THE EFFICACY OF PERCUTANEOUS TETRACYCLINE INSTILLATION FOR SCLEROSIS OF RECURRENT THYROID CYSTS - A MULTIVARIATE-ANALYSIS

A dichotomy exists in the literature concerning the efficacy of sclero sing agent tetracycline hydrochloride for treatment of thyroid cysts. However, the studies vary in patient selection and none employed a sta tistical method for simultaneous analysis of multiple factors that mig ht affect the outcome of therapy. We, therefore, studied the efficacy of percutaneous instillation of tetracycline for eradication of recurr ent thyroid cysts, using a multivariate analysis. Thirty-seven patient s with recurrent, cytologically benign thyroid cysts (not cured after 3 aspirations) were studied. Twenty-three patients were given tetracyc line instillations [100 mg/ml, range (R): 1-4 ml]. The remainder under went only repeated needle aspiration. They were followed for 33+/-12 ( SD) months, R: 12-58 months. Cure was achieved in 21 out, of 23 cases after tetracycline instillation within 2+/-1.7 months (R: 1-6 months) and in 12 out of 14 cases after aspiration alone within 9.9+/-11.3 mon ths (R: 1-43 months, 4-10 aspirations). Multivariate survival analysis using the Cox proportional-hazards regression model demonstrated sign ificantly shorter time interval before cure in the group with tetracyc line instillation (p=0.001). The volume, color or duration of cysts an d levothyroxine (L-T4) treatment did not appear to influence, the outc ome of therapy. After initial cure by tetracycline instillation, 5 cas es had relapse. Three were later cured by reinstillation of tetracycli ne or by repeated aspirations (R: 1-3 times). Complications of tetracy cline instillation included brief episode of neck pain and development of a foreign body granuloma in a single patient. In conclusion, tetra cycline instillation is a quick and effective procedure for treating r ecurrent thyroid cysts. The duration, characteristics of cysts and L-T 4 administration do not influence the outcome of therapy.