Age-related differences in cancer relative survival in the US: a SEER-18 analysis
Importance: In the United States (US) in 2017, nearly half a million adults aged 75 and older were diagnosed with cancer. Cancer survival has improved since the 1990s, but to different extents across age groups, with a disadvantage for older adults. Documenting age-related differences in cancer survival in the US can help to inform prioritization efforts to narrow the age-related gap in cancer survival. Objective: To quantify age-related differences in relative survival by stage at diagnosis
... 10 cancer types. Design: Retrospective population-based observational study of cancers diagnosed between 2012-2016 with follow-up through December 31, 2017 Setting: 18 US Surveillance Epidemiology and End Results cancer registries Participants: 844,296 individuals aged 50 and over with first primary cancers of the prostate, breast, rectum, colon, ovary, esophagus, stomach, liver, lung, and pancreas. Exposure: Age at cancer diagnosis (50-64, 65-74, 75-84, 85-99) and stage at diagnosis (localized, regional, distant, and unknown/unstaged). Main Outcome(s) and Measure(s): One-year relative survival (RS). We estimated the absolute difference in 1-year RS between the 50 to 64 age group and the 75 to 84 age group. Results: The smallest age-related differences were observed for prostate and breast cancers (1.8%-points [95% confidence interval (CI): 1.5-2.1] and 1.9%-points [95% CI: 1.5-2.3], respectively). The largest was for ovarian cancer (27 points, 95%CI: 24-29). For other cancers, differences ranged between 7 (95% CI: 5-9, esophagus) and 18%-points (95% CI: 17-19, pancreas). With the exception of pancreatic cancer, cancer type and stage combinations with either very high (e.g., >95%) or very low (e.g., <40%) 1-year RS tended to have smaller age-related differences in survival than those with mid-range prognoses. Conclusions and Relevance: The broad age-related variation in survival across cancer types and stages may reflect the degree to which cancers are amenable to anti-cancer treatment. Future work to measure the extent of age-related differences that are avoidable, and identify how to narrow the survival gap, may have most benefit by prioritizing cancers with relatively large age-related differences in survival, especially at earlier stages (e.g., stomach, esophagus, liver and pancreas).