Successful CT guided cryoablation of phosphaturic mesenchymal tumor in the soft tissues causing tumor-induced osteomalacia: a case report

Orthopedic Surgical Treatment of Patients with Tumor-induced Osteomalacia Located in the Hip Bones: A Retrospective Analysis of 10 Years in a Single Center

OBJECTIVE

The orthopedic surgical treatment strategies for patients with tumor-induced osteomalacia (TIO) require improvement, especially for patients where the causative tumors are located in surgically challenging areas, requiring a greater degree of in-depth investigation. This work aims to summarize and investigate clinical features and orthopedic surgical treatment effects of patients with tumor-induced osteomalacia (TIO), whose causative tumors are located in the hip bones.

METHODS

A retrospective analysis was conducted on the clinical data of all patients diagnosed with culprit tumors located in the hip bones who underwent surgical treatment at the orthopedic bone and soft tissue tumor sub-professional group of Peking Union Medical College Hospital from January 2013 to January 2023. This retrospective study summarized the clinical data, preoperative laboratory test results, imaging findings, surgery-related data, perioperative changes in blood phosphorus levels, and postoperative follow-up data of all patients who met the inclusion criteria. Normally distributed data are presented as mean and standard deviation, while non-normally distributed data are shown as the means and 25th and 75th interquartile ranges.

RESULTS

The clinical diagnostic criteria for TIO were met by all 16 patients, as confirmed by pathology after surgery. Among the 16 patients, we obtained varying degrees of bone pain and limited mobility (16/16), often accompanied by difficulties in sitting up, walking, and fatigue. An estimated 62.5% (10/16) of patients had significantly shorter heights during the disease stages. All 16 patients underwent surgical treatment for tumors in the hip bones, totaling 21 surgeries. In the pathogenic tumor, there were 16 cases of skeletal involvement and none of pure soft tissue involvement. Out of the 16 patients, 13 cases had a gradual increase in blood phosphorus levels following the latest orthopedic surgery, which was followed up for 12 months to 10 years. Due to unresolved conditions after the original surgery, four patients received reoperation intervention. Two cases of refractory TIO did not improve in their disease course.

CONCLUSION

In summary, the location of the causative tumor in the hip bone is hidden and diverse, and there is no defined orthopedic surgical intervention method for this case in clinical practice. For patients with TIO where the tumors are located in the hip bones, surgical treatment is difficult and the risk of postoperative recurrence is high. Careful identification of the tumor edge using precise preoperative positioning and qualitative diagnosis is crucial to ensure adequate boundaries for surgical resection to reduce the likelihood of disease recurrence and improve prognosis.

Preoperative evaluation and orthopedic surgical strategies for tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is very rare, with about 1000 reported cases globally. Removing most TIO culprit tumors requires the evaluation and intervention of orthopedic doctors. However, orthopedic doctors often have a poor understanding of the optical treatment of TIO due to its rarity. In addition, most TIO patients lack specific clinical manifestations. Also, the clinical localization and qualitative diagnosis of TIO are difficult and thus can easily be misdiagnosed and mistreated. Furthermore, the true incidence rate of TIO may be underestimated. Although many breakthroughs have been made in exploring the pathogenesis, clinical diagnosis, and treatment of TIO, rational and standardized orthopedic surgical treatment experience summary and sorting for TIO patients are lacking. In this article, the recent experience and progress in the field of orthopedic surgical treatment for TIO globally have been summarized, providing a theoretical basis and new clinical practice guidance for the rational treatment of TIO patients.

Tumor-induced osteomalacia: An overview

Tumor-induced osteomalacia (TIO) is rare paraneoplastic syndrome of hypophosphatemic osteomalacia, caused by phosphaturic factors secreted by small mesenchymal origin tumors with distinct pathological features, called 'phosphaturic mesenchymal tumors'. FGF23 is the most well-characterized of the phosphaturic factors. Tumors are often small and located anywhere in the body from head to toe, which makes the localisation challenging. Functional imaging by somatostatin receptor-based PET imaging is the first line investigation, which should be followed with CT or MRI based anatomical imaging. Once localised, complete surgical excision is the treatment of choice, which brings dramatic resolution of symptoms. Medical management in the form of phosphate and active vitamin D supplements is given as a bridge to surgical management or in inoperable/non-localised patients. This review provides an overview of the epidemiology, pathophysiology, pathology, clinical features, diagnosis, and treatment of TIO, including the recent advances and directions for future research in this field.

