The risk has risen rapidly and dramatically since the 70s; only lung cancer exceeds NHL at the rate at which it is increasing. It has been rising at least since WWII, all around the world. The rate of increase is beginning to slow down a little.
NHLs are the sixth most common cause of cancer related deaths in the U.S. Since many
lymphoma patients are still young on the average, the resulting losses rank fourth
in economic impact among cancers in the U.S.
Geographic distribution
Finally, some more definitive information is emerging regarding
the worldwide distribution of nonHodgkin's lymphomas. Annals of
Oncology #9 (July 1998) published an article by Drs Anderson,
Armitage and Weisenburger which sheds some light on this topic.
Substantial differences were found. A greater percentage of follicular lymphomas was found in North America, England and South Africa. The lowest rates were in Hong Kong. Lower rates of follicular lymphoma have been reported in Asian populations and developing countries.
Italy holds the record for mantle cell lymphoma; South Africa has the lowest rates. Diffuse large cell was highest in Italy and
Hong Kong, but also pretty high at all other locations studied.
MALToma was the highest in France and lowest in England. Small
B-lymphocytic was highest in Germany, lowest in Canada and Hong Kong.
Relative frequency
This information is taken from De Vita's Principles and Practice
of Oncology, 1997, p 2166. It shows the relative frequency of
lymphoid neoplasms; I excerpted the adult B cell.
B cell lymphomas (adults) comprise 85% [T cell 15%]
----------------------------------------------------------
Follicular 35%
Diffuse large cell 30%
Mantle cell 5%
B-CLL/SLL 5%
Immunocytoma/Waldenstrom's 1-2%
MALT/monocytoid 1-2%
All others <8%
1) Congenital and acquired immunodeficiencies are associated with an increased rate of lymphomas. Patients have a history of immune dysregulation and ongoing, chronic antigenic stimulation. Aggressive NHLs typically develop, and there is correlation with Epstein Barr Virus infection. About 10-35% of children with certain congenital immunodeficiencies develop NHLs.
Lymphomas also sometimes develop in patients who have undergone organ or bone marrow transplant and have received immunosuppressive drugs. The pathologies that develop range from B cell hyperplasias to aggressive lymphomas. In some cases, the lymphomas disappear after the immunosuppressive drugs are stopped.
Lymphomas frequently develop in HIV positive people. It is expected that the incidence of HIV-related lymphoma will increase as people with AIDS live longer. It is thought that these lymphomas emerge in patients where underlying immunosuppression is coupled with chronic overstimulation of the immune system.
Several studies have shown some correlation between blood transfusions and lymphoma. Apparently, blood transfusions lead to immune problems in about 20% of recipients, some of whom may develop lymphoma. (Other studies have failed to show a link.) Certain vaccinations may also play a role.
2) Some autoimmune disorders have been linked to NHL; for example, Hashimoto's thyroiditis and Sjögren's syndrome sometimes lead to MALT lymphoma of the thyroid, lacrimal or salivary glands. Celiac disease can lead to T-cell lymphomas. Rheumatoid arthritis and lupus erythematosus have a less clear association with lymphoma, and this link may be due to the chronic use of immunosuppressive drugs by these patients.
3) Infectious agents have been implicated. Helicobacter pylori infects the stomach, leading to chronic gastritis, ulcers, and MALT and primary gastric lymphoma. A significant number of cases are cured of their lymphoma after the administration of antibiotic therapy.
Epstein Barr Virus is a herpes virus that causes mononucleosis and infects B lymphocytes. The infected cells are subject to impaired immunosurveillance. HTLV-1 is a retrovirus associated with T-cell lymphoma/leukemias. And Kaposi's sarcoma-associated herpesvirus may play a role in HIV-related lymphomas. A human retrovirus HERV-K may play a role in low grade lymphomas. And splenic lymphoma may be linked with chronic malaria.
Animal lymphomas have been definitively linked to certain viruses. For example, a deadly lymphoma in chickens, Marek's disease, is caused by a herpesvirus, and can now be prevented by a vaccine.
4) Environmental toxins, and various physical and chemical agents play a role. The anticonvulsant Dilantin can induce lymphadenopathies and lymphomas that usually, but not always, disappear when the drug is stopped. Herbicides and organophosphate fertilizers seem correlated with the higher incidence of lymphomas in the midwest. The various solvents and chemical that have been mentioned include benzene, styrene, butadiene, trichlorethylene, perchlorethylene, creosote, lead arsenate, formaldehyde, PCBs, paint thinner, and oils and greases. Hair dyes have been suspected but the most recent information indicates that they do not cause lymphoma. Non-ionizing radiation of over 100cGy can cause lymphoma, which as been noted in people who were irradiated in atomic explosions, or for the treatment of disease. NHLs also occur as secondary cancers following radiotherapy and chemotherapy for cancer. Certain occupations show a higher incidence of lymphoma; for example, Vietnam veterans, and flour, meat and petroleum industry employees are at increased risk. As are woodworkers and pulp and paper mill workers.
The various correlations mentioned above do not hold equally strongly. Some are relatively confirmed, while others are tentative. A 3-year study is currently underway, studying the various exposures in 1200 NHL patients. Blood, water, soil and carpet samples will be analysed, and questionnaires will be given, in the hope of arriving at more definitive information regarding the causes.
Compiled by Vera Bradova © 1998
Updated 11-15-1998
Get your own Free Home Page