The associations between household food insecurity and cancer: A comprehensive systematic review and meta-analysis of observational studies among adults.

BACKGROUND: Household food insecurity (HFI) is a critical social determinant of health that can adversely influence cancer prevention, treatment, and survivorship, while a cancer diagnosis with its financial and functional consequences may also increase the risk of HFI. This study aimed to examine the associations between HFI and cancer-related outcomes. METHODS: A systematic search was done in PubMed, Embase, Scopus, Web of Science, and Cochrane Library until July 29, 2025. Eligible studies were observational in adults (≥18 years) evaluating the associations between HFI and cancer outcomes, with effects operating in both directions. The quality assessment was done using the Newcastle-Ottawa Scale. Pooled relative effect estimate with 95% confidence intervals (CIs) were calculated using random-effects models. Subgroup, sensitivity, and publication bias analyses were performed, and the certainty of evidence was assessed using GRADE tool. RESULTS: Forty-four studies (n = 1,135,888 adults) from high- (United States) and middle-income (Iran and Brazil) countries met inclusion criteria. Meta-analysis of six studies (509,291 participants; nine effect sizes) showed that HFI was significantly associated with lower cancer screening uptake (pooled relative effect estimate = 0.91; 95% CI: 0.87, 0.96; I2 = 78.8%; p < 0.001). Subgroup analyses demonstrated significant associations for both colorectal cancer screening (pooled relative effect estimate = 0.83; 95% CI: 0.70, 0.98; I2 = 72.9%; p = 0.025) and breast cancer screening (pooled relative effect estimate = 0.72; 95% CI: 0.54, 0.96; I2 = 85.9%; p = 0.026). HFI prevalence reported in the included studies among cancer patients ranged from 14% to 78%, with highest rates in low-income clinical sub-populations. HFI predicted worse treatment outcomes, including higher surgical complications, longer hospital stays, increased mortality, and lower quality of life. Among cancer survivors, HFI was associated with poor diet quality, treatment non-adherence, psychosocial distress, and increased all-cause and cancer-specific mortality. CONCLUSIONS: HFI can act as a barrier to cancer screening, treatment adherence, and survivorship, thereby contributing to inequities in cancer outcomes. Integrating HFI screening and nutrition support into the continuum of oncological care, alongside the implementation of equity-driven policies, will be important to addressing survival rates and enhance the quality of life for vulnerable populations.