Abstract and Introduction
Abstract
Background: The 2014 British Thyroid Association thyroid cancer guidelines recommend lifelong follow-up of all thyroid cancer patients. This is probably unnecessary, particularly for differentiated thyroid cancer (DTC) patients with an excellent response to treatment and places significant demand on health service resources.
Design: Single centre retrospective cohort analysis of patients diagnosed and treated at the Leeds Cancer Centre between 2001 and 2014.
Patients: A total of 756 patients were dynamically risk-stratified (DRS) as having 'excellent response to treatment' after total thyroidectomy and radioiodineremnant ablation (RRA) for DTC.
Results: Median follow-up was 11.2 (range: 6.5–18.5) years. Radiological recurrence occurred in 15/756 (2.0%) patients and was always preceded by a raised thyroglobulin or thyroglobulin antibody level. The vast majority of tumour recurrences (13/15, 85%) were identifiable within 5 years of diagnostic surgery. Patients classified as having high-risk disease as per American Thyroid Association (ATA) guidelines had an almost threefold higher recurrence rate (2/34 [5.9%] vs. 13/722 [1.8%]) than those with ATA low-risk or intermediate-risk disease. Tumour histology subtype was a significant contributing factor, with Hürthle cell cancer having a worse prognosis than papillary thyroid cancer (PTC) (5/68 [7.4%] vs. 9/582 [1.5%]; relative risk: 4.76 [95% confidence interval: 1.64–13.8]).
Conclusions: The recurrence rate of DRS patients with excellent response to treatment is low. It is reasonable to consider discharge of ATA low-risk or intermediate-risk patients with PTC who remain disease-free after 5 years of secondary care follow-up. Lifelong follow-up, however, currently remains the standard for subgroups at greater risk.
Introduction
Thyroid cancer is the most common endocrine neoplasm worldwide. Differentiated thyroid cancer (DTC) is classified as either papillary thyroid cancer (PTC) or follicular thyroid cancer (FTC), including oncocytic follicular (Hürthle) cell carcinoma. The incidence of DTC is increasing globally,[1] due to an increase in small PTC discovered incidentally during radiological investigations or thyroid surgery for benign conditions.[2] The long-term outcome for patients treated effectively for DTC is usually favourable, with DTC-related deaths occurring primarily in the few patients with more advanced disease.
In the United Kingdom, management of thyroid cancer follows specialist multidisciplinary team decisions in accordance with guidelines from the British Thyroid Association (BTA).[3] Use of prognostic scoring and staging systems, as well as accurate risk stratification of patients, are recommended to tailor treatment and follow-up strategy. Postoperative risk stratification adapted from the American Thyroid Association (ATA) informs the probability of persistent or recurrent disease at a pretreatment stage of the patient pathway. The 2009 ATA initial risk stratification system classifies DTC patients into high-, intermediate- and low-risk cohorts calculated from each patient's disease stage following thyroidectomy.[4] High-risk (HR) ATA patients demonstrate evidence of gross extra-thyroidal extension (T4 disease), presence of distant metastases (M1 disease status) or incomplete macroscopic tumour resection (R2 margin status). In the revised 2015 ATA classification, the presence of lymph node metastasis larger than 3 cm was added to the above criteria.[5]
Dynamic risk stratification (DRS) was introduced in the 2014 BTA guidelines for DTC patients who undergo total thyroidectomy and subsequent radioiodine remnant ablation (RRA) to define the initial response to treatment and guide further management. The 9–12 months postradioiodine DRS is based upon the combined outcome of radiological and biochemical data. At this time point, stimulated thyroglobulin (sTg) less than 1.0 µg/L in the absence of structurally identifiable disease, classifies patients as having an excellent response to treatment with low risk (LR) of recurrence. In these patients, the degree of TSH suppression can be relaxed, aiming for the lower half (0.3–2.0 mU/L) of the reference range.[6,7]
The aim of this study is to identify key prognostic factors important for defining surveillance protocols and assess whether a subset of these patients can be safely discharged from secondary care.
Clin Endocrinol. 2022;96(3):395-401. © 2022 Blackwell Publishing
