The present invention relates to the field of cancer. More specifically, the present invention provides methods and compositions useful for treating thyroid cancer. In certain embodiments, the method comprises the steps of (a) treating DNA isolated from a sample collected from the patient using bisulfite； (b) measuring the DNA methylation level of the promoter region of the RASAL1 gene from the bisulfite-treated DNA using methylation-specific polymerase chain reaction (MSP), wherein the MSP creates a methylation and unmethylation band； (c) normalizing the measured DNA methylation level using an internal reference gene； (d) calculating the percentage of allelic methylation using the formula [M/(M+U]×100%, wherein M and U represent the density of the methylation and unmethylation band； and (e) predicting an increased risk of thyroid cancer in the subject if the percentage of allelic methylation is at least 40%.
