HIV and Other Risk Factors for Esophageal Squamous Cell Carcinoma in Malawi

Summary

Participation Requirements

Description

RATIONALE FOR RESEARCH The Rift Valley of Africa is a 'hot spot' for ESCC, yet little is known about the etiology of this disease in Sub-Saharan Africa. In Malawi, ESCC is the third commonest cancer nationwide behind Kaposi sarcoma and cervical carcinoma. Among cancers that are not classically HIV-r...

RATIONALE FOR RESEARCH The Rift Valley of Africa is a 'hot spot' for ESCC, yet little is known about the etiology of this disease in Sub-Saharan Africa. In Malawi, ESCC is the third commonest cancer nationwide behind Kaposi sarcoma and cervical carcinoma. Among cancers that are not classically HIV-related, ESCC has the highest incidence in Malawi. The ESCC burden recorded in the national cancer registry is also likely an underestimate, as many cases may go undiagnosed and unregistered. Additionally, few data are available on the epidemiology of ESCC in Malawi, and underlying reasons for high frequency of the disease are largely unknown. This knowledge gap is a major barrier to public health prevention efforts. Given that survival after ESCC diagnosis is dismal in Malawi (12% at 1 year), developing evidence-based prevention efforts is paramount. The proposed study will make a significant contribution to existing literature from Malawi and Sub-Saharan Africa in several important respects. First, previous epidemiologic studies of ESCC in Malawi have been limited by challenges with appropriate control selection, which may have limited the validity of their findings. Secondly, our study will include prospective clinical follow-up of confirmed ESCC cases as they receive treatment under local conditions to provide accurate survival estimates. Thirdly, biospecimens from consenting patients will permit etiology and pathogenesis studies to understand mechanisms of ESCC development, which can be correlated with high-quality clinical and epidemiologic data. Finally, we plan to coordinate with other ESCC researchers in eastern and southern Africa to harmonize data collection, and help create a regional consortium in which Malawi can be a founding member and active participant. Primary Objective: Identify demographic and environmental risk factors for ESCC through a case-control study implemented at KCH and SGH. Hypothesis: Modifiable risk factors contribute significantly to ESCC. These include polycyclic aromatic hydrocarbon (PAH) exposure from various sources, excessively hot beverages, dietary factors such as maize fumonisin and low selenium, and HIV infection. Secondary Objective: Identify common genetic and epigenetic alterations in germline and somatic DNA associated with ESCC development. Hypothesis: Recurring genetic and epigenetic alterations can facilitate risk stratification, development of early detection biomarkers, and identification of novel treatment strategies. Procedures After informed consent and study enrollment, subjects will be interviewed using a structured questionnaire and provide biological samples including saliva, blood, urine, and toenail clippings. Esophageal biopsies will be taken for diagnostic confirmation and to support molecular studies. If patients suspected to have ESCC are enrolled but then pathologically confirmed to have an alternate diagnosis, they will be withdrawn. HIV testing will be offered to all participants, and CD4, HIV RNA, and ART status documented for HIV-infected participants. Exposures will be measured using the questionnaire and laboratory analyses of saliva, blood, urine, and toenail samples. We will collect information on: demographic characteristics; HIV status; tobacco and drug use; alcohol consumption; medical history; family history of cancer; indoor air pollution; occupational history; diet, cooking, and food preservation; beverage history including temperature; farming; signs and symptoms of upper gastrointestinal disease; oral health; anthropometric indices; and reproductive history. To examine correlates with patient outcomes, telephone follow-up to assess vital status will be done every 3 months until 2 years from enrollment. Biological samples will be stored in freezers and transferred to the US only for assays that are currently unavailable in Malawi. Laboratory testing will include serum selenium level, blood and urine testing for PAH exposure, tumor immunohistochemistry assays, salivary DNA isolation for genetic studies, and molecular profiling of ESCC tumors. Analysis Sample size will include 300 ESCC cases and 300 controls; 66-68 case control pairs will be enrolled per year, over 3 years, assuming a response rate of 75% in the endoscopy clinic. With 300 case-control pairs, estimated statistical power for an exposure with control population prevalence of 10% and OR 2.0 is 81%, using alpha level 0.05, with higher power for higher control exposure rates and odds ratios. Expected prevalence for key exposures (tobacco and alcohol, hot tea, PAH exposure, selenium deficiency, HIV) is 10-50% in the control population. To assess epidemiologic risk factors for ESCC, we will use logistic regression to estimate odds ratios and 95% confidence intervals for each exposure, while controlling for possible confounders. Survival estimates will be generated using Kaplan-Meyer curves to estimate overall survival at 6, 12 and 24 months.

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