Does cancer chemotherapy increase Covid-19 risks?

Q. I have cancer and am being treated with chemotherapy. Am I at increased risk of getting sick and dying from Covid-19?

A: People with cancer, and particularly those with leukaemia, seem to have a higher death rate from Covid-19 than the general population does, though cancer chemotherapy does not appear to further increase the risk of dying from Covid-19. Studies, however, have been limited and results are sometimes difficult to interpret.

Many types of chemotherapy work by disrupting the cancer cell’s machinery that allows it to divide and grow so rapidly. Unfortunately, chemotherapy can also disrupt healthy cells that grow rapidly in the body, including the bone marrow cells that make our immune system. Consequently, people receiving chemotherapy are at risk of becoming immunocompromised. The immune system, our body’s primary line of defense against microbes, can also be corrupted by blood and bone marrow cancers such as leukaemia, which can prevent the immune system from maturing, rendering it incompetent to fight infections.

It’s a logical assumption that people with compromised immune systems would be more susceptible to catching the novel coronavirus and getting sick from it. In one recent study, patients with cancers of the blood and bone marrow had higher coronavirus viral loads, which was associated with higher mortality. But there has been a paucity of population-based studies of coronavirus infection rates in people with cancer, so we don’t know for sure.

A few studies have explored the severity of Covid-19 infections in people with cancer. One study from Britain of more than 1,000 cancer patients seen over a seven-week period during the pandemic found a twofold death rate for patients with leukaemia, but not for those with other cancers, compared with a similar group of cancer patients from three years earlier, before Covid-19.

In another study of more than 900 patients with ongoing or previous cancers and Covid-19 infections from the United States, Canada and Spain, 13% died and 26% either died or had illness severe enough to require intensive care. These rates are much higher than for the general population; among those with Covid-19, the estimated case-fatality rate is 3% in the United States.

Cancer patients receiving chemotherapy did not appear to have higher death rates or more severe disease than other cancer patients, although in patients with cancers of the blood or bone marrow, such as leukaemia and lymphoma, 14% died and 35% developed severe illness.

Another international study of almost 200 patients with chronic leukaemia found even higher death rates from Covid-19, 33%, though again, rates were no greater for those receiving chemotherapy. Interestingly, patients receiving palliative cancer care, which focuses on improving quality of life and providing symptom relief rather than active cancer treatment, were more likely to die outside an intensive care unit, likely because they declined aggressive therapy given their cancer prognosis.

In an ongoing Covid-19 registry through the American Society of Hematology, the death rate among almost 600 patients with blood and bone marrow cancers was high, at 20%. More than half of patients were hospitalized, and 23% were sick enough to require a stay in an intensive care unit. More than 50 patients decided to forgo ICU admission and chose a palliative treatment approach, illustrating the difficulty in interpreting Covid-19 severity and death rates in patients who have other serious illnesses like cancer.