MA EPHT - Cancer

Cancer is not one disease, but a group of diseases that may be caused by several factors acting together over time. Massachusetts Environmental Public Health Tracking provides direct incidence rates and standardized incidence ratios for many types of cancer for different geographies within Massachusetts.

Explore Cancer Data 

The social, physical, and built environments in which people live may increase their exposure to environmental risks for cancer, limit their ability to practice healthy behaviors, and restrict access to the care and support they need to prevent, treat, an

What is cancer?

Cancer is a term used to describe a variety of diseases associated with abnormal cell and tissue growth. There are more than 100 different types of cancer, each with separate causes, risk factors, characteristics, and patterns of survival. 

A risk factor is anything that affects a person's chance of developing cancer. They may include inherited conditions, medical conditions or treatments, lifestyle factors, or environmental exposures. An individual’s risk of developing cancer may depend on several risk factors that act together and can change over time. 

Cancers are classified by the location in the body where the disease originated (the primary site) and the tissue or cell type (histology). Cancers that occur as the result of metastasis (or spread) of a cancer to another location in the body are not considered separate cancers.

In general, most cancers have a long period of development (also known as a latency period) thought to range from 10 to over 50 years. While not much is known about the latency period for cancers that occur in children, it is assumed to be considerably shorter than in adults.  

How does MA EPHT track cancer incidence?

The data on cancer incidence (new diagnoses) provided by MA EPHT are collected by the Massachusetts Cancer Registry (MACR) within the DPH Office of Health Data, Strategy, and Innovation. The MACR is a population-based cancer registry established in 1980. All health care facilities in Massachusetts are required by law to report diagnoses of certain cases of malignant disease and benign brain-related tumors. 

Each year, the North American Association of Central Cancer Registries (NAACCR) reviews cancer registry data for quality, completeness, and timeliness. For each year during 2000-2018 and 2020, NAACCR estimated the MACR’s annual case count to be more than 95% complete (gold standard) and more than 90% complete in 2019 (silver certification).  

Cancer incidence data, coupled with environmental data, can be used to evaluate potential relationships between cancer and the environment. The goal of tracking cancer incidence is to provide information that can be used to plan, evaluate, and take actions to prevent and control cancer in Massachusetts. 

What is a cancer cluster?

Cancer is common. According to the American Cancer Society, one in three people will develop cancer during their lifetime. For this reason, cancers often appear to occur in “clusters,” and it is understandable that someone may feel that the number of cancer diagnoses in their neighborhood or town is unusual. Upon close examination, many of these “clusters” are not unusual as first thought, but are due to population density, shared behaviors or risk factors, or random chance. Sometimes higher rates are due to improved diagnostic techniques and changes in data collection. Yet, others are unusual; that is, they represent a true excess of cancer in a community, workplace, or other subgroup of people. A suspected cluster is more likely to warrant further investigation if it involves many diagnoses of one type of cancer, a rare cancer type, or diagnoses among individuals in age groups not usually affected by that cancer type. 

The U.S. Centers for Disease Control and Prevention (CDC) defines a cancer cluster as a greater than expected number of cancer diagnoses that occurs within a group of people in a geographic area over a period of time. In other words, the pattern of cancer appears unusual. A person may suspect that a cancer cluster exists when several loved ones, neighbors, or coworkers are diagnosed with cancer -- but what appears to be a cluster may actually reflect the expected number of cancer diagnoses within the group or area. 

How are perceived cancer clusters evaluated?

The Massachusetts Department of Public Health's Bureau of Climate and Environmental Health uses a phased approach for community-specific environmental health assessments. This approach aligns with CDC’s Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns published in 2022.  

The number of diagnoses of a specific cancer type that occur over a certain time among residents of a city, town, or census tract is compared to the number that would be expected based on the statewide experience. Statistics tell us if the difference between the observed and expected number of diagnoses is meaningful or likely due to random chance. For screening-level reviews, analysts assess this data over time to look for trends. They also look at the ages at diagnosis, specific cancer cell type (called histology), and relevant risk factors. Analysts use mapping software (called Geographic Information Systems, or GIS) to look at the point pattern of cancer diagnoses relative to population density, distance to contaminated sites, or other factors. Taken together, this information can indicate whether an unusual pattern of cancer exists. In some cases, the findings may warrant additional public health investigation.

Cancer incidence evaluations are available online for many regions and communities in Massachusetts.

For more information on challenges and limitations of investigating patterns of cancer, see CDC’s fact sheet.  

What is known about cancer and the environment?

Many cancers occur because of changes to cells that happen by random chance. Referred to as sporadic or spontaneous mutations, they are not due to any particular exposure to a cancer-causing agent (called a carcinogen). Other times, exposure may be an initiating or contributing factor to the development of cancer in an individual. If a person is exposed to something, it does not necessarily mean that their health will be affected. The risk from exposure to certain chemicals or radiation depends on the type, extent, and duration of exposure. For example, inhaling a certain chemical may increase your risk of getting cancer but touching the same chemical may not. In addition, some substances may increase your risk only if you are exposed to high amounts over a long time. 

Because of the complex interplay of many factors, it is not possible to predict whether a specific environmental exposure will cause a particular person to develop cancer. We know that certain genetic and environmental factors increase the risk of developing cancer, but we rarely know the exact combination of factors responsible for a person's cancer. This also means that we usually don't know why one person gets cancer and another does not. 

Available data

Use the Explore Maps & Tables link to access the following measures. The most current available data will be shown. Be sure to check the site periodically for new data as it becomes available. 

