The research team, headed by Gobi Hariyanayagam Gunasekaran and colleagues, registered their protocol with PROSPERO and searched five major databases — Scopus, Web of Science, MEDLINE, CINAHL, and Cochrane — from inception to May 2026. From an initial pool of 4,262 citations, 95 studies met the inclusion criteria, and 30 were ultimately pooled in the meta-analysis. The team used a random-effects model to account for the expected heterogeneity across diverse health systems, patient populations, and treatment eras. Their primary outcomes were adherence rates and overall survival, with subgroup analyses by tumour site and disease stage.

The headline finding is nuanced. Across all tumour sites, adherence to clinical practice guidelines was associated with a survival benefit that did not reach statistical significance — a pooled risk ratio of 0.90 with a 95 percent confidence interval of 0.67 to 1.20. The heterogeneity was extreme, with an I-squared value of 99.78 percent, meaning nearly all of the variation between studies reflected genuine differences in populations, interventions, and measurement approaches rather than chance. But when the researchers drilled down by tumour stage, a clearer picture emerged.

For Stage II colon cancer, guideline adherence was associated with a significant survival advantage, with a risk ratio of 0.58 and a confidence interval of 0.34 to 0.99. Stage III colon cancer showed an equally compelling signal, with a risk ratio of 0.58 and a confidence interval of 0.41 to 0.80. In both cases, the confidence intervals excluded the null value of 1.0, indicating that patients whose care followed the guidelines had meaningfully better odds of survival. For Stage II-III rectal cancer, however, the trend toward improved survival was present but did not reach statistical significance, with a risk ratio of 0.59 and a confidence interval of 0.34 to 1.03. The lower heterogeneity in the rectal cancer subgroup — an I-squared of 35.53 percent — suggests the findings there were more consistent across studies, even if the pooled effect was less definitive.

Why the difference between colon and rectal cancer? The authors point to the complexity of rectal cancer management, which typically involves multimodality treatment — surgery, radiotherapy, and chemotherapy in various sequences — where deviations from guidelines may reflect clinical judgment about individual patient factors rather than simple noncompliance. The heterogeneity in colon cancer subgroups, by contrast, was extremely high, reflecting the wide range of health systems, time periods, and adherence definitions across the included studies. This is a critical caveat: the meta-analysis pools observational data, not randomized trials, so the associations cannot be interpreted as definitive causal proof.

Perhaps the most striking findings concern who is most likely to fall outside the guidelines. Non-adherence was consistently more common among patients of advancing age and those facing structural disadvantage — lower socioeconomic strata, non-white ethnicity, and treatment in non-accredited facilities. These are not random variations; they map onto documented patterns of structural inequity in cancer care delivery. The authors frame this as a systemic issue rather than a matter of individual clinician judgment, noting that disparities in guideline adherence reflect structural and systemic disparities in how cancer care is organized and delivered.

The evidence base underpinning this review draws on decades of real-world data. Studies from the Netherlands, Canada, Australia, the United States, Spain, France, Japan, and Sub-Saharan Africa all contributed to the pooled analysis, spanning treatment patterns from the 1990s through the 2020s. Earlier work, such as a 1997 French study published in JAMA, demonstrated that clinical guidelines programs could improve outcomes in breast and colon cancer, while more recent analyses from the National Cancer Database and SEER-Medicare have refined our understanding of how age, comorbidity, and hospital characteristics influence adherence. The current review synthesizes this entire body of evidence into a single, coherent picture.

The technical rigor of the meta-analysis is worth noting. The researchers used the CASP checklist for cohort studies to assess quality, applied VanderWeele’s methods for converting odds ratios and hazard ratios to risk ratios, and employed Duval and Tweedie’s trim-and-fill method alongside Egger’s regression to assess publication bias. They used Comprehensive Meta-Analysis software for the pooled analyses. The extremely high heterogeneity values — approaching 100 percent in the overall analysis — are a signal that the individual studies differed substantially in their populations, interventions, and outcome definitions, which the authors acknowledge as a limitation of pooling observational data across such diverse settings.

The implications for clinical practice and health policy are significant. The findings underscore that simply publishing guidelines is insufficient; health systems must actively address the barriers that prevent adherence, particularly among high-risk populations. The authors call for interventions targeting the structural and systemic factors that contribute to non-adherence — from hospital accreditation status to socioeconomic support for patients navigating complex treatment pathways. Implementation science frameworks, patient navigation programs, and multidisciplinary team approaches have all shown promise in prior research, and this review provides the quantitative evidence base to justify scaling such interventions.

Ultimately, this study reframes guideline adherence not as a binary measure of clinical quality but as a window into the equity of cancer care delivery. The survival benefits of following evidence-based recommendations are real for Stage II and III colon cancer, but they are not distributed equally. As colorectal cancer incidence continues to rise globally — with projections suggesting a substantial increase in burden through 2040 — ensuring that guideline-concordant care reaches all patients, regardless of age, ethnicity, socioeconomic status, or the type of facility where they receive treatment, will be one of the defining challenges of modern oncology.

Subject of Research: Disparities in adherence to colorectal cancer clinical practice guidelines and their association with survival outcomes

Article Title: Exploring disparities in adherence to colorectal cancer clinical practice guidelines and associated survival outcomes: a systematic review and meta-analysis

Article References: Gunasekaran, G. H., Ibrahim, B., Saleem, F., & Shabaruddin, F. H. (2026). Exploring disparities in adherence to colorectal cancer clinical practice guidelines and associated survival outcomes: a systematic review and meta-analysis. Supportive Care in Cancer, 34(9), Article 923. https://doi.org/10.1007/s00520-026-11134-7

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11134-7

Keywords: colorectal cancer, clinical practice guidelines, guideline adherence, survival outcomes, health disparities, meta-analysis, systematic review, colon cancer, rectal cancer, health equity, oncology, adjuvant chemotherapy