Stage
An important predictor of long-term cancer survival is the stage of the disease at the time of diagnosis. According to the National Cancer Institute (2016), treatment can be more effective for some cancers if they are caught before spreading throughout the body.
Comparisons of net survival between stages can be misleading. One needs to consider lead time bias.
In the example figure above, both subjects A and B develop cancer at age 70 and die at age 76. A’s cancer is diagnosed one year after developing, while it’s still at an early stage. B’s cancer is diagnosed three years after developing at a late stage. In this example, an earlier diagnosis did not extend A’s life compared to B’s.
However, the date a cancer develops is not known. What we do know is when a cancer is diagnosed and when a patient dies, so net survival is measured in time since diagnosis. In the above example, A will increase the five-year net survival rate, but B will decrease it, despite the two having the same actual outcomes.
Stage distribution
Among cancers diagnosed in 2015, close to 40.7 percent had already progressed to a late stage.
Because leukemia and myeloma occur in blood and platelet cells, nearly all cases (99.9 and 96.7 percent, respectively) were considered late stage. For both cancers, certain subtypes can be diagnosed as localized, and any cases reported by death certificate alone are of unknown stage.
Net cancer survival by stage and primary site
Some cancers had net survival rates above 100 percent for localized diagnoses: prostate cancer (103.6) and thyroid cancer (102.3). This is likely caused by qualities these patients share not controlled in the population life tables. One possibility is that early-staged cancers are often caught when patients undergo regular screenings. These patients probably practice other healthy habits, which would reduce their risk of all causes of death. If the increase in mortality risk is only slightly raised, it might be overcome by the reduced risk from a healthy lifestyle.
Brain and other nervous system cancer appears to have a higher net survival rate for distant-staged diagnoses compared to regional-staged. However, this difference is not statistically significant, so it cannot be said which is higher.
Lowest rates by stage
All net survival rates are estimates, so it is not always possible to confidently state which rates are lower than others. For each stage at diagnosis, the tables below list the cancer types which might have the lowest five-year net survival rates.
Localized
| Cancer type | Net survival (%) |
|---|---|
| Liver and intrahepatic bile duct | 29.3 |
| Brain and other nervous system | 32.5 |
Regional
| Cancer type | Net survival (%) |
|---|---|
| Liver and intrahepatic bile duct | 8.5 |
Distant
| Cancer type | Net survival (%) |
|---|---|
| Liver and intrahepatic bile duct | 2.6 |
| Pancreas | 3.2 |
| Esophagus | 4.9 |
| Stomach | 5.6 |
| Lung and bronchus | 5.6 |
| Urinary bladder | 7.2 |
Liver and intrahepatic bile duct cancer claimed the top spot for worst net survival rates in every stage at diagnosis. Looking back to the chart in the Summary chapter, the overall five-year net liver cancer survival rate of 16.1 was above the pancreatic cancer rate of 11.0 only because a higher proportion of liver cancers were caught early.