Postponement of I-131 safe for post-surgical patients with low-risk differentiated thyroid cancer

Issue: June 2015

NASHVILLE, Tenn. — Patients with low-risk differentiated thyroid cancer can safely rely on observation and defer postoperative radioiodine ablation if their nonsuppressed thyroglobulin levels are less than 2 ng/mL 2 weeks after surgery.

Kathleen E. Hands, MD, of the University of Texas Health Science Center at San Antonio, followed 378 patients who underwent surgery for differentiated thyroid cancer from 2005 to 2012 (268 women; ages 18 to 79 years).

Patients were categorized by risk of recurrence. Tumor sizes ranged from 0.8 mm to 4 cm. Lymph node metastasis smaller than 5 mm — 34% multifocal — were found in 21 patients younger than 45 years. Patients older than 45 years and younger patients with BRAF-positive status underwent careful central neck inspection or dissection.

Patients whose nonsuppressed thyroglobulin level was less than 2 ng/mL at 2 weeks after surgery were started on levothyroxine and did not undergo radioiodine (I-131) ablation. If thyroglobulin level was between 2 ng/mL and 5 ng/mL, patients were evaluated for possible residual disease. Suppressed thyroglobulin tests were done at 3, 6 and 9 months after surgery and then every 6 months thereafter. Patients also underwent a post-operative neck surveillance ultrasound at 6 months and then only if thyroglobulin levels were elevated. Thyroid-stimulating hormone was suppressed to below .5 µU/L for the first year and then to less than 2 µU/L for low-risk patients.

Surgical complications included transient recurrent laryngeal nerve effect in 1.9% of cases and transient hypoparathyroidism in less than 2% of cases. During 8 years of follow-up none of the patients requested I-131 ablation. In addition, none of the cancers recurred.

According to Hands, 90% of patients were comfortable deferring I-131 while 10% expressed some discomfort with the decision, even though they were within the conservative boundaries of American Thyroid Association guideline recommendations.

“They were edgy simply because somebody else recommended or told them that they should get I-131 following their surgery even though they didn’t know what the pathology was going to be [or] what the outcome was going to be,” Hands said in her presentation. “So it becomes hard for [physicians]. Again, you’ve got to educate the patient that it’s not what’s necessary in [their] situation.” – by Jill Rollet

Reference:

Hands K, et al. Abstract #1058. Presented at: AACE 24th Annual Scientific & Clinical Congress; May 13-17, 2015; Nashville, Tenn.

Disclosure: Hands reports no relevant financial disclosures.