On the Use of Local Assessments for Monitoring Centrally Reviewed Endpoints with Missing Data in Clinical Trials*

Due to ethical and logistical concerns it is common for data monitoring committees to periodically monitor accruing clinical trial data to assess the safety, and possibly efficacy, of a new experimental treatment. When formalized, monitoring is typically implemented using group sequential methods. In some cases regulatory agencies have required that primary trial analyses should be based solely on the judgment of an independent review committee (IRC). The IRC assessments can produce difficulties for trial monitoring given the time lag typically associated with receiving assessments from the IRC. This results in a missing data problem wherein a surrogate measure of response may provide useful information for interim decisions and future monitoring strategies. In this paper, we present statistical tools that are helpful for monitoring a group sequential clinical trial with missing IRC data. We illustrate the proposed methodology in the case of binary endpoints under various missingness mechanisms including missing completely at random assessments and when missingness depends on the IRC’s measurement

Associations of Low Vitamin D and Elevated Parathyroid Hormone Concentrations With Bone Mineral Density in Perinatally HIV-Infected Children

BACKGROUND: Perinatally HIV-infected (PHIV) children have, on average, lower bone mineral density (BMD) than perinatally HIV-exposed uninfected (PHEU) and healthy children. Low 25-hydroxy vitamin D [25(OH)D] and elevated parathyroid hormone (PTH) concentrations may lead to suboptimal bone accrual. METHODS: PHIV and PHEU children in the Pediatric HIV/AIDS Cohort Study had total body (TB) and lumbar spine (LS) BMD and bone mineral content (BMC) measured by dual-energy x-ray absorptiometry; BMD z-scores (BMDz) were calculated for age and sex. Low 25(OH)D was defined as ≤20 ng/mL and high PTH as >65 pg/mL. We fit linear regression models to estimate the average adjusted differences in BMD/BMC by 25(OH)D and PTH status and log binomial models to determine adjusted prevalence ratios of low 25(OH)D and high PTH in PHIV relative to PHEU children. RESULTS: PHIV children (n = 412) were older (13.0 vs. 10.8 years) and more often black (76% vs. 64%) than PHEU (n = 207). Among PHIV, children with low 25(OH)D had lower TB-BMDz [SD, -0.38; 95% confidence interval (CI), -0.60 to -0.16] and TB-BMC (SD, -59.1 g; 95% CI, -108.3 to -9.8); high PTH accompanied by low 25(OH)D was associated with lower TB-BMDz. Among PHEU, children with low 25(OH)D had lower TB-BMDz (SD, -0.34; 95% CI, -0.64 to -0.03). Prevalence of low 25(OH)D was similar by HIV status (adjusted prevalence ratio, 1.00; 95% CI, 0.81 to 1.24). High PTH was 3.17 (95% CI, 1.25 to 8.06) times more likely in PHIV children. CONCLUSIONS: PHIV and PHEU children with low 25(OH)D may have lower BMD. Vitamin D supplementation trials during critical periods of bone accrual are needed

Fractures in children and adolescents living with perinatally acquired HIV

Background: Across numerous settings, bone mineral density for age and sex is lower in children/adolescents living with perinatally-acquired HIV (PHIV) compared to uninfected peers. We assessed incidences of any fracture/any long bone fracture, and osteoporosis prevalence in PHIV and HIV-exposed uninfected (PHEU) participants in the Pediatric HIV/AIDS Cohort Study (PHACS). Methodology: Lifetime history of fracture events from birth up to age 20 years was obtained by chart review and/or interview, including age at fracture, mechanism, and bone(s) fractured. Poisson regression models were fit comparing fracture incidence by HIV status adjusted for age, sex, and race, with effect modification by age (<6, ≥6 yr). Results: PHIV (N = 412) were older (median 17.5 vs 16.7 yr) and more frequently reported black race (72% vs 61%) than PHEU children/adolescents (N = 206). 17% of PHIV and 12% of PHEU ever reported a fracture. Among children <6 yr, the adjusted incidence rate ratio of ≥1 fracture was higher (7.23; 95% CI 0.98, 53.51) in PHIV than PHEU, but similar among children/adolescents ≥6 years (1.20; 95% CI: 0.77, 1.87). Results were similar for long bone fracture. The most common fracture mechanisms were falling to the ground from a standing height (23.6% PHIV vs 8.8% PHEU) and sports injuries (21.3% vs 32.4%), and the most commonly fractured sites were the forearm and small bones of the wrist/hands. None of the children had osteoporosis. Conclusions: Among children/adolescents ≥6 yr of age, fractures were similar by perinatal HIV status. Prospective, targeted collection of fracture history will be necessary to determine rates of fracture as PHIV and PHEU age into adulthood. Summary: Lifetime fracture history was collected in children/adolescents living with perinatally-acquired HIV (PHIV) and HIV-exposed uninfected (PHEU) children from birth up to age 20 years. Fracture incidence was higher in PHIV compared to PHEU among children <6 years old, but not among older children/adolescents

