Racial disparities in neutrophil counts among patients with metastatic breast cancer during treatment with CDK4/6 inhibitors

Racial disparities in treatment and outcomes between Hispanic and non-Hispanic black women with triple-negative breast cancer

INTRODUCTION

Triple-negative breast cancer (TNBC) is an aggressive breast cancer (BC) subtype with higher incidence and mortality rates in non-Hispanic Black (NHB) women than non-Hispanic Whites. Studies assessing disparities between NHB and Hispanic women, the two largest US racial/ethnic minorities, are lacking. This study evaluates disparities in the treatment and outcomes between NHB and Hispanic women with non-metastatic TNBC.

METHODS

This observational, population-based study using the SEER database included adult, female patients diagnosed with non-metastatic TNBC between 2010 and 2015 and identified as NHB or Hispanic. Logistic regression analysis was used to examine the adjusted odds of receiving breast cancer-directed treatment. Kaplan-Meier and cumulative incidence of death curves were plotted to assess overall survival (OS) and risk of breast cancer-related death, respectively. Multivariate regression analyses with Cox and Fine-Gray methods were calculated to assess factors associated with OS and breast cancer-related death, respectively.

RESULTS

There were 3426 Hispanic and 5419 NHB patients with non-metastatic TNBC. Hispanics had better 5-year OS relative to NHB (76% vs. 72%). No differences in the odds of receiving chemotherapy or surgery between cohorts was seen. However, the odds of undergoing breast-conserving surgery (BCS) and receiving radiation was higher in NHB than Hispanics, (OR, 1.22; 95% CI, 1.10-1.36) and (OR, 1.50; 95% CI, 1.36-1.66), respectively. Lack of radiation therapy was associated with increased BC-related death in NHB relative to Hispanics (sHR, 1.40; 95% CI, 1.19-1.65). Nevertheless, this difference was not seen when radiation was given, (sHR, 1.03; 95% CI, 0.87-1.23).

CONCLUSIONS

We found racial disparities in treatment and outcomes between NHB and Hispanics. NHB were more likely to receive radiation therapy and have BCS. Still, after adjusting for demographic and treatment-related factors, NHB had worse OS and BCSS relative to Hispanics. Additional research is needed to understand the drivers of these disparities.

Influence of ethnicity on cyclin-dependent kinase inhibitor efficacy and toxicity: A systematic review and meta-analysis

BACKGROUND

The combination of cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) with endocrine therapy (ET) is the standard of care for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (aBC). While the efficacy and safety profiles of CDK4/6i and ET have been extensively evaluated in phase II and III trials worldwide, it remains unclear whether the response to CDK4/6i and toxicity profile vary among Asian and non-Asian patients. Therefore, we aimed to assess the treatment efficacy of ET with and without CDK4/6i by comparing outcomes in Asian and non-Asian subgroups included in these clinical trials. In addition, we evaluated the toxicity profiles of the treatments by estimating the risk of treatment-related adverse events (AEs).

METHODS

We conducted a meta-analysis including the most recent randomized trial data systematically searched from PubMed, Embase, Web of Science, Cochrane CENTRAL (from inception to May 31st, 2024) or presented in abstracts or oral presentations at the ESMO, ASCO, and SABCS international congresses. We included studies comparing CDK4/6i (palbociclib, ribociclib, abemaciclib, dalpiciclib) + ET versus placebo + ET. Progression-free survival (PFS) and overall survival (OS), hazard ratios (HR), and 95 % confidence intervals (CI) were extracted for the two subgroups of interest. To evaluate the treatment-related toxicity profiles, we extracted the number of side effects to estimate the risk of treatment-emergent AEs.

