OBJECTIVE: We aimed to describe the clinical characteristics of a large cohort of patients diagnosed with tumor-induced osteomalacia (TIO), with a focus on patients with non-localizing and malignant TIO.
METHODS: This is a retrospective cohort of TIO patients in an academic medical center, diagnosed between January 1998 to May 2023. We described their demographics, biochemistries, tumor features, localization, treatment and complications.
RESULTS: Of 68 patients diagnosed with TIO, 49 (72%) were localizing and 5 (7.4%) were malignant. Of 50 patients who attempted localizing procedures, 29 (58%) achieved cure. 20 (40%) had persistent disease due to wrong tumor targeted, or refractory or recurrent tumors, despite up to 6 procedural attempts. There was no difference in demographics, phosphorus or baseline fibroblast growth factor-23 (FGF23) levels between localizing versus non-localizing groups, and malignant versus non-malignant groups. Lower extremity was the commonest site of localization (37%), with 47% in bone and 53% in soft tissue. 60% of malignant cases were located in the trunk. Tumor size correlated with peak FGF23 (R=0.566, p<0.001) but was not associated with malignancy risk (p=0.479). A cut-off FGF23 of >20 times upper limit of normal in the presence of normal renal function (p=0.025), and recurrence after initial cure (p=0.013) were factors significantly associated with malignancy. The non-localizing group had lower survival than localizing group (p=0.0097).
CONCLUSIONS: TIO is a condition with significant morbidity. Very high FGF23 level and disease recurrence are associated with malignant disease. Reasons behind the observation of higher mortality in non-localizing TIO should be further explored.

To determine whether advanced imaging is cost-effective compared to primary bilateral neck exploration in the management of non-localizing primary hyperparathyroidism.
Cost-effectiveness analysis.
Cost-effectiveness analysis based on decision tree model and available Medicare financial data using data from 347 consecutive patients having parathyroidectomy for primary hyperparathyroidism with either 1) positive, concordant ultrasound and sestamibi or 2) negative sestamibi and negative ultrasound.
Bilateral neck exploration (BNE) costs $9578 and has a success rate of 97.3%. Single photon emission computed tomography (SPECT) + minimally invasive parathyroidectomy (MIP) was modeled to have a total cost of $8197 with a success rate of 98.6%. SPECT/computed tomography (CT) + MIP was modeled to have a total cost of $8271 and a 98.9% success rate. Four-dimensional (4D)-CT + MIP was modeled to cost $8146 with a success rate of 99%. Incremental cost-effectiveness ratios (IECR) (as compared to BNE) were -536.1, -605.5, and -701.6 ($/percent cure rate) for SPECT, SPECT/CT, and 4D-CT respectively. One-way sensitivity analyses demonstrate the change in IECR and cut-off points (IECR = 0) for four major variables.
In patients with non-localizing primary hyperparathyroidism, advanced imaging is associated with cost-savings compared to routine bilateral neck exploration. Increased cost-savings were predicted with increased imaging accuracy and decreased imaging costs. Increasing time for BNE or decreasing time for MIP were associated with increased cost savings.
III Laryngoscope, 2020.