Late Cervical Lymph Node Recurrence in Differentiated Thyroid Carcinoma

Follicular variant of papillary thyroid carcinoma presenting as a toxic nodule by I-123 scintigraphy

The risk of malignancy in a "hot" thyroid nodule detected by radioiodine scintigraphy is rare. We report a case of a 63-year-old man with a hyperfunctioning nodule demonstrated by radioiodine scintigraphy and cytology suspicious for follicular variant of papillary thyroid carcinoma (FVPTC). There were no locoregional or distant metastases at initial diagnosis. Histopathologic examination following thyroidectomy confirmed the presence of an encapsulated FVPTC. A year into follow-up, his I-131 whole body scan performed following the withdrawal from exogenous thyroid hormone was negative, whereas his serum thyroglobulin (Tg) levels were intermediate. A subsequent PET/CT scan revealed a small, but stable, metabolically active pretracheal lymph node, which on biopsy was confirmed to be stage III FVPTC. In conclusion, the presence of hyperfunctioning thyroid nodule(s) does not preclude malignancy and, therefore, proper cytohistologic evaluation in such patients may help to exclude a coexistent thyroid carcinoma. Patients treated for localized PTC may benefit from serial PET/CT follow-up in the early detection and management of recurrence or distant metastases.

Feasibility of a randomized trial on adjuvant radio-iodine therapy in differentiated thyroid cancer

BACKGROUND

Justification for adjuvant radio-iodine (I-131) therapy in differentiated thyroid cancer (DTC) is purely based on retrospective data. This is true for ablative therapy and even more so for high-dosage adjuvant schedules. Randomized trials on the latter application are considered impossible due to anticipated formidable sample sizes required in a disease with an overall excellent prognosis like DTC.

OBJECTIVE

To develop and validate a model that could stratify for risk of recurrence, rather than survival, as is usually done in prognostic indices, and secondly, to use this model to estimate the sample size required for a randomized trial.

DESIGN, PATIENTS AND RESULTS

From databases of three large Dutch centres, we identified 342 consecutive patients without known residual DTC after (near-) total thyroidectomy. Using Cox proportional hazards analysis, a model was validated that clearly distinguished risk categories of recurrence using commonly available baseline variables. The model included age, N stage at presentation and T stage in papillary carcinoma. According to this stratification, a subset of patients at substantial risk for relapse (30-40%) was identified. They could be eligible for a trial assessing the impact of high-dose adjuvant I-131 on recurrence rates. Assuming a clinically relevant effect of 30% reduction of relapses, 290 patients would have to be entered in either arm (alpha 0.05, power 80%).

CONCLUSION

We conclude that even though a randomized trial on this issue will be difficult to design and conduct, sample size is not the main problem.

Thyroid cancer

Four types of thyroid cancer comprise more than 98% of all thyroid malignancies. Papillary thyroid carcinoma (PTC) may have a very benign course while undifferentiated thyroid carcinoma (UTC) belongs to the most aggressive human malignancies. A variety of genes have been identified to be involved in the pathogenesis of thyroid carcinoma. Somatic Ras mutations seem to be an early event and are frequently found in follicular thyroid carcinomas. Somatic rearrangements of RET and TRK are almost exclusively found in PTC and may be found in early stages. Germline RET missense mutations lead to hereditary medullary thyroid carcinoma (MTC). In contrast, the significance of somatic RET mutations in sporadic MTC is unknown. p53 seems to play a crucial role in the dedifferentiation process of thyroid carcinoma. The precise role of PTEN remains to be elucidated. The only clearly identified exogenous factor that may lead to thyroid carcinoma (mainly PTC) is radiation. Of interest, radiation is capable to induce RET rearrangements. In general, early diagnosis is mandatory to enable the chance of cure. Surgery is the treatment of choice. Depending on the tumour type, surgery in combination with either radioiodine, external radiation or chemotherapy often enables the control of local tumour burden. In MTC and UTC, once thyroid cancer is spread to distant organs, efficacious therapeutic agents are almost non-existing. However, our growing knowledge of genes involved in thyroidal oncogenesis may contribute to the development of more effective treatment modalities. Some preliminary data on gene therapy are quite promising.

Gamma probe-guided resection of a lymph node metastasis with I-123 in papillary thyroid carcinoma

The authors report the case of a 27-year-old woman with gamma probe-guided resection of a recurrent regional lymph node metastasis in papillary thyroid cancer. Reoperation is often impaired in cases with extensive scarring because of previous surgery, high-dose radioiodine therapy, and external irradiation. In this case with nodal metastasis, the high I-123 uptake allowed more rapid intraoperative detection and influenced the surgical approach. Evidence of complete removal of tumor tissue could be given intraoperatively by measuring the tumor bed, and this was confirmed by postoperative normalization of Tg levels and a negative I-131 scan. In other locations, and especially for small solitary lesions, gamma probe-guided surgery may be a promising alternative to high dose I-131 therapy.