1. Diagnostic importance of contrast enhanced 18 F- fluorodeoxyglucose positron emission computed tomography (FDG PET-ceCT) in patients with tumor induced phosphaturic osteomalacia – Our experience. Abstract Id: IRIA-1225

2. AIM To assess the diagnostic utility of FDG PET-ceCT in localisation of tumours in patients with clinical diagnosis of tumor induced phosphaturic osteomalacia (TIO) To correlate PET-ceCT findings with histopathological results.

3. MATERIALS AND METHODS Prospective study of 8 patients (M/F: 5/3, mean age: 42 yrs, range: 24-60 yrs) with clinical diagnosis of TIO referred for body FDG PET-ceCT scans. Whole body (head to toe + upper limbs) PET-ceCT scans were acquired on Philips GEMINI TOF PET-CT scanner with 64 slice CT scanner following a standard protocol. 5 /8 patients had estimation of serum FGF-23 levels. FDG PET-ceCT findings were correlated with postoperative histology findings and clinical follow up.

4. RESULTS FDG PET-ceCT localised site of tumor in 7/8 patients Sensitivity – 87.5%, Positive predictive value – 100% 1 patient had atypical presentation, the site of tumor was localised in conjunction with 68 Ga DOTANOC PET-CT Site: Bone – 3/8 patients, Craniofacial – 5/8 patients All the patients had phosphaturic mesenchymal tumor on histolopathological examination. FDG PET-ceCT & HPE were concordant in 7/8 patients.

5. RESULTS - BIOCHEMICAL PARAMETERS Biochemical parameters Pre- operative Post- operative P value (Wilcoxon Signed ranks test) S. Calcium (mg/dl) 8.2 (7.92-8.45) 9.5 (8.97-9.95) 0.012 S. Phosphorus (mg/dl) 1.15 (0.75-1.5) 3.10 (2.72-3.85) 0.012 S. FGF 23 (RU/mL) 1620 (1434-2858) 152 (69.5-169.0) 0.043

6. CASE 1 H/o polyarthritis for 7 years and progressive weakness of all 4 limbs with wasting of muscles for 5 years Bed ridden for 5-6 years RA factor & HLA B27negative S. Calcium8.2 mg/dl S. Phosphorus1.1 mg/dl S. FGF 231620 RU/ml S. 1, 25 dihyroxy vitamin D314 pg/ml S. ALP679 U/L S. PTH171.8 pg/ml S. potassium4.0 mEq/L

7. 99m Tc-MDP WHOLE BODY BONE SCINTIGRAPHY

8. 18 F-FDG PET-ceCT WHOLE BODY SCAN MIP IMAGE SUVmax – 5.2

9. Biopsy – spindle cell neoplasm with pericytomatous features. The possibilities include glomangiopericytoma (Sinonasal – type hemangiopericytoma, hemangiopericytoma like tumor)

10. CASE 2 H/o weakness and pain in bilateral hips for 2 years, difficulty in walking S. Calcium9.8 mg/dl S. Phosphorus1.5 mg/dl S. FGF-233360 RU/ml S. ALP384 U/L S. I, 25 dihyroxy vitamin D310 pg/mL S. PTH44 pg/mL S. Creatinine0.8 mg/dl 24 hour urine inorganic phosphorus 0.5g/24 hours

11. 99m Tc-MDP WHOLE BODY BONE SCINTIGRAPHY

12. 18 F-FDG PET-ceCT WHOLE BODY SCAN MIP IMAGE SUVmax 4.4SUVmax 5.7 SUVmax 5.4

13. CASE 2 Patient underwent tonsillectomy. (HPE – reactive lymphoid follicles.) Curettage and bone grafting was done for lesion in right greater trochanter. (HPE – fragmented atypical spindle cells) S. Phosphorus transiently increased to 2mg/dl after surgery, following which again it dropped to 1.5 mg/dl Resistance to treatment with Tab. Shelcal 68 Ga DOTANOC PET-ceCT was planned for further localisation since this tumors express somatostatin receptors

14. 68 Ga DOTANOC PET-ceCT WHOLE BODY SCAN MIP IMAGE

15. HPE – Bony trabeculae with nests of cellular nodules composed of bland spindle and epitheloid cells and moderate cytoplasm arranged around blood vessels.

16. REVIEW OF LITERATURE NoAuthorNResults 1. Jadhav S et al (2014) 16 FDG PET-CT positivity – 50% Gallium DOTATATE PET-CT positivity – 100% 2. Chong WH et al (2013) 31 FDG PET-CT sensitivity – 88 %, Octreo-SPECT sensitivity- 0.95% 3. Shamim SA et al (2010) 15 FDG PET-CT positivity - 9/15 patients 4. Our study with TOF PET-ceCT (64 slice) scanner 8Sensitivity – 87.5%

17. CONCLUSION 18F-FDG PET-ceCT is a sensitive modality for localisation of tumors in patients with TIO Since these tumors are small in size and can be located anywhere in body, whole body (head to toe+ upper limbs) acquisition should be performed. Careful scrutiny of appendicular skeleton should be performed in the scans 18F-FDG PET-ceCT can serve as a first line imaging modality in TIO, to facilitate early diagnosis as 68 Ga- DOTANOC PET-CT facility is not readily available.

18. Clinical diagnosis of TIO (thorough clinical history, biochemical parameters, exclude familial forms) 18 F-FDG PET-ceCT whole body scan (head to toe + upper limbs) + - + - Surgery & clinical monitoring Medical therapy MRI (regional) 68 Ga-DOTANOC PET-CT PROPOSED FLOWCHART