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BMD Drops More Than 3% in up to One
Third of MSM Using TDF PrEP for 2 Years
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17th European AIDS Conference, November 6-9, 2019, Basel
Mark Mascolini
One quarter to one third of men who have sex with men (MSM) taking daily preexposure prophylaxis (PrEP) including tenofovir disoproxil fumarate (TDF) for 2 years lost more than 3% of bone mineral density (BMD) at all three bone sites assessed [1]. Researchers as Sydney's St. Vincent's Hospital suggested regular DXA scanning may be appropriate for TDF PrEP users with higher fracture risk.
The Sydney team reported that about 18,000 Australian MSM take daily TDF/emtricitabine (FTC) PrEP. These investigators previously reported more than 3% BMD loss at 1 or more sites in 82% of MSM taking PrEP for 12 months. Half of these 32 MSM had more than 5% BMD loss in that time. Research in the general population links 3% or greater BMD loss to a doubled fracture risk [2]. Another study of TDF/FTC PrEP in MSM recorded BMD loss exceeding 1% over 24 months [3], but the Australian team finds that result difficult to interpret because of imperfect adherence by these men.
The Australian study involved MSM starting daily TDF-based PrEP in a demonstration project. Health workers offered men DXA scans at a baseline visit and after 1 and 2 years of PrEP. A single scanner performed all DXAs for this analysis. Scans focused on the lumbar spine (L1-L4), total hip, and femoral neck. PrEP adherence calculated by pill returns approached 100%.
Of the 485 men who began daily PrEP, 185 (38%) had a baseline DXA, 118 (24%) had a scan after 1 year, and 51 (10.5%) had a scan after 2 years. Age at baseline, year 1, and year 2 averaged 37, 38, and 42, and body mass index at all three points averaged 25 kg/m2 (the overweight threshold). Median PrEP duration at those three points was 7 days, 420 days, and 824 days. Only 5% of men smoked at the time of the three scans, and 12% had more than 3 alcoholic drinks daily. No one used corticosteroids.
After 1 year of daily PrEP in 118 men, BMD fell by an average 1.3% at the femoral neck (P = 0.124), 0.86% at the spine (P = 0.023), and 0.74% at the total hip (P = 0.015). Among the 51 men with complete data through year 2, BMD declines averaged 0.68% at the femoral neck, 1.64% at the spine, and 1.53% at the total hip. In these 51 men percent changes in BMD from year 1 to year 2 were +0.45% at the femoral neck, -0.24% at the spine, and -0.15% at the total hip. At 2 years, 24% of these 51 men had more than a 3% drop in BMD at the femoral neck, 31% had more than a 3% drop at the spine, and 35% had more than a 3% drop at the total hip.
No one had a low-trauma fracture during the study period.
The St. Vincent's investigators noted four limitations to their analysis: data came from a single site, all participants were MSM, most men declined follow-up testing, and the sample remains too small to identify predictors of BMD change with PrEP. They pointed out that BMD loss in these men appeared to stabilize after 1 year, as it has in studies of HIV-positive adults starting a TDF-containing antiretroviral regimen. Still, the Sydney researchers proposed that "DXA on TDF-based PrEP may be reasonable for those at higher fracture risk." The findings also lend weight to arguments for as-needed sex-timed PrEP rather than daily PrEP [4].
References
1. Carr A, McAllister J, Holliday S, Richardson R, Hesse K, Comben S. Changes in bone mineral density over 2 years in men who have sex with men on tenofovir disoproxil fumarate-based HIV pre-exposure prophylaxis: longitudinal cohort data. 17th European AIDS Conference, November 6-9, 2019, Basel. Abstract 11/5.
2. Kanis JA, Johansson H, Oden A, et al. A meta-analysis of prior corticosteroid use and fracture risk. J Bone Miner Res. 2004;19:893-899.
3. Liu AY, Vittinghoff E, Sellmeyer DE, et al. Bone mineral density in HIV-negative men participating in a tenofovir pre-exposure prophylaxis randomized clinical trial in San Francisco. PLoS One. 2011;6:e23688.
4. Molina JM, Capitant C, Spire B, et al. On-demand preexposure prophylaxis in men at high risk for HIV-1 infection. N Engl J Med. 2015;373:2237-2246.
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