Cancer Concerns and Investigations

Cancer Concerns in the Community

Transcript of video:

00:00:01
Welcome to this training on community cancer concerns and cancer cluster investigations hosted by New Hampshire's Division of Public Health Services Cancer program and the Dartmouth Cancer Center's community outreach and engagement program. My name is Judy Reese and I am an Associate Professor of Epidemiology at Dartmouth.
00:00:19
We met with some Town officers and legislative stakeholders to understand what kinds of concerns they or you are hearing from your communities and the kinds of resources that might be helpful in addressing those concerns. We identified training topic areas and design resources to help legislators, city and town health officers, municipal officials, administrators, and other stakeholders find the appropriate State resource or agency and respond to address environmental concerns raised by your communities. The first step in that process is understanding how the state responds to cancer cluster concerns and that is what we'll discuss in this presentation.
00:01:02
Today we will cover four major topics starting with a brief introduction to cancer in the context of environmental concerns and the causes of cancer. We'll talk about the situation in which a Community member is concerned about high numbers of cancers in their neighborhood school or place of employment and then we'll talk about how cancer concerns are investigated what the statistical analyzes mean and then how you can engage in the process. The goal of the training is to understand the following objectives
00:01:34
* First that there are hundreds of different types of cancer and hundreds of possible causes.
* We'll discuss what cancer registries are and what they do,
* The difference between incidents and prevalent cancer and why that's important in assessing cancer concerns,
* The features of a cancer cluster that raise alarm bells in terms of being caused by a specific factor or factors in the environment,
* We'll talk about how cancer concerns are investigated by the state and what the statistics mean, and 
* Finally, what to do if someone contacts you with concerns about high numbers of cancers in a town or community.
00:02:14
Let us start with cancer. We have all heard of it but what is it really and what causes it. What is cancer the body is made up of tiny cells of various kinds when cells in the body grow out of control they can form abnormal masses called tumors and when a tumor grows out of control it can invade neighboring tissues or spread to other parts of the body like the lung liver or brain. Tumors that invade are called malignant tumors and we call the disease cancer. Tumors can be solid masses but sometimes as in leukemia the cancer consists of too many cells circulating in the blood in either case this uncontrolled growth of cells can be fatal. Cancer Treatments aim to remove or kill these fast-growing cells.
00:03:06
It is important to understand that cancer is not a single disease a hundred years ago, that is what was assumed about cancer but as scientific methods have advanced, it has become clear that there are hundreds of different types of cancer. For example, everyone has probably heard of lung cancer but did you know that there are four major classifications of lung cancer adenocarcinoma squamous cell carcinoma large cell and small cell carcinoma. Each type of cancer can be defined further by things called tumor markers, which are caused by differences in the molecules of the cancer. Common tumor markers that people may have heard of in breast cancer are the estrogen receptor and the her2 receptor. Cancers can be classified even further based on the genetic sequence in the tumor. The bottom line is that there are hundreds of different types of cancer. This will become important when we talk about cancer clusters in the community and what is causing them.
00;04:05
So having discussed the many different subtypes of cancer now we turn to the different things that can cause cancer. Things like cigarette smoke and arsenic that cause cancer are called carcinogens but exposure to a carcinogen does not always lead to cancer and everyone exposed to it. Other factors often play a role and often we cannot pinpoint an exact cause for any individual cancer. Let's think about lung cancer now we'll consider an example of a person who developed lung cancer because they smoked they had a high level of radon in their home and they were elderly indicating that they had long-term exposure to those cancer-causing agents cigarette smoke and radon.
00:04:49
A second person might develop lung cancer because they are exposed to asbestos. A third person had a combination of exposures smoking, use of a wood stove in their home and inhalation of the smoke from that, and genes that made them susceptible to lung cancer.
