# Bone Density and Trabecular Bone Score Decline Rapidly in the First Year After Bone Marrow Transplantation with a Marked Increase in 10-Year Fracture Risk

## TL;DR

Bone density and bone structure decline rapidly after bone marrow transplantation, leading to a higher risk of fractures than predicted by standard tools.

## Contribution

This study reveals that bone mineral density and trabecular bone score decline independently and rapidly after BMT, with higher fracture rates than predicted.

## Key findings

- Bone density declines most rapidly at the femoral neck and total hip in the first year after BMT.
- Trabecular bone score declines independently of bone mineral density T-scores at all sites.
- Fracture prevalence after BMT is higher than predicted by FRAX® estimates despite antiresorptive therapy in some patients.

## Abstract

As outcomes from allogeneic bone marrow transplantation (BMT) have improved, prevention of long-term complications, such as fragility fractures, has gained importance. We aimed to assess areal bone mineral density (aBMD) and trabecular bone score (TBS) changes post BMT, and determine their relationship with fracture prevalence. Patients who attended the Royal Melbourne Hospital (RMH) BMT clinic between 2005–2021 were included. Patient characteristics and dual-energy X-ray absorptiometry (DXA) values were collected from the electronic medical record and a survey. TBS iNsight™ was used to calculate TBS for DXA scans performed from 2019 onwards. 337 patients with sequential DXAs were eligible for inclusion. Patients were primarily male (60%) and mean age ± SD was 45.7 ± 13.4 years. The annualised decline in aBMD was greater at the femoral neck (0.066g/cm2 (0.0038–0.17)) and total hip (0.094g/cm2 (0.013–0.19)), compared to the lumbar spine (0.049g/cm2 (− 0.0032–0.16)), p < 0.0001. TBS declined independently of aBMD T-scores at all sites. Eighteen patients (5.3%) sustained 19 fractures over 3884 person-years of follow-up post-transplant (median follow-up 11 years (8.2–15)). This 5.3% fracture prevalence over the median 11-year follow-up period is higher than what would be predicted with FRAX® estimates. Twenty-two patients (6.5%) received antiresorptive therapy, and 9 of 18 (50%) who fractured received or were on antiresorptive therapy. In BMT patients, aBMD and TBS decline rapidly and independently in the first year post BMT. However, FRAX® fracture probability estimates incorporating these values significantly underestimate fracture rates, and antiresorptive treatment rates remain relatively low.

The online version contains supplementary material available at 10.1007/s00223-024-01189-1.