Immunomodulatory effects of CDK4/6 inhibitors

The dysregulation of the cell cycle is one of the hallmarks of cancer. Cyclin-dependent kinase 4 (CDK4) and CDK6 play crucial roles in regulating cell cycle and other cellular functions. CDK4/6 inhibitors have achieved great success in treating breast cancers and are currently being tested extensively in other tumor types as well. Accumulating evidence suggests that CDK4/6 inhibitors exert antitumor effects through immunomodulation aside from cell cycle arrest. Here we outline the immunomodulatory activities of CDK4/6 inhibitors, discuss the immune mechanisms of drug resistance and explore avenues to harness their immunotherapeutic potential when combined with immune checkpoint inhibitors (ICIs) or chimeric antigen receptor (CAR) T-cell therapy to improve the clinical outcomes.

A real-world US study of recurrence risks using combined clinicopathological features in HR-positive, HER2-negative early breast cancer

Aim: To assess invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) in hormone receptor-positive, HER2-negative early breast cancer with combined clinicopathological criteria from monarchE, a phase III study of abemaciclib. Methods: US electronic health records were used to compare outcomes between high-risk (≥4 lymph nodes, or 1-3 lymph nodes and grade 3, tumor ≥5 cm, or Ki-67 ≥20%) versus nonhigh-risk groups using Kaplan-Meier methods and Cox regression models. Results: The high-risk group (n = 557) was at higher risk for IDFS and DRFS events than the nonhigh-risk group (n = 3471). IDFS events (hazard ratio: 3.07; 95% CI: 2.45-3.83) and DRFS events (hazard ratio: 3.15; 95% CI: 2.49-3.97) were significantly higher for the high-risk group. Conclusion: Risk of recurrence was three-times greater in the high-risk group, highlighting the need for better therapies.

Feasibility of Adjuvant Treatment with Abemaciclib—Real-World Data from a Large German Breast Center

Abemaciclib significantly improves invasive disease-free survival when combined with endocrine therapy in clinical high-risk patients with HR+/Her2− early breast cancer (eBC). The objective of the following study was to model how many patients with eBC would be available for adjuvant treatment with abemaciclib in a real-world setting. Patients that underwent complete surgical treatment for eBC between January 2018 and December 2020 in a large single-center university hospital in Germany were eligible. Descriptive statistics were used to describe the patient population that could benefit from abemaciclib according to the inclusion criteria of monarchE. Of 1474 patients with eBC, 1121 (76.1%) had a HR+/Her2− subtype. Of these, 217 (19.4%) fulfilled the monarchE inclusion criteria. Within patients that fulfilled the monarchE inclusion criteria, 48.9% received no adjuvant or neoadjuvant chemotherapy. Thus, in a real-world situation, fewer patients will be pretreated with chemotherapy than was the case in monarchE. Breast care units are facing a significant patient burden, since the 2-year abemaciclib therapy requires regular monitoring of toxicities. Specific care concepts to strengthen therapy adherence as well as further studies to deescalate adjuvant systemic treatment and individualize CDK 4/6 inhibitor therapy are therefore needed.

Biomarkers of Response and Resistance to Palbociclib Plus Letrozole in Patients With ER+/HER2- Breast Cancer

PURPOSE

To determine (i) the relationship between candidate biomarkers of the antiproliferative (Ki67) response to letrozole and palbociclib alone and combined in ER⁺/HER2^- breast cancer; and (ii) the pharmacodynamic effect of the agents on the biomarkers.

EXPERIMENTAL DESIGN

307 postmenopausal women with ER⁺/HER2^- primary breast cancer were randomly assigned to neoadjuvant treatment with letrozole for 14 weeks; letrozole for 2 weeks, then letrozole+palbociclib to 14 weeks; palbociclib for 2 weeks, then letrozole+palbociclib to 14 weeks; or letrozole+palbociclib for 14 weeks. Biopsies were taken at baseline, 2 and 14 weeks and surgery at varying times after stopping palbociclib. Immunohistochemical analyses were conducted for Ki67, c-PARP, ER, PgR, RB1, CCNE1, and CCND1.

RESULTS

Higher baselines ER and PgR were significantly associated with a greater chance of complete cell-cycle arrest (CCCA: Ki67 <2.7%) at 14 weeks and higher baseline Ki67, c-PARP, and CCNE1 with a lower chance. The interaction with treatment was significant only for c-PARP. CCND1 levels were decreased c.20% by letrozole at 2 and 14 weeks but showed a tendency to increase with palbociclib. CCNE1 levels fell 82% (median) in tumors showing CCCA but were unchanged in those with no CCCA. Only 2/9 tumors showed CCCA 3-9 days after stopping palbociclib. ESR1 mutations were found in 2/4 tumors for which surgery took place ≥6 months after starting treatment.

CONCLUSIONS

High CCNE1 levels were confirmed as a biomarker of resistance to letrozole+palbociclib. Ki67 recovery within 3-9 days of discontinuing palbociclib indicates incomplete suppression of proliferation during the "off" week of its schedule.

Benefit of adjuvant chemotherapy in patients with lobular breast cancer: A systematic review of the literature and metanalysis

The role of adjuvant chemotherapy (aCT) for patients with localized lobular breast cancer (ILC) is still controversial. It is unclear what is the magnitude of benefit of the CT in this setting. In this systematic review of the literature and metanalysis, we aimed to estimate the benefit of aCT in addition to the standard treatments in the early ILC setting. We identified the records by searching Medline, CENTRAL, Web of Science, SCOPUS, and Google Scholar, and the meeting proceeding of the principal oncology meetings of the last 10 years, with no language or time restriction. A research strategy was developed with mapped and MeSH terms. Studies on the clinical use of aCT reporting survival outcomes in the ILC setting were double-screened and tabulated. PRISMA methodology was used for data extraction and synthesis. We extracted information on the study design and setting, eligible population and population size, histology variants, menopausal status, treatment regimens, follow-up duration. Hazard ratios (HR) and 95% confidence interval (CI) were extracted and transformed into logHR and corresponding standard error to obtain the Summary HR (SHR). Heterogeneity (I² statistics) and publication bias (Macaskill test) were tested; a random effect models provided by SAS Proc Mixed was used for data analysis. Sensitivity analysis was conducted to examine the impact of inclusion criteria on the summary results. Disease-free (DFS), overall (OS) and cancer-specific survival (BCSS) were the primary endpoints of the investigation. The systematic review and metanalysis included 38,387 patients across 8 clinical studies. aCT was not associated with an improvement of OS (SHR 0.99; 95%CI 0.86-1.14), with low heterogeneity (I² = 28%) and no publication bias (p = 0.43). Sensitivity analysis resulted in unchanged conclusions. We did not perform a metanalysis of the DFS estimates, as only reported in 3 studies. The value of aCT in improving DFS was unconfirmed, consistently with the OS results. Our research did not confirm a certain role of aCT for patients with ILC. Research gaps were identified, warranting the development of prospective, controlled ad hoc investigations.