0.57) were observed. pCR rates were similar between AA (43%) and non-AA patients (48%; P = 0.71). Three-year EFS rates were 78.3% and 71.4% in non-AA and AA patients, respectively [HR, 1.451; 95% confidence interval (CI), 0.524-4.017; P = 0.474]; 3-year OS was 87% and 81%, respectively (HR, 1.72; 95% CI, 0.481-6.136; P = 0.405). The incidence of irAEs was similar between AA and non-AA patients and no significant associations were found between irAEs and pathologic response.

CONCLUSIONS

pCR rates, 3-year OS and EFS after neoadjuvant immunotherapy and chemotherapy were similar in AA and non-AA patients. Toxicities, including the frequency of irAEs, were also similar.

SP142 PD-L1 Assays in Multiple Samples from the Same Patients with Early or Advanced Triple-Negative Breast Cancer

Simple Summary

The IMpassion130 trial suggests that metastatic triple-negative breast cancer (TNBC) patients with PD-L1+ derived a clinical benefit from atezolizumab-combined treatment regardless of the sample collection time or origin. Therefore, if the PD-L1 test is positive at least once in multiple samples, the patient could have an opportunity to receive atezolizumab-based treatments. We aimed to know whether multiple PD-L1 testing might increase a rate of PD-L1+ in patients with TNBC. SP142 PD-L1 assays were performed in multiple samples from 77 patients in early TNBC. Multiple PD-L1 test using multiple samples raised the PD-L1+ rate more than a single biopsied sample test (68.8% vs. 37.6%, p = 0.00002). Among the group with metastatic TNBC treated with atezolizumab and nab-paclitaxel, PD-L1 assays were performed at least twice in 8/12 patients; 5/8 had heterogeneous results of PD-L1 assays. Consequently, a vigorous PD-L1 test using multiple samples was considered necessary in TNBC because a single test might be insufficient to represent the PD-L1 status.

Abstract

Purpose: The discernible PD-L1 staining of tumor-infiltrating lymphocytes occupying ≥ 1% of the tumor area is considered SP142 PD-L1 positive for atezolizumab, and the PD-L1 status of multiple samples within a single patient could be discrepant. In this study, we evaluated the PD-L1 status by using the SP142 clone in serially collected matched samples from the same individuals with early or metastatic triple-negative breast cancer (TNBC). Method: the SP142 PD-L1 assay was performed using biopsies and surgical specimens from 77 patients with early TNBC. Among these patients, 47 underwent upfront surgery, and 30 underwent neoadjuvant chemotherapy (NAC) between biopsy and surgery. PD-L1 assays were performed at least twice in 8/12 (66.7%) patients with metastatic TNBC treated with atezolizumab and nab-paclitaxel. Results: Of the 47 patients who underwent upfront surgery, 15/47 (31.9%) had PD-L1+ on biopsied samples. PD-L1+ rates in the biopsy and surgical specimens increased to 66.0% (33 of 47) after subsequent surgery. Similarly, in the 30 patients with residual invasive cancer who underwent neoadjuvant chemotherapy, the PD-L1+ rate increased from 46.6% at baseline to 74.2% after surgery. In the 77 patients with early TNBC, multiple PD-L1 testing in the biopsies and surgical specimens significantly increased the number of patients with PD-L1+ compared with the number of patients with PD-L1+ assessed with initial biopsy samples alone (68.8% vs. 37.6%; p = 0.00002). Among the metastatic TNBC patients, those with constant PD-L1+ over 1% positivity in multiple samples showed a response which was longer than 12 months. Conclusions: Our findings reveal the heterogeneous SP142 PD-L1 expression in TNBC and suggest that PD-L1 evaluation in baseline biopsy might be insufficient to represent the PD-L1 status of whole tumors. In TNBC, vigorous PD-L1 examination using multiple available tumor samples could identify more patients eligible for immune checkpoint blockade.

PD-L1 (SP142 and 22C3) Immunohistochemistry in Clinical Metastatic Triple Negative or Low Hormone Receptor Breast Carcinomas: Experience from a Large Academic Institution

The discovery of new immune checkpoint molecules has led to the emergence of new treatment for metastatic breast carcinoma. We aimed to investigate PD-L1 (SP142 and 22C3) expression in 77 clinical metastatic triple negative or low hormone receptor (<10%) breast carcinomas (TNBC/LHRBC). SP142 was positive in 23.4% (18/77) of cases. SP142 positive (SP142+) cases showed lower liver metastasis and androgen receptor expression, but increased tumor infiltrating lymphocytes than SP142 negative (SP142-) cases in univariate analysis, but only increased tumor infiltrating lymphocyte in multivariate analysis. 22C3 testing was available in 21 cases including 14 with combined positive score (CPS) ≥10 (9 SP142- and 5 SP142+) and 7 with CPS <10 (7 SP142-). Ten (13%) patients received immunotherapy including 8 SP142+ (7 with atezolizumab, 1 with pembrolizumab) and 2 SP142- cases (2 with pembrolizumab). Survival data showed a trend of increased survival rate in SP142+ (72.2%) when comparing to SP142- patients (55.9%). Our study provides unique insights into the distribution of PD-L1 staining in metastatic breast carcinomas in a real-world clinical setting.

Prognostic Role of PD-L1 Expression in Invasive Breast Cancer: A Systematic Review and Meta-Analysis

Simple Summary

The role of PD-L1 expression in breast cancer remains controversial. Therefore, we performed a systematic review and meta-analysis to assess the association of PD-L1 expression with clinicopathological variables, overall survival (OS), and disease-free survival (DFS) in invasive breast cancer. PD-L1 expression was associated with age ≥ 50 years, lymph node status-negative, progesterone receptor-negative, Ki67 ≥ 20%, and human epidermal growth factor receptor 2 (HER2)-negative. PD-L1 positivity was associated with worse OS; however, there was no significant improvement in DFS. PD-L1 positivity was significantly associated with the clinicopathological characteristics of favorable and unfavorable prognoses. However, the final clinical outcome was associated with lower OS and had no significant association with DFS.

Abstract

Programmed death ligand 1 (PD-L1) has been investigated in various types of cancer; however, the role of PD-L1 expression in breast cancer remains controversial. We performed a systematic review and meta-analysis to assess the association of PD-L1 expression with clinicopathological variables, overall survival (OS), and disease-free survival (DFS) in invasive breast cancer. A total of 965 articles were included from CINAHL, Embase, PubMed, and Scopus databases. Of these, 22 studies encompassing 6468 cases of invasive breast cancer were included in the systematic review, and 15 articles were included in the meta-analysis. PD-L1 expression was associated with age ≥ 50 years, lymph node status-negative, progesterone receptor-negative, Ki67 ≥ 20%, and human epidermal growth factor receptor 2 (HER2)-negative. PD-L1 positivity was associated with worse OS (hazard ratio, HR, 2.39; 95% confidence interval, CI, 1.26–3.52; p =< 0.000); however, there was no significant improvement in DFS (HR 0.17; 95% CI −0.12–0.46; p =< 0.252). PD-L1 positivity was significantly associated with the clinicopathological characteristics of favorable and unfavorable prognoses. However, the final clinical outcome was associated with lower OS and had no significant association with DFS.