Patterns of age disparities in colon and lung cancer survival: a systematic narrative literature review

<h4>Objective</h4> To identify patterns of age disparities in cancer survival, using colon and lung cancer as exemplars. <h4>Methods</h4> We conducted a systematic review of literature published in EMBASE, MEDLINE, Scopus, and Web of Science according to PRISMA guidelines. We included population-based studies in patients with colon or lung cancer. We assessed the quality of included studies against selected evaluation domains from the QUIPS Tool, and items concerning statistical reporting. We evaluated age disparities using the absolute difference in survival or mortality rates between middle-aged group and the oldest age group, or by describing survival curves. <h4>Results</h4> Out of 2,162 references reviewed, we retained 35 studies (15 for colon, 18 for lung, 2 for both sites). Regardless of the cancer site, included studies were highly heterogeneous and often of poor quality. The magnitude of age disparities in survival varied greatly by sex, ethnicity, socio-economic status, stage at diagnosis, cancer site and morphology, the number of nodes examined, and by treatment strategy. Although results were inconsistent for most characteristics, we consistently observed greater age disparities for females with lung cancer compared to males. Also, age disparities increased with more advanced stages for colon cancer, and decreased with more advanced stages for lung cancer. <h4>Conclusions</h4> Although age is one of the most important prognostic factors in cancer survival, age disparities in colon and lung cancer survival have so far been understudied in population-based research. Further studies are needed to better understand age disparities in colon and lung cancer survival. (PROSPERO registration number: CRD42020151402). <h4>Article Summary</h4> <h4>Strengths and limitations of this study</h4> For the first time, we conducted a systematic review of population-based studies relating to differences in cancer survival between middle-aged and older patients, using colon and lung cancer as exemplar cancers. We limited our search to peer-reviewed original articles and letters to Editors published in English up until 30 September 2019. We excluded clinical studies and trials because of the strict selection of patients and the common underrepresentation of older patients in these studies. We could not conduct any quantitative analysis (such as meta-analysis) because of the vast heterogeneity of studies included, which prevented us from quantifying the relationship between increasing age and cancer survival.