Challenges in the management of tumor-induced osteomalacia (TIO)

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare acquired paraneoplastic disease, which is challenging to diagnose and treat. TIO is characterized by hypophosphatemia resulting from excess levels of tumor-secreted fibroblast growth factor 23 (FGF23), one of the key physiological regulators of phosphate metabolism. Elevated FGF23 results in renal phosphate wasting and compromised vitamin D activation, ultimately resulting in osteomalacia. Patients typically present with progressive and non-specific symptoms, including bone pain, multiple pathological fractures, and progressive muscle weakness. Diagnosis is often delayed or missed due to the non-specific nature of complaints and lack of disease awareness. Additionally, the disease-causing tumour is often difficult to detect and localize because they are often small, lack localizing symptoms and signs, and dwell in widely variable anatomical locations. Measuring serum/urine phosphate should be an inherent diagnostic component when assessing otherwise unexplained osteomalacia, fractures and weakness. In cases of hypophosphatemia with inappropriate (sustained) phosphaturia and inappropriately normal or frankly low 1,25-dihydroxy vitamin D, differentiation of the potential causes of renal phosphate wasting should include measurement of FGF23, and TIO should be considered. While patients experience severe disability without treatment, complete excision of the tumour is typically curative and results in a dramatic reversal of symptoms. Two additional key current unmet needs in optimizing TIO management are: (1 and 2) the considerable delay in diagnosis and consequent delay between the onset of symptoms and surgical resection; and (2) alternative management. These may be addressed by raising awareness of TIO, and taking into consideration the accessibility and variability of different healthcare infrastructures. By recognizing the challenges associated with the diagnosis and treatment of TIO and by applying a stepwise approach with clear clinical practice guidelines, patient care and outcomes will be improved in the future.

Phosphaturic mesenchymal tumors: radiological aspects and suggested imaging pathway

Phosphaturic mesenchymal tumors (PMTs) are rare mesenchymal neoplasms of soft tissue or bone origin that can give rise to a challenge in diagnostic imaging. These tumors are frequently associated with tumor-induced osteomalacia, also called oncogenic osteomalacia, which is a rare paraneoplastic syndrome characterized by ectopic secretion of fibroblast growth factor 23, a hormone that regulates serum phosphate level. PMTs show polymorphic features on both radiological findings and histological examination, causing problems in diagnosis owing to their similarity with other mesenchymal tumors. Thus, this paper aims to describe radiological aspects of PMTs and suggest an imaging pathway for accurate diagnosis throughout the evidence from the literature review.

The phosphaturic mesenchymal tumor as a cause of oncogenic osteomalacia. Three cases and review of the literature

INTRODUCTION

The phosphaturic mesenchymal tumour (PMT) is a very uncommon cause of oncogenic osteomalacia (OO), which is a paraneoplastic syndrome with severe clinical osteomalacia. The PMT is a neoplasia that produces the fibroblast growth factor FGF23, resulting in reduced proximal tubular phosphate reabsorption leading to hyperphosphaturia and hypophosphatemia. Our aim is to present our experience and complications in diagnosis and treatment of PMT in three patients.

MATERIAL AND METHODS

We propose an observational, descriptive and retrospective study of three cases of OO secondary to PMT found in our database of bone and soft tissue tumours. The inclusion criteria were: symptoms related with OO, presence of hyperphosphaturic hypophosphatemia, elevated levels of FGF23 in blood and pathological diagnosis of PMT.

RESULTS

In all cases, the disease showed asthenia, non-specific bone pain, progressive functional weakness, and pathological fractures. The average delay time in diagnosis was 7 years. All presented with hyperphosphaturic hypophosphatemia, elevated levels of alkaline phosphatase as well as FGF23. The use of Octreoscan and PET-CT were essential to find the producing tumour and its subsequent biopsy. Treatment was surgery in two cases and one case was treated by CT-guided cryotherapy with neurophysiological control. Once the surgery was performed, the blood parameters normalized. There is no recurrence.

