A pair of new studies documents initial drops—and, in some cases, rebounds—in cancer diagnoses in Canada and the United States in the first year of the COVID-19 pandemic.
Diagnosis rates varied by cancer type
In Canada, researchers from the Paul Albrechtsen Research Institute CancerCare Manitoba led a study of 48,378 cancer patients listed in the Manitoba Cancer Registry from January 2015 through December 2021. The study was published yesterday in JAMA Network Open. Median patient age at diagnosis was 68 years, and 49.6% were women.
"Disruptions to health care during the COVID-19 pandemic may have led to missed cancer diagnoses," the study authors wrote. "It is critical to evaluate the association between the COVID-19 pandemic and cancer incidence to address public and patient anxiety, inform recovery efforts, and identify strategies to reduce the system's vulnerability to future disruptions."
In April 2020, diagnoses fell 23% for any type of cancer, 46% for breast, 35% for colon, 47% for rectal, 50% for head and neck, 65% for melanoma, and 33% for endocrine cancer and rose 12% for blood cancer and 8% for cancers with an unknown primary site.
Lung cancer incidence was stable until December 2020, when it declined 11%. Brain and central nervous system and urinary cancer diagnoses fell 26% and 12%, respectively, from April 2020 to December 2021.
It is critical to evaluate the association between the COVID-19 pandemic and cancer incidence to address public and patient anxiety, inform recovery efforts, and identify strategies to reduce the system's vulnerability to future disruptions.
No link was observed between the pandemic and gynecologic (1% increase), other digestive (1% decrease), or pancreatic (7% increase) cancer rates. By December 2021, 5.3% fewer cancers than expected had been diagnosed. The largest estimated deficits were for breast (14.1% deficit), colon (12.2%), and lung (7.6%) cancers.
Breast and lung cancer rates in patients aged 75 years and older, urinary cancer, and brain and central nervous system cancers showed sustained decreases. There was little long-term change in the incidence of all other cancer types.
"However, the cumulative deficit for some high-fatality cancers is concerning and needs attention from health care delivery organizations," the researchers wrote. "Because of the heterogeneity in the association between the COVID-19 pandemic and cancer incidence, observational studies should be done to examine this association in other regions."
Largest drops in early, less aggressive melanomas
A Harvard Medical School–led study today in JAMA Dermatology analyzed data from 17 Surveillance, Epidemiology, and End Results (SEER) registries to examine melanoma diagnosis rates in the United States during the pandemic.
The team identified 76,846 new diagnoses of first primary localized or invasive cutaneous (originating in the pigment skin layer) melanoma from January 2018 to December 2020. Rates of localized melanoma diagnoses remained stable from 2018 and 2019 (−0.4% change), but significant declines were seen in 2020 versus 2019 (−24.5%), mostly among older (−27.5%), male (−26.4%), and White patients (−23.4%).
Rates of invasive melanoma weren't significantly different in 2019 versus 2018 (−0.1%), but 2020 brought significant decreases in diagnoses versus 2019 (−19.5%), primarily among White patients (−18.7%).
These findings may reflect decreased skin cancer screening examinations or access to dermatologic care during the pandemic, both of which may lead to reduced melanoma diagnoses.
In 2020, the incidence of new diagnoses fell significantly for superficial spreading melanomas (−19.6%), T1 (thin) melanomas (−25.5%), nonulcerated melanomas (−21.2%), and nonmitogenic (non–cell-dividing) melanomas (−24.4%). Rates of stage 1 melanomas—but not other stages—fell significantly in 2020 (−22.3%).
"The largest incidence decreases were seen in early-stage and less aggressive melanomas," the study authors wrote. "These findings may reflect decreased skin cancer screening examinations or access to dermatologic care during the pandemic, both of which may lead to reduced melanoma diagnoses."
The relative increase in thick melanomas in 2020 was primarily tied to a marked decrease in thin melanomas rather than an absolute increase in thicker melanomas. "Longer-term studies are needed to examine the implications of the pandemic for melanoma incidence and may help inform screening and overdiagnosis efforts," they concluded