Changing the paradigm: lobectomy for sporadic medullary thyroid cancer

Abstract

Objectives: Total thyroidectomy is the treatment of choice for medullary thyroid cancer (MTC), although the sporadic forms are usually monocentric. Aim of the present study was to evaluate i) the performance of calcitonin (Ct) levels, ultrasound scans (US) and cytology in the preoperative identification of MTC and ii) the number of total thyroidectomies that could have been avoided being the location of the MTC diagnosed preoperatively.

Materials and methods: We retrospectively analyzed 89 RET germline negative patients diagnosed with MTC in the past 30 years, treated with total thyroidectomy ± lymphadenectomy, and followed in our Tertiary Care Center. In a subgroup of 55 patients, divided in those with a mono- or bi-lateral goiter, we applied ex-post criteria for the presurgical identification of the lobe holding the MTC nodule.

Results: Only 2/89 patients (2.2%) had a bilateral MTC at histology. A strongly significant correlation was found between preoperative basal Ct levels and MTC size. According to the ex-post identification criteria, the 84.4 and 56.5% of the nodules would have been identified preoperatively as MTC in monolateral and bilateral goiters, respectively.

Conclusions: This is the first European study that aims to evaluate the feasibility of lobectomy as first-line therapy for MTC based on the evaluation of thyroid US and serum Ct levels. These tools have been shown to have a good accuracy in detecting the affected lobe and strongly support the possibility to perform a more conservative surgery to treat RET-negative patients with suspicious MTC and nodular goiter.

Keywords: RET; lobectomy; medullary thyroid cancer; sporadic medullary thyroid cancer.

Figure 1

Panel A, Scatter plot of MTC histological size and basal serum levels of calcitonin; the dashed gray line represents the direction of the correlation. Spearman correlation test showed a significant association of moderate power between the two variables: rho = 0.62, P-value = 0.00000003. Panel B, Scatter plot of MTC histological size and MTC size measured during thyroid ultrasound evaluation; the dashed gray line represents the direction of the correlation. Spearman correlation test showed a significant strong association between the two variables: rho = 0.80, P-value = 0.0000000006.

Figure 2

Monolateral and bilateral goiter patients whose MTC nodule would have been identified according to the ex-post criteria. 0) No suspicious nodules were identified at US, cytology was not suspicious and Ct was not consistent with the nodule/s volume; A) the nodule was the only nodule in the thyroid, possibly characterized by US suspicious features, serum Ct levels were consistent with the nodule volume and the stimulated Ct (if obtained) was above the cut-off limits; B) the nodule was the only nodule in the thyroid, possibly with US suspicious features, and cytological evaluation was positive or suspicious for MTC or malignancy and/or calcitonin measurement on the fine-needle washout fluid was positive; C) there were more than one nodule, but only one nodule had US suspicious features and/or volume consistent with Ct serum levels, and the stimulated Ct (if obtained) was above the cut-off limits; and D) there were more than one nodule, but only one nodule had a cytology positive or suspicious for MTC or malignancy and/or calcitonin measurement on the fine-needle washout fluid was positive.

Figure 3

Suggested algorithm to be followed in patients with mono- or bi-lateral goiter, with Ct basal levels above the normal reference value. US, ultrasound; Ct, calcitonin; MTC, medullary thyroid cancer.