00:05:09
If a fourth person developed lung cancer because they had very high radon levels in their home and breathed it into their lungs during 30 years. By the way, there are free radon tests available from your State's radon program. Please let your community know that they should test their homes. There are many more carcinogens and combinations of carcinogens that can start off those first few cells that turn into lung cancer. The point of this series of examples is to show you how difficult it is to identify one particular cause of cancer in one particular person and that is why lawsuits over environmental hazards can run into problems even when a person is exposed to one chemical that is known to cause cancer. Whether it cause cancer in that specific person is often very hard to prove. In a community cancer concern we often have to start by looking at the big picture is a specific type of cancer in a community occurring more often than expected and if so why might that be.
00:06:19
During decades of research, the causes of cancer have been described in many ways and one way to think of them is in categories like this:  things that we can change include smoking, diet, and obesity, and alcohol consumption. Regular exercise and a good diet can lower the risk of cancer. There are some risk factors that we cannot change. Cancer is a disease of the elderly. We cannot change our age, or being male or female. We can't change who our parents were and what inherited characteristics they gave us and if we're being treated with certain medications for serious health conditions we generally can't change those either.
00:07:00
Radiation is a risk factor for cancer. We can get exposed to radiation through medical imaging or through radiotherapy for cancer. And as mentioned a minute ago everyone should have tested their home for Radon because high levels are a significant risk factor for lung cancer. There are a lot of environmental carcinogens some have been proven to cause cancer and others do not yet have enough evidence to prove the link a few possible examples of the hundreds of carcinogens are shown here.
00:07:30
How do we monitor cancer in New Hampshire? By law, we have a state cancer registry, which is mandated to collect information about every new cancer diagnosed in a New Hampshire resident. We collect data from multiple sources pathology labs, hospitals, physician offices, cancer treatment centers, death certificates, the VA medical system, and from other states. We send our data each year to the CDC where everything gets compiled and national cancer statistics are published. Please note that we do not send identifiable information to the CDC.
00:08:04
We collect information for New Hampshire residents only. Other cases are sent to the states where the patient lives. We have the address at diagnosis but we do not have a history of previous addresses this is a limitation for environmental investigations because exposure to a carcinogen can happen many years before the cancer develops. We also collect information about occupation, which could be useful in an investigation, but we don't know about work related exposures to specific chemicals so that is a limitation. So to summarize the registry gives us accurate data on the numbers and types of cancers diagnosed in the state including the location of patient�s homes at the time of diagnosis. If more detailed information is needed about things like specific chemical exposures previous homes, consumption of tap water, bottled water, and so on then a personal interview is likely to be needed.
00:09:00
Moving on we will now discuss cancer clusters. The way we think of cancer clusters or possible cancer clusters is if somebody often someone in the community notices more cancers than expected in a particular group of people or in a town or group of towns or over a period of time.
00:09:25 
Sometimes someone in the community notices that a lot of their friends or neighbors are being diagnosed with cancer or dying from cancer. For Town managers and legislators these are the kinds of concerns you may hear about. The second way that cancer clusters can come to light is a report from Physicians or other Healthcare healthcare providers who notice something unusual. Sometimes it is the environmental issue in the neighborhood that is the cause of concern and then the question that follows we know we have a problem with pollution is it causing cancer.
00:09:57
The role we are interested in today is to find out if there is a real excess of cancer in a neighborhood and if so does it have a preventable cause. What do you do if someone from your community contacts you and says there is a lot more cancer in their neighborhood than they used to be? If there's an environmental hazard causing cancer we would expect the number of new cases to increase, but other things can also cause the number of cancer diagnoses to rise and these various different reasons should be considered. The cancer registry collects information on newly diagnosed cancer cases called incident cases. The number of new cases is generally higher in an aging population. If someone moves to a community with a lot of retired people for example they would likely hear about more cancer diagnoses than they were previously used to. In populations with more obesity, smoking, and other health risk factors, we would expect to see more cancers as well. Introducing a new screening program or advertising the program and increasing the number of people who attend for screening can also increase incidence by identifying more cancers at an earlier stage. Pollution could cause an increase in cancers and this is often what community members are concerned about.
