The rise in the incidence of thyroid cancer is a world-wide phenomenon. National Cancer Database showed that the incidence of thyroid cancer increased from 7.1 per 100,000 in 2000 to 17.6 per 100,000 in 2013 in United States. During this period, stage IV disease increased 1 per 100,000. Because early diagnosis and treatment should lead to a decrease in metastatic disease, it is regarded as results of over-diagnosis and that more aggressive disease is not being removed by early detection. However, the situation in Korea suggest a different scenario. We reported that age-standardized mortality rates from thyroid cancer increased until 2004 (from 0.17 per 100,000 in 1985 to 0.85 per 100,000 in 2004) and then continuously decreased until 2015 to 0.42 per 100,000 suggesting the early detection might be responsible for decrease.
However, early detection of thyroid cancer seems not to be cost-effective. So, risk stratification of thyroid cancers is important. Most prognostic factors known are based on those obtainable after surgery.
So, identifying prognostic indicator(s) before treatment is an unmet clinical need for thyroid cancer. I would like to discuss on those factors which our group have recently discovered.
Another unmet clinical need is management of patients with radioiodine refractory (RAI-R) differentiated thyroid cancer (DTC). Though sorafenib and lenvatinib had been available, we need novel drug(s). We recently found that PHGDH, a critical enzyme for serine biosynthesis, could be a novel therapeutic target in thyroid cancer.
We found that the lymphocyte-to-monocyte ratio, which reflects the tumor infiltrating immune cell status and host immunity, is a prognostic marker in predicting the survival of patients with anaplastic thyroid carcinoma, and of RAI-R DTC patients. So, we need to get deep insight into tumor-host interaction in our future research in thyroid cancer for better clinical outcomes.