Most Cancer Patients With Breakthrough
COVID-19 Infection Experience Severe Outcomes

Sharon Worcester

December 28, 2021

Patients with cancer remain vulnerable to breakthrough COVID-19 infection after vaccination and most experience severe outcomes, according to a review of patient data from the international COVID-19 and Cancer Consortium (CCC19) registry.

Of 54 fully vaccinated patients with cancer and COVID-19, 35 (65%) were hospitalized, 10 (19%) were admitted to the intensive care unit or required mechanical ventilation, and 7 (13%) died within 30 days.

Although the study did not assess the rate of breakthrough infection among fully vaccinated patients with cancer, the findings do underscore the need for continued vigilance in protecting this vulnerable patient population by vaccinating close contacts, administering boosters, social distancing, and mask-wearing.

"Overall, vaccination remains an invaluable strategy in protecting vulnerable populations, including patients with cancer, against COVID-19. However, patients with cancer who develop breakthrough infection despite full vaccination remain at risk of severe outcomes," the authors wrote.

The analysis, which appeared online in Annals of Oncology December 24 as a pre-proof but has not yet been peer-reviewed, analyzed registry data from 1787 adults with current or prior invasive cancer and laboratory-confirmed COVID-19 between November 1, 2020 and May 31, 2021, before COVID vaccination was widespread. Of those, 1656 (93%) were unvaccinated, 77 (4%) were partially vaccinated, and 54 (3%) were considered fully vaccinated at the time of COVID-19 infection.

Of the fully vaccinated patients with breakthrough infection, most experienced a severe outcome: two thirds had to be hospitalized, nearly 1 in 5 went to the ICU or needed mechanical ventilation, and 13% died within 30 days.

"Comparable rates were observed in the unvaccinated group,” the investigators write, adding that there was no statistical difference in 30-day mortality between the fully vaccinated patients and the unvaccinated cohort (adjusted odds ratio [aOR], 1.08).

Factors associated with increased 30-day mortality among unvaccinated patients included lymphopenia (aOR, 1.68), comorbidities (aORs, 1.66 - 2.10), worse performance status (aORs, 2.26 - 4.34), and baseline cancer status (active/progressing vs not active/ progressing, aOR, 6.07).

No significant differences were observed in ICU, mechanical ventilation, or hospitalization rates between the vaccinated and unvaccinated cohort after adjustment for cofounders (aORs,1.13 and 1.25, respectively).

Notably, patients with an underlying hematologic malignancy were overrepresented among those with breakthrough COVID-19 (35% vs 20%). Compared to those with solid cancers, patients with hematologic malignancies also had significantly higher rates of ICU admission, mechanical ventilation, and hospitalization.

This finding is "consistent with evidence that these patients may have a blunted serologic response to vaccination secondary to disease or therapy,” the authors note.

Although the investigators did not evaluate the risk of breakthrough infection postvaccination, recent research indicates that receiving a COVID-19 booster increases antibody levels among patients with cancer under active treatment and thus may provide additional protection against the virus.

Given the risk of breakthrough infection and severe outcomes in patients with cancer, the authors propose that "a mitigation approach that includes vaccination of close contacts, boosters, social distancing, and mask-wearing in public should be continued for the foreseeable future." However, "additional research is needed to further categorize the patients that remain at risk of symptomatic COVID-19 following vaccination, and test strategies that may reduce this risk."

The findings are from a pre-proof that has not yet been peer-reviewed or published. First author A.L. Schmidt, MD, reported nonfinancial support from Astellas, nonfinancial support from Pfizer, outside the submitted work. Other co-authors reported a range of disclosures as well. The full list can be found with the original article.

Annals Onc. Published online December 24, 2021 as a pre-proof. Full text

Sharon Worcester is an award-winning medical journalist at MDedge News, part of the Medscape Professional Network

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