Transportation Insecurity, Cancer Screening, and Stage at Diagnosis: A Systematic Review

Introduction: Over 4 million Americans miss healthcare appointments – including for cancer screening and treatment – due to transportation insecurity. The purpose of this systematic review was to understand how transportation insecurity affects screening and stage at diagnosis, and to make recommendations for measuring transportation insecurity in this context.

Methods: We searched PubMed, TRID, Embase, Scopus, and Web of Science for full-length English-language articles published after 2003. We included observational studies on screening or stage at diagnosis measuring transportation barriers quantitatively at the patient level. Two authors reviewed content, extracted data, and assed quality. We compared methods of measuring transportation insecurity and associations between transportation insecurity and screening/stage at diagnosis.

Results: We screened 3204 publications, reviewed 299 full texts, and identified 42 screening and 38 stage at diagnosis studies after quality assessment. Transportation exposures were classified into six categories: Travel distance/time, vehicle access, public transit, needing help to travel, patient perception of distance/time as barrier, and patient perception of transportation access as barrier. Travel distance/time accounted for 85% of analyses, and results were evenly split between worse outcomes (56%) and null or reversed results. Table 1 presents sources of possible bias and strategies for mitigation; the literature is susceptible to referral and information bias, and spatial autocorrelation and hierarchical data are frequently ignored leading to inflated effects.

Conclusions: Future research should include alternative measures of transportation access such as private vehicle ownership, public transit accessibility, and needing help to travel to wholistically evaluate transportation as a social determinant of health.