Usefulness of 68Ga-DOTATOC PET/CT to localize the culprit tumor inducing osteomalacia

Phosphaturic mesenchymal tumor demonstrated by 68Ga-DOTATATE PET/CT in a patient: a case report

Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome caused by abnormally high levels of fibroblast growth factor 23 (FGF-23), most commonly produced and secreted by small phosphaturic mesenchymal tumors (PMT). These tumors can show various anatomic locations throughout soft tissue and bone. The presence of the tumor itself rarely causes symptoms. Nonspecific symptoms such as muscle weakness and musculoskeletal pain are related to the developing hypophosphatemia and osteomalacia as a secondary effect of the increased circulating levels of FGF-23. Therefore, as the initial presentation can mimic a wide range of metabolic or inflammatory diseases, proper diagnosis is often delayed. Localization of the tumor is crucial, as its complete surgical resection is the only curative treatment. Whole-body functional imaging targeting the overexpression of somatostatin receptors (SSTR) on the surface of the PMT cells, is a highly specific and sensitive imaging method to detect the primary tumor site. Here, we discuss a case of TIO in a patient initially presenting with symptoms of inflammatory spondyloarthritis. SSTR positron emission imaging using 68Ga-DOTATATE was central in diagnosing and localizing the primary tumor.

Diagnostic accuracy of 99mTc-HYNIC-TOC SPECT/CT for detecting osteomalacia-associated tumors

OBJECTIVES

Tumor-induced osteomalacia (TIO) is a rare acquired paraneoplastic disorder characterized by hypophosphatemia resulting from tumor-secreted fibroblast growth factor-23 (FGF23). Surgical resection of the culprit TIO is the first choice of treatment. However, TIO is difficult to detect with conventional diagnostic tools due to its small size and variable location in the body. Somatostatin receptor scintigraphy (SSR) has recently emerged as a functional molecular imaging choice for TIO detection and localization. This research was undertaken to evaluate the efficacy of 99mTc-labeled hydrazinonicotinyl-Tyr3-octreotide (99mTc-HYNIC-TOC) SPECT/CT in detecting TIO.

METHODS

99mTc-HYNIC-TOC SPECT/CT and the available clinical data of 25 patients with suspected TIO were analyzed retrospectively. The 99mTc-HYNIC-TOC SPECT/CT findings were compared with the post-surgical pathology diagnosis and clinical follow-up results.

RESULTS

Using 99mTc-HYNIC-TOC SPECT/CT, suspicious tumors were found in 18 of the 25 patients, and 15 of them underwent surgical resection. The post-operative pathology confirmed a TIO in those 13 patients whose symptoms and biochemical anomalies gradually resolved after the surgery. The remaining five patients were finally considered false positives. Moreover, the 99mTc-HYNIC-TOC SPECT/CT results were negative in seven patients, with six patients being true negative (4 patients were diagnosed with acquired Fanconi syndrome and 2 patients responded well to conservative therapy) and one being false negative. Therefore, the sensitivity and specificity values of 99mTc-HYNIC-TOC SPECT/CT in the evaluation of TIO were 92.9% (13/14) and 54.5% (6/11), respectively. The overall accuracy of 99mTc-HYNIC-TOC SPECT/CT for detecting TIO was 76.0% (19/25).

CONCLUSIONS

The 99mTc-HYNIC-TOC SPECT/CT is an accurate imaging modality for locating culprit tumors in TIO.

Tumor induced osteomalacia - A long way toward correct diagnosis and management

Tumor-induced osteomalacia (TIO) is an uncommon type of osteomalacia associated with phosphaturic mesenchymal tumors (PMTs). Due to nonspecific symptoms, the diagnosis and appropriate management of the disease is often delayed for many years. Involvement of spine with TIO associated tumors is exceedingly rare. We present a 53-year-old woman with a 10-year history of bone pain, muscle weakness and multiple bone fractures that markedly impaired her quality of life. Biochemical evaluation revealed hypophosphatemia due to renal phosphate wasting and elevated plasma fibroblast growth factor 23 (FGF-23) concentration indicating PMT. It was found using ⁶⁸Ga DOTA TOC PET/CT scan in the vertebral body L2. The patient underwent surgical resection of the tumor. Postoperatively, there was a significant decrease in phosphaturia, normalization of serum phosphate, 1.25 dihydroxyvitamin D and plasma FGF23 concentration. Thereafter the patient's condition markedly improved concerning her motility and basic daily activities.

This case report demonstrates the first known case of TIO in the Slovakia and points to a long way from onset of symptoms toward correct diagnosis and successful surgical management.

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Phosphaturic mesenchymal tumor (PMT) as a cause of TIO

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Due to nonspecific symptoms, the diagnosis of TIO is often delayed for many years.

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Hypophosphatemia, hyperphosphaturia, elevated FGF23 are leading laboratory markers.

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Successful identification of PMT is a key to appropriate management of the patient.

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We report case of female patient with TIO caused by PMT of the vertebral body L2.

KSNM60 in Nuclear Endocrinology: from the Beginning to the Future

Nuclear endocrinology is the main ignitor for founding the Korean Society of Nuclear Medicine (KSNM) in the early 1960s by outstanding pioneering medical doctors. Management of thyroid diseases required nuclear medicine technology in the early days of the KSNM and was rapidly developed by advancements in nuclear medicine technology. Nuclear thyroidology remains one of the main clinical applications in nuclear medicine worldwide. Nuclear medicine technology provides essential information for diagnosing and assessing diseases of the parathyroid glands, pituitary gland, and neuroendocrine tumors (NETs). In addition, therapeutic nuclear medicine is essential for managing nonresectable NETs. Nuclear endocrinology remains a major section in clinical nuclear medicine, and members of the KSNM have contributed to progressing better management of benign and malignant endocrine diseases. This review summarizes the historical activities and milestone contributions to nuclear endocrinology made by the members of the KSNM over the past 60 years to congratulate the KSNM on its 60-year anniversary.