Deborah Ford

Genetic Heterogeneity and Penetrance Analysis of the BRCA1 and BRCA2 Genes in Breast Cancer Families

The contribution of BRCA1 and BRCA2 to inherited breast cancer was assessed by linkage and mutation analysis in 237 families, each with at least four cases of breast cancer, collected by the Breast Cancer Linkage Consortium. Families were included without regard to the occurrence of ovarian or other cancers. Overall, disease was linked to BRCA1 in an estimated 52% of families, to BRCA2 in 32% of families, and to neither gene in 16% (95% confidence interval [CI] 6%-28%), suggesting other predisposition genes. The majority (81%) of the breast-ovarian cancer families were due to BRCA1, with most others (14%) due to BRCA2. Conversely, the majority of families with male and female breast cancer were due to BRCA2 (76%). The largest proportion (67%) of families due to other genes was found in families with four or five cases of female breast cancer only. These estimates were not substantially affected either by changing the assumed penetrance model for BRCA1 or by including or excluding BRCA1 mutation data. Among those families with disease due to BRCA1 that were tested by one of the standard screening methods, mutations were detected in the coding sequence or splice sites in an estimated 63% (95% CI 51%-77%). The estimated sensitivity was identical for direct sequencing and other techniques. The penetrance of BRCA2 was estimated by maximizing the LOD score in BRCA2-mutation families, over all possible penetrance functions. The estimated cumulative risk of breast cancer reached 28% (95% CI 9%-44%) by age 50 years and 84% (95% CI 43%-95%) by age 70 years. The corresponding ovarian cancer risks were 0.4% (95% CI 0%-1%) by age 50 years and 27% (95% CI 0%-47%) by age 70 years. The lifetime risk of breast cancer appears similar to the risk in BRCA1 carriers, but there was some suggestion of a lower risk in BRCA2 carriers <50 years of age.

Risks of cancer in BRCA1-mutation carriers

Germline mutations in a gene on chromosome 17q known as BRCA1 are responsible for a large proportion of inherited predispositions to breast and ovarian cancer. In 33 families with evidence of linkage to BRCA1, we estimated the risks of breast and ovarian cancer from the occurrence of second cancers in individuals with breast cancer, and examined the risks of other cancers in BRCA1 carriers. 26 contralateral primary breast cancers occurring more than 3 years after a first breast cancer were observed before age 70, giving an estimated cumulative risk of breast cancer in gene carriers of 87% by age 70.23 primary ovarian cancers occurred in women with a previous breast cancer, resulting in an estimated cumulative risk of ovarian cancer of 44% by age 70.87 cancers other than breast or ovarian cancer were observed in individuals with breast or ovarian cancer and their first-degree relatives compared with 69.3 expected, based on national incidence rates. Significant excesses were observed for colon cancer (estimated relative risk [RR] to gene carriers 4.11 [95% CI 2.36-7.15]) and prostate cancer (3.33 [1.78-6.20]). No significant excesses (or deficits) were noted for cancers of other sites. Our study provides estimates of breast and ovarian cancer risks which are useful for counselling BRCA1-mutation carriers. It also shows that carriers are at increased risk of colon and prostate cancer, which may be of clinical significance in certain families if the risks are associated with specific mutations.

Cancer risks in two large breast cancer families linked to BRCA2 on chromosome 13q12-13.

The penetrance of the BRCA2 gene on chromosome 13q12-13 has been estimated in two large, systematically ascertained, linked families, by use of a maximum-likelihood method to incorporate both cancer-incidence data and 13q marker typings in the families. The cumulative risk of breast cancer in female gene carriers was estimated to be 59.8% by age 50 years (95% confidence interval [95% CI] 25.9%-78.5%) and 79.5% by age 70 years (95% CI 28.9%-97.5%). The cumulative risk of breast cancer in male carriers was estimated to be 6.3% (95% CI 1.4%-25.6%) by age 70 years. There was no evidence of any risk difference between the two families. These results indicate that the lifetime breast cancer risk in BRCA2 carriers, for at least a subset of mutations, is comparable to that for BRCA1. A significant excess of ovarian cancer in gene carriers was observed (relative risk 17.69, based on three cases), but the absolute risk of ovarian cancer was less than that reported for BRCA1. Significant excesses of laryngeal cancer (relative risk 7.67, based on two possible carriers) and prostate cancer (relative risk 2.89, based on five possible carriers) were also observed. One case of ocular melanoma, as well as a second eye cancer of unspecified histology, occurred in obligate gene carriers.

