Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns

Background

State, tribal, local, and territorial (STLT) health departments play the primary role in examining unusual patterns of cancer in communities, including those associated with local environmental concerns. CDC/ATSDR provides scientific guidance to health departments related to environmental health concerns and unusual patterns of cancer.

In 2022, CDC/ATSDR released Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns to help health departments as they investigate patterns of disease in communities. This document updates the 2013 Morbidity and Mortality Weekly Report (MMWR) article: Investigating Suspected Cancer Clusters and Responding to Community Concerns: Guidelines from CDC and the Council of State and Territorial Epidemiologists.

About the guidelines update

In fall 2018, CDC/ATSDR began working to update the 2013 guidelines in accordance with the Trevor’s Law provision within the Frank R. Lautenberg Chemical Safety for the 21^st Century Act. This update ensures that STLT public health agencies and other stakeholders have access to information about current scientific tools. It also provides the latest guidance on approaches to evaluating and addressing unusual patterns of cancer within communities.

This Act calls for periodic updates to guidelines for investigating potential cancer clusters.

Methods

CDC/ATSDR followed a stepwise approach to update the guidelines, including:

1. Soliciting input from subject matter experts, STLT public health agencies, the public, and other collaborators.
2. Reviewing the latest scientific literature on related topics, including epidemiology of clusters, cancer genomics, geospatial analysis, and risk communication.
3. Developing a draft of the updated guidelines based on inputs received.
4. Posting for public review and comment in the Federal Register notice.
5. Finalizing guidance.

Activities

Activities included:

• Establishing an internal steering committee of experts from across CDC to oversee and carry out the process.
• Seeking public input via a Federal Register notice announcing the planned update of the guidelines. CDC/ATSDR received comments from individuals, academic institutions, and community groups. A final Federal Register notice can be found at https://www.regulations.gov; Docket No. CDC-2022-0070)
• Convening an external expert panel of scientists representing various disciplines. Experts provided input to ensure that proposed revisions to the guidelines represent best practices.
• Conducting a comprehensive literature review on topics related to cancer cluster investigations. The review examined recent findings in the fields of cluster epidemiology, cancer genomics, geospatial analysis, statistics, and risk communication to inform the update.
• Administering an online survey to STLT health departments about how public health agencies respond to community concerns about unusual patterns of cancer. This survey was completed by all 50 states, the District of Columbia, and two U.S. territories (Guam and Puerto Rico).
• Conducting focus groups with STLT health officials to guide the update and the development of accompanying tools, templates, and other materials for health agencies to use to help implement the guidelines.
• Convening STLT workgroups with the Council of State and Territorial Epidemiologists (CSTE) and the Association of State and Territorial Health Officials (ASTHO) to review the 2013 Guidelines and provide feedback and recommendations on facilitators and barriers to implementing the guidelines and specific tools, trainings, and non-financial resources to enable STLT agencies to better implement the guidelines. Final reports from the workgroups are available on the CSTE and ASTHO websites.
• Holding a meeting with collaborators, including non-government researchers, community members, and advocacy groups, in April 2021 to gather feedback about concerns associated with current guidelines.
• Conducting focus groups with community members and advocates to hear suggestions for how to improve communication and community engagement activities related to the guidelines, as well as other suggestions on improving cancer cluster investigations from individuals.

Enhancements

Notable enhancements to the guidelines included the following:

• Expanding the name of the guidance document to include examining patterns of cancer and environmental concerns
• Revising the definition of a cancer cluster to include cancers that may be etiologically similar
• Introducing the concept of "unusual patterns of cancer" to describe situations that may warrant further assessment
• Including specific and standardized approaches to better engage community advocates
• Providing a standardized template to better document the nature and extent of cancer and environmental concerns
• Updating approaches to identify and investigate unusual patterns of cancer, including the suggestion for proactive evaluation and routine monitoring
• Providing criteria to help guide community cancer investigations
• Enhancing appendices describing statistical and geospatial methods supporting the evaluation of unusual patterns of cancer

Limitations

While the revised guidance includes new methods to better engage with community members and advocates, statistical and other scientific challenges may make it difficult to directly associate factors that may play a role in the cause(s) of unusual patterns of cancer.

Although limitations and challenges remain, the revised guidelines propose an approach to identifying and investigating unusual patterns of cancer as part of routine surveillance activities as well as new criteria and decision trees for responding to cancer and environmental concerns.

CDC/ATSDR involvement

States play the primary role in responding to community concerns about cancer. CDC/ATSDR provides technical assistance to states when requested.

States may choose to share information about the inquiries they receive regarding unusual patterns of cancer (excluding personally identifiable information) with CDC. Sharing this information may allow for evaluation of any potential regional or national trends requiring follow up. It may also allow federal officials to report the number of community cancer inquiries occurring nationally.

Related materials

Survey results

Results from a State and Territorial Survey about Updating the 2013 CDC Guidelines for Investigating Cancer Clusters

Archived guidelines

Archived guidelines are provided for historical purposes only.

Investigating Suspected Cancer Clusters and Responding to Community Concerns: Guidelines from CDC and the Council of State and Territorial Epidemiologists (2013)

Guidelines for Investigating Clusters of Health Events (1990)