"Earlier use of prostate cancer vaccines urged by Hopkins scientists"

Shockingly, the researchers also called for more funding for their research.

This is a press release, not a news article, but still. Of course, whatever Researcher X is working on is incredibly interesting, underfunded and about to lead to a big breakthrough, according to Researcher X.

That said, I agree that cancer vaccines are likely to be most effective when used early, perhaps even before cancer develops.

The concept of cancer vaccination is straightforward, but proof of efficacy has been hard to come by. Just as exposing someone to antigens expressed by viruses or bacteria generates an immune response that can prevent infection, immunizing them with tumor antigens should lead to an immune response to the cancer. Harnessing the awesome power of the immune system (think about the toll of rheumatoid arthritis or multiple sclerosis if you think awesome is overkill) against cancer seems great. The problem is that cancers have already avoided the immune system. Or at least to the ones we see; it is likely that a lot of potential cancers are eliminated before they are clinically apparent, which is why medicines like Elidel and Protopic, which supress T cells, a key component of the immune system, may lead to increase risk of cancer

Growth of a cancer is basically evolution at work. Cells that grow faster have a selective advantage and so do those that can avoid immune surveillance. Cancerous cells seem to use a variety of mechanisms to avoid elimination by the immune system.

Unsurprisingly, new cancer therapies are generally tested on patients who have failed more standard therapies. This guarantees advanced tumors and poor prognosis. For some therapies this may be good as it may be easy to see benefit (see lung cancer drugs that extend life 2 months). However, for drugs that rely on the immune system it may be too late as tumors have become too large or cells too resistant to the immune system. The study above shows vaccination in a mouse model of prostate cancer is much more effective when done early.

Cautionary note: it is a lot easier to "cure" cancer in a mouse model than in wild-type humans, so many promising "cures" never make it through clinical trials