A new study suggests that thyroid cancer that develops after treatment for another form of cancer, is more dangerous than primary thyroid cancer.

The researchers said the results demonstrate that young cancer survivors should be screened to detect early signs of secondary thyroid cancer.

In coming to their conclusion, researchers gathered data from more than 41,000 cases of thyroid cancer in teens and young adults in the U.S. between 1998 and 2010 from the American College of Surgeons National Cancer Database. Three percent of the patients studied had been previously treated for a separate form of cancer.

The study found that secondary thyroid cancers were more likely to be small but occur in multiple locations. They were more likely to be less than one cm in diameter and less likely to be greater than 4 cm. While survival rates for both groups were over 95 percent, those with secondary cancer were found 6.6 percent times more likely to die than those with primary cancer. Patients with secondary cancer include those who have had previous adolescent/young adult malignancies such as central nervous system tumors, acute lymphocytic leukemia, and bone and soft tissue sarcomas, possibly caused by chemotherapy or radiation therapy.

The researchers noted that, according to current Children's Oncology Group guidelines, routine thyroid ultrasound is no longer recommended.

"These numbers are not insignificant considering that thyroid cancer is one of the most common adolescent and young adult cancers, especially among females, and patients need to be counseled appropriately," Melanie Goldfarb, MD and David Freyer, DO of the University of Southern California wrote online in Cancer.

Thyroid cancer is among the five most common malignancies in adolescent and young adult patients (ages 15 to 39). It can form as an initial cancer or, in rare cases, after treatment for a previous cancer. While primary tumors comprise the majority of thyroid cancers in young people, approximately three to four percent are secondary. The study suggests that there may be a difference between initial thyroid cancer and those that are secondary.

"This study will hopefully spur future research that will investigate if there are any causes - biological, environmental, prior treatment-related, or access to care disparities - to account for the survival differences in these secondary cancers," Goldfarb said.

Goldfarb and Freyer claimed that the results of the study may have implications for thyroid cancer screenings in young survivors of cancer.