Arran Turnbull

Stromal cell composition has been proposed as a potential biomarker in ductal carcinoma in situ (DCIS) for assessing the risk of subsequent recurrence or progression to invasive breast cancer (IBC). However, the characteristics of the tumor microenvironment within DCIS associated with these outcomes remain poorly understood. Here, we perform spatial transcriptomic analyses of 49 primary DCIS specimens from patients with no recurrence, DCIS recurrence, or recurrence as IBC. Cell mapping reveals spatially organized stromal cell gradients within DCIS, with enrichment of TREM2 ⁺ macrophages and myofibroblastic cancer-associated fibroblasts (myCAFs) in tumor-proximal niches. Notably, the abundance of TREM2 ⁺ macrophages near tumor nests is associated with subsequent recurrence as IBC. Moreover, ligand-receptor pair analysis identifies GRN–SORT1, SPP1–CD44, and LGALS9– CD44 interactions as spatially plausible signaling interactions between TREM2⁺ macrophages and epithelial cells. Finally, these findings are validated at the protein level by multiplex immunostaining of serial sections. This study characterizes the spatial landscape of the DCIS tumor microenvironment associated with subsequent recurrence, providing a basis for developing biomarkers of disease progression and identifying potential therapeutic targets.

Background/Aim: Triple-negative breast cancer (TNBC) is an aggressive subtype for which pembrolizumab-based neoadjuvant therapy has demonstrated improved outcomes. However, immune checkpoint inhibitors, including pembrolizumab, are associated with endocrine toxicities such as hypothyroidism, hypophysitis, and adrenal insufficiency, which may significantly complicate perioperative care. This study aimed to evaluate real-world preoperative endocrine testing and propose a practical management protocol. Methods: This retrospective study evaluated 28 patients with TNBC at Western General Hospital who received pembrolizumab before surgery between March 2023 and December 2024. Clinical data, endocrine function tests, surgical outcomes, and adverse events were analyzed. Results: Endocrinopathies occurred in a subset of patients, including one case of hypothyroidism and two cases of adrenal insufficiency. Only 36% of patients underwent cortisol testing preoperatively. Conclusion: We propose a protocol for routine preoperative endocrine screening in this population, including early-morning cortisol and thyroid function tests. Although the incidence is low, these complications may be severe, and implementing this protocol may reduce the risk of perioperative complications associated with immunotherapy-induced endocrinopathies.

The majority of breast cancers are oestrogen receptor-positive (ER+). In ER+ cancers, oestrogen acts as a disease driver, so these tumours are likely to be susceptible to endocrine therapy (ET). ET works by blocking the hormone’s synthesis or effect. A significant number of patients diagnosed with breast cancer will have the spread of tumour cells into regional lymph nodes either at the time of diagnosis, or as a recurrence some years later. Patients with node-positive disease have a poorer prognosis and can respond less well to ET. The nodal metastases may be genomically similar or, as is becoming more evident, may differ from the primary tumour. However, nodal metastatic disease is often not assessed, and treatment decisions are almost always based on biomarkers evaluated in the primary tumour. This review will summarise the evidence in the field on ER+, node-positive breast cancer, including diagnosis, treatment, prognosis and predictive tools.

Supplementary Figure from Integrated DNA and RNA Sequencing Reveals Drivers of Endocrine Resistance in Estrogen Receptor–Positive Breast Cancer

Supplementary Figure from Integrated DNA and RNA Sequencing Reveals Drivers of Endocrine Resistance in Estrogen Receptor–Positive Breast Cancer

Purpose:Endocrine therapy resistance (ETR) remains the greatest challenge in treating patients with hormone receptor–positive breast cancer. We set out to identify molecular mechanisms underlying ETR through in-depth genomic analysis of breast tumors.Experimental Design:We collected pre-treatment and sequential on-treatment tumor samples from 35 patients with estrogen receptor–positive breast cancer treated with neoadjuvant then adjuvant endocrine therapy; 3 had intrinsic resistance, 19 acquired resistance, and 13 remained sensitive. Response was determined by changes in tumor volume neoadjuvantly and by monitoring for adjuvant recurrence. Twelve patients received two or more lines of endocrine therapy, with subsequent treatment lines being initiated at the time of development of resistance to the previous endocrine therapy. DNA whole-exome sequencing and RNA sequencing were performed on all samples, totalling 169 unique specimens. DNA mutations, copy-number alterations, and gene expression data were analyzed through unsupervised and supervised analyses to identify molecular features related to ETR.Results:Mutations enriched in ETR included ESR1 and GATA3. The known ESR1 D538G variant conferring ETR was identified, as was a rarer E380Q variant that confers endocrine hypersensitivity. Resistant tumors which acquired resistance had distinct gene expression profiles compared with paired sensitive tumors, showing elevated pathways including ER, HER2, GATA3, AKT, RAS, and p63 signaling. Integrated analysis in individual patients highlighted the diversity of ETR mechanisms.Conclusions:The mechanisms underlying ETR are multiple and characterized by diverse changes in both somatic genetic and transcriptomic profiles; to overcome resistance will require an individualized approach utilizing genomic and genetic biomarkers and drugs tailored to each patient.

Purpose:Endocrine therapy resistance (ETR) remains the greatest challenge in treating patients with hormone receptor–positive breast cancer. We set out to identify molecular mechanisms underlying ETR through in-depth genomic analysis of breast tumors.Experimental Design:We collected pre-treatment and sequential on-treatment tumor samples from 35 patients with estrogen receptor–positive breast cancer treated with neoadjuvant then adjuvant endocrine therapy; 3 had intrinsic resistance, 19 acquired resistance, and 13 remained sensitive. Response was determined by changes in tumor volume neoadjuvantly and by monitoring for adjuvant recurrence. Twelve patients received two or more lines of endocrine therapy, with subsequent treatment lines being initiated at the time of development of resistance to the previous endocrine therapy. DNA whole-exome sequencing and RNA sequencing were performed on all samples, totalling 169 unique specimens. DNA mutations, copy-number alterations, and gene expression data were analyzed through unsupervised and supervised analyses to identify molecular features related to ETR.Results:Mutations enriched in ETR included ESR1 and GATA3. The known ESR1 D538G variant conferring ETR was identified, as was a rarer E380Q variant that confers endocrine hypersensitivity. Resistant tumors which acquired resistance had distinct gene expression profiles compared with paired sensitive tumors, showing elevated pathways including ER, HER2, GATA3, AKT, RAS, and p63 signaling. Integrated analysis in individual patients highlighted the diversity of ETR mechanisms.Conclusions:The mechanisms underlying ETR are multiple and characterized by diverse changes in both somatic genetic and transcriptomic profiles; to overcome resistance will require an individualized approach utilizing genomic and genetic biomarkers and drugs tailored to each patient.

Supplementary Figure from Integrated DNA and RNA Sequencing Reveals Drivers of Endocrine Resistance in Estrogen Receptor–Positive Breast Cancer

Supplementary Figure from Integrated DNA and RNA Sequencing Reveals Drivers of Endocrine Resistance in Estrogen Receptor–Positive Breast Cancer

Supplementary Data from Integrated DNA and RNA Sequencing Reveals Drivers of Endocrine Resistance in Estrogen Receptor–Positive Breast Cancer