RESULTS

Eleven studies (n = 5129) were included in this meta-analysis. The addition of CDK4/6i to ET consistently improved PFS in both Asian (HR = 0.52, 95 % CI 0.47-0.60; p < 0.001) and non-Asian (HR = 0.58, 95 % CI 0.52-0.64; p < 0.001) groups. Similarly, the combination of CDK4/6i + ET led to an OS improvement in both Asian (HR = 0.75, 95 % CI 0.62-0.91; p = 0.003) and non-Asian (HR = 0.81, 95 % CI 0.73-0.89; p < 0.001) patients. The risk of treatment related toxicity was higher in the CDK4/6i + ET arm in both Asian and non-Asian groups. Interestingly, a numerically higher rate of treatment-related hematological toxicity was observed in Asian patients, although no significant interethnic difference was found in the relative risk of these events.

CONCLUSIONS

The combination of CDK4/6i and ET significantly improves PFS and OS compared to ET alone in both Asian and non-Asian patients with HR+/HER2-aBC. Although the magnitude of benefit appears to be independent of ethnicity, future clinical trials should devise a standardized method for stratifying patients by ethnicity to more effectively assess potential differences in treatment benefits.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42024543217.

Trilaciclib dosage in Chinese patients with extensive-stage small cell lung cancer: a pooled pharmacometrics analysis

This study aimed to analyze potential ethnic disparities in the dose-exposure-response relationships of trilaciclib, a first-in-class intravenous cyclin-dependent kinase 4/6 inhibitor for treating chemotherapy-induced myelosuppression in patients with extensive-stage small cell lung cancer (ES-SCLC). This investigation focused on characterizing these relationships in both Chinese and non-Chinese patients to further refine the dosing regimen for trilaciclib in Chinese patients with ES-SCLC. Population pharmacokinetic (PopPK) and exposure-response (E-R) analyses were conducted using pooled data from four randomized phase 2/3 trials involving Chinese and non-Chinese patients with ES-SCLC. PopPK analysis revealed that trilaciclib clearance in Chinese patients was approximately 17% higher than that in non-Chinese patients with ES-SCLC. Sex and body surface area influenced trilaciclib pharmacokinetics in both populations but did not exert a significant clinical impact. E-R analysis demonstrated that trilaciclib exposure increased with a dosage escalation from 200 to 280 mg/m2, without notable changes in myeloprotective or antitumor efficacy. However, the incidence of infusion site reactions, headaches, and phlebitis/thrombophlebitis rose with increasing trilaciclib exposure in both Chinese and non-Chinese patients with ES-SCLC. These findings suggest no substantial ethnic disparities in the dose-exposure-response relationship between Chinese and non-Chinese patients. They support the adoption of a 240-mg/m2 intravenous 3-day or 5-day dosing regimen for trilaciclib in Chinese patients with ES-SCLC.

Racial Disparities in Breast Cancer: from Detection to Treatment

PURPOSE OF REVIEW

Update on current racial disparities in the detection and treatment of breast cancer.

RECENT FINDINGS

Breast cancer remains the leading cause of cancer death among Black and Hispanic women. Mammography rates among Black and Hispanic women have surpassed those among White women, with studies now advocating for earlier initiation of breast cancer screening in Black women. Black, Hispanic, Asian, and American Indian and Alaskan Native women continue to experience delays in diagnosis and time to treatment. Further, racial discrepancies in receipt of guideline-concordant care, access to genetic testing and surgical reconstruction persist. Disparities in the initiation, completion, toxicity, and efficacy of chemotherapy, endocrine therapy, and targeted drug therapy remain for racially marginalized women. Efforts to evaluate the impact of race and ethnicity across the breast cancer spectrum are increasing, but knowledge gaps remain and further research is necessary to reduce the disparity gap.

Social determinants of health and CDK4/6 inhibitor use and outcomes among patients with metastatic breast cancer

BACKGROUND

Survival outcomes in metastatic breast cancer (MBC) have improved due to novel agents such as CDK4/6 inhibitors (CDK4/6i). Nevertheless, Black patients and patients with lower socioeconomic status (SES) continue to bear a disproportionate mortality burden.

