The Covid-19 pandemic has impacted virtually every aspect of cancer care and research - from introducing new risks for cancer patients to disrupting the delivery of cancer treatment and the continuity of cancer research, a review of scientific literature shows.

The report, by researchers at Dana-Farber Cancer Institute and other institutions, suggests that while Covid-19 has complicated the treatment of cancer patients, it has also spurred creative solutions to challenges in clinical care, and research into the new disease is benefiting from insights gained over years of cancer research.

While much remains to be learned about the intersection of cancer and Covid-19, the new paper, published online by Cancer Cell, represents the most comprehensive survey to date about what physicians have learned, and what research is suggesting, about the interrelationship between the two diseases, the authors say.

Ziad Bakouny, co-lead author of the study, said: "Covid-19 has been responsible for killing more than one million people worldwide. Among those most at risk of developing severe forms of the illness are patients with cancer. Research into why patients with cancer are at heightened risk is moving very quickly. In this paper, we look at the state of the science in this area and others related to these two illnesses."

Cytokine storm and cancer patients

The paper summarises findings in four areas: the interconnected biology of cancer and Covid-19; changes in patient care prompted by the pandemic; effects on cancer research; and insights from cancer research applicable to the treatment of Covid-19.

The researcher said that one of the most dangerous consequences of Covid-19 is an overaggressive immune response known as a "cytokine storm," which can damage lung and other tissues. Patients with cancer treated with immune-stimulating therapies such as immune checkpoint inhibitors, chimeric antigen receptor (CAR) T-cell therapies and bi-specific T-cell engagers (BiTEs) are at risk for complications if the immune response produced by these therapies results in an attack on normal, healthy tissue.

Patients treated with CAR T-cell therapies and BiTEs, in particular, can develop a side effect known as cytokine release syndrome, which is similar to the cytokine storm in patients with Covid-19. Researchers have theorised that Covid-19 could exacerbate cytokine release syndrome in patients treated with certain immunotherapies, but studies have not definitely shown that this is happening, the new report states.

Role of telehealth in cancer care

Around the world, efforts to thwart the spread of Covid-19 included steps to decrease in-person visits between patients and physicians. Among these was a jump in the use of telemedicine, which, some studies indicate, can be just as effective as in-person meetings.

One study involving patients with breast cancer found that telehealth was associated with a higher quality of life and less depression and distress compared with usual care. While virtual visits offer a variety of benefits - less need to travel to physician appointments and incur the costs and inconvenience associated with travel - they're valuable only insofar as they don't take the place of in-person visits for exams, treatment, or diagnosis, research shows.

"It is also important to consider the unintended consequences of widespread adoption of technology," Bakouny said. "There is a serious potential risk of compounding health disparities between patients of different socioeconomic status, if telehealth services are mandated."

The research paper also highlighted the sharp decline in cancer diagnoses and screening during the peak of the pandemic. One study found that routine screening dropped by 85-90%. Delays in diagnosing cancer are likely to have long-term ripple effects. A British study estimates that, because of diagnostic delays, deaths five years from now may be 4-17% higher, depending on tumor type, than they would have been had the pandemic not occurred.

Bakouny added: "Since the start of the pandemic, we've accumulated a substantial amount of evidence about the dynamic between cancer and Covid-19. This review gave us an opportunity to take a step back and take stock of what we've learned - to get a sense of the most promising directions for patients, as well as where more study is needed, what we need to dig deeper into."