00:11:26
Prevalence is a term that refers to the number of people alive with cancer or with a history of cancer and there are several reasons why the number of prevalent cases can increase. One is if treatments improve then we see increasing prevalence and that would happen even if the number of newly diagnosed cases stayed the same. Another thing that can increase prevalence is cancer screening.  Screening identifies more cancers and so it increases incidence at least at first. In addition, those cancers tend to be diagnosed at an earlier stage.
00:12:04
When treatments are more effective so prevalence increases. Finally, the number of people alive with cancer also tends to increase if the number of new cases also increases. Because this is all a bit complicated, it is important when looking at community concerns about cancer to make sure that we are looking at incidents using cancer registration data and not prevalence. This takes some of the variables out of the equation and leaves a simpler assessment. The U.S government agency the CDC has developed a protocol for states to follow to investigate cancer concerns using cancer registry data. According to the protocol we start by collecting preliminary data about the number and types of cancer of concern, the location of the community, and any known hazards in that community like a factory or a landfill site. In the second phase, we use registry data to find out if there is a pattern of excess cancers in that location, we will discuss that next. If the analysis shows, a higher rate of cancer than expected that finding is regarded as a signal to move into phase three. In Phase 3, the state convenes a group of experts to assess whether a detailed study might be warranted and if one would even be possible. If it is and if resources are available phase 4 takes us into a detailed study to try to identify the cause of a cancer cluster. This figure shows the same thing in more detail. The message is that there is a protocol and a rationale to the investigation and it is important to follow that protocol each time rather than dive straight in to conduct a study.
00:14:07
If we are concerned about a specific environmental hazard. The cancer cluster should have some characteristic features. Some features that may alert Public Health departments to a true cluster include when the excessive cancers involves the same cancer subtype or a rare cancer subtype or when the cancers occur in an age group that is usually not affected so much by the cancer in question. Clustering of cases around a specific environmental concern is also a red flag although in practice it may not be straightforward because Water and Air traveling in different directions may take hazardous chemicals away from the source.
00:15:00
Many investigations do not proceed beyond data analysis. Why is that? If there are many types of cancer involved that tends to be less convincing about a cluster or point source. Sometimes the initial report from the community turns out to include various diseases that in fact are not all verified as cancer so the role of the registry is critical to confirm all of the cases. Sometimes there just is not an excess of cancers that's their statistics show to be concerning and sometimes there is no common geographic location for the cases or a plausible environmental cause. In many investigations the number and distribution of cancer cases is well within the range that we expect to see. The bottom line is that the state will follow established protocols to assess cancer concerns and as it, turns out many investigations stop after phase one.
00:15:59
Let us talk now about how we can tell if a cancer cluster is real or the result of random variation or what do the statistics mean. If we are playing pool and the balls look like this we just assume they got there randomly there does not seem to be a pattern. Here we see a definite pattern and it is clear that somebody put balls like this this is not a random arrangement. Sometimes we are not sure this arrangement might have happened by chance or there may be a reason why more stripes seem grouped together and more spots seem grouped together. Sometimes it is hard to tell if something happened by chance. How do we tell if a pattern is really a pattern or just something that happened by chance?
