Tumors which may originate from B or T
lymphocytes are known as non-Hodgkin lymphomas (NHL). They account for approximately 3% of the worldwide cancer
Most epidemiological studies of NHL have been carried out in
North American and European populations, with a few focusing on East
Asian populations. Very few epidemiological studies have been conducted
on B-cell non-Hodgkin lymphoma (B-NHL) in Middle Eastern populations.
‘B-cell non-Hodgkin lymphoma was associated with recreational sun exposure, black hair-dye use, a history of hospitalization for infection, and having a first-degree relative with a blood cancer.’
Since Israelis and Palestinians represent genetically and culturally
diverse populations living in geographic proximity, research analyzing
their risk factors can enrich our understanding of genes and environment
in the causation of lymphoma.
Despite sharing the same ecosystem, the
populations differ in terms of lifestyle, health behaviors and medical
systems. Yet both populations report high incidences of NHL, which
represents the fifth most common malignancy in Israel and the eighth
most common malignancy among West Bank Palestinians. (As of 2012, Israel
also ranked first in the world in NHL incidence rates.)
Now, Israeli and Palestinian researchers have conducted a large
scale epidemiological study examining risk factors for B-NHL and its
subtypes in these two populations. The team was led by Prof. Ora
Paltiel, Director of the Hebrew University-Hadassah Braun School of
Public Health and Community Medicine, in the Hebrew University's Faculty
of Medicine, and a Senior Physician in Hadassah's Hematology
Recruiting from both the Palestinian Arab and Israeli Jewish
populations, the researchers looked at medical history, environmental
and lifestyle factors among 823 people with B-cell non-Hodgkin lymphoma
(B-NHL) and 808 healthy controls. Using data from questionnaires,
pathology review, serology and genotyping, they uncovered some risk
factors common to both populations and other factors unique to each
The data, reported in the peer-reviewed journal PLOS ONE
showed that in both populations, overall B-NHL was associated with
recreational sun exposure, black hair-dye use, a history of
hospitalization for infection, and having a first-degree relative with a
blood cancer. An inverse association was noted with alcohol use. Some
exposures, including smoking and greater-than-monthly indoor pesticide
use, were associated with specific subtypes of B-NHL.
The data also pointed to differences between the populations. Among
Palestinian Arabs only, risk factors included gardening and a history of
herpes, mononucleosis, rubella, or blood transfusion, while these
factors were not identified in the Israeli Jewish population. In
contrast, risk factors that applied to Israeli Jews only included
growing fruits and vegetables, and self-reported autoimmune diseases.
The researchers concluded that differences in the observed risk
factors by ethnicity could reflect differences in lifestyle, medical
systems, and reporting patterns, while variations by lymphoma subtypes
infer specific causal factors for different types of the disease. These
findings require further investigation as to their mechanisms.
The fact that risk factors operate differently in different ethnic
groups raises the possibility of gene-environment interactions, that is,
that environmental exposures act differently in individuals of
different genetic backgrounds. But this divergence may reflect
differences in diet, cultural habits, socioeconomic, environmental and
housing conditions, medical services, exposure to infections in early
life or other factors.
This study reflects a unique joint scientific effort involving
Israeli and Palestinian investigators, and demonstrates the importance
of cooperative research even in politically uncertain climates. Cancer
epidemiology will be enriched through the broadening of analytic
research to include under-studied populations from a variety of
ethnicities and geographic regions.
"Apart from the scientific contribution that this research provides
in terms of understanding risk factors for NHL, the study entails an
important research cooperation among many institutions. The study
provided opportunities for training Palestinian and Israeli researchers,
and will provide for intellectual interaction for years to come. The
data collected will also provide a research platform for the future
study of lymphoma.
Epidemiologic research has the potential to improve
and preserve human health, and it can also serve as a bridge to dialogue
among nations," said Prof. Ora Paltiel, Director of the Hebrew
University-Hadassah Braun School of Public Health and Community
Medicine, and a Senior Physician in Hadassah's Hematology Department.