I understand your argument: you're saying that by treating stage 1–3 patients early on, the stage 4 patients will have a shorter survival. But in the US, stage 4 patients also include many patients that would have been stage 1–3 in a different country, and because these cancers may not be quite as aggressive as the other stage 4 cancers, the 5-year survival will be higher. I'm on board with this part of your argument.
The part that doesn't hold up is patients regularly coming in to their doctors with symptomatic early stage cancer. In early stages, many cancers are completely asymptomatic. Even when we screen completely asymptomatic patients for early stage cancer in the US, we don't actually see clear cut overall mortality benefits. So how is it that these Australians are presenting to their doctors so early on with cancer symptoms?
EDIT: The holy grail of cancer screening has three features:
- Identifies dangerous cancers shortly after they form
- Perfectly separates cancer from non-cancer
- Patients live longer
Medical science itself (regardless of healthcare system and country) can't reliably meet the above three goals. So I'm skeptical that patients having easy access to medical care like in Australia would result in improved cancer survival.