00:17:00
We start with the state cancer registry. We define the geographic area and years of interest and we use the registry to estimate how many cancers we would expect to see in that town based on what we know in the rest of the state. In this example that number is 50. The estimate uses information about the population of the town making adjustments for the age, in case the town has a lot more older people than the rest of the state. Next, we count the number of cancers that occurred in the town here that number is 60. We calculate the ratio between what we see and what we expect to see. If the observed number of cases equals the expected number, the ratio is one, more on that in a minute.  Our ratio is 1.2 suggesting a 20 percent excess of cancers in the town. We also calculate a 95 percent confidence interval, which is a way to indicate the uncertainty in the analysis, but more on that later
00:18:16
This map shows cancer rates in the U.S. Highest rates in darker blue. This is a huge country with enormous variation in racial and socioeconomic composition in lifestyle and cancer risk factors and there is enormous variation in cancer incidents between regions. Even in the Northeast, there is variation in rates with lower rates in Vermont and Massachusetts than in New Hampshire or Maine. There has been some controversy about choosing a comparison for cancer cluster analyzes if we are concerned about something in the environment in a New Hampshire town causing cancer our comparison should be with a community that has similar features except for that environmental exposure. This is clearly stated in the CDC protocol that we discussed earlier. We are more likely to find a suitable comparison population in New Hampshire than in the country as a whole. Let us look at the interpretation of the standardized incidence ratio or SIR. An SIR of 1 means that we are seeing the same number of cases that we expected to see so there is no excessive cancer. Next, an SIR of 1.2 means that there are 20 more cancers than we expected. Finally, an SIR of 0.8 means that we saw 20 fewer cases than we expected. The SIR of 1.2 means 20 more cancers than there would be if the rest of New Hampshire is anything to go by. And you can see here, the excessive cancers on the left. How sure are we of this result and how accurate is it? Statisticians have come up with a measure that helps us understand how reliable this result might be and we will talk about this next.
00:20:28
So now, we will turn to the topic of statistical power and the detection of patterns. If we toss a coin and it lands on heads we would not be very surprised we know there is an equal chance of it landing on heads or tails. If we toss the second coin and it lands on heads both times, still we are not very surprised after all, we only did it twice and each time we had a 50 percent chance of it being heads. What happens if we toss the coin 15 times and every time it lands on heads at this point we're starting to think something odd is going on because we're seeing a pattern and in this final scenario with more than a hundred attempts if we get heads every time we toss the coin we really know there's something wrong. In general, the more data we have the more confident we can be in assessing any patterns that we see. In statistics we use something called a 95 percent confidence interval to try to understand how confident we can be in the analyzes.  An SIR calculated for a town is an estimate of the truth. Why is it called an estimate? And why is there any uncertainty about the SIR?
00:21:48
Populations are dynamic. People move into and out of a town all the time and more people are diagnosed with cancer as time goes by so the SIR measured at any time is only an estimate of the truth. Remember how we tossed two coins and both of them landed on heads. We expected the proportion landing on heads to be 50 percent but it was actually a hundred percent that value of a hundred percent is true for the data we collected but it may not represent the truth that we would observe if we continued to collect more data. If we threw the coin again and got tails now our estimate is two out of three or 67 percent and if a fourth throw, is also tails now our estimate is fifty percent our ability to understand the truth about the coin depends on the number of throws and on the results that we obtained. The estimates change when we have different sets of data.
00:22:45
The same is true of the SIR. We can measure it at different times and through random variation, we may see different results. The SIR is an estimate of what is going on and statisticians have developed a tool called a confidence interval to help us understand and interpret that estimate. The 95 percent confidence interval gives us a range of plausible values that might be true. When we toss a coin we expect heads and tails half the time though the range of possible values is between zero and a hundred percent.  If we toss a coin 10 times and get head, six times the proportion that we get is 6 out of ten or sixty percent could the coin still be fair. We calculate a 95 percent confidence interval and we get 0.3 to 0.9 meaning 30 to 90 percent what this means is that the truth for this coin is likely to fall within that range because 50 falls in that range the coin could still be fair. If we toss the coin a thousand times and we get 600 heads that's still sixty percent but now we have a new confidence interval telling us that the truth about this coin is likely between 57 and 63 percent because 50 is outside this range we conclude that the coin is unfair. The 95 percent confidence interval tells us the plausible range of values for the truth based on the sample data that we're looking at the more data we have the narrower the confidence interval tends to be and the more precise the estimate.
