(HealthDay News) — Among adolescents and young adults, those who develop thyroid cancer as a secondary malignant neoplasm have decreased overall survival as compared with those with primary thyroid cancer, according to research published online Feb. 24 in Cancer.
Melanie Goldfarb, MD, and David R. Freyer, DO, of the University of Southern California in Los Angeles, analyzed data for 41,062 adolescents and young adults with thyroid cancer from the 1998 to 2010 American College of Surgeons National Cancer Database.
The researchers found that 1,349 (3.3%) of the cases had a prior malignancy.
Secondary malignant neoplasms, compared with primary thyroid cancers, were significantly more likely to be multifocal (odds ratio [OR] = 1.173; 95% confidence interval [CI],1.049-1.313) microcarcinomas less than 1 cm (OR = 1.496; 95% CI, 1.327-1.687) with tall/columnar cells (OR = 2.187; 95% CI, 0.534-0.692) in white patients (OR = 2.643; 95% CI, 1.310-5.331) and those aged 35 to 39 years (OR = 1.239; 95% CI, 1.093-1.404).
Also compared with primary thyroid cancers, secondary malignant neoplasms were less likely to occur in women (OR = 0.608; 95% CI, 0.534-0.692), Hispanic patients (OR = 0.779; 95% CI, 0.642-0.946), and those aged 15 to 19 years (OR = 0.624; 95% CI, 0.510-0.763) or 25 to 29 years (OR = 0.711; 95% CI, 0.604-0.837). They were also less likely to be larger than 4 cm (OR = 0.610; 95% CI, 0.493-0.758).
Relative risk of death was 6.63 times (95% CI, 4.97 to 8.86) greater for secondary versus primary thyroid cancers after adjustment for demographic, tumor, and thyroid treatment factors.
Factors that decreased overall survival for secondary malignant neoplasms were Hispanic origin, tall/columnar cell histology, and distant metastases.
“Adolescents and young adults who develop thyroid cancer as a secondary malignant neoplasm have a significantly decreased overall survival compared to adolescents and young adults with primary thyroid cancer,” the researchers wrote. “Whether the outcome disparity results from previous cancer treatment or differences in biology, environment, or access to care are areas needing further investigation.”