Highlights
- Among adults in Ontario recently diagnosed with cancer, higher COVID-19 infection rates during the first year of the pandemic occurred among cancers diagnosed at a younger age and among hematological cancers.
- Understanding who is more affected by COVID-19 allows for the implementation of interventions that mitigate infection and can guide future research on the populations at greatest risk.
During the first year of the COVID-19 pandemic in Ontario, there were 1,676 COVID-19 infections among 177,281 people who had been recently diagnosed with cancer. The age-adjusted rates of COVID-19 infection were similar (not statistically significant, p greater than 0.05) between people recently diagnosed with cancer (1.89 per 100 people) and the general Ontario population (2.02 per 100 people).
Before age-adjustment, the highest rates of COVID-19 infection among people with cancer were seen in cancers that occur more commonly at younger ages and in hematological cancers. These data included people in Ontario age 20 and older who were diagnosed with cancer from March 15, 2018 to March 14, 2020.
Cancer types significantly (p less than 0.05) associated with younger age at diagnosis include:
- testicular (mean age at diagnosis 37.2 years)
- cervical (48.0 years)
- thyroid (51.3 years)
These compare with an average age at diagnosis of 64.5 years among all cancers combined.
Hematological cancers, which begin in the immune system or in tissues that create blood[1], include Hodgkin lymphoma, non-Hodgkin lymphoma, leukemia and myeloma.
From March 15, 2020 to February 28, 2021, the highest 10 COVID-19 infection rates (defined as the first COVID-19 positive test per person) among Ontario adults recently diagnosed with cancer ranged from 2.60 (testis) to 1.53 (non-Hodgkin lymphoma), as shown in the figure.
Of all cancer types, only testicular and thyroid cancer had COVID-19 infection rates significantly higher (p less than 0.05) than for all cancers combined, which is likely related to younger age at diagnosis. This finding is consistent with the mean age of 45.3 years of people with COVID-19 infection in the general Ontario population.
The tendency for higher COVID-19 infection rates among people in Ontario with hematological cancers is consistent with other studies. This tendency may be related to the higher risk of infection due to elevated immunosuppression compared with other cancer types in this group of people with cancer.[2][3] However, this analysis shows that COVID-19 infections are also associated with solid tumours (i.e., non-hematological).
People recently diagnosed with cancer are likely to be actively undergoing treatment, monitoring or follow-up[4] and therefore may be more affected by the pandemic than others because:
- their immunity may be suppressed
- they cannot isolate when they need to interact with the healthcare system
- their access to care may be delayed or interrupted
Ontario’s surgical shutdown date (March 15, 2020) was used to define the start of the first year of the COVID-19 pandemic. The Ontario Cancer Registry was used to identify the cancer cases (except non-melanoma skin cancers, which are not collected by the registry[5]). The registry was linked to the Ontario Laboratory Information System, which was used to identify COVID infection based on lab test results for both people with cancer and the general Ontario population. This analysis did not include institutional residents such as people residing in long-term care.
Characterizing the impacts of COVID-19 among people with cancer has the following benefits:
- Provides a foundation to better understanding who is affected
- Helps the health system be more vigilant about groups of people at the greatest risk
- Allows for the implementation of interventions that mitigate infection
- Can guide epidemiologic investigations of the impact of COVID-19 among people with cancer
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