Associations between comorbidities and survival outcomes in older adults with cancer: a scoping review of international and Japanese evidence.

Authors

Yuki Itani, Ayumu Matsuoka, Kyoko Obama, Maiko Fujimori

Published in

BMC geriatrics. Volume 26. Issue 1. Jul 22, 2026. Epub Jul 22, 2026.

Abstract

Advances in cancer treatment have improved survival among older adults with cancer, many of whom experience multiple comorbidities. This scoping review synthesized international and Japanese evidence regarding associations between comorbidities and survival outcomes in older adults with cancer.
We conducted a two-stage scoping review using PubMed and Ichushi. In the primary analysis, we searched for large-scale population- or registry-based studies globally to examine whether the pathways through which comorbidities influence survival outcomes in older adults with cancer, previously described for diabetes, are similarly applicable to comorbidities in general. In the secondary analysis, we searched for Japan-based studies to examine whether similar associations and mechanisms were observed in smaller clinical cohort settings in Japan. Data extraction focused on comorbidity measures, survival outcomes, and proposed mechanisms linking comorbidities to prognosis, which were categorized according to six conceptual pathways.
Eighteen international studies and 17 Japan-based studies met the eligibility criteria. Across both evidence streams, greater comorbidity burden was consistently associated with poorer overall survival. The Charlson Comorbidity Index was the most frequently used comorbidity measure. International studies more commonly suggested that comorbidities contributed to cancer-related mortality through restricted access to standard treatment (Pathway II). By contrast, Japanese studies more often reported associations with competing non-cancer mortality (Pathway I). Evidence remained limited for mechanisms involving increased malignancy, reduced treatment responsiveness, and delayed cancer detection, highlighting substantial gaps in the literature.
Comorbidities were consistently associated with poorer survival outcomes among older adults with cancer. International and Japanese studies appeared to emphasize different mechanisms linking comorbidities to prognosis; however, these differences should be interpreted cautiously owing to heterogeneity in study design, outcome definitions, and data sources. Further large-scale studies incorporating standardized comorbidity assessment are needed to clarify the mechanisms through which comorbidities affect prognosis and to inform survivorship care for aging cancer populations.

PMID:
42902221
Bibliographic data and abstract were imported from PubMed on 21 Oct 2026.

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