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More than 134,000 cancers might have gone undiagnosed during the first 10 months of the COVID-19 pandemic, according to a study of national trends in cancer incidence.

Annual cancer incidence fell almost 30% short of the expected rate from March through December 2020. The difference represented potentially 134,395 undiagnosed cancers during that period. Diagnosis of early- and late-stage cancers declined. Prostate, breast, and lung cancers accounted for the most potential missed cases. Overall, rates of "screenable" cancers decreased by 13.9% versus expected rates.

Rates of breast cancer began returning to norms after the first 3 months of the pandemic, but the incidence of colorectal, cervical, and lung cancers remained low, reported Krystle A. Lang Kuhs, PhD, MPH, of the University of Kentucky Markey Cancer Center in Lexington, and co-authors in .

"To our knowledge, this is the first study to offer a nationwide analysis using U.S. cancer registry data on the cancer case deficit experienced during the COVID-19 pandemic in 2020," the authors wrote. "The findings from this analysis can inform the U.S. healthcare system as decisions are made to recover the deficit through focused cancer screening and detection. These findings may also assist with planning for any future disruptions that would otherwise affect the timeliness of cancer diagnosis."

Actionable Information

Co-author Todd Burus, MA, MAS, also of the University of Kentucky Markey Cancer Center, told MedPage Today that the study highlights the impact of a disruption in routine healthcare visits and cancer screening on cancer detection and suggests potential action to offset or mitigate the effects.

"It is important to increase messaging and promotion of the screening guidelines among eligible populations to help re-establish good health-seeking behaviors," he wrote via email. "Our analysis of which cancer sites and population subgroups were most affected can help better target this messaging."

"We believe strong, consistent health messaging is crucial to helping establish (or re-establish) appropriate screening patterns," he continued. "We noted in the article how such strong messaging around female breast cancer screening likely contributed to the rapid recovery of female breast cancer incidence observed following the initial pandemic period."

The results also highlight a need for investment in technology and processes to increase the speed of cancer data reporting.

"Nationwide cancer incidence data for 2020 were not available until June 2023, at which point many of the best options for 'catching up' on missed cancer diagnoses from 2020 were off the table," Burus noted.

While the world focused on the threat posed by COVID-19, the threat of cancer remained ever present, the authors pointed out in their introduction. A decrease in observed cancer incidence during the period gives cause for concern. A decline in new cancer diagnoses in 2020 did not mean that the occurrence of cancer decreased, but that new cancers went undetected, an observation confirmed by multiple reports.

For this study, the authors analyzed data from the U.S. Cancer Statistics 2001-2020 Public Use Database, which included data from the CDC's National Program of Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology, and End Results program. The records encompassed 99.7% of all cancer cases in the 50 states and the District of Columbia.

Lang Kuhs and colleagues calculated cancer incidence by month of diagnosis from Jan. 1, 2018 through Dec. 31, 2020, capturing cancer diagnoses before and during the pandemic. They also collected patient demographics and cancer stage at diagnosis. The analysis excluded Indiana and Nevada, due to the unavailability of 2020 data.

National Impact

The results showed that 1,297,874 new cancers were reported from March 1 through Dec. 31, 2020. Male-female distribution was essentially 50/50, individuals 65 or older accounted for 58.3% of the cases, and 82% of the cancers occurred in white patients.

The total number of new cancer diagnoses translated into an incidence of 326.5 cases per 100,000 population, reflecting a 13% decrease from the expected rate of 375.4 per 100,000. In absolute terms, the difference amounted to 134,395 potentially missed cancer diagnoses from March through December 2020.

The disruption in healthcare had the biggest impact from March to May 2020, when total cancer diagnoses decreased by 28.6% from the expected rate. Rates recovered slightly from June to December but remained significantly below estimates.

Prostate cancer accounted for the largest number of potentially missed cases (22,950), followed by breast (16,870) and lung (16,333) cancers. Diagnosis rates for breast cancer showed evidence of recovery after the first 3 months of the pandemic, but this was not the case for colorectal, cervical, and lung cancers. The investigators found that states with the most restrictive COVID-19 responses had the greatest disruption in cancer diagnoses, but differences were nonsignificant by the end of 2020, with the exception of lung, kidney, and pancreatic cancers.

From March through May 2020, diagnoses of melanoma had the largest decrease from expected (43.4%). Statistically significant reductions persisted from June through December for all cancer sites except breast and pancreatic cancers.

An analysis of stage at cancer diagnosis showed that early-stage diagnoses were 38% lower than expected for March through May 2020, 6.3% lower for June through December, and 15.8% lower than expected for the full study period of March through December. Somewhat surprisingly, rates of late-stage diagnoses also decreased: 26.7% from March-May, 4.7% for June-December, and 11.5% for March-December.

"It is important that we continue to evaluate the trends identified in this study as U.S. cancer incidence data for years after 2020 become available," the authors wrote. "Pandemic-associated disruptions will continue to affect rates of cancer incidence, and how long it will be until we fully recover is still unknown."

"Beyond incidence, it is important that we measure the pandemic's contribution to future trends in cancer mortality and survival," they added. "With a near 10% reduction from expected rates in overall late-stage incidence from March to December 2020, there will undoubtedly -- and unfortunately -- be a subsequent rise in cancer mortality. How substantial a rise and for how long will provide a more complete picture of the consequences of COVID-19 disruptions on the burden of cancer in the U.S."

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