Cancer data are presented on the MA EPHT website using two different types of statistics:

Direct age-adjusted incidence rates

• A direct age-adjusted incidence rate is the most appropriate statistic to compare cancer incidence in one relatively large area like a county or state to another.
• Direct rates are age-adjusted because cancers do not impact different age groups equally. Rates are calculated by applying age-specific cancer rates in an area to the U.S. standard population.
• Annual direct rates are available statewide. Annual average rates are available for a given 5-year period at the county level and statewide.
• Direct rates are provided for 15 cancer types and two leukemia subtypes (acute myeloid leukemia and chronic lymphocytic leukemia) for individuals of all ages.
• Direct rates are also provided for childhood cancers for cancers of the brain and central nervous system, leukemia, and two leukemia subtypes (acute lymphoid leukemia and acute myeloid leukemia) for two age groups (0-15 and 0-19 years of age).
• One calculation will generate the number of diagnoses and a direct age-adjusted cancer incidence rate. 

Standardized incidence ratios (SIRs)

• The observed value is the number of new diagnoses of a particular cancer type that occurred among residents in an area during a given 5-year period.
• The expected number of diagnoses is calculated by applying the age and gender-specific statewide incidence rates to the population distribution of the community or census tract. It reflects the number of diagnoses that would be expected during a given 5-year period if the population of the community or census tract had the same cancer experience as a larger comparison population designated as "normal" or average. In this case, the state as a whole is used as the comparison population.
• A Standardized Incidence Ratio (SIR) is the most appropriate statistic to examine cancer incidence in a small area, such as a community or a census tract. It is the ratio of observed cancer diagnoses in an area to the number of expected diagnoses multiplied by 100.
• SIRs for different communities or census tracts cannot and should not be compared to each other because the age distribution of a community has a strong effect on its cancer rates, and no two communities have the same age distributions within their populations. Rather, an SIR indicates whether the cancer incidence of a community or census tract differs from that of the state as a whole. For more information on SIRs, see CDC’s fact sheet.
• Statistical significance indicates whether the difference between the observed number and expected diagnoses is statistically meaningful, or if the difference may be due to random chance. Statistical significance is determined at the 95% confidence interval.
• SIRs are available for 24 different types of cancer and all cancers combined, which is a measure of the overall cancer burden experienced by a community or census tract.
• One calculation will generate the observed and expected numbers of diagnoses, SIR, and 95% confidence interval. 

Data considerations

When reviewing and interpreting cancer incidence data, it is important to consider the following:

• The data for invasive melanoma of the skin are incomplete for 2018, 2019, and 2020 due to processing issues of pathology laboratory reports. As a result, the melanoma numbers reported for 2018-2020 are underestimated. It is anticipated that most of these backlogged data will be added in future data updates.
• The COVID-19 pandemic disrupted health services, leading to delays and reductions in cancer screenings and diagnoses. This may have contributed to the decrease in diagnoses for many cancer types in 2020. Please refer to the MACR’s Statewide Report for 2016-2020 for more details on the number of diagnoses by individual year.
• Data are only presented if the confidentiality rules of MPH and the MACR are met. These are rules requiring data aggregation and suppression to protect privacy.
• Stability tells us about the reliability of the measure and depends on the sample size (in this case, the number of new diagnoses). MA EPHT uses the Relative Standard Error (RSE) to assess stability. When the RSE is greater than 30%, the rate is unstable and results should be interpreted with caution.
• Numbers and rates may differ slightly from those contained in other publications. These differences may be due to file updates, differences in calculation methods (such as grouping ages differently or rounding off numbers at different points in calculations), and updates or differences in population estimates.

Related links

Cancer Risk Factor Summaries  

Additional resources

Massachusetts

• Massachusetts Department of Public Health/Bureau of Climate and Environmental Health: Provides a coordinated response for residents on environmental health issues.
• Massachusetts Department of Public Health/Bureau of Climate and Environmental Health/Cancer in Massachusetts Information Sheet: Provides an overview of general cancer information and how cancer is monitored in Massachusetts.
• Massachusetts Department of Public Health/Bureau of Climate and Environmental Health/Environmental Health Investigations: Access to environmental health reports.
• Massachusetts Department of Public Health/Office of Health Data, Strategy, and Innovation/Massachusetts Cancer Registry: Responsible for the collection of information on all new diagnoses of cancer in Massachusetts.
• Massachusetts Comprehensive Cancer Control Program: Provides a collaborative process that encompasses all points on the cancer continuum to have the greatest impact on decreasing and eliminating death and suffering caused by cancer.
• Massachusetts Comprehensive Cancer Coalition: Provides information about the coalition and link to become a member.
• Wellness Guide for Cancer Survivors: A guide to improve quality of life after cancer treatment.

National

• National Environmental Public Health Tracking: To view the National Environmental Public Health Tracking website.
• American Cancer Society: General and cancer-specific information.
• CDC Information about Unusual Patterns of Cancer: Information and resources for cancer concerns.
• CDC Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns: Provides information and guidelines for examining unusual patterns of cancer in communities, including those associated with local environmental concerns.
• CDC Fact Sheet on Investigating Cancer Clusters and Unusual Patterns of Cancer: Challenges and Limitations: Provides information on challenges and limitations of investigating unusual patterns of cancer.
• CDC Fact Sheet on Standardized Incidence Ratios: A math-based approach to evaluating unusual patterns of cancer: Provides information on the method of calculating SIRs.