Endocrine Abstracts

Background: Cystic Fibrosis-related bone disease (CFBD) increases morbidity and mortality. Treatment varies across UK CF centres. Dual-energy X-ray absorptiometry (DEXA) is used for bone mineral density (BMD) evaluation: CFBD is diagnosed when Z-score<-2. European Cystic Fibrosis Society (ECFS) criteria for prescribing bisphosphonates:

1. Presence of low-trauma fracture 2. Lumbar spine/ total hip/femoral neck Z-score <-2 and significant bone loss (>4% /year) on serial DEXA despite optimal therapy 3. Patient awaiting or has undergone solid organ transplantation and Z-score <−1.5 4. Patient: prolonged course of oral glucocorticoids (>3 months) and Z-score <−1.5. Challenges encountered with this approach.

Methods: Retrospective audit analyzing CF database, January 2017-December 2020. Data sets included: demographics; Zscore; bisphosphonate treatment; treatment response; contraindications to bisphosphonates (pregnancy, jaw osteonecrosis, active tooth disease, CrCl<30ml/min, oesophageal reflux, decline treatment).

Results: 248 patients screened: 18 met ECFS criteria for bisphosphonate treatment. 3/18 eligible for bisphosphonates having contraindications excluded. Audit included 15/18. Average age: 33.8years. 45% (7/15) were prescribed bisphosphonates. Of the 7 prescribed bisphosphonates, 2(29%) had DEXA repeated for monitoring treatment response. Repeat DEXA not done in 5/7. Among untreated 8, 1 was being trialled off steroids, 4 were pending multidisciplinary review regarding treatment concerns. 1 had 13% increase in BMD though still meeting criteria for bisphosphonate therapy. 1 had not achieved peak bone mass due to age, 1 had missed clinic follow-up. All 15 patients were on steroids: 5 for solid organ transplant, 10 for allergic bronchopulmonary aspergillosis. Mean duration of steroids with no transplant: 3.5years.

Conclusions: Challenges noted in CFBD treatment with bisphosphonates as per ECFS guidance. E.g., management of patients who hadn’t achieved peak bone mass; had improvement in BMD but Z score remained <-2. Long-term oral steroids impact on BMD was noted and hence importance of optimizing doses. A case-by-case approach is often indicated (+/-rheumatology input).