Treatment for microcarcinoma of the thyroid--clinical experience.

AIMS AND BACKGROUND

Papillary microcarcinoma of the thyroid is a specific subgroup of papillary thyroid carcinoma (PTC) and account for up to 30% of all PTC. According to the World Health Organization, papillary microcarcinoma of the thyroid (PMC) is defined as a papillary thyroid carcinoma measuring <or=10 mm in the greatest dimension. The relative rate of PMC is increasing in patients with differentiated thyroid carcinoma (DTC) mainly due to more frequent use and improvement of ultrasonography and fine-needle aspiration biopsy, and also more accurate histopathological examination of surgical specimens. The high incidence of PMC found in autopsy studies (up to 35%) suggests that most of them have a benign behavior. The locoregional recurrence has been reported in up to 20% of PMC patients and several cases of distant metastases have also been described. The 'ideal' therapeutic approach in PMC patients remains a subject of debate among endocrinologists and surgeons. Treatment of PMC in different departments varies from partial thyroidectomy to total thyroidectomy and radioiodine treatment. The main question in this group of patients is "How should PMC patients be treated?" The aim of this study was to investigate retrospectively the frequency and clinical behavior of PMC of the thyroid gland in our department and also to identify the optimal treatment of this group of patients.

MATERIALS AND METHODS

For this retrospective study, we evaluated 120 patients with PMC in our department (between 1997 and 2005). The mean age of patients at diagnosis was 43 +/- 13 years (range 17-67 years). The female to male ratio was 87.5% (105 females, 15 males). The mean follow-up period of patients in this study was 45 months (16-84 months). Surgical treatment of patients with PMC in our department consisted of a bilateral total thyroidectomy in 25 patients (21%), and a bilateral near total thyroidectomy in 95 patients (79%). In the evaluation of our patients, multifocal PMC had a relative frequency of 15% (18/120 patients). The patients were informed about the different therapeutic strategies and the possible necessity for more frequent radioiodine treatment to eliminate thyroid remnants. All of the patients in our retrospective study had radioiodine (RAI) ablation therapy for residual thyroid tissue.

RESULTS

All patients received an RAI treatment dose which ranged from 75-150 mCi (2.7-5.5 GBq). Our criteria for ablation are as follows: negative I-131 WBS and very low serum Tg levels (<1 ng/mL). In 112/120 patients (93.3%), the thyroid remnant was ablated with a single dose of I-131 75-150 mCi (2.7-5.5 GBq). A second radioiodine treatment was necessary in 8 patients (7%), because of locoregional recurrence (required mean cumulative doses of 8.2-11 GBq I-131). Locoregional reccurence occurred in 2 patients with unifocal tumor, without capsular invasion or lymph node metastases and in 6 patients with multifocal tumor and/or in patients with capsular invasion or lymph node metastases. After a second radioiodine treatment, all of these 8 patients were ablated. All 120 patients remained free from disease (negative I-131 whole body scan, unmeasurable thyroglobulin levels) after a median follow-up period of 45 months and there was no recorded disease-related mortality.

CONCLUSION

The treatment of patients with PMC should be no different from the treatment of patients with PTC, and thyroidectomy followed by radioiodine therapy may be a possible option for treatment of papillary microcarcinoma.