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Question: I live in a community that has had an unusually high percentage of people develop cancer. I think it might be due to common exposure. Do you have information on such events and how to investigate them?
Answer: Discrete episodes in which cancer occurs with greater frequency within a fairly short timespan and in a limited geographic area is referred to as a time-space cancer cluster. A true cluster will involve only one type of cancer or very closely related types. Investigations of such clusters have usually involved descriptive ad hoc studies of individual clusters. In most cases, this type of study has included pathological confirmation on individual cases, verification of higher frequency of disease, determination of when and where they occur, additional cases, and collection and analysis of case data. These studies have involved consideration of environmental, familial, and interpersonal exposures that might have produced the cluster.
As time has passed, attempts have been made to carry out increasingly analytical investigations such as surveys and case-control studies. Unfortunately, many clusters are too small for these approaches to have statistically significant results. In addition, these clusters are usually poorly defined, have inadequately characterized exposures, and involve publicity which makes unbiased data collection difficult. After decades of effort, these clusters are still poorly understood and many difficulties still hinder their study. Only rarely have such ad hoc studies and statistical methods clearly dismissed chance and possibility and pinpointed the likely cause of a time-space cancer cluster.
If you are concerned about the occurrence of several cancer cases in your community and the possibility of a developing cancer cluster, contact the epidemiology section of your state's department of health. They have trained professionals who can adequately assess your situation and evaluate the available case data. If the data warrants further examination, health officials can collect more information concerning both disease incidence and mortality and possible sources of exposure gathered from existing registries and data banks. However, further investigation only occurs if there is enough information of a high enough quality to allow a good epidemiological study to be performed.
Question: Can you supply information on reports on cadmium as a cause for developing prostate cancer?
Answer: Epidemiological studies of cadmium exposure by inhalation (workplace studies) provide evidence that cadmium, (long term exposure high doses) can cause lung cancer. For this reason cadmium is regarded as a human carcinogen, (IARC 1993) and this is the position expressed in the recent draft of the background document for cadmium for the next edition of the NIEHS (NTP) report on human carcinogens.
Evidence for the relationship between cadmium exposure and prostate cancer is much weaker and somewhat controversial.
For further discussion see the Draft background document for cadmium, NICHES (NTP report on human carcinogens, September 29, 1997).
Cadmium is regarded as a human carcinogen based largely on evidence for lung cancers from long-term inhalation of cadmium at high exposure levels. The relationship with prostate cancer is less clear.
A team of U.S. and visiting Russian scientists at the National Institute of Environmental Health Sciences reported today it has used its new "shortcut" means of isolating and cloning genes in common yeast to make quick duplicates of the breast cancer gene BRCA2.
The scientists said the BRCA2 gene -- the second gene for breast cancer to be discovered -- can be cloned in about two weeks by the new method, compared to previous approaches that typically took a year.
By providing a quick and endless supply of clones of the gene, the new method will enable scientists to study mutant and normal forms of the gene and will "greatly facilitate analysis of the gene and its contribution to breast cancer," diagnosis and gene therapy -- the use of genes to modify or cure disease -- according to the authors, writing in the July 1997 issue of Proceedings of the National Academy of Sciences (Vol. 94, pp 7384-7387).
The same journal last year published the team's report of their initial development of the gene isolation and cloning system, known as Transformation-Associated Recombination in Yeast, or TAR for short.
According to the new report, the TAR system has already proven successful for quickly isolating and cloning key disease genes such as the first-discovered breast cancer gene, BRCA1, as well as BRCA2; HPRT, a gene involved in Lesch-Nyhan syndrome, a form of retardation; and rDNA, genes involved in enzyme production.
Michael Resnick, Ph.D., of NIEHS, said the institute, which is a part of the National Institutes of Health, is establishing a Gene Isolation Unit in its Laboratory of Molecular Genetics to exploit the capabilities of the TAR system.
The approach was developed in the NIEHS Chromosome Stability Group by Dr. Resnick in collaboration with two visiting Russian scientists, Vladimer Larionov, Ph.D., and Natasha Kouprina, Ph.D., who are on leave from the Institute of Cytology in St. Petersburg. Dr. Larionov has been named to head the new Gene Isolation Unit within the Resnick lab.
Also collaborating on the isolation of the BRCA2 gene and coauthoring the article were J. Carl Barrett, Ph.D., NIEHS Scientific Director and Chief of the Laboratory of Molecular Carcinogenesis, and Gregory Solomon of this laboratory.
NIEHS scientists made key discoveries in 1994-95 leading to the identification of the first breast cancer gene, BRCA1, and participated in the successful identification of BRCA2 as well.
For more information on Cancer please see:
- The National Cancer Institute (NCI) http://www.nci.nih.gov/