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The decline in cancer diagnoses during the 2020 COVID pandemic did not translate into a spike in diagnoses in 2021, according to two separate studies.

Analysis of an NCI database showed that the actual number of cancer diagnoses in 2021 fell about 100,000 cases short of the expected number. Though not statistically significant, the trend toward fewer diagnoses held up across multiple disease sites, with a few notable exceptions, reported Nadia Howlader, PhD, of the NCI Division of Cancer Control and Population Sciences, in Bethesda, Maryland, and coauthors in the

"Our analysis indicates that overall incidence rates for all cancer sites and the five specific cancer sites examined in this study returned to prepandemic levels," Howlader and colleagues stated. "They did not, however, display a rebound to account for potential delayed diagnoses in 2020. Disruptions caused by the pandemic to the healthcare system leading to delays in cancer screenings and diagnoses resulted in a decline in reported cancer incidence rates in 2020 which seem not to have fully recovered in 2021."

The researchers noted that multiple studies have documented substantial declines in cancer incidence across multiple types of cancer in 2020. The declines were attributed to disruptions in cancer screening, diagnostic services, and routine medical visits during the pandemic, not issues related to data reporting.

Missed diagnoses during the pandemic will likely result in delayed diagnoses and diagnosis of more advanced-stage cancers in the coming years, they said. Knowing whether cancer rates returned to prepandemic levels in subsequent years is crucial to cancer care.

Meanwhile, a study based on the National Cancer Database showed that the total number of cancer diagnoses in 2021 had increased from 2020 but still remained about 45,000 cases below 2019. Nova Yang, MSPH, of the American Cancer Society in Atlanta, will report those findings later this week at the in San Francisco.

Yang and colleagues compared rates of cancer diagnosis for adults in all 50 states and the District of Columbia for 2019, 2020, and 2021. They calculated monthly cases, stage distribution, and adjusted odds ratios for stage I versus stages II-IV.

These data showed 864,430 cancer diagnoses in 2019, followed by 780,478 in 2020 and 819,791 in 2021. Stage I diagnoses as a proportion of the total decreased from 39.6% in 2019 to 31.1% in April 2020 and then rebounded to 39.2% in 2021. Comparison of diagnoses by stage showed a 5.98% decrease in stage I diagnoses from 2019 to 2021, and a 4.55% decrease in stage IV diagnoses.

Updated data that included 2022 showed that increases in diagnosis were most prominent for early breast cancer, lung cancer, and stomach cancer.

On the other hand, Howlader's group queried the NCI's Surveillance, Epidemiology, and End Results (SEER) database for the years 2019-2021 to determine the extent of rebound in cancer diagnoses after 2020. This group defined a rebound as a statistically significant increase in rates for 2021 as compared with expected rates for the year.

The SEER data covered 22 cancer registries representing about 48% of the U.S. population. The study included all cancers combined and five selected cancer sites -- breast, prostate, lung, pancreas, and thyroid -- that have screening recommendations, that are often detected by symptoms, or that are usually detected incidentally.

Howlader and colleagues reported various expected age-adjusted rates and observed rates of cancer diagnosis (in thousands) in 2021, with the accompanying rate ratios (RRs) of observed-to-expected not reaching statistical significance in most cases:

• All sites: 459.06 vs 458.33 (RR 1.00, 95% CI 0.97-1.03)
• Breast: 140.49 vs 137.42 (RR 0.98, 95% CI 0.87-1.09)
• Prostate: 135.06 vs 127.07 (RR 0.95, 95% CI 0.80-1.10)
• Lung/bronchus: 49.40 vs 46.93 (RR 0.95, 95% CI 0.94-0.96)
• Pancreas: 14.25 vs 13.92 (RR 0.98, 95% CI 0.95-0.99)
• Thyroid: 14.57 vs 13.62 (RR 0.93, 95% CI 0.85-1.02)

Additional analysis by stage at diagnosis showed significant rebound only for localized breast cancer (87.16 vs 89.75, RR 1.03, 95% CI 1.00-1.06) and metastatic breast cancer (7.76 vs 8.44, RR 1.09, 95% CI 1.04-1.13).

"Ongoing monitoring and targeted interventions are needed to address the long-term consequences of the COVID-19 pandemic on cancer care and outcomes," Howlader's group urged.

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