Scientists Look for Repeats in DNA as Evidence of Radiation Exposure in Thyroid Cancer

It has been known for some time that exposure of the head and neck to radiation therapy increases the subsequent risk of thyroid cancer. Now, a pair of researchers from Germany and the UK are looking into the likelihood that papillary thyroid cancer - which features DNA changes that were once thought to be due to aging - can be caused by radiation exposure.

Their results, which appeared in the journal Clinical Oncology, suggest that it may be feasible to test papillary thyroid cancer samples for copy number alterations (CNAs), which could indicate damage caused by ionizing radiation.

CNAs are variations in the sequence of base pairs found in the DNA of a human cell. While some CNAs are relatively harmless, others may cause serious health risks.

The authors of the new study noted that when scientists sequence the genes of tumor cells, CNAs are often found within their DNA. That principle holds true for papillary thyroid cancer, which is the most common type of thyroid cancer, according to the Columbia University Medical Center.

Papillary thyroid tumors account for at least 70 percent of all diagnosed cases of thyroid cancer, the Center specifies. In the new medical review, the authors suggested that researchers consider looking for the CNAs that papillary thyroid cancer cells have in common, since their discovery might provide biomarkers that diagnosticians could use to determine how the cancer originated.

They said that the only effective way to determine which CNAs are radiation-related is to compare the sequencing results from a number of closely related cancer study cohorts. By "closely related," the researchers meant that papillary cancer CNAs should be studied based on samples taken from patients who are very similar in age, health status and genetic background.

The team also made suggestions for maximizing the potential of comparative genetic study, such as sequencing DNA with the best integrity or the least degradation from fresh biopsies or blood samples.

Researchers concluded that compiling a list of radiation-caused CNAs will have a number of benefits in the detection and treatment of papillary thyroid cancer.  Currently, nearly 1,700 Americans die of thyroid cancer each year, according to the National Cancer Institute.