Successful Use of CT-Guided Cryoablation for Inoperable Tumor-Induced Osteomalacia

Presentation Number: OR07-1
Date of Presentation: April 2nd, 2017

Sri Harsha Tella*1, Bradford J Wood2, Richard Chang3, Elliot Levy2, Hayet Amalou2, Venkatesh Krishnasamy2, Rachel I Gafni4 and Michael T. Collins5
1National Institutes of Health (NIH/NICHD), Bethesda, MD, 2National Institutes of Health (NIH), 3Radiology and Imaging Sciences, National Institutes of Health, Bethesda, MD, 4National Institute of Dental and Craniofacial Research/NIH, Bethesda, MD, 5National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD

Abstract

Context: Tumor-induced osteomalacia (TIO) is a rare and debilitating paraneoplastic condition caused by small phosphaturic mesenchymal tumors (PMTs) that secrete large amounts of the phosphate- and vitamin D-regulating hormone, FGF23. Tumor removal results in cure. However, due to high perioperative comorbidity, either from tumor location or host factors, surgery is sometimes not an option. Cryoablation involves tissue destruction by freezing. A CT-guided needle introduces noble gases, such as argon and helium that on combination undergo an endothermic reaction, producing local temperatures of approximately -160˚C. Cryoablation may be an option for inoperable phosphaturic mesenchymal tumors.

Patients and Methods: Three patients with the diagnosis of TIO, confirmed by biochemical evidence of acquired FGF23-mediated hypophosphatemia and renal phosphate wasting, underwent cryoablation of suspected PMTs. The patients were 58-, 72-, and 24-years old, and had been experiencing symptoms of hypophosphatemia for 10, 5, and 3 years, respectively. For each subject, serum phosphate levels were 1.8, 1.5, and 1.1 mg/dl (nl 2.5-4.5), tubular reabsorption of phosphate was 16, 19, and 14% (nl>85), 1, 25 (OH) 2 vitamin D levels were 32, 26 and 16 (nl 18-64 pg/ml) and Intact FGF23 levels were markedly elevated at 1382, 131, 509 pg/ml (nl <50). In all three patients the suspect PMT was identified on either DOTA PET/CT or octreoscan SPECT/CT, and/or FGD-PET/CT, and confirmed on anatomical imaging with CT and MRI, as well as selective venous sampling for intact FGF23. All three tumors were small, 1.4 x 1.2 cm, 0.8 x 0.4 cm, 2.5 x 1.4 cm and not operable either due to high operative risk due to significant medical comorbidities or anatomical location. The subjects underwent CT-guided cryoablation with at least 3 freeze-thaw cycles. Patient 3 also had tumor embolization 24-hours prior to cryoablation due to the size of the tumor.

Results: Cryoablation resulted in a rapid decrease in plasma intact FGF23 by 24-hours post-procedure (0, 2, and 9 pg/ml, respectively), and correction of the hypophosphatemia by post-procedure day #3 (3.5, 4.6 and 3.6 md/dl). Day # 3 renal tubular reabsorption of phosphate increased to 76%, 94% and 95.2%, respectively and 1, 25 (OH) 2 vitamin D increased to 84, 138 and 196 respectively. No patient had significant procedure-related pain, and all 3 had dramatic clinical improvement in baseline pain and weakness.

Conclusions: Although surgery remains the treatment of choice, cryoablation may be an effective, less invasive, and safe treatment for patients with inoperable TIO.

 

Disclosure: RIG: , Shire. Nothing to Disclose: SHT, BJW, RC, EL, HA, VK, MTC