00:24:40
One more example, in Merrimack, a recent analysis in 2022 showed a 42 percent higher incidence of kidney cancer than the rest of the state. The confidence interval excluded one so we can say that the result is statistically significant. This is important because it indicates to us that we have a signal that we should follow up to see if there is more to investigate for kidney cancer in Merrimack.
00:25:09
To summarize a raised SIR above one indicates excess risk in a town. For example, 1.20 means a 20 percent higher risk of cancer than expected. If the 95 percent confidence interval excludes one the result is statistically significant. For example, an SIR of six with a confidence interval of 1.9 to 18.5 is a statistically significant elevated SIR. It does not indicate the cause of the high cancer rate. It indicates just a signal that something may need further investigation and it might still be wrong in the sense that data analyzed later on with more data or a different time may come out with different numbers. Small numbers of cancers can cause wide confidence intervals and low precision. The small population in New Hampshire often makes it hard to assess trends. Often multiple years have to be analyzed together and this can cause problems if we want to see changing trends. For example after pollution events or a spill.
00:26:35
A statistically significant elevated SIR does not indicate the cause of the high cancer rates. As I mentioned it is a signal that something may need further investigation. It is also worth noting that a statistically significant SIR is not always correct. Meaning that the way these statistics are designed a small proportion of the time, a significant result could still be wrong.  In other words, it may not represent the truth.
00:27:06
One problem we see often in New Hampshire is that the population is small. Small numbers can cause problems in statistics making it hard to assess trends. Often multiple years of data or multiple towns must be analyzed together and this can cause problems if we want to see changing trends. Earlier we talked about investigations that do not proceed beyond phase one. It turns out that many investigations also do not proceed beyond phase two the SIR analysis phase. Why should that be? Because in many investigations the number and distribution of cancer cases is within the range that we expect to see either fewer cancers than expected or the same number as expected or the confidence interval includes one meaning that we can't be sure of the importance of the findings statistically. The bottom line is that the state follows established protocols to assess cancer cluster concerns and in these situations, the protocol rightly indicates that the investigation should not proceed to phase three. On the other hand, if we see an excess of cancers in a town and we consider taking the investigation to phase three we need to keep in mind that may or may not be a single carcinogen that accounts for the findings. If there is a single cause, a detailed study will not always find it. Phase 3 involves discussing the feasibility of a detailed study, which may involve questioning patients, reviewing medical records, collecting environmental samples, and testing biological specimens. These kinds of studies are expensive and often logistically difficult. It is always difficult to enroll all of the patients that are needed and to get detailed accurate histories of possible exposure including residential histories, which may have happened many years ago. On the other hand, if we are to improve our understanding of cancer and of the environment it is important to look for ways to do these kinds of studies in our communities. Remember we talked earlier about how cancers can be caused by many different things or combinations of things. This complexity makes the investigations potentially very complicated.
00:29:31
So what should you do if somebody calls you about their concerns relating to cancer or any other health condition in their community? First, make sure to take contact information so they can be called or emailed back after your conversation. Get an idea of the types of cancers they are seeing and any concerns about possible causes that they are worried about. Avoid taking private health information about individual cancer patients. The cancer registry has got all the information needed to investigate so taking notes on confidential information is not required or advised. At most, note the types of cancer and the numbers of patients with those with those types of cancers. You can either pass along the concern to the cancer program at DHHS yourself or you can provide the email address shown here so that they can do it themselves. If you provide your contact information to DHHS staff at the email address shown, here you can keep in touch about the investigation and get updates on behalf of your community the state also offers social media sites to learn more.
00:30:48
So to recap what we have talked about here. First, we have discussed the complex nature of cancer and the many different causes of cancer. We have discussed what a cancer cluster is and how it is investigated.  And what to do if someone contacts you with concerns about high rates of cancer in a population. Please feel free to contact the state if you have questions about this presentation or about cancer concerns in your community. There will be one more training in this series that delves further into the issues of environmental contamination and risk.