Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns

In general, state, tribal, local, and territorial 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.

CDC/ATSDR has released an updated guidance document, 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 MMWR article: “Investigating Suspected Cancer Clusters and Responding to Community Concerns: Guidelines from CDC and the Council of State and Territorial Epidemiologists.”

Notable enhancements to the guidelines include 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 and 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
  • Suggesting what information to share with CDC/ATSDR
  • Enhancing appendices describing statistical and geospatial methods supporting the evaluation of unusual patterns of cancer

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.

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 21st Century Act [PDF – 377 KB]. This update ensures that state, tribal, local, and territorial (STLT) public health agencies and other stakeholders have access to information about current scientific tools and approaches to assess and respond to unusual patterns of cancer in communities.

CDC followed a stepwise approach in updating 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 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; 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 [PDF – 1 MB] 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 [PDF – 400 KB] and ASTHO [PDF – 153 KB] 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.

Questions & Answers

Why did CDC update their guidelines?

In 2016, the Frank Lautenberg Chemical Safety for the 21st Century Act was enacted, which included a provision called “Trevor’s Law” that addresses cancer clusters. The Act calls for periodically updating guidelines for investigating potential cancer clusters.  In FY 2019, Congress appropriated $1M to CDC/NCEH to update the 2013 guidelines. Funding in FY 2020-2022 supported the activities undertaken to complete the 2022 guidelines.

The updates ensure that STLT public health agencies and other stakeholders have access to information about current scientific tools and approaches to assess and respond to potential cancer clusters in communities.

Will CDC be more involved in ongoing or new state investigations?

States will retain the primary role in responding to community concerns about cancer. The guidelines update ensures that public health agencies have the most recent scientific tools to address community concerns.

CDC/ATSDR will continue to provide technical assistance to states as requested. Additionally, states may elect to share information about the inquiries they receive regarding unusual patterns of cancer (excluding personally identifiable information) with NCEH’s Health Studies program. Sharing this information may allow for evaluation of any potential regional or national trends requiring follow up and may allow federal officials to report the number of community cancer inquiries occurring nationally.