Incidence of rare cancers during the COVID-19 pandemic: a US population-based study

Recent media reporting has suggested an increase in the incidence of rare cancers in 2021 as a result of the COVID-19 pandemic, raising concern for possible carcinogenic effects of severe acute respiratory syndrome coronavirus 2 infection. We aimed to identify cancers that increased in incidence in the United States during 2021 compared with 2018-2019.

We analyzed data from Surveillance, Epidemiology, and End Results (SEER-22) using a systematic classification schema including rare cancers. We estimated age-standardized incidence rate ratios (aIRRs) comparing the year 2021 to 2018-2019 for 693 individual cancer types and highlight those with an aIRR > 1 based on a Bonferroni-corrected P-value threshold. Cancer types of particular interest included cholangiocarcinoma, diffuse large B-cell lymphoma, Kaposi sarcoma, and lung cancer.

Among 693 unique cancer types evaluated, 9 showed a significant increase in incidence in 2021 compared with 2018-2019 and did not also increase in prior years, including 4 subtypes of thymoma (type-A aIRR = 2.50; type-AB aIRR = 2.78; type-B aIRR = 1.90; type not otherwise specified aIRR = 1.60), granulosa cell tumor of the ovary (aIRR = 2.72), peripheral neuroectodermal tumors of the bone (aIRR = 10.6) and soft tissue (aIRR = 3.20), pheochromocytoma (aIRR = 4.59), and paraganglioma (aIRR = 3.30). Increases for all 9 cancer types could be attributed to changes in cancer registry reporting practice. Cancer types of particular interest did not increase in incidence during 2021.

Our study does not support an increase in cancer incidence in the United States in 2021 due to the COVID-19 pandemic. It is important to monitor future trends, which may reveal longer-term effects of COVID-19.