Deregulation of the cell cycle machinery is a hallmark of cancer. While CDK4/6 inhibitors are FDA approved (palbociclib) for treating advanced estrogen receptor-positive breast cancer, two major clinical challenges remain: (i) adverse events leading to therapy discontinuation and (ii) lack of reliable biomarkers. Here we report that breast cancer cells activate autophagy in response to palbociclib, and that the combination of autophagy and CDK4/6 inhibitors induces irreversible growth inhibition and senescence in vitro, and diminishes growth of cell line and patient-derived xenograft tumours in vivo. Furthermore, intact G1/S transition (Rb-positive and low-molecular-weight isoform of cyclin E (cytoplasmic)-negative) is a reliable prognostic biomarker in ER positive breast cancer patients, and predictive of preclinical sensitivity to this drug combination. Inhibition of CDK4/6 and autophagy is also synergistic in other solid cancers with an intact G1/S checkpoint, providing a novel and promising biomarker-driven combination therapeutic strategy to treat breast and other solid tumours.

Androgen receptor-targeted treatments for breast cancer are in development and have shown promising preliminary results. In-depth understanding of AR and AR-related signaling pathways would improve the treatment strategies for AR-positive breast cancer. Further preclinical and clinical studies of AR-targeted drugs alone and in combination with other drugs are justified and warranted to clarify the biology of AR and inform the development of AR-targeted therapies to improve survival outcome in patients with breast cancer.

Chemotherapy-related cognitive impairment (CRCI) can occur during or after chemotherapy and represents a concern for many patients with cancer. Among older patients with cancer, in whom there is little clinical trial evidence examining side effects like CRCI, many unanswered questions remain regarding risk for and resulting adverse outcomes from CRCI. Given the rising incidence of cancer with age, CRCI is of particular concern for older patients with cancer who receive treatment. Therefore, research related to CRCI in older patients with cancers is a high priority. In this manuscript, we discuss current gaps in research highlighting the lack of clinical studies of CRCI in older adults, the complex mechanisms of CRCI, and the challenges in measuring cognitive impairment in older patients with cancer. Although we focus on CRCI, we also discuss cognitive impairment related to cancer itself and other treatment modalities. We highlight several research priorities to improve the study of CRCI in older patients with cancer.

Purpose: Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are currently used in combination with endocrine therapy to treat advanced hormone receptor-positive, HER2-negative breast cancer. Although this treatment doubles time to progression compared with endocrine therapy alone, about 25%-35% of patients do not respond, and almost all patients eventually acquire resistance. Discerning the mechanisms of resistance to CDK4/6 inhibition is crucial in devising alternative treatment strategies.Experimental Design: Palbociclib-resistant cells (MCF-7 and T47D) were generated in a step-wise dose-escalading fashion. Whole-exome sequencing, genome-wide expression analysis, and proteomic analysis were performed in both resistant and parental (sensitive) cells. Pathway alteration was assessed mechanistically and pharmacologically. Biomarkers of altered pathways were examined in tumor samples from patients with palbociclib-treated breast cancer whose disease progressed while on treatment.Results: Palbociclib-resistant cells are cross-resistant to other CDK4/6 inhibitors and are also resistant to endocrine therapy (estrogen receptor downregulation). IL6/STAT3 pathway is induced, whereas DNA repair and estrogen receptor pathways are downregulated in the resistant cells. Combined inhibition of STAT3 and PARP significantly increased cell death in the resistant cells. Matched tumor samples from patients with breast cancer who progressed on palbociclib were examined for deregulation of estrogen receptor, DNA repair, and IL6/STAT3 signaling, and results revealed that these pathways are all altered as compared with the pretreatment tumor samples.Conclusions: Palbociclib resistance induces endocrine resistance, estrogen receptor downregulation, and alteration of IL6/STAT3 and DNA damage response pathways in cell lines and patient samples. Targeting IL6/STAT3 activity and DNA repair deficiency using a specific STAT3 inhibitor combined with a PARP inhibitor could effectively treat acquired resistance to palbociclib.

PURPOSE This phase I study (RAD1901-005; NCT02338349) evaluated elacestrant, an investigational oral selective estrogen receptor degrader (SERD), in heavily pretreated women with estrogen receptor–positive, human epidermal growth factor receptor 2–negative metastatic breast cancer, including those with estrogen receptor gene alpha ( ESR1) mutation. The primary objective was to determine the maximum tolerated dose and/or recommended phase II dose (RP2D). METHODS The study consisted of a 3 + 3 design (elacestrant capsules) followed by expansion at RP2D (400-mg capsules, then 400-mg tablets) for the evaluation of safety and antitumor activity. Elacestrant was taken once daily until progression or intolerability. RESULTS Of 57 postmenopausal women enrolled, 50 received RP2D (400 mg once daily): median age, 63 years; median three prior anticancer therapies, including cyclin-dependent kinase 4,6 inhibitors (CDK4/6i; 52%), SERD (52%), and ESR1 mutation (circulating tumor DNA; 50%). No dose-limiting toxicities occurred; the most common adverse events at RP2D (400-mg tablet; n = 24) were nausea (33.3%) and increased blood triglycerides and decreased blood phosphorus (25.0% each). Most adverse events were grade 1-2 in severity. The objective response rate was 19.4% (n = 31 evaluable patients receiving RP2D), 15.0% in patients with prior SERD, 16.7% in patients with prior CDK4/6i, and 33.3% in patients with ESR1 mutation (n = 5/15). The clinical benefit rate (24-week) was 42.6% overall (n = 47 patients receiving RP2D), 56.5% (n = 23, ESR1 mutation), and 30.4% (n = 23, prior CDK4/6i). Elacestrant clinical benefit was associated with decline in ESR1 mutant allele fraction. CONCLUSION Elacestrant 400 mg orally once daily has an acceptable safety profile and demonstrated single-agent activity with confirmed partial responses in heavily pretreated patients with estrogen receptor–positive metastatic breast cancer. Notably, responses were observed in patients with ESR1 mutation as well as those with prior CDK4/6i and prior SERD. A phase III trial investigating elacestrant versus standard endocrine therapy is ongoing.

