Age-related differences in cancer relative survival in the United States: A SEER-18 analysis.

Cancer survival has improved since the 1990s, but to different extents across age groups, with a disadvantage for older adults. We aimed to quantify age-related differences in relative survival (RS-1-year and 1-year conditioning on surviving 1 year) for 10 common cancer types by stage at diagnosis. We used data from 18 United States Surveillance Epidemiology and End Results cancer registries and included cancers diagnosed in 2012 to 2016 followed until December 31, 2017. We estimated absolute differences in RS between the 50 to 64 age group and the 75 to 84 age group. The smallest 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). Except for pancreatic cancer, cancer type and stage combinations with very high (>95%) or very low (<40%) 1-year RS tended to have smaller age-related differences in survival than those with mid-range prognoses. Age-related differences in 1-year survival conditioning on having survived 1-year were small for most cancer and stage combinations. The broad variation in survival differences by age across cancer types and stages, especially in the first year, age-related differences in survival are likely influenced by amenability to 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 (eg, stomach, esophagus, liver and pancreas).