A study by researchers at Mayo Clinic Cancer Center has found that patients with cancer who receive chemotherapy, and some targeted therapies including CDK4/6 inhibitors and therapies targeted at B cells, may mount an inadequate immune response to COVID-19 vaccination. The findings are published in Mayo Clinic Proceedings: Innovation, Quality & Outcomes.
SARS-CoV-2 mRNA vaccines have been demonstrated to have remarkable efficacy in healthy individuals with robust and durable humoral immune response, but their effectiveness in immunocompromised patients remains less known. Emerging data suggests that cancer patients may not mount adequate protective immune response after SARS-CoV-2 infection.
“It is important for patients with cancer who are receiving chemotherapy to receive a COVID-19 vaccine,” says Saranya Chumsri, a Mayo Clinic hematologist and oncologist, and lead author of the paper. Chumsri says this advice also applies to patients with cancer who are taking CDK 4/6 inhibitors. These inhibitors are a newer class of medicines used to treat hormone-receptor-positive and HER2-negative breast cancers.
The study looked at 201 patients. Sixty-one were immunocompetent, 91 had a hematologic malignancy, and 49 had a solid malignancy on treatments associated with cytopenia, including chemotherapy or cyclin-dependent kinase 4/6 inhibitors (CDK4/6i).
A significantly greater proportion of immunocompetent patients (97%) had anti-S Ab titer ≥ 500 U/mL compared to patients with hematologic (8%) and solid malignancy (55%, p < 0.001). Despite 2 doses of SARS-CoV-2 mRNA vaccines, 53% of hematologic malignancy patients and 8% of solid malignancy patients on cytopenic therapy had no seroconversion (< 0.8 U/mL). Two patients subsequently developed breakthrough COVID-19 infection after full vaccination.
Chumsri says that while CDK 4/6 inhibitors are not conventionally considered to be as immunosuppressive as chemotherapy, her research on patients with breast cancer who take these drugs found that they exhibited less optimal neutralizing antibody activity. Chumsri recommends that antibody levels be tested in these patients after vaccination, and they should consider receiving booster vaccinations for COVID-19.
“Our study adds to growing body of literature suggesting that immunosuppressed patients have suboptimal humoral response to COVID-19 vaccination. Our study also underscores the significance of assessing antibody response after COVID-19 vaccines in these vulnerable patients.” the researchers write.
Chumsri anticipates having additional data later this year regarding broader immune responses to COVID-19 vaccinations, including cellular and antibody responses in patients receiving chemotherapy and targeted therapies with booster vaccinations.