Cancer mortality in relatives of women with ovarian cancer: The OPCS study

Mortality from cancer and other causes in first‐degree relatives of women with ovarian cancer diagnosed before age 60 has been examined in a large population‐based cohort study in England and Wales. Relatives of 1,188 ovarian‐cancer cases diagnosed between 1954 and 1981 were identified through a register of households established in 1939. Some 4,111 first‐degree relatives living in the same household and having the same surname as the index case were followed up through national records until the end of 1992. Over this period, 1,950 deaths (including 574 cancer deaths) occurred in the relatives. Mortality rates within the cohort were compared with age‐, sex‐ and period‐adjusted mortality rates for England and Wales. Mortality from ovarian cancer in first‐degree relatives was significantly raised (SMR 223, 95% CI 155‐310) although the excess was smaller than that found in case‐control studies. The SMR increased with decreasing age of the relative, though not with decreasing age of the index case. After allowing for age, sisters of cases had higher ovarian‐cancer mortality than mothers (sister:mother SMR ratio 1.89, p = 0.06). The SMR was greater in individuals having 2 first‐degree relatives with ovarian cancer (4 deaths versus 0.17 expected, SMR 242). Relatives of ovarian cancer cases also had significantly increased mortality from cancers of the stomach (SMR 146, 69 deaths) and rectum (SMR 150, 33 deaths), and increased mortality from colon cancer, breast cancer and pancreatic cancer which failed to reach statistical significance. Individuals having a relative with colorectal cancer and a relative with ovarian cancer showed a high mortality from both cancers (11 colorectal‐cancer deaths versus 1.23 expected, 4 ovarian‐cancer deaths versus 0.66 expected).

Daily co-trimoxazole prophylaxis in severely immunosuppressed HIV-infected adults in Africa started on combination antiretroviral therapy: an observational analysis of the DART cohort

Summary Background Co-trimoxazole prophylaxis can reduce mortality from untreated HIV infection in Africa; whether benefits occur alongside combination antiretroviral therapy (ART) is unclear. We estimated the effect of prophylaxis after ART initiation in adults. Methods Participants in our observational analysis were from the DART randomised trial of management strategies in HIV-infected, symptomatic, previously untreated African adults starting triple-drug ART with CD4 counts lower than 200 cells per μL. Co-trimoxazole prophylaxis was not routinely used or randomly allocated, but was variably prescribed by clinicians. We estimated effects on clinical outcomes, CD4 cell count, and body-mass index (BMI) using marginal structural models to adjust for time-dependent confounding by indication. DART was registered, number ISRCTN13968779. Findings 3179 participants contributed 14 214 years of follow-up (8128 [57%] person-years on co-trimoxazole). Time-dependent predictors of co-trimoxazole use were current CD4 cell count, haemoglobin concentration, BMI, and previous WHO stage 3 or 4 events on ART. Present prophylaxis significantly reduced mortality (odds ratio 0·65, 95% CI 0·50–0·85; p=0·001). Mortality risk reduction on ART was substantial to 12 weeks (0·41, 0·27–0·65), sustained from 12–72 weeks (0·56, 0·37–0·86), but not evident subsequently (0·96, 0·63–1·45; heterogeneity p=0·02). Variation in mortality reduction was not accounted for by time on co-trimoxazole or current CD4 cell count. Prophylaxis reduced frequency of malaria (0·74, 0·63–0·88; p=0·0005), an effect that was maintained with time, but we observed no effect on new WHO stage 4 events (0·86, 0·69–1·07; p=0·17), CD4 cell count (difference vs non-users, −3 cells per μL [−12 to 6]; p=0·50), or BMI (difference vs non-users, −0·04 kg/m2 [−0·20 to 0·13); p=0·68]. Interpretation Our results reinforce WHO guidelines and provide strong motivation for provision of co-trimoxazole prophylaxis for at least 72 weeks for all adults starting combination ART in Africa. Funding UK Medical Research Council, the UK Department for International Development, the Rockefeller Foundation, GlaxoSmithKline, Gilead Sciences, Boehringer-Ingelheim, and Abbott Laboratories.

