Bone Abstracts

Objectives: To describe a prospective series of pediatric CNO (pCNO) patients treated with IV-Pamidronate (IV-PAM) regarding effect on 1) pain, 2) Whole Body Magnetic Resonance Imaging (WBMRI) documented inflammation; 3) Spinal CNO and 4) bone turnover.

Methods: All pCNO patients (<18 years at diagnosis) with WBMRI confirmed active CNO who were treated with IV-PAM between 2003–2018. IV-PAM: First dose 0.5 mg/kg; subsequently 1 mg/kg (max dose 60 mg), administered once monthly x 9 (max) initially and after WBMRI confirmed flare. Pain: Visual analogue scale for pain (VAS) with ‘0’ indicating no pain and ‘10’ maximum pain was administered at baseline, at each IV-PAM, and at suspected flare. Imaging: WBMRI before 1st IV-PAM, at 6 and 12 months, at suspected flare and after retreatment. Complete resolution (CR) was defined as >95% resolution of abnormal signal on WBMRI. UNtx/Cr was collected at baseline and monthly.

Results: 17 patients (9F, 8M) were included with median [range] follow-up 9.2[1–15] years. The median [range] age at CNO diagnosis was 10.3[4–15] years, and at first IV-PAM 11.6[4–20] years. CNO was unifocal in 6/17; spinal in 4/17 (baseline vertebral fractures in 2/4) and multifocal in 7/17. VAS was uniformly 10/10 at baseline, and decreased to 0–1/10 after 1st IV-PAM. All patients reached CR at 6 months. No flares occurred in 5/17; 12/17 relapsed at 9–36 months and 11/17 received 2nd course of IV-PAM (1–9 doses). With flare, VAS ranged from 4–9/10 and decreased to 0–3/10 after 1st IV-PAM. On final WBMRI, 12/17 (70%) had CR and 5/17 (30%) stable increased signal but no clinical symptoms. No new spinal fractures developed. UNtx/Cr decreased after 1st IV-PAM and no flares occurred while UNtx/Cr remained suppressed. Arthritis developed in 3/17. At last follow-up, 10/17 (59%) patients required no medications, 4/17 (24%) required prn Naproxen and 3/17 (18%) DMARDS for arthritis.

Conclusion: Long-term follow-up confirms that initial beneficial effects of IV-PAM are sustained with flares with no further spinal fractures. No flares occurred while UNTX/Cr remained suppressed, suggesting a role of osteoclasts in CNO. Further multicenter studies are required to define the long-term clinical and imaging response to IV-PAM.

Disclosure: The authors declared no competing interests.