False positive diagnosis on (131)iodine whole-body scintigraphy of differentiated thyroid cancers

(131)Iodine is used both to ablate any residual thyroid tissue or metastatic disease and to obtain whole-body diagnostic images after total thyroidectomy for differentiated thyroid cancer (DTC). Even though whole-body scan is highly accurate in showing thyroid residues as well as metastases of DTC, false positive results can be found, possibly leading to diagnostic errors and unnecessary treatments. This paper reviews the physiological and pathological processes involved as well as the strategy to recognize and rule out false positive radioiodine images.

Patient and tumor factors contributing to distant metastasis in well-differentiated thyroid cancer: a retrospective cohort study

BACKGROUND

Distant metastasis in thyroid cancer significantly reduces survival in patients with well-differentiated thyroid carcinoma (WDTC). There is limited information available to clinicians regarding pathological features that confer a higher risk of distant metastasis (DM). This study aimed to identify patient and tumor factors that were associated with the development of DM over time in patients with WDTC.

METHODS

A retrospective cohort analysis of patients with WDTC (n = 584) at our institution was performed between 2007 and 2017. A total of 39 patients with DM and 529 patients with no DM (NDM) were included. Patient demographics, tumor characteristics and patient survival were compared between the DM and NDM groups using a univariate analysis. Multivariate Cox-proportional hazards model was used to evaluate the risk of developing distant metastasis over time. Kaplan-Meier analysis was used to compare survival between the DM and NDM groups.

RESULTS

Distant metastasis had a substantial impact on disease-specific survival (DSS) at 5 and 10-years in the DM group; 71.0% (SE 8.4%) and 46.9% (SE 11.6%) respectively, compared to 100% survival in the NDM group (p < 0.001). The DM group had significantly higher proportions of males, lymphovascular invasion (LVI), nodal metastasis (NM), large tumor size (TS), extrathyroidal extension (ETE), positive resection margins, multifocality, follicular thyroid cancer (FTC), tall cell variant of papillary thyroid cancer (PTC), and Hurthle cell carcinoma (HCC), when compared to the NDM group (p < 0.05). A TS ≥ 2 cm (Hazard Ratio (HR) 1.370), NM (HR 3.806) and FTC (HR 7.068) were associated with a significantly increased hazard of developing distant metastasis in patients with WDTC.

CONCLUSIONS

TS ≥ 2 cm, NM and FTC are associated with a significantly increased propensity for developing DM in our cohort of WDTC patients.

Molecular profiles of cancer stem-like cell populations in aggressive thyroid cancers

A substantial proportion of patients with advanced thyroid carcinoma fail to respond to or at some point become refractory to conventional therapies. This resistance and the phenomena of thyroid cancer progression and metastasis themselves are thought to be related to tumor-cell sub-populations with stem-like properties. We isolated thyrospheres from four advanced thyroid carcinomas that were resistant to radioiodine therapy and analyzed their molecular profiles. ALDH activity and proteomic profile of main stem cell markers were used to assess stem cell properties. The TaqMan Low Density Array approach was used to evaluate the expression of several genes involved in the EMT process. The phosphorylation status of tyrosine kinase receptors (RTKs) was analyzed to identify potential markers for targeted therapies. We then investigated the effects of the EMT-inhibitor crizotinib on both cell proliferation and phosphorylation status of RTK targets. The cancer stem-like properties of a subset of cells from primary cultures of each tumor were demonstrated. A wide variability among thyrospheres arising from the four thyroid cancers in terms of ALDH activity, stem cell marker expression, and phosphoproteome profiling was present. Dysregulated expression of genes involved in the EMT was observed in all four thyrosphere lines. Treatment with crizotinib was ineffective in cancer stem-like cells, suggesting the presence of a mechanism of resistance in thyrospheres. Collectively, our data indicate that thyroid cancer stem-like populations vary markedly from tumor to tumor and require detailed molecular and biological characterization if they are to be used as the basis of "personalized" treatment of aggressive disease.

