What do cancer registries show about cancer incidence trends before and after 2020?
Executive summary
Population-based cancer registries show steady, long-term shifts in cancer incidence before 2020—declines or stabilization for many male-dominant cancers and small increases for women—but a distinct, pandemic-linked drop in reported new diagnoses in 2020 followed by a rebound to expected levels in 2021, leading analysts to treat 2020 as an anomalous year and often exclude it from trend fits [1] [2] [3].
1. Long-term trends before 2020: slow shifts, not sudden surges
Decades of registry data compiled by SEER, NPCR and NAACCR document gradual, cancer-specific trends rather than a single upward or downward shift across the board: overall incidence among men fell from 2001 through 2013 and then stabilized, while overall incidence among women rose slightly—about 0.3% per year on average from 2003 through 2021 when 2020 is excluded—reflecting changes in risk factors, screening patterns, and demographics [2] [1] [4].
2. The 2020 anomaly: sharp drop in reported diagnoses tied to pandemic disruption
Registries registered a sharp decline in new cancer cases in diagnostic year 2020—prior analyses estimate 9%–10% fewer reported cases than expected overall, with larger shortfalls for some cancer types—an effect the National Cancer Institute, CDC, American Cancer Society and NAACCR attribute to pandemic-related disruptions in health care access, screening, and diagnostic pathways rather than to an actual sudden reduction in cancer occurrence [3] [1] [2].
3. The 2021 rebound and how analysts treat 2020 in trend models
By 2021 incidence largely returned to pre-pandemic levels, prompting official reports to display 2020 incidence separately and to exclude it from linear trend fits so that long-term trends are not distorted by the temporary pandemic dip; multiple recent “Cancer Statistics” and Annual Report products therefore present 2020 as a cross-sectional year distinct from trend lines [5] [6] [7].
4. Cancer types that buck long-term trends and where registries spotlight emerging concerns
Registries and pooled reports have highlighted increasing incidence in several cancers linked with obesity and other changing risk profiles—uterine (endometrial), pancreatic, kidney, and liver cancers—and rising colorectal cancer incidence in adolescents and young adults; these increases appeared before the pandemic and continued to shape concern about future burdens even as overall rates showed stability or modest decline for other sites [8] [9] [4].
5. Mortality trends provide essential context: deaths continued to decline
Despite the 2020 diagnostic dip, death rates from cancer continued to decline through the early pandemic years, with the Annual Report finding steady decreases in cancer mortality from 2001 through 2022—evidence that improvements in prevention, early detection (over a longer timeframe), and treatment are altering outcomes even as short-term diagnostic turmoil occurred in 2020 [2] [1].
6. Data caveats: delay adjustment, coverage, and interpretation pitfalls
Registries adjust incidence rates for reporting delays and age-standardize to enable comparisons, but coverage varies (SEER covers roughly half the U.S. population and NPCR complements that coverage), and analysts warn that the 2020 dip reflects missed or delayed diagnoses rather than biological changes; consequently, many tables explicitly show 2020 separately or exclude it from trend models to avoid misinterpretation [10] [5] [3].
7. Competing narratives and implicit agendas in reporting the change
Public and media narratives sometimes overinterpret the 2020 drop as “fewer cancers,” when registry investigators explicitly link it to reduced health-care use; advocacy groups may emphasize missed diagnoses and backlog impacts, while health systems and researchers stress recovery by 2021 and the need to catch up on screening—these different emphases reflect distinct agendas: public-health caution about delayed care, research focus on valid trend estimation, and media desire for concise headlines [3] [1] [8].
8. Bottom line for policymakers and clinicians
Cancer registries show that the pandemic produced a measurable interruption in case ascertainment in 2020, that overall incidence trends before and after that year vary by sex and cancer type (men stable after earlier declines; women rising slightly), and that 2021 largely restored expected case counts—interpretation requires using delay-adjusted data, treating 2020 as an anomalous year in trend analyses, and tracking site-specific signals like obesity-linked cancers and early-onset colorectal cancer for planning and prevention [3] [2] [1].