Treatment of benign thyroid cysts by intracystic injection of OK-432

Benign thyroid cysts have been successfully treated with nonoperative sclerotherapy. Although OK-432 is a safe and effective sclerosing agent used to treat benign cystic lesions, little is known about its effectiveness in thyroid cysts. This study tested the efficacy of OK-432 sclerotherapy for thyroid cysts.

This was a prospective cohort study of 45 consecutive patients with benign thyroid cysts, as assessed by ultrasound (US)-guided biopsy. After evacuation, about 50% of the aspirated fluid volume was replaced with saline solution containing 0.1 to 0.2 mg OK-432. Recurrences were treated by repeat treatments, to a maximum of 3. Outcome was cyst volume on US 6 months after the last treatment.

Median pretreatment cyst volume was 15 mL (range, 3.5-110). Of the 45 patients, 33 (73%) were cured, defined as a residual cyst volume <1 mL; 20 were cured after 1 treatment, 8 after 2 treatments, and 5 after 3 treatments. Of the 12 patients (27%) not cured, 7 had >50% of the original cyst volume and 5 had <50% volume reduction; 3 of these patients underwent hemithyroidectomy. Multivariate analysis showed that the chance of success decreased with the number of previous aspirations and with increased cyst volume (P < .015 each). Transient mild local pain and low-grade fever were observed in 26 (58%) and 19 (42%) patients, respectively, but there were no significant treatment-related complications.

Intracystic injection of OK-432 may be a safe and effective treatment for benign thyroid cysts.