Local ablative therapy of oligoprogressive TKI-treated thyroid cancer

Metastatic cancer patients generally respond well to treatment with tyrosine kinase inhibitors (TKIs). However, TKI resistance occurs in almost all cases and often leads to a change in treatment. Recent guidelines, including thyroid cancer, raised the possibility of locally treating TKI-resistant oligoprogressive disease, i.e., one or a few progressing lesions in an otherwise treatment-responsive metastatic cancer, thereby obviating the need to change the ongoing TKI. To determine the benefits of this intervention, we reviewed studies on the use of LAT for TKI-treated oligoprogressive cancers. We found that in non-small cell lung cancer at least, LAT prolongs disease control and the duration of exposure to a TKI irrespective of the LAT used. Moreover, we reviewed the local ablative therapies (LATs) that are feasible for the local control of oligoprogressive thyroid cancer. Lastly, we report two illustrative cases of patients with oligoprogressive thyroid cancer treated with two different LATs while on therapy with TKIs. Both LATs extended the duration of disease control and the time of exposure to the ongoing TKI, thereby indicating that LAT is a favorable option for TKI-treated oligoprogressive thyroid cancer. Prospective randomized studies are needed to verify the benefit of LATs in terms of progression-free and overall survival in this increasingly frequent clinical setting.

Combined BRAFV600E analysis and 99mTc-MIBI scintigraphy can be a useful diagnostic tool in differentiated thyroid cancer patients with incomplete bio-chemical response to first radioiodine therapy (RAIT): a pilot investigation

PURPOSE

The aim of the present study was to evaluate the possible diagnostic role of the combined performance of BRAF mutation analysis and MIBI scintigraphy in papillary thyroid cancer (PTC) patients with incomplete bio-chemical response to first radioiodine therapy (RAIT) performed for thyroid remnant ablation.

METHODS

The records of 15 PTC patients with bio-chemical incomplete response to first RAIT were retrospectively analyzed. BRAF^V600E analysis on primary tumor samples was obtained in all cases along with neck ultrasonography and ^99mTc-MIBI scintigraphy of the neck-thorax regions at first follow-up. All patients then underwent RAIT with high radioiodine activities. A post-therapy whole-body scan (pT-WBS) was acquired 5-7 days after RAIT.

RESULTS

Abnormal radioiodine uptake was found in 10 out of the 15 patients (67%, ¹³¹I+ve), while in the remaining 33%, no abnormal radioiodine uptake was detected (5/15, ¹³¹I-ve). Abnormal tracer uptake was found in 6 out of 10 ¹³¹I+ve patients at ^99mTc-MIBI scintigraphy (MIBI+ve). BRAF^V600E mutation was not found in the majority of ¹³¹I+ve patients (9 out of 10 BRAF^V600E-ve). On the contrary, in the 5 ¹³¹I-ve patients, ^99mTc-MIBI scintigraphy did not show any abnormal tracer uptake (MIBI-ve), while BRAF^V600E mutation was present (BRAF^V600E+ve). Thus, in our series, the association between MIBI-ve scintigraphy and BRAF+ve mutation was a useful diagnostic tool in predicting negative pT-WBS outcome.

CONCLUSION

Albeit obtained in a small retrospective series, our results suggest that the combination of BRAF^V600E+ve mutation and MIBI-ve scintigraphy may be considered a negative prognostic clue, which predicts the absence of radioiodine uptake at pT-WBS in DTC patients with incomplete bio-chemical response to first RAIT.

Metastatic BRAF V600E-Mutated Thyroid Carcinoma: Molecular/Genetic Profiling Brings a New Therapeutic Option

We describe a case of a 46-year-old woman diagnosed with localized PTC 20 years ago, having already undergone several treatments with iodine-131 and then treatment with lenvatinib for metastatic disease, to which she developed intolerance. In 2020, in addition to pleural, thoracic, and abdominal lymph node metastasis, progression with symptomatic vertebral bone metastasis was detected, which led to the equation of new therapeutic options. In this context, a genetic/molecular test was carried out, which identified the BRAF V600E mutation and enabled the start of treatment with dabrafenib/trametinib since June 2020. This treatment allowed functional gain, symptomatic relief, and stabilization of the disease. It demonstrates how, in rare tumors, the personalized medicine approach can bring new treatment possibilities.