CONCLUSIONS

Phosphaturic mesenchymal tumor is a very rare entity as part of bone and soft tissue tumors, it may occur in both tissues. The phosphate-calcium homeostasis is altered due to high serum levels of FGF23 because of PMT. Delay in diagnosis is usual, leading to renal and skeletal comorbidities. To avoid this, knowledge of this entity together with high diagnostic suspicion are critical. Surgical treatment leads to normalization of serum levels and systemic symptoms.

Application of ultrasound-guided biopsy and percutaneous radiofrequency ablation in 2 cases with phosphaturic mesenchymal tumor and literature review

Tumor-induced osteomalacia (TIO) is a vanishingly rare paraneoplastic syndrome which is usually caused by phosphaturic mesenchymal tumors (PMTs). The conventional treatment for PMTs is total resection, and ultrasound-guided radiofrequency ablation (RFA) can also be used for the treatment of PMTs patients, especially for patients in whom complete resection may lead to serious complications. We report two cases with PMT who presented syndrome with progressive musculoskeletal complaints and performed ultrasound-guided biopsy and RFA. Ultrasound-guided RFA, which is a safe and effective minimally invasive treatment option, appears to be a valuable alternative to surgery for patients presenting with PMT. We are the first reported case of RFA guided by ultrasonography in the treatment of PMT.

CT and MR imaging features in phosphaturic mesenchymal tumor-mixed connective tissue: A case report

Phosphaturic mesenchymal tumor-mixed connective tissue (PMT-MCT) is rare and usually benign and slow-growing. The majority of these tumors is associated with sporadic tumor-induced osteomalacia (TIO) or rickets, affect middle-aged individuals and are located in the extremities. Previous imaging studies often focused on seeking the causative tumors of TIO, not on the radiological features of these tumors, especially magnetic resonance imaging (MRI) features. PMT-MCT remains a largely misdiagnosed, ignored or unknown entity by most radiologists and clinicians. In the present case report, a review of the known literature of PMT-MCT was conducted and the CT and MRI findings from three patient cases were described for diagnosing the small subcutaneous tumor. Typical MRI appearances of PMT-MCT were isointense relative to the muscles on T1-weighted imaging, and markedly hyperintense on T2-weighted imaging containing variably flow voids, with markedly heterogeneous/homogenous enhancement on post contrast T1-weighted fat-suppression imaging. Short time inversion recovery was demonstrated to be the optimal sequence in localizing the tumor.

Multimodality Image-Guided Cryoablation for Inoperable Tumor-Induced Osteomalacia

Tumor-induced osteomalacia (TIO) is a debilitating paraneoplastic condition caused by small phosphaturic mesenchymal tumors (PMTs) that secrete large amounts of the phosphate-regulating and vitamin D-regulating hormone, FGF23. Tumor removal results in cure. However, because of high perioperative comorbidity, either from tumor location or host factors, surgery is sometimes not an option. Tumor destruction via cryoablation may be an effective option for inoperable PMTs. Three subjects with a confirmed diagnosis of TIO were studied. All three underwent cryoablation of suspected PMTs rather than surgery due to significant medical comorbidities or challenging anatomical location. Subject 3 had tumor embolization 24 hours prior to cryoablation because of the size and hypervascularity of the tumor. The success of the tumor cryoablation was defined by normalization of serum phosphate and FGF23. Cryoablation resulted in a rapid decrease in plasma intact FGF23 by 24 hours postprocedure in all three subjects (0, 2, and 9 pg/mL, respectively) with normalization of blood phosphate by postprocedure day 3. Three-day renal tubular reabsorption of phosphate increased to 76%, 94%, and 95.2%, respectively; 1, 25(OH)₂ vitamin D increased to 84, 138, and 196 pg/ml, respectively. All three had dramatic clinical improvement in pain and weakness. Two subjects tolerated the procedure well with no complications; one had significant prolonged procedure-related localized pain. Although surgery remains the treatment of choice, cryoablation may be an effective, less invasive, and safe treatment for patients with difficult to remove tumors or who are poor surgical candidates. © 2017 American Society for Bone and Mineral Research.