Cancer mortality in relatives of women with ovarian cancer: the OPCS Study. Office of Population Censuses and Surveys.

Mortality from cancer and other causes in male and female first‐degree relatives of women with breast cancer diagnosed before age 60 has been examined in a large population‐based cohort study, providing estimates of familial risks free from ascertainment or recall bias. Relatives of 3,295 patients with breast cancer diagnosed in the UK between 1954 and 1981 were identified through a register of households established in 1939. The 11,678 first‐degree relatives thus identified were followed up through national records until the end of 1992. Over this period 5,421 deaths (including 1,527 cancer deaths) occurred in these relatives. Mortality from breast cancer was significantly raised in first‐degree relatives (SMR 187, 248 deaths), and there was also significant excess mortality from cancers of the larynx (SMR 177, 17 deaths), endometrium (SMR 166, 29 deaths) and unspecified neoplasms (SMR 153, 70 deaths). The SMR for ovarian cancer was 130, based on 58 deaths (p = 0.06). There was no marked excess for other sites or for non‐neoplastic causes of death, but there was a significant deficit in mortality from cervical cancer (SMR 63, 18 deaths). The SMR for breast cancer increased significantly with decreasing age of the relative. After allowing for age, sisters of cases had a slightly (though non‐significantly) higher risk than mothers (ratio of SMRs 1.22). These results, together with penetrance estimates from linked families, suggest that approximately one woman in 800 carries BRCAI, the susceptibility gene on chromosome 17q, and that this gene causes about 1% of all breast cancers.

Sustainable HIV treatment in Africa through viral-load-informed differentiated care

There are inefficiencies in current approaches to monitoring patients on antiretroviral therapy in sub-Saharan Africa. Patients typically attend clinics every 1 to 3 months for clinical assessment. The clinic costs are comparable with the costs of the drugs themselves and CD4 counts are measured every 6 months, but patients are rarely switched to second-line therapies. To ensure sustainability of treatment programmes, a transition to more cost-effective delivery of antiretroviral therapy is needed. In contrast to the CD4 count, measurement of the level of HIV RNA in plasma (the viral load) provides a direct measure of the current treatment effect. Viral-load-informed differentiated care is a means of tailoring care so that those with suppressed viral load visit the clinic less frequently and attention is focussed on those with unsuppressed viral load to promote adherence and timely switching to a second-line regimen. The most feasible approach to measuring viral load in many countries is to collect dried blood spot samples for testing in regional laboratories; however, there have been concerns over the sensitivity and specificity of this approach to define treatment failure and the delay in returning results to the clinic. We use modelling to synthesize evidence and evaluate the cost-effectiveness of viral-load-informed differentiated care, accounting for limitations of dried blood sample testing. We find that viral-load-informed differentiated care using dried blood sample testing is cost-effective and is a recommended strategy for patient monitoring, although further empirical evidence as the approach is rolled out would be of value. We also explore the potential benefits of point-of-care viral load tests that may become available in the future.This article has not been written or reviewed by Nature editors. Nature accepts no responsibility for the accuracy of the information provided.

Effect of cotrimoxazole on causes of death, hospital admissions and antibiotic use in HIV-infected children.

