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The Natural History of Benign Thyroid Nodules

Friday, we discussed the UBER sexy topic of thyroid nodules:

Durante et al, “The Natural History of Benign Thyroid Nodules,” JAMA. 2015; 313(9):926-935

Why do we care?

We all have “that patient” who has to get repeat thyroid ultrasounds and aspirations for either a nodule or multinodular disease. More than 90% of detected nodules are clinically insignificant benign lesions, but we are picking up more thyroid nodules everyday with our non-evidence-based annual physicals and incidentalomas on CT/MRI.

Currently, established guidelines for initial biopsy include:

– nodule size: > 1 cm

– sonographic characteristics: hypoechogenicity, irregular margins, taller-than-wide shape, intranodular vascular spots, microcalcifications

Furthermore, current guidelines recommend serial ultrasound exams for benign thyroid nodules and repeat needle biopsy if a nodule grows by 20%. The problem is that not much is known about the correlation between nodule growth and actual cancer.

This was a prospective study that followed some middle-aged Italian folks over five years with benign nodules, confirmed via laboratory testing and needle aspiration at the baseline evaluation. They received serial ultrasounds and a needle aspiration if they experienced nodule growth of 20% or if the ultrasound met the above-mentioned criteria for biopsy.

P: About a thousand Italian people, with a mean age of 52 years, 82% of whom were female. After loss to follow up and people who no longer met criteria (developed thyroid dysfunction), they were left with 992 patients.

I: This study wasn’t really about an “intervention,” rather it followed growth of nodules over time, so the groups were split into those who experienced growth vs…

C: Those who experienced no growth.

O: In 69% of patients, the thyroid nodules remained stable. 18% shrank spontaneously. In 2%, the nodules *disappeared.* 15% grew, most of which were in patients who had multiple nodules at baseline. 9% developed new nodules. “Over the course of the 5 years, 37% met re-aspiration criteria (growth or concerning features on ultrasound).” (growth or concerning features on ultrasound). Of these, 98.9% confirmed the baseline benign diagnosis.  Thyroid cancer was detected in 0.3% of the 1567 original nodules. 

Limitations:

– 1k patients in the grand scheme of things isn’t a whole lot, but it helps that this study underlines what we already suspected about thyroid nodules

– This doesn’t help us with younger people, in whom thyroid cancer is more prevalent

– 5 years of follow up is a drop in the bucket compared to the usual length of time our patients get follow up (eons) — additional studies should have a longer follow up time

– This was the most boring article EVER. Seriously. OMG.

Bottom Line: Don’t freak out about thyroid nodules! And the guidelines should probably space out ultrasounds because most of them won’t grow, anyway.