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Frequently Asked QuestionsNeighborhood Cancer Concerns: Frequently Asked QuestionsFrequently Asked Questions
What does California do to monitor cancer?The California Cancer Registry (CCR) monitors the occurrence of cancer among Californians, both incidence (new diagnoses) and mortality (deaths). The CCR, which is operated by the California Department of Health Services in collaboration with the Public Health Institute and ten regional cancer registries, is an essential tool for the prevention and control of cancer in California. By law, all new cancer cases diagnosed in California residents since January of 1988 have been reported to the CCR, with strict guidelines to maintain patient confidentiality. The CCR uses these data for its own research and for active collaboration with other health researchers seeking to lessen the impact of cancer on the citizens of California. In addition, it publishes reports each year summarizing statewide cancer case rates and deaths, changes in rates over time, and differences according to age, race/ethnicity and types of cancer. Special reports address specific concerns, such as a 2003 report on breast cancer. The CCR responds to questions from cancer patients, the community, public health officials, researchers, legislators, and other people with cancer-related concerns. All reports are available free of charge upon request.
Where can I find cancer rates for California, for my county, and for my city?The California Cancer Registry (CCR) produces annual reports on statewide cancer incidence and mortality rates from 1988 through the most recent year for which data are complete . The reports are usually published in the spring of each year, and are available on request, and on our web site under Publications. Cancer rates for individual counties that have populations large enough to produce stable rates are available from the regional cancer registries that cover those counties. All reports are available free of charge. The regional registries and the counties they cover are listed below, together with the phone numbers and e-mail addresses of the regional epidemiologists. The estimated number of new cancer cases and deaths for the current year in California and in each county are in California Cancer Facts and Figures, published each year by the American Cancer Society and the CCR. This publication is available on request to ACS (1-800- ACS-2345), and is also available on our web site. The CCR does not produce cancer rates for cities, because population data for cities are not available in the age group, gender, and race/ethnicity categories required for the population denominators to calculate rates.
What data are available from the California Cancer Registry for uses such as research, planning, and grant applications?Several types of data are available from the California Cancer Registry (CCR): State and regional reports containing tabulated data on cancer incidence and mortality, from 1988 through the most recent year for which data are complete, can be requested and are free of charge. They can also be downloaded from our web site under Publications. The California Cancer Registry is no longer able to provide a public use file. Confidential data required for research are provided only to bona fide researchers with research projects that meet stringent requirements for scientific merit and handling of confidential information.
How complete are California Cancer Registry data?Every cancer diagnosis made in California from 1988 onward is required by law to be reported to the California Cancer Registry (CCR). The exceptions are the common skin cancers (basal and squamous cell carcinomas) and certain non-invasive cancerous conditions of the uterine cervix. The CCR, as well as the regional registries, the cancer registrars, and others who collect cancer data for the CCR, all make a major effort to ensure that the data are as accurate and complete as possible. The level of completeness increases with time. The level of completeness increases with time. As of December 2006, case reporting for diagnosis year 2004 was estimated to be 99% complete.
Why are California Cancer Registry cancer data almost two years behind?All cancer registries which publish high quality data have a substantial lag period before the data for a given year are complete. The California Cancer Registry (CCR) puts a high priority on reducing this lag period as much as possible without compromising data quality. A number of circumstances are involved in the delay before a cancer case is reported to the CCR. Complete information on the case and on the first course of treatment may not be available until six months after the initial diagnosis. Many cases are reported to the regional registries by multiple facilities or health care providers, and all the reports must be consolidated into a single record containing the best information available. Another factor is the increasing number of cancer patients who are diagnosed and treated in doctors' offices without ever being admitted to a hospital; more effort is required to find these cases. In addition, the strict quality control procedures needed to produce complete and accurate data are labor intensive, and the CCR has limited resources. The vast majority of cases are reported to the CCR within 12 months of the diagnosis date, but the data cannot be published until case reporting is estimated to be at least 95 percent complete - and the last 10 percent are the hardest to complete.
How does cancer compare to other causes of death in California such as heart disease?Cancer is the second leading cause of death in California and the United States. In 2003, 23 percent of all California deaths were due to cancer, compared to 29 percent due to heart disease, the leading cause of death, and 7 percent due to stroke, the third leading cause of death. However, cancer has surpassed heart disease as the leading cause of death for Americans under the age of 85.
