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PurposeWe examined gene expression, germline variant, and somatic mutation features associated with pathologic response to neoadjuvant durvalumab plus chemotherapy in basal-like triple-negative breast cancer (bTNBC).Experimental designGermline and somatic whole-exome DNA and RNA sequencing, programmed death ligand 1 (PD-L1) IHC, and stromal tumor-infiltrating lymphocyte scoring were performed on 57 patients. We validated our results using 162 patients from the GeparNuevo randomized trial.ResultsGene set enrichment analysis showed that pathways involved in immunity (adaptive, humoral, innate), JAK-STAT signaling, cancer drivers, cell cycle, apoptosis, and DNA repair were enriched in cases with pathologic complete response (pCR), whereas epithelial-mesenchymal transition, extracellular matrix, and TGFβ pathways were enriched in cases with residual disease (RD). Immune-rich bTNBC with RD was enriched in CCL-3, -4, -5, -8, -23, CXCL-1, -3, -6, -10, and IL1, -23, -27, -34, and had higher expression of macrophage markers compared with immune-rich cancers with pCR that were enriched in IFNγ, IL2, -12, -21, chemokines CXCL-9, -13, CXCR5, and activated T- and B-cell markers (GZMB, CD79A). In the validation cohort, an immune-rich five-gene signature showed higher expression in pCR cases in the durvalumab arm (P = 0.040) but not in the placebo arm (P = 0.923) or in immune-poor cancers. Independent of immune markers, tumor mutation burden was higher, and PI3K, DNA damage repair, MAPK, and WNT/β-catenin signaling pathways were enriched in germline and somatic mutations in cases with pCR.ConclusionsThe TGFβ pathway is associated with immune-poor phenotype and RD in bTNBC. Among immune-rich bTNBC RD, macrophage/neutrophil chemoattractants dominate the cytokine milieu, and IFNγ and activated B cells and T cells dominate immune-rich cancers with pCR.

* Context.--Neoadjuvant systemic therapy refers to the use of systemic agent(s) for malignancy prior to surgical treatment and has recently emerged as an option for most breast cancer patients eligible for adjuvant systemic therapy. Consequently, treated breast carcinomas have become routine specimens in pathology practices. A standard protocol has not yet been universally adopted for the evaluation and reporting of these specimens. The American Joint Committee on Cancer staging system recognizes the challenges in staging breast carcinomas after neoadjuvant treatment and provides important data points but does not currently provide detailed guidance in estimating the residual tumor burden in the breast and lymph nodes. The Residual Cancer Burden system is the only Web-based system that quantifies treatment response as a continuous variable using residual tumor burden in the breast and the lymph nodes. Objective.--To provide clarifications and guidance for evaluation and reporting of postneoadjuvant breast specimens, discuss issues with the current staging and reporting systems, and provide specific suggestions for future modifications to the American Joint Committee on Cancer system and the Residual Cancer Burden calculator. Data Sources.--English-language literature on the subject and the data from the I-SPy 2, a multicenter, adaptive randomization phase 2 neoadjuvant platform trial for early-stage, high-risk breast cancer patients. Conclusions.--This article highlights challenges in the pathologic evaluation and reporting of treated breast carcinomas and provides recommendations and clarifications for pathologists and clinicians. It also provides specific recommendations for staging and discusses future directions. doi: 10.5858/arpa.2022-0021-EP, Neoadjuvant systemic therapy (NST) in the treatment of breast cancer involves the administration of chemotherapy (NCT) or endocrine therapy prior to definitive surgery. Initially, NCT was implemented as a standard [...]

* Context.--Ductal carcinoma in situ (DCIS) represents 20% of screen-detected breast cancers. The likelihood that certain types of DCIS are slow growing and may never progress to invasion suggests that our current standards of treating DCIS could result in overtreatment. The LORIS (LOw RISk DCIS) and LORD (LOw Risk DCIS) trials address these concerns by randomizing patients with low-risk DCIS to either active surveillance or conventional treatment. Objective.--To determine the upgrade rate of DCIS diagnosed on core needle biopsy to invasive carcinoma at surgery and to evaluate the safety of managing low-risk DCIS with surveillance alone, by characterizing the pathologic and clinical features of upgraded cases and applying criteria of the LORD and LORIS trials to these cases. Design.--A 10-year retrospective analysis of DCIS on core needle biopsy with subsequent surgery. Results.--We identified 1271 cases of DCIS on core needle biopsy: 200 (16%) low grade, 649 (51%) intermediate grade, and 422 (33%) high grade. Of the 1271 cases, we found an 8% upgrade rate to invasive carcinoma (n = 105). Nineteen of the 105 upgraded cases (18%) had positive lymph nodes. Low-grade DCIS was least likely to upgrade to invasion, comprising 10% (10 of 105) of upgraded cases. Three of the 105 upgraded cases (3%) met criteria for the LORD trial, and all were low-grade DCIS on core needle biopsy with favorable biology on follow-up. Conclusions.--There is a clear risk of upgrade to invasion on follow-up excision; however, applying strict criteria of the LORD trial effectively decreases the likelihood of a missed invasive component or missed aggressive pathologic features. doi: 10.5858/arpa.2017-0268-OA, Ductal carcinoma in situ (DCIS) makes up approximately 20% of all screen-detected breast cancers. (1,2) This diagnosis is typically made after a radiologically suspicious area presenting as calcifications or less [...]