April 26, 2022
The vaccines protecting patients against COVID-19 are highly effective in healthy individuals. Their efficacy in patients who are immunocompromised, such as those in active cancer treatment, is less understood. A study published in the April 2022 issue Mayo Clinic Proceedings sought to evaluate the humoral response to the mRNA COVID-19 vaccine in patients undergoing treatment for a cancer diagnosis.
"Patients with cancer, especially those on immunosuppressive chemotherapy or even with a targeted therapy CDK4/6 inhibitor, seem to have decreased humoral response and can develop an infection," said Saranya Chumsri, M.D., a hematologist oncologist at Mayo Clinic in Jacksonville, Florida. "We included a variety of different types of cancer, including solid tumors and hematologic malignancies."
Humoral response for various cancers and therapies
The retrospective study included 201 adult patients who had not had a prior COVID-19 infection. Patients on an immunosuppressant for an indication other than cancer were not included.
In this study, 61 patients were immunocompetent and 25 of those were healthy with no history of cancer. The other 36 were patients with cancer who were not on an immunosuppressive therapy. Of the 140 immunocompromised patients, 91 had hematologic malignancies and 60 of those were patients with chronic lymphocytic leukemia (CLL). The remaining 49 patients had solid tumor malignancies and were on treatments associated with low blood count (cytopenia), including chemotherapy and cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6 inhibitor).
All patients in the study had an anti-S antibody titer performed at one of Mayo Clinic's three sites in Arizona, Florida and Minnesota between Jan. 1, 2021, and May 10, 2021. All titers were performed after two doses of the COVID-19 vaccine. Vaccines were split nearly equally by the developer, with 106 patients receiving a Pfizer-BioNTech vaccine and 95 receiving a Moderna vaccine. This is the first study that evaluated either vaccine type using the same antibody assay (anti-SARS-CoV-2 spike antibody, or anti-S Ab).
Patients with cancer showed impaired humoral response
Immunocompetent patients had significantly higher antibody levels than the other patients. A greater proportion of immunocompetent patients also mounted a humoral response. More patients with hematologic malignancies had extremely low titers with 48 patients having negative titers and 67 patients with titers of 50 units per milliliter or less. Of the patients with CLL, 63.3% (38 patients) had negative titer results.
In patients with solid malignancies, four patients received negative titers and 10 patients had titers of 50 units per milliliter or less. Although not statistically significant, a greater percentage of patients on chemotherapy had anti-S Ab titers of 500 units per milliliter or less than those who received CDK4/6 inhibitors. This study did show, however, that patients on CDK4/6 inhibitors may have impaired antibody responses even though this therapy is not generally considered an immunosuppressant.
There was no significant difference in age or sex associated with antibody results. Two of the 201 patients in the study had a breakthrough infection, one each in the immunocompetent and immunocompromised patient groups.
Precautions for patients with cancer
This study showed that patients with cancer, particularly those with hematologic malignancies, had significantly impaired humoral responses after two doses of the COVID-19 vaccine. It is very important to continue to evaluate seroconversion for patients in active cancer treatments.
"Our data suggest that patients on chemotherapy as well as some targeted therapies like CDK4/6 inhibitor, which is commonly used in breast cancer, should also have antibody tests performed," said Dr. Chumsri. "These patients should also consider booster vaccines as well as continued COVID-19 precautions."
Dr. Chumsri and her colleagues are continuing to study in this area and will soon publish additional prospective research analyzing the effect of booster vaccines in this population, as well as comparing these antibody responses and breakthrough infection rates with those of healthy individuals and those with natural immunity to COVID-19.
For more information
Chumsri S, et al. Humoral responses after SARS-CoV-2 mRNA vaccination and breakthrough infection in cancer patients. Mayo Clinic Proceedings. 2022;6:120.
Refer a patient to Mayo Clinic.