How do cancer rates in California compare to the United States as a whole?California cancer rates cannot be compared precisely to national cancer rates. This is because cancer rates differ among persons of different race/ethnicity, and California uses a slightly different classification to characterize race/ethnicity groups than is used by the National Cancer Institute's Surveillance, Epidemiology and End Results Program which produces national cancer rates.
Are cancer rates in California going up?In California, since 1988, the rates of certain cancers have decreased, especially those associated with tobacco use: cancers of the lung, bladder, mouth and throat, stomach and pancreas. Breast cancer rates, which increased sharply in the U.S. in the 1980s, have been stable or decreasing slightly in California since 1988. In the last few years, the likelihood of being diagnosed with prostate cancer has increased dramatically in California and elsewhere in the U. S., largely because of the introduction of a new screening test. If prostate cancers are excluded, overall cancer rates have decreased somewhat since 1988 for both men and women. However, even if the rates of cancer change very little, the number of people who develop cancer will increase as the population gets older. Combined with the fact that more people are surviving cancer and that people discuss cancer more readily, this may have contributed to the widespread impression that the risk of developing cancer has increased recently.
How common is cancer?Cancer is very common in California and the United States as a whole, and in most other developed countries. In California, more than 120,000 people are diagnosed every year with some form of invasive cancer, not including the common skin cancers. Based on current statistics, more than two out of every five Californians will develop cancer at some time in their lives, and about one in 320 children will be diagnosed with cancer before age 20. Many cancers are now curable and cancer treatment continues to improve. Nonetheless, nearly one out of four Californians is likely to die from cancer.
Which types of cancer are most common?There are many different kinds of cancer depending on where in the body the cancer starts and the type of cell involved. The most common types are prostate, breast, lung, and colorectal cancers. Out of every twenty cancer diagnoses, about three will be breast cancers, three will be prostate cancers, three will be lung cancers, and two will be colorectal. There will be about one in the bladder or kidney, one in the ovary, uterus or cervix, and one will be a lymphoma. The remaining six will include a variety of types, such as melanoma, leukemia, cancers of the mouth and throat, pancreas, stomach and many others.
How common is skin cancer?This depends on the type of skin cancer. Most common are the non-melanoma skin cancers, basal and squamous cell carcinomas. The American Cancer Society estimates that approximately one million basal and squamous cell carcinomas of the skin will have been diagnosed in the US in 1998, compared with a total of 1.23 million invasive cancers of all other types combined. Precise information on the incidence of basal and squamous cell carcinomas is very difficult to collect because these cancers are mostly diagnosed and treated in doctors' offices and rarely lead to serious disease. The other type of cancer that commonly occurs on the skin is melanoma. Melanomas were the sixth and seventh most common cancers diagnosed overall among California men and women respectively during the period 1991-1995. They made up a higher percentage of cancers in the age group 15-44 years.
Who gets cancer?Unfortunately, almost anyone can develop cancer, even children and young adults who lead active, healthy lives. However, nearly 60 percent of the cancers diagnosed in California are among people 65 and older, who make up only about 10 percent of the population. Surprisingly, there are large differences among people of different ethnic origin. African American men have the highest cancer risk, and non-Hispanic white people have substantially higher cancer rates than persons of Latino or Asian origin. Children have few differences in their cancer rates regardless of their ethnic origin.
How many people currently have cancer?The current estimate in the recent California Cancer Facts and Figures is that more than 15 million Californians alive in 2007 have a history of cancer, not including basal or squamous cell carcinomas of the skin or certain non-invasive cancerous conditions of the uterine cervix. Many of these individuals have no further evidence of the disease, and have the same life expectancy as people who have never been diagnosed with cancer.
