A series of recent studies have affirmed that many cancer patients are at high risk for developing severe forms of COVID-19. One study of nearly 900 cancer patients infected with SARS-CoV-2 in the United Kingdom, for instance, estimated the mortality rate to be 33.6%, substantially higher than the rate in the general population.1

But many of those studies have largely focused on hospitalized patients — often a necessary bias due to early shortfalls in testing capacity — and so far, a comprehensive picture of the outcomes of SARS-CoV-2 infections in cancer patients has been lacking.

Now, a recent study of more than 1100 patients receiving treatment in oncology outpatient clinics in Germany reported that the vast majority of patients who tested positive for SARS-CoV-2 did not show any symptoms. Moreover, asymptomatic infections did not seem to impact the outcomes of further treatment such as chemotherapy. The findings — presented in a poster at the European Society of Medical Oncology (ESMO) Virtual Congress 2020 — conflicted with the belief that cancer patients in general tend to develop more severe forms of COVID-19.2

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“This particular piece of research . . . is very relevant to complete the picture in terms of how severe COVID is” in cancer patients, said David Pinato, MD, PhD, a clinician scientist and consultant medical oncologist in the department of surgery and cancer at Imperial College London, who wasn’t involved in the study. Such findings “are reshaping the way we think about COVID in cancer.”

The study comprised 1127 cancer patients visiting one of 7 outpatient clinics in Bavaria between April 15 and April 26, 2020. Most patients had solid cancers (62%). Many patients had underlying comorbidities such as hypertension (26%) and diabetes (13%), but data were not available for approximately 60% of patients. The patients received a range of treatments including chemotherapy (20%), chemoimmunotherapy (14%), antihormone therapy (12%), immunotherapy (10%), tyrosine kinase inhibitors (4%), and 16% underwent surgery.

All patients received a throat swab and SARS-CoV-2 RT-qPCR test, whether or not they displayed symptoms. Of the 78 patients who tested positive, only 2 had mild symptoms and 1 developed pneumonia. The remaining 75 (96.1%) were asymptomatic — a finding that surprised Louisa Hempel, BscMed, of Sigmund Freud University’s Medical School in Vienna, Austria.

“What we expected first was that . . . cancer patients, because of their treatment and immune-suppressive therapies, might develop severe forms of COVID, but that wasn’t the case,” Hempel said. The discrepancy with the results of previous studies is likely due to the fact that those largely focused on hospitalized patients, where “you have a bias because these patients might be in a worse condition anyway,” she added. “In outpatient settings, the picture is completely different,” she said, although further studies are needed.  

To Hempel, given the known potential of asymptomatic individuals to transmit SARS-CoV-2, the findings highlighted that testing should include all outpatients, not just those that display symptoms. Up to 50% of transmission between people occurs from asymptomatic individuals, noted director of the National Institute of Allergy and Infectious Diseases Anthony Fauci, MD, at a keynote presentation at ESMO.3

In addition, asymptomatic COVID-19 status appeared to have no impact on the further course of the patients’ therapy — a finding that underscored the importance of continuing routine therapy amidst the pandemic, as long as patients don’t develop complications, Hempel noted. She and her colleagues observed that mortality in the SARS-CoV-2–positive group (1 patient died, ie, 1%) was not significantly higher than in the group of patients who tested negative for the virus (13 patients, ie, 1%).