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Long-Term Bone Loss Similar With PI- and NRTI-Sparing Regimens
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5th IAS Conference on HIV Pathogenesis, Treatment and Prevention, July 19-22, 2009, Cape Town
Mark Mascolini
Drops in spine and hip bone mineral density (BMD) appeared to bottom out by weeks 24 and 48 of a 144-week randomized trial comparing a nucleoside (NRTI)-sparing regimen with a protease inhibitor (PI)-sparing regimen in 59 previously untreated people [1]. BMD changes did not differ substantially between the two treatment arms.
Researchers at three Danish centers used DEXA scans to measure lumbar spine and femoral neck (hip) BMD at study entry and 24, 48, 96, and 144 weeks after 59 antiretroviral-naive people were randomized to lopinavir/ritonavir (533/133 mg twice daily) plus efavirenz (the NRTI-sparing regimen) or efavirenz plus zidovudine/lamivudine (the PI-sparing regimen). The bone analysis was a substudy of a larger trial comparing the impact of these regimens on peripheral fat loss. The trial did not call for specific interventions to delay bone loss, and investigators did not monitor use of supplements that may affect bone density.
Of the 29 people in the NRTI-sparing group, 26 were men, while 27 of 30 people in the PI-sparing group were men. All but 4 study participants were white, and most were in their mid-30s to mid-50s. Median pretreatment CD4 counts were 240 in the NRTI-sparing group and 170 in the PI-sparing group, while median pretreatment viral loads were 5.2 and 5.4 log copies/mL.
When the study began, median spine and hip density measured 1.08 g/cm(2) and 0.91 g/cm(2), with no substantial differences between treatment arms. Twenty-five people (42%) had DEXA-defined osteopenia and 8 (13.5%) had osteoporosis. Median pretreatment body mass index stood at 22.7 kg/m(2) in the NRTI-sparing group and 21.6 kg/m(2) in the PI-sparing group.
Treatment assignment did not affect BMD changes in the lumbar spine (P = 0.70) or hip (P = 0.55). Median spine BMD declines appeared to stabilize after the first 24 weeks of treatment, while hip BMD hit bottom around week 48:
Median (interquartile range) change in spine BMD:
· Week 24: -0.034 (-0.054 to -0.007)
· Week 48: -0.023 (-0.053 to -0.006)
· Week 96: -0.020 (-0.040 to 0.004)
· Week 144: -0.024 (-0.047 to 0.005)
Median (interquartile range) change in hip BMD:
· Week 24: -0.028 (-0.048 to -0.020)
· Week 48: -0.049 (-0.086 to -0.024)
· Week 96: -0.039 (-0.065 to -0.014)
· Week 144: -0.033 (-0.067 to -0.0150)
Statistical analysis adjusted for BMD, body mass index, smoking, gender, age, and treatment assignment determined that lower pretreatment CD4 count predicted a greater change in spine BMD (P = 0.007), while lower CD4 count (P = 0.04) and lower body mass index (P = 0.03) predicted a greater change in hip BMD. Age and smoking status did not influence BMD change in this analysis.
The investigators speculated that the initial drop in BMD may reflect either (1) delayed reversal of ongoing BMD loss in immunosuppressed people not yet taking antiretrovirals, or (2) antiretroviral-induced immune alterations resulting in a temporary imbalance between bone resorption and bone formation.
Reference
1. Hansen ABE, Pedersen C, Nielsen H, Obel N, Gerstoft J. Bone mineral density (BMD) changes until week 114 in a randomized trial of protease-inhibitor-sparing versus nucleoside-analogue-sparing HAART. 5th IAS Conference on HIV Pathogenesis, Treatment and Prevention. July 19-22, 2009. Cape Town. Abstract TUAB205.
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