What causes cancer?It is rarely possible to find the cause of a cancer in an individual, but studies on groups of people with cancer have shown specific risk factors to be associated with specific cancers. This suggests that different types of cancer probably have different causes. These studies also indicate that cancer formation is a multi-step process, and that for most cancers the time from a cancer-causing exposure to a clinically diagnosable cancer averages about 20 years. Among the known risk factors for cancer, tobacco stands out. Cigarette smoking is associated with more than 85 percent of all lung cancers, and with a substantial proportion of cancers of the bladder, mouth and throat, stomach, pancreas and others. Diet is also a risk factor; higher cancer rates are seen in people who eat a diet high in fat and low in fresh vegetables and fruits. It is estimated that diet and tobacco together account for approximately two out of three cancers. Breast cancer is the most common cancer among women. About 50 percent of breast cancers are thought to be explained by known risk factors such as a family history of cancer and hormonal functions associated with early onset of menstruation and late menopause, delayed childbearing and having fewer children. Few risk factors have been defined for the most common cancer in men, prostate cancer. Occupational studies have shown certain chemicals and other substances to be carcinogenic; these include asbestos, benzene, arsenic, vinyl chloride and other industrial products. Exposure to these substances is thought to account for about 5 percent of all cancers. 
How did a cancer researcher get my name and phone number?A cancer researcher may have obtained your name and phone number from a hospital or facility where you were treated for cancer, or from the California Cancer Registry (CCR). The state law mandating that all cancers diagnosed in California be reported to the California Department of Health Services, which operates the CCR, requires that the information gathered be used solely for research into the causes and cures for cancer. The law mandates that patient identity be kept confidential, but also that confidential information may be released for such research. Some research requires contacting patients to get information about aspects of their past histories. The CCR provides patient contact information for research into the causes and cures for cancer under strict procedures to protect patient confidentiality. Patient identity is disclosed only to bona fide researchers who are conducting research projects that meet stringent requirements for scientific merit and for handling of confidential information, and whose research has been approved by a federally authorized Institutional Review Board (Committee for the Protection of Human Subjects).
Can you remove my name and personal information from the California Cancer Registry?The state law that mandates that all cancers diagnosed in California be reported to the California Department of Health Services for the California Cancer Registry (CCR) does not provide for removal of cancer patient information from the registry. To fulfill its purpose of providing information to find the causes and cures for cancer, it is vital for the CCR to be complete. The law mandates that CCR data be used solely for research into the causes and cures for cancer and that patient identity be kept confidential, but also that confidential information may be released for such research. However, patients can refuse to participate in any particular research study, or all research studies. Patients who wish never to be contacted for any research study can request to have their CCR record flagged so that the CCR will never release their names to researchers. However, they may still be contacted by researchers who obtained their name directly from a hospital or facility where they were treated.
How can I find out more about a particular cancer?The National Cancer Institute's Cancer Information Service at 1-800-4-CANCER ( 1-800-422-6237), and voluntary organizations such as the American Cancer Society (1-800-ACS-2345) (or the ACS office in your area) provide information on cancers. There are many cancer resources on the Internet, such as the University of Pennsylvania Cancer Center (1-800-789-PENN) web site, which has excellent information.
How can I enroll in a clinical trial for cancer treatment?Information on clinical trials is available from the National Cancer Institute's Cancer Information Service at 1-800-4-CANCER ( 1-800-422-6237), and from their Comprehensive Cancer Database web site.
What can I do to lower my risk of developing or dying from cancer?
Several people in my neighborhood have been diagnosed with cancer. Is this unusual?No, this situation occurs more often than you might expect. People often wonder if there are "too many cancers" in their neighborhoods, but most of the time it turns out that the number is about what we would predict. Here are some reasons why there may be quite a few people living in your neighborhood who have been diagnosed with a cancer:
* Reference: Cancer in California 1988-1999
What is a cancer "cluster"?A cancer "cluster" is a situation in which there are more cancer cases in a group of people, in a location, or in a time period than would be expected based upon usual patterns (see Cancer Clusters Fact Sheet). A cancer "cluster" usually refers to an excess of one particular type of cancer. A grouping of several different types of cancers is not usually considered to be a "cluster". Public health officials and researchers who respond to questions about clusters from the public think of "clusters" in two distinct ways. The first is a suspected cluster (a concern has been reported but not yet evaluated). The second is a confirmed cluster (where officials have confirmed that the number of cases is in fact higher than expected). Public health officials nationwide receive hundreds of inquiries every year about suspected clusters. However, after an evaluation only a small fraction of these suspected clusters are actually confirmed. Many people assume that if a cluster is statistically confirmed it means there is something wrong with the neighborhood environment (such as pollution of the air, water or soil). This is not necessarily the case. Usually the reasons cancers "cluster" in residential neighborhoods have little to do with the physical environment. In most cases, cancers "cluster" in neighborhoods because residents have similar cancer risk factors (such as smoking or being older), or by chance.