METHODS

We conducted a retrospective analysis of EHR-derived data from the Flatiron Health Database (FHD). A dataset was constructed to include Black/African-American (Black/AA) and White patients with hormone receptor (HR)-positive, HER2-negative MBC. Outcomes included CDK4/6i use (overall and first-line), and rates of leukopenia, dose reduction, and time on treatment for first-line CDK4/6i. Multivariable logistic regression was used to evaluate factors associated with use and outcomes.

RESULTS

A total of 6802 patients with MBC were included, of which 5187 (76.3%) received CDK4/6i. Of those, 3186 (61.4%) received CDK4/6i first-line. Overall, 86.7% of patients were categorized as White and 13.3% as Black/AA; 22.4% were > 75 years old; 12.6% were treated at an academic site; 3.3% had Medicaid insurance. In addition to advanced age and poorer performance status, lower use of CDK4/6i was associated with Black/AA vs White race (72.9% vs 76.8%; OR 0.83, 95% CI 0.70-0.99, p = 0.04) and Medicaid vs commercial insurance (69.6% vs 77.4%; OR: 0.68, 95% CI 0.49-0.95, p = 0.02). Odds of CDK4/6i use were twofold higher for patients treated at an academic center (p < 0.001). Rates of CDK4/6i-induced leukopenia and dose reductions did not differ significantly by race, insurance type, or treatment site. Time on CDK4/6i was significantly lower among Medicaid patients (395 days) than patients with commercial insurance (558 days) or Medicare (643 days) (p = 0.03).

CONCLUSION

This analysis of real-world data suggests that Black race and lower SES are associated with decreased CDK4/6i use. However, among patients treated with CDK4/6i, subsequent toxicity outcomes are similar. Efforts to ensure access to these life-prolonging medications are warranted.

Racial disparities in overall survival after the introduction of cyclin-dependent kinase 4/6 inhibitors for patients with hormone receptor-positive, HER2-negative metastatic breast cancer

PURPOSE

CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy have improved HR + /HER2- metastatic breast cancer (MBC) outcomes. However, it is still unclear whether the response to CDK4/6i is similar for all races. Therefore, we aimed to assess overall survival (OS) trends stratified by race in patients with HR + /HER2- MBC after the approval of CDK4/6i, as part of the standard of care, in 2015.

METHODS

We performed a population-based study using the SEER database. Patients with HR + /HER2- MBC were divided into two time-based cohorts: 1) pre-CDK4/6i era (diagnosed in 2011-2013) and 2) post-CDK4/6i era (diagnosed in 2015-2017). We used propensity score matching and identified 2,684 patients in each cohort that matched in several characteristics. Kaplan-Meier methods were used to estimate 2-year OS. Association between cohort and OS was evaluated using marginal Cox proportional hazards models with robust sandwich variance estimator. We conducted competing risk analysis to estimate the risk of breast cancer death in both cohorts.

RESULTS

The 2-year OS rate was 65% for the post-CDK4/6i era and 62% for the pre-CDK4/6i era (stratified log-rank p = 0.025). The 2-year OS for non-Hispanic White (NHW) patients improved in the post-CDK4/6i era compared to the pre-CDK4/6i era (67% vs. 63%, p = 0.033). However, OS did not improve for non-Hispanic Black (NHB) (54% vs. 54%, p = 0.876) or Hispanic (67% vs. 65%, p = 0.617) groups. The risk of breast cancer death decreased in the post-CDK4/6i era as compared to the pre-CDK4/6i era (2-year risk of breast cancer death: 33% vs. 30%, p = 0.015); however, this effect was observed only in NHW (sHR 0.84, p = 0.005) women, but not in NHB (sHR 0.94, p = 0.630) or Hispanic (sHR 0.91, p = 0.550) women.

CONCLUSIONS

Our study confirms that outcomes for HR + /HER2- MBC have improved after CDK4/6i were introduced in 2015. However, this effect is primarily driven by the improved OS in NHW patients, without significant improvement in OS in NHB or Hispanics.