X017

OC3

Advanced medullary thyroid cancer – when to start treatment?

Camilla Lyttle¹, Kate Newbold², Daniel Morganstein¹, ¹Chelsea and Westminster Hospital, ²Royal Marsden Hospital

Introduction: Patients with MTC can have prolonged survival even in the presence of metastatic disease, but progressive disease can be life limiting. Treatment with TKIs prolongs progression free survival, but improvements in overall survival have yet to be demonstrated, and can have significant side effects. Therefore decisions about starting therapy in slowly progressive advanced disease can be challenging.

History: 30 year old male who presented in 2010 with fatigue and breathlessness. He was diagnosed with sporadic medullary carcinoma of the thyroid with metastasis to the mediastinum, liver, and bone. In January 2012 he underwent debulking thyroid surgery and followed by post-operative radiotherapy. He has been followed up in a specialist MTC clinic.

Calcitonin levels have remained high but broadly stable mostly between 108,000 – 146,000 (low of 65800, high of 185000) ng/L. A CT scan in Dec 2013 showed widespread metastatic liver disease, multiple bony metastases, a 12mm right hilum node, multiple lung cysts. Right-sided residual thyroid disease. He was monitored with serial imaging and a CT scan in Aug 2017 was largely unchanged from previous CT scans with no change in the deposit in the right thyroidectomy bed, the extensive pulmonary disease, or intrathoracic nodal disease, but marginal growth of the liver metastases.

He currently has no specific symptoms. Weight has increased from 41 – 44kg over 5 years. Able to tolerate a full diet, not complaining of fatigue or malaise, working full time. He therefore continues to have radiologically and symptomatically stable disease, despite extensive spread, raising the question as to if or when he should start systemic anticancer therapy with a tyrosine kinase inhibitor?

Discussion: This is a case of medullary carcinoma of the thyroid which has remained stable for 5 years, despite the fact no systemic therapy has been trialled. Although calcitonin levels have increased there has been little radiological progression, or symptomatic progression, of disease. This poses the question as to whether or not there is any benefit to starting systemic treatment in the absence of symptoms or rapid progression.  It also highlights the need for more reliable biomarkers to accurately monitor the progression of medullary thyroid cancer and guide therapeutic decisions.