Higher viral loads are associated with a greater risk of death among patients hospitalised with Covid-19 and could provide vital prognostic information, according to new research.

The study published in the journal Cancer Cell also found patients with hematologic malignancies have higher viral loads than patients without cancer.

Initial reports have suggested that patients with cancer may be more likely to develop severe Covid-19 than patients without cancer. This study looked at how admission viral load may affect the clinical outcomes of hospitalised patients who have both cancer and Covid-19.

Michael Satlin, senior study author and an assistant professor of medicine in the Division of Infectious Diseases at Weill Cornell Medicine, said: "As a community, we've only begun to understand the relationship between SARS-CoV-2 viral load and outcomes. Currently, this quantitative information is not given to patient care teams, and providers only know if a patient's test is positive or negative.

"Given this information to providers of patients with cancer who have Covid-19 could help them decide on which patients should receive more intensive monitoring when they are in the hospital and which should receive new antiviral medicines if these treatments are in short supply."

High viral loads in patients with cancer were associated with increased in-hospital mortality

In the new study, Satlin and his team used two standard diagnostic tests to measure the amount of SARS-CoV-2 in nasopharyngeal swab specimens obtained upon admission to three New York City hospitals between March 15 and May 14, 2020. One hundred of the patients had active cancer, and 2,914 patients did not. Among the cancer patients, some had solid tumors, whereas others had hematologic malignancies, which affect blood, blood cell-producing tissue called bone marrow, and lymph nodes - organs making up part of the circulatory and immune systems.

Half of patients with hematologic malignancies had high viral loads, compared to approximately 30% of patients without cancer. Among patients with hematologic malignancies, only those who had received chemotherapy or targeted therapy during the previous six months had significantly higher viral loads than the general inpatient population with Covid-19.

"We suspect that this finding may be from the underlying immunodeficiencies conferred by either the hematologic malignancies or the administered therapies, which may decrease the ability to inhibit proliferation of SARS-CoV-2," says co-first author Lars Westblade, an associate professor of pathology and laboratory medicine at Weill Cornell Medicine and a clinical microbiologist at NewYork-Presbyterian/Weill Cornell Medical Center. "Additional studies with a larger sample size of patients with hematologic malignancies are needed to more definitely assess whether these patients have increased mortality when hospitalized with Covid-19."

Overall, the in-hospital mortality rate was 38.8% among patients with a high viral load, 24.1% among patients with a medium viral load, and 15.3% among patients with a low viral load. Cancer patients showed a similar pattern, with mortality rates of 45.2%, 28.0%, and 12.1%, respectively. High viral loads in patients with cancer were associated with increased in-hospital mortality than low viral loads. This finding remained statistically significant, even after adjusting for factors such as age and need for supplemental oxygen within three hours of presentation to the emergency department.

The researchers added that it is not clear whether viral load predicts mortality rate in non-hospitalised individuals with Covid-19 and they plan to conduct larger studies to confirm their findings and investigate whether specific types of cancer and cancer treatments lead to higher viral loads and worse outcomes.

They would also like to assess whether measuring viral loads over time in a given patient could be used to personalise the type and duration of therapy.