Esophageal cancer is well known for its striking geographical variation in incidence. Endemic areas of very high-risk are found in northern China, northeastern Iran, Kazakhstan, northern France, South Africa, and Kenya. Among such areas, the high-risk populations within Africa have been the least studied. Results from the current study period, 1999–2007, demonstrate that 35% of cancers diagnosed at Tenwek Hospital are esophageal cancer. These results provide further evidence that the area of western Kenya is a high-risk, endemic area for esophageal cancer. A male:female ratio of 1.62:1 and the fact that 89% of the cases were ESCC are characteristics common to endemic areas. Although incidence cannot be adequately evaluated, due to the lack of population-based cancer and death registries, EC appears to be the most common cancer in the population served by Tenwek Hospital.
One difference between the earlier and more recent periods of analysis was the arrival at Tenwek Hospital in 1998 of a thoracic surgeon with a special interest in EC. His presence has resulted in improved diagnostic, treatment, and palliative care capabilities, allowing Tenwek to become a referral center for EC within Kenya. Nearly twice as many pathology-proven cancers were diagnosed in the 8.67 years from 1999 through September 2007 as were diagnosed in the 10 years from 1989 through 1998. Nearly half of this change was due to a 285% increase in EC.
Between the two analyzed periods, the average annual number of EC patients from within the catchment area rose 261%, from 25.0 in 1993–1998 to 65.2 in 1999–2007, and the average number from outside the catchment area rose 806%, from 5.0 in 1993–1998 to 40.3 in 1999–2007. Thus about half of the increase in total EC case numbers came from new referrals from outside the traditional catchment area, but the other half came from increased numbers of cases from within the catchment area. This marked increase from within the catchment area must reflect some combination of changing disease rates, changing population in the affected age range, increased utilization of Tenwek by diseased patients due to increased public awareness of the presence of an EC specialist and stories of successful palliative procedures and occasional cures, and increased utilization of endoscopy and biopsy to confirm suspected tumors. Of interest, a spike in the number of EC cases can be seen in for the year 2001. From 2000 to 2002, a community cytologic screening program was implemented by Tenwek Hospital. It is possible that the increased awareness, both within the general population and in the surrounding health establishments, led to a greater number of cases being referred to Tenwek.
Esophageal cancer is also common in other areas of Kenya. Indeed, EC was the most common cancer diagnosed in both the Nairobi9
studies. However, the relative proportion of EC cases in comparison to other cases of cancer is much higher at Tenwek Hospital. This may be partly due to increased patient referrals and increased public awareness of EC care and palliation possibilities at Tenwek, as noted above, but it may also be due to differences in the populations and/or ethnicities at risk in these different geographical areas. Collaboration among centers and further studies are warranted.
Esophageal cancer is the most common cancer in all age groups in the Tenwek patient population (). However, the most striking feature of EC in this area is the proportion of cases presenting at young ages. In each study period, the youngest diagnosed patient was 14 years old, female, and Kalenjin. In 1989–1998, 11% of the EC cases were ≤30 years old (10). In 1999–2007, 8% of EC cases from within the Tenwek catchment area and 9% of all Kalenjin cases were ≤30, and 18% of cases in the catchment area and 20% of all Kalenjin cases were ≤40 years old. Comparable figures for cases ≤30 and ≤40 years old reported from other high-risk populations include 0.7% and 4.7% in northern China13
, 1% and 4% in northeastern Iran14
, and 8.8% (≤40 years old) in South Africa15
. Low proportions of young patients have also been reported from low-risk populations such as the United States, where comparable figures from the Surveillance, Epidemiology and End Results (SEER) Program registries for 1995–2002 were 0.2% and 1.3%, respectively16
. A comparison of the age distributions of Tenwek patients and patients reported to the SEER registries in the US is shown in .
Age distribution of EC patients seen at Tenwek Hospital (1999–2007) and reported to SEER registries in the United States (1995–2002)
The occurrence of young EC cases in the Tenwek patient population appears to be more related to Kalenjin ethnicity than to residence in the Tenwek catchment area given the difference in the proportions of cases within the catchment area who were ≤30 years old among Kalenjins (8.8%) and non-Kalenjins (3.9%) . The proportions of these cases among Kalenjins and non-Kalenjins outside the catchment area were 11.1% and 1.1%. Patients ≤30 years old were more than five times more likely to be of Kalenjin ethnicity than other ethnicities, after adjusting for place of residence. All 33 EC cases ≤27 were of Kalenjin ethnicity, and all but one of these cases was ESCC. This suggests an increased risk for the development of EC, particularly ESCC, at a young age among Kalenjins, which may be related to lifestyle and/or genetic characteristics, a subject which deserves further study.
A clear limitation of this study is the sole inclusion of pathology-confirmed malignancies, but this is all that is currently possible in the study area. Evaluation of pathology-confirmed case series are still useful, however, especially in low-resource settings, since they allow some comparison of frequencies of different malignancies in the population, comparisons of attributes (such as age distribution) in different subgroups of the covered population, evaluation of disease trends within the population, and comparisons of large differences in cancer occurrence between populations.
A great deal of work remains to be done to reduce the burden of esophageal cancer in Kenya and the rest of sub-Saharan Africa. At Tenwek Hospital, the vast majority of patients present with inoperable, obstructive disease which prevents passage of a 9.8mm diameter endoscope17
. In prior studies, such obstruction has been shown to be locally advanced T3-4 and/or N1 disease in 85% of patients18
. Roughly 10% of all patients with EC at our institution are offered an operation and half of these elect to undergo surgery. Those who decline an operation typically give reasons of expense or a desire to seek alternative treatment (e.g. herbal therapy or traditional healers) with progression of disease. At the time of resection, 71% of patients from this select group are found to have T3-4 and/or N1 disease. Self-expandable metal stent (SEMS) placement is the primary form of palliation17
. Although survival is unknown for the entire cohort of patients and follow-up information is difficult to attain, a prospective analysis of outcomes for SEMS placements demonstrated a median survival of 8.5 months17
. Various future projects are planned at Tenwek Hospital to address the problem of EC in the surrounding population, including the examination of potential risk factors and etiologies, the establishment of an effective and sustainable screening program, the introduction of public health campaigns to encourage early detection and treatment, and continued improvement in palliative care for the many individuals diagnosed with late-stage esophageal cancer. Although some have taken a fatalistic approach to EC within the context of sub-Saharan Africa19
, we think there remains distinct potential for significant advances in the understanding and control of this devastating disease within endemic areas. These advances are essential to maximize preventive, curative, and palliative care for the large number of affected people.
In summary, our study documents that the area of western Kenya surrounding Tenwek Hospital remains a high-risk region for esophageal squamous cell carcinoma, and it appears unique among other endemic areas in its large proportion of young patients with ESCC. Our data since 1989 include the largest series of EC patients under 30 years of age in an endemic area (N=84). In our study, the occurrence of these young EC cases appears be related to Kalenjin ethnicity. These findings deserve further study.