Progesterone and prolactin levels in pregnant women living with HIV who delivered preterm and low birthweight infants: A nested case-control study

Background Antiretroviral therapy (ART) is associated with high rates of adverse birth outcomes, including preterm birth and low birthweight. Studies suggest that progesterone and prolactin may play important intermediary roles. Methods We analyzed data from the Antenatal Component of the PROMISE trial, a multi-center study of pregnant women taking antiretroviral regimens (lopinavir/ritonavir-containing ART or zidovudine alone) to prevent mother-to-child HIV transmission. In a nested case-control study, we compared data from women who gave birth to preterm (<37 weeks gestation) and/or low birthweight (<2500 g) infants to matched individuals who did not. We measured serum progesterone and prolactin at 24–34 weeks gestation. We used conditional logistic regression to describe relationships between hormone levels, birth outcomes, and antiretroviral regimens. Results 299 women and their newborns were included (146 cases, 153 controls). When compared to women receiving zidovudine alone, those on ART had higher odds of progesterone levels under the 10th percentile (adjusted odds ratio [AOR]:2.34, 95%CI:1.41–3.89) and 25th percentile (AOR:2.07, 95%CI:1.46–2.94). However, higher levels of progesterone—rather than lower levels—were associated with our composite case outcome at the 10th percentile (AOR:1.88, 95%CI:0.77–4.59) and 25th percentile (AOR:1.96, 95%CI:1.06–3.61). Associations were not observed between prolactin, antiretroviral regimen, and birth outcomes. Conclusion We observed lower progesterone levels among women allocated to ART regimens; however, higher progesterone levels were associated with preterm birth and/or low birthweight. While features of the study design may have contributed to these findings, they nevertheless highlight the potentially complex mechanisms underpinning adverse birth outcomes and HIV

The multi-country PROMOTE HIV antiretroviral treatment observational cohort in Sub-Saharan Africa: objectives, design, and baseline findings.

CAPRISA, 2018.Abstract available in pdf

Genetic variation in insulin-like growth factor signaling genes and breast cancer risk among BRCA1 and BRCA2 carriers

Abstract Introduction Women who carry mutations in BRCA1 and BRCA2 have a substantially increased risk of developing breast cancer as compared with the general population. However, risk estimates range from 20 to 80%, suggesting the presence of genetic and/or environmental risk modifiers. Based on extensive in vivo and in vitro studies, one important pathway for breast cancer pathogenesis may be the insulin-like growth factor (IGF) signaling pathway, which regulates both cellular proliferation and apoptosis. BRCA1 has been shown to directly interact with IGF signaling such that variants in this pathway may modify risk of cancer in women carrying BRCA mutations. In this study, we investigate the association of variants in genes involved in IGF signaling and risk of breast cancer in women who carry deleterious BRCA1 and BRCA2 mutations. Methods A cohort of 1,665 adult, female mutation carriers, including 1,122 BRCA1 carriers (433 cases) and 543 BRCA2 carriers (238 cases) were genotyped for SNPs in IGF1, IGF1 receptor (IGF1R), IGF1 binding protein (IGFBP1, IGFBP2, IGFBP5), and IGF receptor substrate 1 (IRS1). Cox proportional hazards regression was used to model time from birth to diagnosis of breast cancer for BRCA1 and BRCA2 carriers separately. For linkage disequilibrium (LD) blocks with multiple SNPs, an additive genetic model was assumed; and for single SNP analyses, no additivity assumptions were made. Results Among BRCA1 carriers, significant associations were found between risk of breast cancer and LD blocks in IGF1R (global P = 0.011 for LD block 2 and global P = 0.012 for LD block 11). Among BRCA2 carriers, an LD block in IGFBP2 (global P = 0.0145) was found to be associated with the time to breast cancer diagnosis. No significant LD block associations were found for the other investigated genes among BRCA1 and BRCA2 carriers. Conclusions This is the first study to investigate the role of genetic variation in IGF signaling and breast cancer risk in women carrying deleterious mutations in BRCA1 and BRCA2. We identified significant associations in variants in IGF1R and IRS1 in BRCA1 carriers and in IGFBP2 in BRCA2 carriers. Although there is known to be interaction of BRCA1 and IGF signaling, further replication and identification of causal mechanisms are needed to better understand these associations