Special Issue on Thyroid Cancer

Tracking dynamic evolution of low- and intermediate-risk differentiated thyroid cancer: Identification of individuals at risk of recurrence

OBJECTIVE

The generally good prognosis of low- and intermediate-risk differentiated thyroid cancer (DTC) underscored the need to identify those few patients who relapse.

DESIGN

Records of 299 low- or intermediate-risk DTC patients (mean follow-up 8.2 ± 6.2 years) were retrospectively reviewed. The sample was classified following the American Thyroid Association (ATA) dynamic risk stratification (DRS) system.

PATIENTS AND MEASUREMENT

After classifying patients according to DRS at the first visit following initial therapy (FU1), structural recurrence occurred in 2/181 (1.1%), 5/81 (6.2%) and 13/26 (50.0%) with excellent, indeterminate and biochemical incomplete response to treatment, respectively. All relapses but one happened within 5 years from FU1. Univariate analysis comparing excellent, indeterminate and biochemical incomplete with structural incomplete responses at the end of the follow-up, identified tumour size (p < .001), T status (<0.001), positive lymph nodes (N) (p < .01), multifocality (p < .004), need of additional radioactive iodine (RAI) (p < .0001) and first DRS status (p < .0003) as risk factors of recurrence. In the multivariate analysis, only RAI remained statistically significant (p < .02). Comparison between excellent and indeterminate with biochemical and structural incomplete responses, identified tumour size (p < .0004), T (p < .01), N (p < .0001), bilaterality (p < .03), first DRS status (p < .0001) and RAI (p < .001) as recurrence risk factors. T (p < .01) and first DRS (p < .0006) were confirmed in the multivariate analysis.

CONCLUSIONS

Patients with DTC classified as low- or intermediate-risk of recurrence with excellent response to treatment at FU1 rarely develop structural disease and this occurs almost exclusively in the first 5 years. Initial DRS status is an accurate tool for determining the risk of recurrence.

Outcomes of 756 patients with differentiated thyroid cancer and excellent response to treatment: An evidence-based paradigm for long-term surveillance strategies

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.