Evidence Update – Covid-19 and Cancer

Specialist registrar in Clinical Oncology Dr Stuart Walter reviews two recent papers

He highlights the importance of acknowledging the conclusion in the second paper: ‘While having cancer and receiving certain cancer therapies remain plausible risk factors for both contracting SARSCoV-2 infections and having more severe COVID-19 outcomes, existing data do not yet answer these questions’.

1. Risk factors for SARS-Cov-2 among patients in the Oxford Royal College of General Practitioners Research and Surveillance Centre primary care network: a cross sectional study. de Lusignan et al. Lancet Infect Dis May 2020    

 A nice cross sectional study of 3802 tested patients in Oxford looking at factors which contribute to the likelihood of a positive Cv19 test. 587 positive tests from Jan-Apr this year with univariate and multivariate analysis finding a significantly increased OR with black ethnicity, urban living and increased deprivation score. To a lesser extent male gender, CKD, obesity and respiratory disease also increased the likelihood of testing positive. Oddly being an active smoker seemed protective with a reduced OR but this may represent decreased nasopharyngeal viral load and therefore test sensitivity amongst other co-founding factors.    Of interest to us the significance of a diagnosis of cancer was investigated. However; there was no specification of stage or site of disease and the malignancy group was combined with the ‘immunosuppressed’ population defined as anyone on Prednisolone or DMARDs due to low numbers. Univariate analysis revealed an OR of 1.46 (1.17-1.82) for this group but when assessed with multivariate analysis this difference was lost (OR 1.01 [0.78-1.31]).    In addition to concerns about small numbers and definitions within this group the time period during which the study takes place has seen a huge shift in testing (both numbers and case definition) raising concerns of selection bias. I therefore am not sure we can confidently interpret any difference in the risk of testing positive for Cv-19 in our cancer population based on this. It does provide further good evidence of the increased risks in other groups but does not go as far to correlate this to severity of infection/outcomes.

2. COVID-19 and cancer: do we really know what we think we know? Robinson, Gyawali and Evans. Nature. 2020    

 A comment piece on multiple recent Cv-19 studies and their influence on healthcare planning and implementation in response to the pandemic within the Oncology setting. It highlights a number of issues including case definition of death from Cv-19 and even cancer itself, vast variation in reported prevalence of cancer and Cv-19 in the report populations and often worryingly small numbers. For example it mentions a paper by Liang et al which has been extensively cited as evidence of an increased risk from Cv-19 in patients with malignancy despite being based on only four cancer patients who received a variety of different treatments.    It summarises nicely with a quote from London and Kimmelman stating ‘crises are no excuse to lower scientific standards.’ Although this is certainly an important sentiment I think it somewhat forgets the urgency in which such decisions needed to be made and there was no choice but to accept the best available evidence – albeit reminding us to acknowledge its limitations. Certainly, now we have more time we should push for a return to higher standards of research. 

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Stuart Walter is a Specialty Registrar in Clinical Oncology.

He is based at the Edinburgh Cancer Centre.

Evidence Update – Covid-19 and Cancer

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