The National Cancer Institute's Cancer Information Service: 50 years of service to the nation.

The National Cancer Institute's (NCI) Cancer Information Service (CIS) was founded in 1975 in accordance with a Congressional mandate requiring NCI to provide accurate, timely, and reliable cancer information to the American public as part of the National Cancer Act. For 50 years, the CIS has provided cancer patients, caregivers, healthcare professionals, and the public with high-quality information and resources on topics across the cancer control continuum, cancer clinical trials, and tobacco use cessation. Throughout its history, the CIS has adapted to changes in the health communication environment and evolving consumer needs, for example, by implementing additional access channels and launching a Spanish-language service to better serve the public. In addition to being a premiere cancer information resource, the CIS is a unique laboratory for health communication research as data collected from the program is routinely used to monitor the public's emerging cancer information needs and to study information seeking patterns across a variety of cancer control topics. This commentary aims to spotlight the role of the CIS as a federal health information resource that has been addressing the public's real-time cancer information needs and responding to national cancer research and public health priorities for over five decades.