What are some common misconceptions about cancer clusters?Misconception #1: Cancer "clusters" are rare. Fact: The California cancer registry tracks more than 80 types of cancers. In a state the size of California, we would expect to see many areas that have a substantially greater (or lower) rate than the state average for at least one of these cancers, just by chance alone. Misconception #2: Most cancers and cancer "clusters" in residential neighborhoods are caused by environmental contamination. Fact: The majority of known cancer risk factors are related to individual characteristics (such as age, race/ethnicity or genetic susceptibility) and behaviors (such as smoking, diet, physical inactivity, unsafe sex, and sun exposure) (What are the risk factors for cancer?). The relationship between cancers and environmental contamination in neighborhoods is much less established than most people realize. Nearly every investigation of a residential cancer "cluster" has failed to find a definite environmental cause. Misconception #3: A confirmed statistical excess of cancer cases in a neighborhood proves there is contamination. Fact: Statistics can only tell us whether or not the cancer rate in your neighborhood is truly unusual compared to other times and places. They cannot tell us the reason why rates are unusual. Other information about your neighborhood and its residents would be needed to make sense of the situation. Even unusual rates often turn out to be due to coincidence. Misconception #4: Neighborhood cancer concerns are investigated by testing the air, water and soil for any synthetic chemicals. Fact: Cancer concerns are investigated by determining whether or not there is actually an excess of cancer cases. In most cases, it turns out that there is not. If a statistically significant excess is found, the state and/or local health departments review the situation to determine if any further action is needed. Misconception #5: Causes of cancers are well understood by scientists and doctors. Fact: Although scientists have learned a great deal about the complex nature of cancers, much remains unknown. In populations, we know every year about how many cases of cancers we can expect, and can predict that cancer rates will be higher or lower in different groups of people. In individuals, however, no one can say for certain what exactly caused a cancer to develop.
Why are cancer rates higher in some areas than others?There are three general reasons why cancer rates may be higher in one area than another:
What does it mean when there is a "statistically significant" elevation of cancers in an area?This means that researchers believe that the number of cancer cases in a place or time is greater than would be expected due to normal fluctuations alone. Researchers use statistics to help them decide if a cancer rate is really unusual. For cancer concerns, researchers commonly agree that an excess of cancer cases is "statistically significant" when it is so different from average that you would expect it only 1 out of 100 times by chance alone. The term "statistical significance" is tricky for many people to understand. "Statistical significance" only means that the number of cases that has occurred is unusual. It does not explain why the number of cases is high. Furthermore, it does not rule out chance as a cause.
How do individual characteristics and behaviors affect cancer rates in my neighborhood?By choice or by circumstance, people tend to live in neighborhoods where they have things in common with other residents, such as race or ethnicity, education, income, occupation or lifestyle. These types of characteristics are important elements of cancer risk. Some examples include:
When researchers try to explain differences in cancer rates between neighborhoods, they take age, sex, and race into account.
How can so many cancer cases in my neighborhood be due to chance?Chance is an explanation for cancer "clusters" more often than most people realize. Most people accept the laws of chance when it comes to games like the state lottery. It's harder for most people to accept that these same laws of chance can apply to a serious disease like cancer. A single neighborhood has a low probability of having high cancer rates just due to bad luck (in other words, chance). However, if you look at the entire state, you would see that lots and lots of people get cancers and there are lots and lots of neighborhoods. Therefore, there is a very good probability that some neighborhoods will have this kind of bad luck. If it happens to be your neighborhood, you naturally want to know why this has happened. Most people understandably find that "bad luck" is not a very satisfying explanation and want something --or someone --to be held responsible. Nonetheless, most experts on cancers and cancer "clusters" believe that chance is the explanation for neighborhood cancer "clusters" far more often than most people would think. "Chance" in this situation means that there is no common reason why cancers have occurred in a particular neighborhood. Given the same set of genetic and lifestyle factors, the same people probably would have gotten cancer no matter where they lived. But sometimes several people who develop cancer just happen to live in the same area -- by chance. An investigation into the cause of a chance "cluster" will never result in an answer because none exists.
