In a study reported in a research letter in JAMA Oncology, Cai et al found that the incidence of cutaneous T-cell lymphoma increased in the United States between 2000 and 2018.
The study involved data from 18 Surveillance, Epidemiology, and End Results (SEER) Program registries for 2000 to 2018. A total of 14,942 newly diagnosed cases of cutaneous T-cell lymphoma from 2000 to 2018 were identified. The most common diagnoses were mycosis fungoides (n = 8,445; 57%), primary cutaneous T-cell lymphoma (n = 3,637; 24%), and primary cutaneous anaplastic large cell lymphoma (n = 1,509; 10%).
Key Findings
The overall cutaneous T-cell lymphoma incidence was 8.55 per million persons; incidence significantly increased over the study period, with an annual percent change (APC) of 0.61 (95% confidence interval [CI] = 0.12–1.10). Overall incidence per million persons was 5.42 for mycosis fungoides, 1.50 for primary cutaneous T-cell lymphoma, and 0.86 for primary cutaneous anaplastic large cell lymphoma. The incidence of mycosis fungoides increased significantly over time, with an annual percent change of 1.34 (95% CI = 0.89–1.79). The incidence of primary cutaneous T-cell lymphoma decreased significantly over time, with an annual percent change of −1.39 (95% CI = −2.22 to −0.56). The incidence of primary cutaneous anaplastic large cell lymphoma showed a nonsignificant decrease, with an annual percent change of −0.48 (95% CI = −2.57 to 1.65).
Among other cutaneous T-cell lymphoma subtypes for which change in incidence over time could be analyzed, Sézary syndrome (n = 268) showed the greatest increase among all cutaneous T-cell lymphoma subtypes, with an annual percent change of 3.83 (95% CI = 2.00–5.69). Peripheral T-cell lymphoma not otherwise specified (n = 910) showed a nonsignificant increase, with an annual percent change of 0.31 (95% CI = −0.93 to 1.56).
Overall, cutaneous T-cell lymphoma incidence per million persons was highest in Black persons (11.68), persons in the highest socioeconomic status quintiles (10.31), men (10.06), and those living in metropolitan counties (8.96). Patients aged ≥ 40 years had a substantially higher overall cutaneous T-cell lymphoma incidence per million persons vs those aged < 40 years (16.52 vs 2.52); however, those aged < 40 years had significantly greater increases in incidence over time, with annual percent changes of 2.87 for overall cutaneous T-cell lymphoma and 3.67 for mycosis fungoides. Other groups with significant increases in incidence included persons in the lowest socioeconomic status quintile (APC = 1.87), Black persons (APC = 1.63), women (APC = 0.92), and those living in metropolitan counties (APC = 0.68).
The investigators stated, “We observed an increased overall cutaneous T-cell lymphoma incidence between 2000 and 2018. These findings differ from previous North American studies, which suggested cutaneous T-cell lymphoma incidence stabilized after 1998, but are consistent with recent studies from Europe. These trends are likely multifactorial. Better diagnostic tools and increased awareness among physicians and patients may have led to improved cutaneous T-cell lymphoma detection. Physician density has been associated with higher incidence; therefore, efforts to increase access to health care may contribute to a rise in cutaneous T-cell lymphoma diagnosis. The incidence of primary cutaneous T-cell lymphoma has decreased considerably since 2000, possibly owing to better classification because primary cutaneous T-cell lymphoma is often a diagnosis of exclusion.”
Eleni Linos, MD, DrPH, of the Department of Dermatology, Stanford University School of Medicine, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by grants from the National Institutes of Health and a Melanoma Research Alliance’s L’Oreal Dermatological Beauty Brands-MRA Team Science Award. For full disclosures of the study authors, visit jamanetwork.com.
