Lower Radiation Dose Effective for Thyroid Cancer

TON - JUNE 2012 VOL 5, NO 5 published on June 28, 2012

Lower radioiodine doses given with recombinant human thyrotropin (thyrotropin alfa) was as effective as high-dose radioiodine, and the low-dose treatment was associated with fewer side effects. Use of thyrotropin alfa along with low-dose radiation allows patients to avoid fatigue, lethargy, and weight gain associated with thyroid hormone withdrawal. These results suggest that thyroid cancer treatment can be transformed into a safer, shorter session, according to researchers.

The radioiodine dose used in the HiLo trial was one-third of the currently used level, setting a new standard of care, they said. “We are delighted that this study of thyroid cancer care will change international approaches to treating the disease more safely, by reducing the chance of another cancer developing later in life and other side effects. Patients will have a better quality of life, they will be treated more quickly, which will keep the disruption to their lives at a minimum, as well as saving NHS money,” stated lead author Ujjal Mallick, MD, Freeman Hospital in Newcastle, United Kingdom.

Study results were published in the May 2 issue of the New England Journal of Medicine. HiLo was a randomized, noninferiority trial comparing low-dose and high-dose radioiodine, each in combination with either thyrotropin alfa or thyroid hormone withdrawal before ablation. Of 438 randomized patients with stage T1-3 nonmetastatic thyroid cancer, 421 were evaluable. Successful thyroid ablation was achieved in 85% of the low-dose radioiodine group versus 88.9% in the high-dose radioiodine group and 87.1% in the group undergoing thyroid hormone withdrawal. These percentages were within the 95% confidence intervals for noninferiority. Results were similar for low-dose radioiodine plus thyrotropin alfa (84.3%) versus high-dose radioiodine plus thyroid hormone withdrawal (87.6%) or high-dose radioiodine plus thyrotropin alfa (90.2%).

About 3 times as many patients randomized to high-dose radioiodine were hospitalized for at least 3 days versus those in the low-dose group: 36.3% versus 13%, respectively. More adverse events were observed with high-dose radioiodine as well: 33% versus 21% in the low-dose group (P = .007); adverse events were 23% in the thyrotropin alfa group versus 30% in the group undergoing thyroid hormone withdrawal.

Current treatment is surgical re - moval of the thyroid gland followed by radioactive iodine taken in a capsule to destroy any remaining thyroid tissue that could presumably harbor cancer cells. This high-dose treatment requires at least 2 days of isolation in hospital for the radiation to dissipate. High-dose radioiodine is associated with late-occurring side effects that affect quality of life. The low-dose treatment can be done on an outpatient basis and has fewer side effects. The rationale for the study was that newer surgical techniques are more successful in ablating thyroid tissue and therefore lower radioiodine doses could be adequate.

The trial also showed that patients can continue taking thyroid hormone tablets if they are given thyroid-stimulating hormone (ie, thyrotropin alfa) before they take low-dose radioactive iodine.

Last modified: May 21, 2015