Background This study explores the incidence of patient‐reported major toxicity—symptoms rated “moderate,” “severe,” or “very severe”—for chemotherapy regimens commonly used in early breast cancer. Patients and Methods Female patients aged 21 years or older completed a validated Patient‐Reported Symptom Monitoring instrument and rated 17 symptoms throughout adjuvant or neoadjuvant chemotherapy. Fisher's exact tests compared differences in percentages in symptom ratings, and general linear regression was used to model the incidence of patient‐reported major toxicity. Results In 152 patients, the mean age was 54 years (range, 24–77), and 112 (74%) were white; 51% received an anthracycline‐based regimen. The proportion of patients rating fatigue, constipation, myalgia, diarrhea, nausea, peripheral neuropathy, and swelling of arms or legs as a major toxicity at any time during chemotherapy varied significantly among four chemotherapy regimens (p < .05). The mean (SD) number of symptoms rated major toxicities was 6.3 (3.6) for anthracycline‐based and 4.4 (3.5) for non‐anthracycline‐based regimens (p = .001; possible range, 0–17 symptoms). Baseline higher body mass index (p = .03), patient‐reported Karnofsky performance status ≤80 (p = .0003), and anthracycline‐based regimens (p = .0003) were associated with greater total number of symptoms rated major toxicities (alternative model: chemotherapy duration, p < .0001). Twenty‐six percent of dose reductions (26 of 40), 75% of hospitalizations (15 of 20), and 94% of treatment discontinuations (15 of 16) were in anthracycline‐based regimens. Conclusion Capturing multiple toxicity outcomes throughout chemotherapy enables oncologists and patients to understand the range of side effects as they discuss treatment efficacies. Continuous symptom monitoring may aid in the timely development of interventions that minimize toxicity and improve outcomes. Implications for Practice This study investigated patient‐reported toxicities for 17 symptoms recorded prospectively during adjuvant and neoadjuvant chemotherapy regimens for early breast cancer. An analysis of four commonly used chemotherapy regimens identified significant differences among regimens in both individual symptoms and total number of symptoms rated moderate, severe, or very severe. Longer chemotherapy regimens, such as anthracycline‐based regimens followed by paclitaxel, had higher proportions of symptoms rated major toxicities. The inclusion of patient perspectives on multiple toxicity outcomes at the same time at multiple time points during chemotherapy has the potential for improving patient‐provider communication regarding symptom management, patient satisfaction, and long‐term clinical outcomes.

We aimed to determine if resting state functional magnetic resonance imaging (fMRI) acquired at pre-treatment baseline could accurately predict breast cancer-related cognitive impairment at long-term follow-up. We evaluated 31 patients with breast cancer (age 34–65) prior to any treatment, post-chemotherapy and 1 year later. Cognitive testing scores were normalized based on data obtained from 43 healthy female controls and then used to categorize patients as impaired or not based on longitudinal changes. We measured clustering coefficient, a measure of local connectivity, by applying graph theory to baseline resting state fMRI and entered these metrics along with relevant patient-related and medical variables into random forest classification. Incidence of cognitive impairment at 1 year follow-up was 55% and was predicted by classification algorithms with up to 100% accuracy (p < 0.0001). The neuroimaging-based model was significantly more accurate than a model involving patient-related and medical variables (p = 0.005). Hub regions belonging to several distinct functional networks were the most important predictors of cognitive outcome. Characteristics of these hubs indicated potential spread of brain injury from default mode to other networks over time. These findings suggest that resting state fMRI is a promising tool for predicting future cognitive impairment associated with breast cancer. This information could inform treatment decision making by identifying patients at highest risk for long-term cognitive impairment.

Purpose To determine the frequency and association with relapse-free survival (RFS) of MET and PIK3CA copy number elevations in early stage breast cancer. Methods Tumor DNA was extracted from 971 formalin-fixed paraffin-embedded early breast cancers for molecular inversion probes arrays. Data was segmented using the SNP-FASST2 segmentation algorithm. Copy number gains were called when copy number of each segment was greater than 2.3 or 1.7 respectively. RFS was estimated by Kaplan-Meier. Cox proportional hazards models were fit to determine independent associations of copy number with RFS. Results 82 (8.44%) and 134 (13.8%) of tumors had MET or PIK3CA copy number elevation respectively, and 25.6% with MET copy number elevation had PIK3CA copy number elevation. Patients with either MET or PI3KCA high copy number tended to have poorer prognostic features (larger tumor size, higher grade, and hormone receptor negativity), Both, MET and PIK3CA high copy number were more likely to occur in triple negative disease (P=0.019 and <0.001, respectively). At a median follow-up of 7.4 years, there were 252 recurrences. Five-year RFS were 63.5%, and 83.1% for MET high copy number and MET normal/low copy number respectively, (P=0.06); and 73.1%, and 82.3% for PIK3CA high copy number and PIK3CA normal/low copy number respectively, (P=0.15). High copy number for either gene was not an independent predictor of RFS. Conclusion High copy number of MET or PIK3CA was associated with poorer prognostic features and triple negative disease. Co-amplification was frequent. Patients with high MET copy number tumors tended to have a worst RFS.