Is thyroid cancer being overtreated?
Thyroid cancer is the most common endocrine malignancy. In Australia, diagnoses of thyroid cancer have increased significantly in recent years, and between 1982 and 2017, cases of thyroid cancer more than tripled. We spoke to Associate Professor Roderick Clifton-Bligh, Head of the Department of Endocrinology at Royal North Shore Hospital, to discuss why this may be, along with any new developments in the diagnosis and treatment of thyroid cancer.
“Thyroid cancer incidence has been increasing steadily in recent years, in parallel with the increasing use of neck ultrasound and detection of otherwise incidental thyroid nodules. Nevertheless, thyroid cancer mortality hasn’t changed, and this suggests that thyroid cancer may be over-diagnosed and possibly over-treated.
“In the last five years, a more systematic approach and a change to the diagnostic pathway of thyroid cancers have been introduced. There is now a widespread acceptance of the Bethesda classification which grades biopsies into six categories, from non-diagnostic through to definitely malignant. There has also been a change to ultrasound reporting to indicate which thyroid nodules require biopsy. Ten years ago, we used to biopsy most nodules greater than 1cm but now we are a lot more selective,” said A/Prof Clifton-Bligh.
Surgery is the most common treatment for thyroid cancer. This may be combined with radioactive iodine (RAI) to kill any remaining cancer cells. However, there have been moves to reduce the use of RAI in patients who are otherwise at very low risk of recurrence.
“A concerted effort has been made to try and reduce the use of RAI with a move towards a more personalised approach depending on the type and stage of the cancer. In a small proportion of cases, the thyroid cancer is not suitable or is resistant to RAI and we then use targeted chemotherapy. When RAI stops working, or in cases where the thyroid cancer is not suitable, survival is reduced. Genetic testing for thyroid cancers which are resistant to RAI is important and is extremely useful to find treatment options.
“For instance, we are currently involved in clinical trials using highly specific RET inhibitors to target thyroid cancers containing RET (rearranged during transfection) gene mutations, and the data is extremely promising. This is quite revolutionary and offers hope to people with advanced medullary thyroid cancer” said A/Prof Clifton-Bligh.
Whilst surgery is often recommended for thyroid cancer, it is becoming increasingly clear that regular follow-up (active surveillance) without surgery could be considered for some patients with low-risk cancers. Evidence has shown that for small (less than 1 cm), carefully selected, thyroid cancers there is a low rate of cancer progression. Surgery is performed later if the cancer progresses.
“Active surveillance is gaining international acceptance and is used here in Australia on a case by case basis. However, not all small cancers should be watched, and we must be careful what is termed low risk. Only in experienced hands when the cancer can be confidently termed low risk should surveillance be considered.
“Whilst it is widely considered that thyroid cancer is overtreated, this runs the risk of undertreating people who actually need treatment. The modern risk-based approach is proving useful for determining the de-escalation of therapy, and this needs to be applied in centres that have adequate experience in doing this,” said A/Prof Clifton-Bligh.
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This article appeared in the September 2019 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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