Cancer incidence and digital information seeking in Germany: a retrospective observational study

Awareness is vital for cancer prevention. US studies show a strong link between web searches and cancer incidence. In Europe, the relationship remains unclear. This study characterizes regional and temporal relationships between cancer incidence and web searches and investigates the content of searches related to breast, cervical, colorectal, lung, prostate, and testicular cancer, brain tumors, and melanoma in Germany (July 2018-December 2019). Aggregate data from Google Ads Keyword Planner and national cancer registry data were analyzed. Spearman's correlation coefficient (r_S) examined associations between cancer incidence and web search, repeated measures correlation (r_rm) assessed time trends and searches were qualitatively categorized. The frequency of malignancy-related web searches correlated with cancer incidence (r_S = 0.88, P = 0.007), e.g., breast cancer had more queries than the lower-incidence cervical cancer. Seasonally, incidence and searches followed similar patterns, peaking in spring and fall, except for melanoma. Correlations between entity incidence and searches (0.037 ≤ r_rm ≤ 0.208) varied regionally. Keywords mainly focused on diagnosis, symptoms, and general information, with variations between entities. In Germany, web searches correlated with regional and seasonal incidence, revealing differences between North/East and South/West. These insights may help improve prevention strategies by identifying regional needs and assessing impact of awareness campaigns.