The THINKER Study: A Pilot for a Case-Control of Esophageal Squamous Cell Carcinoma in Western Kenya

This pilot study will assess the feasibility of completing the first formal case-control study to examine etiologic factors for esophageal squamous cell carcinoma (ESCC) in Kenya and will be conducted in Western Kenya, a high-risk area for ESCC.

Esophageal cancer causes over 380,000 deaths per year and ranks as the sixth leading cause of cancer death worldwide. Two primary cell types, squamous cell carcinoma and adenocarcinoma, account for most cases. Although the rates of esophageal adenocarcinoma have risen rapidly in the United States and elsewhere, ESCC still accounts for 80% of all esophageal cancer cases in the world. Many of these cases occur in high-risk areas with sharp geographic boundaries within China, Iran, a small region of South America, South Africa, and Kenya. Studies of ESSC in economically developed countries, such as the US, point to smoking tobacco, heavy alcohol drinking, poor diets deficient in fresh fruits and vegetables, and low socioeconomic status as the main etiologic factors. Other independent risk factors may include being male and being African-American. Smoking tobacco and heavy alcohol consumption do not explain the incidence rates in the high-risk regions because these habits are less common and less intensely practiced in these high-risk areas compared to the low risk area. Also, in highrisk areas the incidence rates are similar in men and women despite differences in the rates of tobacco smoking and alcohol drinking. Therefore, it is important to consider a wide range of etiologic factors to explain the high rates of cancer in these populations.

Tenwek Hospital is a 300 bed mission hospital located in Bomet District, Rift Valley Province, approximately 200 miles from Nairobi in the west of Kenya. Tenwek serves as a primary health care facility for approximately 400,000 people, and it has become a referral center for a broader population. ESCC is the most common malignancy seen at Tenwek Hospital and the patients show a very unusual age distribution with 10% of cases less than or equal to 30 years of age.

We will conduct a pilot for a case-control study of ESCC at Tenwek Hospital, recruiting people that live within 50 km of the hospital. Initial pilot testing showed that neither hospital-visitor controls nor general-population controls were practical control sources. We now plan to test the feasibility of collecting 50 hospital-based non-cancer patient controls. We will then enroll 50 cases and 50 additional hospital-based non-cancer patient controls to test all aspects of our protocol. We will ship the biological samples collected from these individuals to the US and test their suitability for our intended assays. All subjects will be interviewed using a structured questionnaire and will be asked to provide biological samples including blood and urine. Environmental risk factors (including lifestyle, habits, and diet) will be assessed through questionnaires.