Bisphosphonates are the mainstay of osteoporosis treatment. Despite the fact that bisphosphonates have a relatively good safety record and are tolerated well by the majority of patients, serious adverse events have been associated with their use. A 41-year-old man had been diagnosed with osteoporosis and had taken etidronate 200 mg/day daily for 2 years due to the judgmental error. He was referred for the management of refractory bone pain and generalized muscle ache. Serum calcium, phosphate, 25-hydroxy-vitamin D (25(OH)D), and immunoreactive parathyroid hormone (iPTH) were within normal range. Plain X-ray showed multiple fractures. Whole body bone scan confirmed multiple sites of increased bone uptakes. Tetracycline-labeled bone biopsy showed typical findings of osteomalacia. He was diagnosed with iatrogenic, etidronate-induced osteomalacia. The patient received daily parathyroid hormone (PTH) injection for 18 months. PTH effectively reverses impaired bone mineralization caused by etidronate misuse. Currently, he is doing well without bone pain. Bone mineral density significantly increased, and the increased bone uptake was almost normalized after 18 months. This case seems to suggest that human PTH (1-34) therapy, possibly in association with calcium and vitamin D, is associated with important clinical improvements in patients with impaired bone mineralization due to the side effect of bisphosphonate.
Adult ; Biopsy ; Bone Density ; Calcification, Physiologic ; Calcium ; Diphosphonates ; Etidronic Acid ; Humans ; Judgment ; Muscles ; Osteomalacia ; Osteoporosis ; Parathyroid Hormone ; Reference Values ; Vitamin D

Purpose: GC1118 is a novel antibody targeting epidermal growth factor receptor (EGFR) with enhanced blocking activity against both low- and high-affinity EGFR ligands. A phase 1b/2a study was conducted to determine a recommended phase 2 dose (RP2D) of GC1118 in combination with 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) (phase 1b) and to assess the safety and efficacy of GC1118 plus FOLFIRI as a second-line therapy for recurrent/metastatic colorectal cancer (CRC) (phase 2a). Materials and Methods: Phase 1b was designed as a standard 3+3 dose-escalation study with a starting dose of GC1118 (3 mg/kg/week) in combination with biweekly FOLFIRI (irinotecan 180 mg/m2; leucovorin 400 mg/m2; 5-fluorouracil 400 mg/m2 bolus and 2,400 mg/m2 infusion over 46 hours) in patients with solid tumors refractory to standard treatments. The subsequent phase 2a part was conducted with objective response rate (ORR) as a primary endpoint. Patients with KRAS/NRAS/BRAF wild-type, EGFR-positive, recurrent/metastatic CRC resistant to the first-line treatment were enrolled in the phase 2a study. Results: RP2D of GC1118 was determined to be 3 mg/kg/wk in the phase 1b study (n=7). Common adverse drug reactions (ADRs) observed in the phase 2a study (n=24) were acneiform rash (95.8%), dry skin (66.7%), paronychia (58.3%), and stomatitis (50.0%). The most common ADR of ≥ grade 3 was neutropenia (33.3%). ORR was 42.5% (95% confidence interval [CI], 23.5 to 62.0), and median progression-free survival was 6.7 months (95% CI, 4.0-8.0). Conclusion GC1118 administered weekly at 3 mg/kg in combination with FOLFIRI appears as an effective and safe treatment option in recurrent/metastatic CRC.