Does the environment cause cancer?Yes it can, but it plays less of a role than many people believe. One reason for confusion about this is that the term "environment" means something different to researchers than it does to most members of the public. For researchers, the "environment" usually means any factor that is not hereditary. This may include things like cigarette smoking, diet, sunlight and infections in addition to factors in the air, soil and water. If we use this broad definition, we would say that the "environment" is a big factor in cancer risk. However, when most members of the public think of cancer and the "environment" they are thinking of contaminants in the air, water, or soil that might cause cancers (called carcinogens). We all live in environments that contain carcinogens, and we are all exposed to a greater or lesser degree every day. The relationship between these carcinogens and cancer development is subtler, more complex and less established than most people think. Much of what we know about these carcinogens has been learned from studies of exposures in the workplace. In the workplace, unlike in neighborhoods, chemical exposures are more often known, and occur at high levels for prolonged periods of time. Learning more about environmental carcinogens and their role in cancer development is very important. Because their effects are complex and difficult to detect, studies of environmental carcinogens and cancer must be carefully designed and include large numbers of people. A neighborhood with a cancer "cluster" is not a very good place to study the effects of environmental carcinogens because usually the number of cases is too small, and the number of possible carcinogens is too large to be able to make a connection.
Why haven't investigations of cancer clusters been useful in identifying environmental causes of cancers?Over the years, nearly every neighborhood cancer "cluster" investigation has failed to identify any environmental cause. This is not for lack of trying, but because cancers are very complex diseases. Methods that work well to identify the cause of an infectious disease outbreak do not work well with neighborhood cancer clusters. The reasons include: Cancers take a long time to develop. For most cancers, the period between exposure to a carcinogen and the development of cancer may be ten to twenty years or more. By the time cancer rates have increased in an area, the carcinogen may no longer be measurable in the environment. People change residences. In many cases, by the time a person is diagnosed with a cancer, he or she no longer lives in the area where an exposure may have occurred. Cancer registries have no way to track where people lived before or after developing a cancer. Residential cancer clusters contain few cases. Even if the cancer rate in an area is found to be "statistically significant" there usually are too few cases and too many possible exposures to allow scientists to work backward to find the cause. Carcinogens that may be found in a neighborhood with several cancer cases are also likely to be found in areas without many cases. It is not currently possible to determine the cause of cancer in an individual. When a person gets a cancer, doctors may suspect that certain risk factors are largely to blame. However, doctors do not have any reliable way to determine the exact cause or combination of causes for the cancer. Therefore, in a neighborhood "cluster" situation, doctors cannot be certain about what caused a cancer in any individual resident.
If there are a lot of pets in my neighborhood with cancer does it mean there is a problem with the environment?The state does not track cancers in animals. Therefore, there really is no way to tell if the number of animal cancers in any particular neighborhood is truly unusual. However, we know that cancers are common especially among older animals. This is because cancer risk increases with age, just as it does in people. Humans and animals have different cancer risks. Cancers that are uncommon in humans may be very common among dogs, for example, and vice-versa. Cancer risks also vary between different animals, and even within breeds of the same species. There is no reason to suspect that groupings of different types of animals with different types of cancers have an underlying common cause.
Who should I contact with my questions about cancers in my community?You may call either your county or local health department or the regional registry that covers the county in which the community is located (see Resources) In most counties, the county health department should be contacted first. These departments will usually be familiar with local issues, and you may find that officials are already aware of the area you are concerned about. County health departments may respond to community cancer concerns themselves or refer callers to the regional registry depending upon the resources available in each county.
How will my concern be addressed?The first step is to determine whether or not you are asking about a pattern of cancers that is really unusual. People often report cancer concerns that include lots of different types of cancers, or sometimes diseases that aren't actually cancers at all. In most cases, the epidemiologist is able to address the questions of the caller by providing current information about cancers, and to explain why the concern may not represent a real cancer excess. Sometimes, further evaluation is necessary. The epidemiologist first works to identify the number of all observed cases of the cancer in the area and time period of concern. Then this observed number is compared to the number that would be expected based upon rates in other areas or other time periods, after adjusting for differences in the age, sex and race/ethnicity make-up of the populations. A statistical test is used to judge whether or not the difference between the number of cases observed and the number expected is likely to be due to normal random variation. If an excess number of cancer cases is confirmed, the situation is reviewed further by the health department to determine if any further investigation is needed. Although this brief description may make this procedure sound simple, in fact it may require a considerable amount of registry staff time and resources, and may take several weeks to complete. Resources
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