Correlation Among Cancer Incidence and Mortality Rates and Internet Searches in the United States
Population-level disease metrics are critical to guide the distribution of resources and implementation of public health initiatives. Internet search data reflect population interest in health topics and may be an alternative metric of disease characteristics when traditional sources are lacking, such as in basal and squamous cell carcinomas, which are not included in national cancer registries. However, these data are not yet well validated or understood.Objective
To evaluate whether state-specific normalized internet search volume correlates with incidence and mortality rates of common cancers in the United States, including melanoma.Design, Setting, and Participants
This was a cross-sectional analysis of Google search volume index data and US cancer incidences and mortalities of 8 of the most incident cancers in the United States in 2009 to 2013, at the state level, per the National Program of Cancer Registries. Participants were people performing Google searches and patients diagnosed as having cancers reported to cancer registries.Main Outcomes and Measures
Correlation between Google search volumes, normalized to total Google search volume, and National Program of Cancer Registries recorded cancer incidence and mortality rates.Results
By state, relative Google search volume statistically significantly correlated with cancer incidence rates in 5 of 8 commonly diagnosed cancers in the United States (colon cancer: R = 0.61; P < .001; lung cancer: R = 0.73; P < .001; lymphoma: R = 0.51; P < .001; melanoma: R = 0.36; P = .01; and thyroid cancer: R = 0.30; P = .03). For 4 of those 5 cancers (colon cancer: R = 0.61; P < .001; lung cancer: R = 0.62; P < .001; lymphoma: R = 0.38; P = .006; and melanoma: R = 0.31; P = .03), relative Google search volume also correlated with mortality rates.Conclusions and Relevance
Population-level internet search behavior may be a valuable real-time tool to estimate cancer incidence and mortality rates, especially for cancers not included in national registries, such as basal and squamous cell carcinomas.