In this study we found that NHL has different characteristics among the Bedouin compared to Jewish population in the south of Israel. Disease characteristics at diagnosis tend to be worse among the Bedouin. Extra-nodal involvement, high LDH, and poor performance status are more frequent among the Bedouin. Advanced disease at presentation is more common among the Bedouin, but the difference is not significant. The incidence of aggressive lymphomas is also significantly higher among Bedouin. Jews have a higher rate of follicular lymphoma whereas the Bedouins have higher rates of T-cell Lymphoma and other aggressive pathologies.
Similar findings were found in a study conducted at Ben-Gurion University (Levy et al. 2002). The study compared characteristics of Hodgkin’s Lymphoma between Bedouin and other populations in southern Israel. The characteristics of the disease at diagnosis were different between groups. Histology of mixed cellularity and more advanced disease at diagnosis were more common among the Bedouin. Results for treatment response and prognosis were also similar to those seen in the current study. Bedouin had a higher rate of resistant disease, and lower overall survival and survival without disease.
There are several possible explanations for these differences in the presentation of Lymphoma among Bedouin in this study.
Lower availability and reduced use of medical services among the Bedouin result in the diagnosis of Lymphoma at a later stage. This is a result of low socioeconomic level, low awareness of preventive medicine, and lack of access to medical service.
It also may be possible that exposure to chemical contaminants plays a role in the development of Lymphoma. As noted above, there is a study that examined the relationship between residential proximity to Ramat Hovav and incidence of NHL (Dreiher et al. 2005). The study found that living near the Ramat Hovav site constitutes a risk factor for morbidity in NHL. The study was conducted among a population that included mostly an urban Jewish population. Presumably Bedouin, who live even closer to the site, are more exposed to these toxic substances. However, it is impossible to estimate with certainty how many Bedouin who were included in our study have been exposed to environmental pollutants near their residence.
An important factor in development of some malignant disease is nutrition habits. Two studies (Fraser et al. 2001, 2008) compared diet and eating patterns among Jewish and Bedouin populations in southern Israel. Bedouin nutrition was found to be characterized with lower intake of fat, cholesterol, and protein and higher intake of carbohydrates and fibers. However, there are no public data regarding the influence of this diet on NHL severity or survival.
It might be that genetic and geographic differences play a role in the differences between the groups, mainly in the histological type of the Lymphoma. T-cell Lymphomas, for instance, are more common in Asia, while the B-cell Lymphomas are more common in Western countries (Rüdiger et al. 2002).
A study from the north of Israel showed higher prevalence of nodular lymphoma in Ashkenazi Jews and higher prevalence of extranodal lymphoma in Arabs and non-Ashkenazi Jews (Cohen et al. 1989). A study that evaluated frequencies of NHL subtype in Kuwait found a higher prevalence of DLBCL and extranodal presentation compared to the Western world (Ameen et al. 2010). A study from Jordan classified 111 cases of NHL from two major medical centers (Almasri et al. 2004). Aggressive lymphoma accounted for the majority of NHL, while indolent lymphomas were rare and accounted for less than 15% of all NHLs. Our results are similar to these results. Higher incidence of aggressive lymphomas such as Burkitt’s and Lymphoblastic lymphoma in the Bedouin as in other Arab populations may have a common mechanism. This may indicate genetic and environmental factors that are responsible for the greater presentation of aggressive histological subtypes in Bedouin compared to the Jewish population. Because of the small number of patients in this study, we cannot evaluate accurately how this study represents the distribution of histological subtypes of Lymphoma among all the population, and especially among the Jewish population in Israel.
Our results show decreased response to treatment among the Bedouins. OS and DFS are significantly better among Jews compared to Bedouins. These results can be explained by two main reasons: more aggressive and advanced disease at diagnosis and lower compliance with treatment compared to Jewish patients, partly because of poor living conditions. Two studies from the south of Israel (Tamir et al. 2007; Cohen et al. 2008) found that low compliance with drug therapy and follow-up tests, and non-attendance to the clinic are major problems in the Bedouin population. These findings may suggest that an important reason for lower response rate of Bedouin to chemotherapy is poor compliance.
Due to the different distribution of histological subtypes between the groups, and the influence of histology on prognosis, we decided to test whether differences between populations are maintained when comparing subgroups of patients with identical pathology. The characteristics of DLBCL at presentation are significantly worse among Bedouins (mean LDH was higher, poorer performance status, and higher IPI). Similarly, the survival was lower among the Bedouins, with borderline significance.
There are several limitations to this study. There was no randomization in selecting populations. The study group included all the Bedouin patients who were found suitable for inclusion. The comparison group was selected randomly by matching age, sex, and year of diagnosis to those of the study group. This method may have created selection bias. We do not know whether the comparison group represents the entire Jewish population of NHL patients in the Negev. We might have found a higher rate of aggressive lymphoma if we reviewed all records of Jewish NHL patients. In addition, we do not know whether there is a difference in the age of lymphoma onset between the two populations.
As is known, the characteristics of NHL at diagnosis are predictors of the response to treatment. In the current study we found that NHL indices among the Bedouin at diagnosis were worse, in accordance with lower response rate to treatment and lower survival. Because we did not compare response to treatment in patients with the same IPI, we cannot determine whether the lower survival rate among the Bedouin is due to different characteristics of the lymphoma at diagnosis or whether the difference may also depend on other factors affecting the course of the disease. This comparison could not be done due to the small size of the sample.
In summary, NHL has different characteristics among the Bedouins in the Negev compared to Jews. Among the Bedouins, the disease tends to emerge in later stages, with a higher IPI and more aggressive appearance. The response to treatment and survival rate is lower among the Bedouins.
The inverse relationship between socioeconomic level and morbidity and mortality is known for many diseases. Our study results are compatible with this finding. Authorities should invest in establishing a medical infrastructure available to this population, together with an educational program to raise awareness for early detection and treatment of diseases. Medical staff should be aware of the difficulties for parts of the Bedouin population in approaching medical services. This requires attention and effort, but will certainly increase the number of patients diagnosed at the initial stages of disease. As the availability of medical care and compliance of this population to treatment will increase as a result of education, we hope that the outcome of treatment will also improve.