October - December 2015, Volume 11, Issue 4

Kulshreshtha B, Sharma LK, Sharma N, Singh Y, Aggarwal A, Dharmshaktu P, Yadav R, Dutta D

Octreotide and Cinacalcet Have Limited Role in Managing Surgically Incurable Tumor Induced Osteomalacia

Acta Endo (Buc) 2015, 11 (4): 517-523
doi: 10.4183/aeb.2015.517

Context and objective. Somatostatin analogues and cinacalcet have been suggested to have some role in managing hypophosphatemia. This report highlights challenges in managing surgically incurable tumor induced osteomalacia (TIO) with somatostatin analogues and cinacalcet. Patient and methods. A twenty-two year old patient with severe osteomalacia was diagnosed to have TIO due to left hemipelvis tumor (June 2013). Partial surgical removal of tumor (due to its proximity to neurovascular bundles), led to transient remission for 6 weeks. Clinical worsening in spite of maximum tolerable phosphate and calcitriol dose led to trial of octreotide. Acute improvement in phosphate following subcutaneous octreotide 100 mcg was the basis for use of long acting depot octreotide, which was associated with maximal improvement for 4 months, followed by reduced efficacy. Repeated MRI revealed an increase in residual tumor size. Reevaluation revealed very a high parathyroid hormone. Cinacalcet titrated to 90 mg/day induced hypoparathyroidism, improved hypophosphatemia but caused symptomatic hypocalcemia. Cinacalcet at lower doses (30mg/day), though well tolerated, was less effective in improving hypophosphatemia. There was a near 10-fold reduction (2406 to 246RU/ml) in C-terminal FGF-23 levels with cinacalcet. Reduction in phosphate and calcitriol requirements with cinacalcet may contribute to decreased FGF-23. There was no decrease in tumor size. Conclusion. Octreotide and cinacalcet are effective in controlling hypophosphatemia over short periods. Progressive nature of TIO leading to an increased disease severity, tachyphylaxis may explain decreased efficacy of octreotide, higher cinacalcet requirement, poor tolerability, thus limiting their role in long-term management of TIO.

Keywords: tumor induced osteomalacia, octreotide, cinacalcet, somatostatin analogue, hypophosphatemia, hypocalcemia.

Correspondence: Deep Dutta MD, Nursing Home Annex, Post Graduate Institute of Medical Education & Research (PGIMER), Department of Endocrinology, Endocrine Clinic, “Dr. Ram Manohar Lohia” (RML) Hospital, Baba Kharak Singh Marg, New Delhi, India, E-mail: deepdutta2000@yahoo.com