CALCA and medullary thyroid gland carcinoma: However, because of (1) the challenges of long-term monitoring of serum calcitonin in combination with (2) recognition of MTC as an aggressive cancer, only curable if diagnosed when still intrathyroidal, the ATA currently cautions that “...there are significant risks in delaying surgery in family members who have inherited a mutated RET allele, regardless of the patient’s age one must balance the risks of thyroidectomy against the possibility that the thyroidectomy will be incurable if it is delayed” (7).