An analysis of aggressive papillary thyroid carcinoma (PTC) subtypes indicated that treatment of these variants should be tailored to the specific histologic subtypes present.
According to the JAMA Oncology study, “collectively, aggressive PTC subtypes are often lumped together as intermediate risk: too serious to ignore but too nebulous to separate.”
To better understand these subtypes, researchers looked at data from 2000 to 2016 from hospital-based and population-based cancer registries in the United States in the search for aggressive PTC variants. Included cases were 415 diffuse sclerosing (DSV), 3339 tall-cell variant (TCV), and 1331 poorly differentiated (PDTC) variants. These cases were then compared against other well-differentiated papillary thyroid carcinoma (WDPTC) and anaplastic cases.
Over the study period, there was an increase in the incidence of aggressive variants, with the annual percentage change of 9.1 (P <.001) compared with a relative increase for WDPTC of 5.1 (P <.001) and 1.9 for anaplastic cases (P <.007).
“Our results reframe the conventional view regarding the rise in incidence of well-differentiated thyroid cancers,” the researchers wrote. “While the increase documented for WDPTC is substantial, the growth for aggressive PTC variants is even greater over the same period and beyond what might be expected by chance.”
They also noted that the increased incidence of these aggressive subtypes is less likely to be drawn from incidental diagnoses.
Additionally, the researchers observed a wide spectrum of mortality risk. The 10-year overall survival was 85.4% for WDPTC and 79.2% for DSV, 71.9% for TCV, 45.1% for PDTC, 27.9% in the insular variants, and 8.9% for anaplastic cases.
“Aggressive subtypes serve deeper understanding and greater vigilance, because they constitute a rising fraction of incidence and a lopsided share of cancer-associated mortality,” the researchers concluded. “Our data suggest that broader integration of unique PTC histological characteristics may improve the dynamic risk stratification supported in current treatment guidelines.”
Ho AS, Luu M, Barrios L, et al. Incidence and mortality risk spectrum across aggressive variants of papillary thyroid carcinoma [published online March 5, 2020]. JAMA Oncol. doi: 10.1001/jamaoncol.2019.6851