In a prospective study in Israel, 90% of cancer patients were seropositive for antibodies
The vast majority of patients undergoing active systemic therapy for cancer exhibited an adequate immune response to the Pfizer/BioNTech COVID-19 vaccine, according to a prospective cohort study.
A total of 90% of patients with solid tumors undergoing active intravenous cancer treatment were seropositive for SARS-CoV-2 antispike IgG antibodies after a second dose of the vaccine (BNT62b2), although their antibody titers were significantly lower than those of healthy controls, reported Salomon M. Stemmer, MD, of Rabin Medical Center of Bellinson Hospital in Petah Tikva, Israel, and colleagues.
“The findings of this study suggest that patients with cancer who are receiving active treatment and are at higher risk for severe COVID-19 disease respond well to messenger RNA SARS-CoV-2 vaccines and that vaccination of these patients should be seriously considered,” the team wrote in the study online in JAMA Oncology.
Stemmer and co-authors noted that cancer patients have a higher risk of developing COVID-19 complications and death, and while both the Pfizer and Moderna mRNA vaccines have proven to be extremely effective, the ability of cancer patients to produce an adequate antibody response to these vaccines has been unclear.
The investigators therefore conducted a prospective cohort study to evaluate the rates of antibody response to the BNT162b2 vaccine in 102 cancer patients on active treatment compared with 78 healthy controls.
In the cancer group, median age was 66, and 57% were men; in the control group, median age was 62 and 52% were women. The most common tumor types were gastrointestinal (28%), lung (25%), and breast (18%), and the most common cancer treatments of the patients were chemotherapy alone (29%), immunotherapy alone (22%), and chemotherapy plus biological therapy (20%).
All participants received a second dose of the Pfizer vaccine at least 12 days before enrollment in the study, and seropositivity was defined as 50 or greater AU/mL.
A total of 92 of the 102 cancer patients in the study were found to be seropositive for SARS-CoV-2 antispike IgG antibodies after the second dose of vaccine, compared with 100% of the controls, the researchers reported, adding, however, that the median IgB titer in cancer patients was significantly lower than in controls (1,931 vs 7,160 AU/mL).
Lower IgB titers were seen in patients who underwent chemotherapy plus immunotherapy and immunotherapy and biological therapy, and in a multivariate analysis the only variable significantly associated with lower titers was chemotherapy plus immunotherapy.
“As the correlation between antibody levels after vaccination and clinical protection has not yet been established, further research is required to determine the magnitude and duration of protection the vaccine provides to patients with cancer,” the authors concluded. “Nonetheless, our findings do suggest that vaccinating such patients during anticancer treatment of any kind should be a top priority.”
Until that correlation between antibody levels and protection against COVID-19 is confirmed, patients with cancer should continue to wear masks and practice social distancing, the team advised.
The results of the study should reassure cancer patients on active treatment about the effectiveness of the vaccine, Stemmer and co-authors said. Fear of exposure to the virus may prevent cancer patients from visiting their medical providers for treatment or deter them from participating in clinical trials. “The confidence of patients with cancer in their ability to be effectively vaccinated may help address both issues,” the researchers wrote.
In an editorial accompanying the study, Lova Sun, MD, of the University of Pennsylvania in Philadelphia, and colleagues agreed that seropositivity is a key, yet imperfect, correlate for protection against SARS-CoV-2 infection.
They asked, therefore, whether a statistically significant difference in IgG titer between patients with cancer and controls is truly clinically significant given the wide range of median titer values. In addition, the editorialists asked: Is it possible to accurately interpret differences in titer values in settings where many patients were likely never exposed to SARS-CoV-2?
The duration of protective immunity, particularly in patients who receive immunomodulatory cancer therapy, is another unanswered question, Sun and co-authors noted.
They added that several prospective studies are now ongoing, investigating the immune response to COVID-19 vaccination in cancer patients – studies that should provide important data about the safety and efficacy of vaccination, as well as the duration of protective immunity from vaccination, among these patients.
Mike Bassett is a staff writer focusing on oncology and hematology. He is based in Massachusetts.
This article was published by Medpage Today.