Background:Cotrimoxazole prophylaxis reduces morbidity and mortality in HIV-1-infected children, but mechanisms for these benefits are unclear. Methods:CHAP was a randomized trial comparing cotrimoxazole prophylaxis with placebo in HIV-infected children in Zambia where background bacterial resistance to cotrimoxazole is high. We compared causes of mortality and hospital admissions, and antibiotic use between randomized groups. Results:Of 534 children (median age, 4.4 years; 32% 1–2 years), 186 died and 166 had one or more hospital admissions not ending in death. Cotrimoxazole prophylaxis was associated with lower mortality, both outside hospital (P = 0.01) and following hospital admission (P = 0.005). The largest excess of hospital deaths in the placebo group was from respiratory infections [22/56 (39%) placebo versus 10/35 (29%) cotrimoxazole]. By 2 years, the cumulative probability of dying in hospital from a serious bacterial infection (predominantly pneumonia) was 7% on cotrimoxazole and 12% on placebo (P = 0.08). There was a trend towards lower admission rates for serious bacterial infections in the cotrimoxazole group (19.1 per 100 child-years at risk versus 28.5 in the placebo group, P = 0.09). Despite less total follow-up due to higher mortality, more antibiotics (particularly penicillin) were prescribed in the placebo group in year one [6083 compared to 4972 days in the cotrimoxazole group (P = 0.05)]. Conclusions:Cotrimoxazole prophylaxis appears to mainly reduce death and hospital admissions from respiratory infections, supported further by lower rates of antibiotic prescribing. As such infections occur at high CD4 cell counts and are common in Africa, the role of continuing cotrimoxazole prophylaxis after starting antiretroviral therapy requires investigation.

The Impact of Daily Cotrimoxazole Prophylaxis and Antiretroviral Therapy on Mortality and Hospital Admissions in HIV-Infected Zambian Children

BACKGROUND Data on the population effectiveness of cotrimoxazole prophylaxis and antiretroviral therapy (ART) in human immunodeficiency virus (HIV)-infected African children are few. METHODS A total of 534 Zambian children with HIV infection were randomized to receive daily cotrimoxazole prophylaxis or placebo in the Children with HIV Antibiotic Prophylaxis trial. Following trial closure, children who received the placebo initiated cotrimoxazole prophylaxis, and all children were observed in a closed cohort. Mortality and hospital admission rates were compared, over calendar time, in 9-month periods: trial recruitment (March 2001 to April 2002, May 2002 to January 2003), trial follow-up to closure (February 2003 to October 2003), initial follow-up posttrial (November 2003 to July 2004), and early and later ART availability (August 2004 to April 2005, and May 2005 to May 2006, respectively). RESULTS A total of 546 child-years of follow-up, 40 deaths, and 80 hospital admissions were observed between the time of trial closure and June 2006. A total of 117 of 283 children who were alive at trial closure received ART in the posttrial period (median child age at first use of ART, 8.8 years). Rates decreased in both groups during the trial period, suggesting a survivorship effect. Mortality and hospital admission rates before trial closure were 14 (95% confidence interval [CI], 9-21) deaths per 100 child-years and 24 (95% CI, 15-39) hospital admissions per 100 child-years, respectively, for children who were receiving cotrimoxazole, and were 23 (95% CI, 16-34) deaths per 100 child-years and 35 (95% CI, 23-53) hospital admissions per 100 child-years, respectively, for children who were receiving the placebo. After trial closure, rates remained stable in the cotrimoxazole group, but decreased to 15 (95% CI, 8-26) deaths per 100 child-years and 19 (95% CI, 10-41) hospital admissions per 100 child-years, respectively, for the group of children who received placebo and then initiated cotrimoxazole prophylaxis. In both groups combined, mortality rates decreased to 6 (95% CI, 3-11) deaths per 100 child-years and then 2 (95% CI, 0.8-6) deaths per 100 child-years during periods of ART availability; hospital admission rates decreased to 17 (95% CI, 11-27) hospital admissions per 100 child-years and 8 (95% CI, 4-15) hospital admissions per 100 child-years, respectively. CONCLUSION The benefits of once-daily cotrimoxazole prophylaxis continued throughout the trial and after trial closure. Mortality and hospital admissions decreased (by approximately 6-fold and approximately 3-fold, respectively) following ART availability, similar to findings observed in resource-rich countries.

Absence of linkage to the ataxia telangiectasia locus in familial breast cancer

Heterozygotes for ataxia-telangiectasia (AT) are known to have an increased risk of breast cancer. The gene (or genes) responsible for almost all cases of AT has been localised to chromosome 11q by genetic linkage analysis. To examine the possibility that AT heterozygosity may account for a substantial proportion of familial breast cancer, we have typed five markers on chromosome 11q in 16 breast cancer families. We have found no evidence for linkage between breast cancer and chromosome 11q markers and conclude that the contribution of AT to familial breast cancer is likely to be minimal.