A Population-Based Study on NIFTP Incidence and Survival: Is NIFTP Really a “Benign” Disease?
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This study aimed to determine the incidence of noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP) in Ontario, Canada and the predictors of disease-free survival (DFS) by comparing patients with follicular variant papillary thyroid cancer (FVPTC) and patients with NIFTP.
This population-based retrospective cohort study included all patients who had definitive surgery for well-differentiated thyroid cancer (WDTC) in Ontario, Canada between 1990 and 2001 and were followed until 2014. A conservative decision rule was applied to subtype-select FVPTCs into NIFTPs after pathology report review. The primary outcome was DFS, for which Cox proportional hazard regression analysis was performed to assess the impact of FVPTC versus NIFTP.
At pathology re-review of the 725 FVPTC cases, 318 were reclassified as potential NIFTP. The median follow-up time was 15.3 years for the entire cohort and 15.9 years for those alive at the last follow-up visit. Disease failure occurred for 109 patients, 79 (19.4%) in the FVPTC group and 30 (9.4%) in the NIFTP group (p < 0.01). This effect was sustained in the multivariable analysis, with FVPTC showing significantly worse DFS than NIFTP (hazard ratio, 1.84; 95% confidence interval, 1.17–2.89). After recategorization of certain FVPTCs into NIFTPs, the findings showed that NIFTP accounted for 16.8% (1.461/8.699 per 100,000) of all WDTCs.
The disease failure rate for NIFTP was 9.4%. The NIFTP diagnosis is challenging for the pathologist and may make tumor behavior difficult to predict for this entity. Caution should be used in the management of patients with an NIFTP.
Funding for the original study, which allowed for pathology report abstraction, was provided from the Canadian Institutes of Health Research MOP #84356 (controversy in the management of differentiated thyroid cancer). This work also was supported by the Kevin and Sandra Sullivan Chair in the Surgical Oncology Fund. Finally, the work also was supported by the Department of Otolaryngology–Head and Neck Surgery at Queen’s University. Ethics approval was obtained from the Ethics Review Board of both Sunnybrook Health Sciences Centre and Queen’s University (OTOL 029-06). The study coordinator was Susan Rohland with assistance from Sarah Pickett. Dr. Marosh Manduch advised on the pathology abstraction. The Institute of Clinical and Evaluative Sciences is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. The project analysis was provided by the ICES Cancer Program, and the analysis was conducted at ICES@Queens. The opinions, results, and conclusions reported in this report are those of the authors and independent from the funding sources. No endorsement by ICES or the Ontario Ministry of Health and Long-Term Care is intended or should be inferred. As a prescribed entity under the Ontario Personal Health Information Protection Act, ICES policies and procedures are approved by Ontario’s Information and Privacy Commissioner. These policies require that access to data be limited to persons who require such access to perform their role on an approved ICES or third-party project. Thus, we are prohibited from making ICES data publicly available. Only the results from analysis of ICES data may be made available. Data management and analysis were undertaken by Rebecca Griffiths at ICES@Queens. We acknowledge the Ontario Cancer Registry and Cancer Care Ontario for providing us with the Ontario Cancer Registry data used in this report.
Conflict of interest
The authors declare that they have no conflicts of interest.
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