JMIR Publications

ABSTRACT

Background:

Internet search engines serve as primary gateways for cancer information, yet the commercialization of health content within organic search results remains understudied. While covert promotional content—such as native advertising and stealth marketing—has been documented in various contexts, systematic comparisons across structurally divergent search platforms are lacking.

Objective:

This study examined the prevalence, distribution, and information quality characteristics of covert promotional cancer-related content across Naver and Google, South Korea's two dominant search engines, which have fundamentally different platform architectures.

Methods:

A two-phase cross-sectional content analysis was conducted. Phase 1 employed natural language processing to identify 33 cancer-related keywords from 1,400 preliminary posts. Phase 2 systematically collected 5,848 posts in October 2023, yielding 919 unique posts (598 from Naver and 321 from Google) that covered seven major cancer types, representing over 70% of Korean cancer incidence. Two trained coders analyzed promotional status, intensity, institutional sources, and information quality indicators (citation practices, information depth, and source attribution), with inter-coder reliability exceeding κ=.80. Chi-square tests examined the associations between platform and cancer type.

Results:

Covert promotional content appeared in 48.6% (447/919) of analyzed posts, with significantly higher prevalence on Google (54.2%, 174/321) than Naver (45.7%, 273/598; χ²₁=5.78, p=.016). Platform differences were pronounced: Naver promotional posts predominantly originated from blogs (96.0%, 262/273) and exhibited full promotional intensity (52.1%, 126/242), while Google posts primarily came from hospital websites (81.0%, 141/174) with simple institutional identification (57.8%, 52/90). Institutional source distribution varied significantly by platform (χ²₅=215.714, P<.001): traditional medicine institutions dominated Naver (99.2%, 119/120), whereas university-affiliated hospitals predominated on Google (85.0%, 96/113). Information quality differed substantially: indirect citation was more common on Google (81.6%, 142/174) than Naver (58.6%, 160/273; χ²₁=25.653, P<.001), while comparative informational depth was higher on Google (55.7%, 97/174) versus Naver (19.4%, 53/273; χ²₂=64.683, P<.001).

Conclusions:

Covert promotional cancer content is pervasive in Korean search results, with platform architecture systematically shaping promotional patterns, institutional sources, and information quality rather than reflecting deliberate marketing strategies. These findings underscore the need for platform-sensitive regulation and enhanced digital health literacy to protect vulnerable cancer information seekers from commercial exploitation embedded within ostensibly neutral search environments.