Immune Response in Breast Cancer Patients Receiving CDK4/6 Inhibitors Following the First Dose of COVID-19 Vaccine

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COVID-19 vaccines undoubtedly have played a critical role in ending the coronavirus pandemic, considering their impact on the population in general.

However, in patients with cancer there are limited data regarding efficacy and safety. In an analysis of 21 patients with breast cancer receiving treatment with cyclin-dependent kinase (CDK)4/6 inhibitors, Zagouri and colleagues provided an initial analysis of immune responses after the first dose of vaccination in a treated population of patients with histologically confirmed breast cancer, who were under treatment with CDK4/6 inhibitors, and who were aged >18 years and eligible for vaccination.

Serial blood samples were analyzed, using an FDA-approved assay to measure SARS-CoV-2 neutralizing antibodies, that were collected on day 1 prior to vaccination and on day 22 after vaccination. For serum samples of the same patient or control subjects, the same ELISA plate was used. Case-control matching to match the 2 groups for age and type of vaccine was used to adjust for potential confounding variables.

The researchers excluded patients and healthy controls known to be previously infected with the COVID-19 virus. Included in the study were 160 controls (median age, 68 years), and 21 female patients with breast cancer with a median age of 63 years who were vaccinated during the same period.

Although 1 patient with breast cancer and 25 controls received the AZD1222 vaccine, the vast majority (95.2%) of patients with breast cancer and 84.4% of controls were vaccinated with an mRNA vaccine (mRNA1273 and BNT162b2).

Between the 2 groups, there was no significant difference in body mass index.

Approximately one-half (52.4%) of patients were treated with ribociclib, one-third (33.3%) with palbociclib, and the remainder (14.3%) with abemaciclib. In the study group, comorbidities included cardiovascular disease in 38.1% of patients, diabetes mellitus in 9.52%, and pulmonary disease in 4.76%.

In both patients and healthy controls, the levels of neutralizing antibodies post-vaccination were similar to the matched healthy controls and no safety issues were raised. To reduce the uncertainty of SARS-CoV-2 immunity among patients with cancer under treatment, research studies are warranted in the future.


Zagouri F, Terpos E, Fiste O, et al. SARS-CoV-2 neutralizing antibodies after first vaccination dose in breast cancer patients receiving CDK4/6 inhibitors. Breast. 2021;60:58-61.

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