Disruptions in health care due to the COVID-19 pandemic caused a reduction in cancer diagnoses in 2020 that may pose challenges for estimating and interpreting long-term cancer trends, according to research published in the Journal of the National Cancer Institute.
The researchers noted that the overall rate of cancer diagnoses in the SEER database decreased by 10% in 2020 relative to 2019. Cancer incidence rates declined 9.6% for men and 9.3% for women.
The largest declines in incidence were seen for melanoma (15.8% for men and 14.3% for women) and thyroid cancer (14.0% for men and 17.9% for women). The smallest decline was seen for pancreatic cancer (4.3% for men and 3.9% for women).
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In addition to calculating changes in cancer incidence in 2020, the researchers demonstrated that including the 2020 cancer incidence rates in joinpoint models can result in less accurate trend estimates.
The researchers fit 3 joinpoint models to age- and delay-adjusted cancer incidence rates using SEER-22 data from the November 2021 submission (2000-2019), the November 2022 submission (2000-2020), and the November 2022 submission excluding 2020.
For all cancer sites combined, the model including the 2020 incidence rate suggested that cancer incidence has been declining at a constant rate since the year 2000 (annual percent change [APC], 0.60%). The models excluding the 2020 rate suggested that overall cancer incidence was stable during 2013-2019.
The model including the 2020 incidence rate suggested that melanoma incidence began to decline by 5.12% per year in 2018. The models excluding 2020 rates suggested that melanoma incidence has been increasing by 1.15% to 1.16% per year since 2005.
The model including the 2020 incidence rate suggested that prostate cancer incidence increased by 2.06% per year during 2014-2020. The models excluding the 2020 rate suggested a greater increase in prostate cancer incidence during 2014-2019. The APC was 3.7% for the November 2021 submission and 3.8% for the November 2022 submission excluding 2020.
The researchers wrote that these examples “clearly demonstrate that the inclusion of 2020 incidence rates in joinpoint models can pose challenges in trends estimates and interpretation, by providing a poorer fit to the data, less accurate and/or less precise long-term trend estimates.”
Based on these findings, the researchers proposed excluding the 2020 cancer incidence rates from trends estimates in the 2023 annual cancer statistics reports.
“The decision to exclude 2020 rates from trend analysis in the future hinges on the 2021 rates,” the researchers wrote. “If the 2021 rates continue to decline, we may reconsider incorporating the 2020 rate. However, if the 2021 rates are similar to pre-pandemic levels, we will likely continue excluding the 2020 incidence rates from joinpoint analysis.”
Reference
Mariotto AB, Feuer EJ, Howlader N, et al. Interpreting cancer incidence trends: Challenges due to the COVID-19 pandemic. Lancet Oncol. Published online May 23, 2023. doi:10.1093/jnci/djad086
