An introduction to managing medullary thyroid cancer

Clinical practice guidelines for management of medullary thyroid carcinoma: An AGREE II appraisal

PURPOSE

Medullary thyroid carcinoma (MTC) is a rare and aggressive form of thyroid neoplasia that requires multidisciplinary collaboration for effective management. We systematically appraise the quality of clinical practice guidelines (CPG) for the diagnosis and treatment of MTC using the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument.

MATERIALS AND METHODS

A systematic literature search was performed to identify CPGs pertaining to the diagnosis and treatment of MTC. Data were abstracted from guidelines meeting inclusion criteria and appraised by four independent reviewers in the six domains of quality defined by the AGREE II. Intraclass correlation coefficients (ICC) were calculated across domains to qualify interrater reliability.

RESULTS

Fourteen guidelines met inclusion criteria. No guideline achieved a score of >60 % in five or more AGREE II quality domains, which is required to gain designation as 'high' quality. One "average quality" guideline authored by the British Thyroid Association achieved a score of >60 % in three quality domains. The remaining thirteen (92.9 %) CPGs demonstrated low quality content, with deficits most pronounced in domains 3, 5, and 6, suggesting a lack of rigorously developed, clinically applicable, and transparent information.

CONCLUSIONS

As the diagnosis and treatment of MTC continues to evolve, the development of high-quality guidelines becomes increasingly important; few existing meet appropriate standards.

Diagnostic Challenges of Medullary Thyroid Carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) comprises 1-2% of all thyroid cancers, yet 15% of all thyroid cancer-related deaths. While up to 20% of cases may be predicted due to autosomal dominant germline mutations, 80% of cases are sporadic. However, due to non-specific presenting symptoms and diagnostic imaging, prompt diagnosis and treatment has remained elusive. This article will further investigate the limitations of MTC diagnosis and look into future areas for diagnostic improvement.

METHODS

Relevant articles were identified using a systematic PubMed and Google Scholar search.

RESULTS

Prophylactic total thyroidectomy for the 20% of MTC cases that are present in autosomal dominant disorder provides definitive treatment. Serum calcitonin (Ctn) screening has several technical limitations due to population variability and laboratory assay interference, but advances in laboratory technology and combined use with fine needle aspiration increase its sensitivity. Other serum assays such as carcinoembryonic antigen and procalcitonin have limited applicability. Thyroid ultrasound remains the gold standard for the initial diagnostic planning, with limited application for CT, MRI, and PET imaging.

CONCLUSION

With complete surgical resection the only definitive treatment, early MTC diagnosis has presented an elusive challenge, mainly due to its relative rarity and difficulty in finding an economic screening strategy. Careful family history combined with fine needle aspiration with serum Ctn analysis can improve diagnostic sensitivity and specificity to greater than 95%.

A phase II trial of imatinib therapy for metastatic medullary thyroid carcinoma

CONTEXT

Medullary thyroid carcinoma (MTC) metastasizes early in its clinical course. No effective systemic therapy is available. Generally (somatic or germline), mutations in the rearranged during transfection gene are considered essential in the pathogenesis of MTC.

OBJECTIVE

We investigated imatinib, a tyrosine kinase inhibitor, as a potential treatment in patients with disseminated MTC.

DESIGN

A phase II study was initiated using 600 mg imatinib daily with a possible dose increase to 800 mg in case of progression. Standard Response Evaluation Criteria in Solid Tumors were used using computed tomography or magnetic resonance imaging every 2 months.

RESULTS

There were 15 patients with disseminated MTC treated for up to 12 months. No objective responses were observed. Four patients had stable disease over 24 months. Three patients stopped treatment due to toxic effects [fatigue (n = 2) and nausea (n = 1)]. In four cases the dose of imatinib was decreased because of toxicity [rash and malaise (n = 2) and laryngeal swelling (n = 2)]. Emergency tracheotomy was performed in two cases due to mucosal swelling of the larynx in patients with recurrent nerve palsy and a narrow vocal cleft. In nine patients with a history of a thyroidectomy, the dose of supplemental thyroid hormone was increased because of serious hypothyroidism.

CONCLUSIONS

Imatinib therapy yielded no objective responses and induced considerable toxicity in patients with MTC. A minority of patients had stable disease. Patients with supplemented hypothyroidism or with recurrent nerve palsy are specifically at risk for serious adverse events and need special attention when treated with imatinib.