Purpose: In the neoadjuvant treatment (NAT) setting, dual HER2-targeted therapy is associated with increased pathologic complete response (pCR) rates compared with each therapy alone. Biomarkers allowing to predict treatment response during NAT are needed. We aim to evaluate whether circulating tumor DNA (ctDNA) is associated with response to anti-HER2–targeted therapy. Experimental Design: Plasma DNA collected before NAT, at week 2, and before surgery from patients enrolled in the NeoALTTO trial was assessed using digital PCR for PIK3CA and TP53 mutation detection. Results: A total of 69 of 455 (15.2%) patients had a PIK3CA and/or TP53 mutation detected in the baseline tumor sample and evaluable ctDNA results from baseline samples. CtDNA was detected in 41%, 20%, and 5% patients before NAT, at week 2, and before surgery, respectively. ctDNA detection before NAT was significantly associated with older age and ER-negative status. ctDNA detection before NAT was associated with decreased odds of achieving pCR (OR = 0.15; 95% CI, 0.034–0.7; P = 0.0089), but not with event-free survival (EFS). Analyses for EFS were underpowered. Interestingly, the patients with HER2-enriched subtype tumors and undetectable ctDNA at baseline had the highest pCR rates. In contrast, patients with persistent ctDNA detection at baseline and week 2 had the lowest rate of pCR. Conclusions: ctDNA detection before neoadjuvant anti-HER2 therapies is associated with decreased pCR rates. Interestingly, patients with HER2-enriched tumors and undetectable ctDNA at baseline had the highest pCR rates, therefore appearing as the best candidates for treatment deescalation strategies.

The incidence of breast cancer among younger East Asian women has been increasing rapidly over recent decades. This international collaborative study systemically compared the differences in age-specific incidences and pathological characteristics of breast cancer in East Asian women and women of predominantly European ancestry. We excerpted analytic data from six national cancer registries (979 675 cases) and eight hospitals (18 008 cases) in East Asian countries and/or regions and, for comparisons, from the US Surveillance, Epidemiology, and End Results program database. Linear regression analyses of age-specific incidences of female breast cancer and logistic regression analyses of age-specific pathological characteristics of breast cancer were performed. All statistical tests were two-sided. Unlike female colorectal cancer, the age-specific incidences of breast cancer among East Asian women aged 59 years and younger increased disproportionally over recent decades relative to rates in US contemporaries. For years 2010–2014, the estimated age-specific probability of estrogen receptor positivity increased with age in American patients, whereas that of triple-negative breast cancer (TNBC) declined with age. No similar trends were evident in East Asian patients; their probability of estrogen receptor positivity at age 40–49 years was statistically significantly higher (odd ratio [OR] = 1.50, 95% confidence interval [CI] = 1.36 to 1.67, P < .001) and of TNBC was statistically significantly lower (OR = 0.79, 95% CI = 0.71 to 0.88, P < .001), whereas the probability of ER positivity at age 50–59 years was statistically significantly lower (OR = 0.88, 95% CI = 0.828 to 0.95, P < .001). Subgroup analyses of US Surveillance, Epidemiology, and End Results data showed similarly distinct patterns between East Asian American and white American patients. Contrasting age-specific incidences and pathological characteristics of breast cancer between East Asian and American women, as well as between East Asian Americans and white Americans, suggests racial differences in the biology.

In breast cancer patients, tumor heterogeneity is associated with prognosis and therapeutic response; however, the epigenetic diversity that exists in primary tumors remains unknown. Using a single-cell sequencing assay for transposase-accessible chromatin (scATAC-seq), we obtained the chromatin accessibility profiles of 12,452 cells from 16 breast cancer patients including 11 luminal, 1 luminal-HER2, 1 HER2⁺, and 3 triple-negative subtypes. Via this profiling process, tumors were classified into cancer cells and the tumor microenvironment, highlighting the heterogeneity of disease-related pathways including estrogen receptor (ER) signaling. Furthermore, the coexistence of cancer cell clusters with different ER binding motif enrichments was identified in a single ER⁺ tumor. In a cluster with reduced ER motif enrichment, we identified GRHL2, a transcription factor, as the most enriched motif, and it cooperated with FOXA1 to initiate endocrine resistance. Coaccessibility analysis revealed that GRHL2 binding elements potentially regulate genes associated with endocrine resistance, metastasis, and poor prognosis in patients that received hormonal therapy. Overall, our study suggests that epigenetic heterogeneity could lead to endocrine resistance and poor prognosis in breast cancer patients and it offers a large-scale resource for further cancer research.

Cyclin‐dependent kinase 4/6 inhibitors (CDK4/6i) significantly improve progression‐free survival and have become the standard therapy for estrogen receptor‐positive/human epidermal growth factor receptor 2‐negative metastatic breast cancer patients. Treatment surveillance by radiological imaging has some limitations in detection and repeated biopsy genomic profiling is not clinically feasible. Serial circulating tumor DNA (ctDNA) analysis may provide insights into treatment response. Here we performed serial ctDNA analysis (n = 178) on 33 patients. Serial ctDNA analysis identified disease progression with sensitivity of 75% and specificity of 92%. In eight of 12 patients (61%) responding to CDK4/6i who eventually developed progressive disease, serial sampling every 3 or 6 months captured the initial rise of ctDNA with an average lead time of 3 months. In three of eight patients that did not respond to CDK4/6i (progressive disease at first radiological assessment, 3 months), biweekly sequencing within the first cycle of CDK4/6i treatment (1 month) detected sustained ctDNA levels (≥0.2% variant allele frequency), with lead time of 2 months. Serial ctDNA analysis tracked RECIST response, including clinically challenging scenarios (bone metastases or small‐sized target lesions), as well as detecting acquired genetic alterations linked to CDK4/6i resistance in the G₁ to S transition phase. Circulating tumor DNA analysis was more sensitive than carcinoembryonic antigen or cancer antigen 15‐3 serum tumor markers at monitoring tumor response to CDK4/6i treatment. Our findings indicated the possible clinical utility of serial ctDNA analysis for earlier progressive disease detection and real‐time monitoring of CDK4/6i response.

Neoadjuvant endocrine therapy (NAE) has been employed to improve surgical outcomes for hormone receptor-positive breast cancers in postmenopausal women. Endocrine responsiveness is estimated by expressions of hormone receptors, but its heterogeneity has been recognized. Autophagy is an evolutionally conserved process associated with cell survival and cell death and has been implicated in cancer treatment. In order to examine the possible association between autophagy and response to endocrine therapy, we evaluated the status of autophagy-associated markers, beclin 1 and LC3, and apoptosis-associated markers, TUNEL and M30, in pre- and post-treatment specimens from 71 patients in a multicenter prospective study of neoadjuvant exemestane (JFMC34-0601). Immunoreactivity of the autophagy-associated markers, beclin 1 and LC3, in carcinoma cells increased in 14 % and 52 % of the patients, respectively, following the exemestane treatment. These increases were statistically significant (beclin 1, p = 0.016, N = 49; LC3, p < 0.0001, N = 33). The status of M30 immunoreactivity decreased (p = 0.008, N = 47) and TUNEL remained unchanged (N = 53). In addition, tumors with pre-treatment stromal beclin 1 immunoreactivity revealed poor clinical and pathological responses compared with those without stromal beclin 1 immunoreactivity (25 % vs 67 % for clinical response, p = 0.011, N = 51; 0 % vs 41 % for pathological response, p = 0.0081, N = 49). Tumors with positive pre-treatment stromal beclin 1 had a higher baseline Ki-67 labeling index (both hot spot and overall average) than those without (p = 0.042 and 0.0075, respectively, N = 53). Results of logistic regression analyses revealed that stromal beclin 1 was a predictor for clinical and pathological responses while ER, PR, Ki-67, and stromal LC3 expressions were not. Results of our present study demonstrated that beclin 1 and LC3 immunoreactivity increased in carcinoma cells following exemestane treatment and that the status of pre-treatment stromal beclin 1 is associated with higher carcinoma cell proliferation and poor clinical and pathological responses to NAE. UMIN C000000345 (2006/03/06)