We need reliable, low-cost, effective cancer therapies as a part of the next few decades of our attempts to live longer, healthier lives. Ultimately, we'll need something better than that - some form of fix or replacement for the very complex, fundamental cellular structures and mechanisms that make our cells work, but in the end lead to cancer - but it doesn't do to look too far ahead when you haven't yet fixed the first rung of the ladder. If the years ahead proceed much as I would expect, we'll see great gains in regenerative medicine and restoration of the newly-understood elderly immune system, amongst other advances. Just these alone will lead to more years of healthy life for average folk who generally took care of their health - and a large jump in the number of cancers in the population. Under the present cellular blueprint, the longer your body runs, the more likely it is to generate the unchecked, malfunctioning cells that cause cancer.
From the high level view - the view of building infrastructure and progress decade by decade - the most promising anti-cancer strategy of the moment appears to be a matter of finding and targeting the most obvious biochemical signatures that distinguish cancerous cells from healthy cells. There are a lot of them, as it turns out, of varying effectiveness. More are discovered with each passing month:
A new class of drugs - being developed by a major pharmaceutical company - targets an enzyme that helps cells divide; in cancer, this enzyme, called Aurora B, goes into overdrive, possibly leading to uncontrolled and abnormal cell divisions.
In essence, cancer cells are quite different. They act differently, and their biochemical programming is different. The breakneck pace of advance in biotechnology, driven by advances in processing power and the ability to engineer ever more effectively at the nanoscale, is now enabling researchers to take advantage of this fact. Firstly, scientists are able to cost-effectively identify actual, detectable differences between cancer cells and healthy cells. Secondly, scientists can cost-effectively design and produce complex molecules - drugs - to interact precisely with cancer cells in a given fashion. This second part of the equation was a tough and uncertain process as recently as 15 years ago; while still a challenge, it has become much easier in recent years. Given another decade of progress, turning out the design for a molecule to precisely perform a given biological task - with no side-effects - will be a short task that a researcher hands off to a computer.
On the practical drug engineering side, one very promising avenue of inquiry is based on the use of dendrimers, branching bush-like molecules that are not at all toxic, and don't trigger the immune system. The Wikipedia entry has a pretty picture, but the National Dendrimer & Nanotechnology Center introdution is somewhat more helpful.
Dendrimers are the first large, man-made molecules with precise, nano-sized composition and well-defined three-dimensional shapes. Current polymer molecules are long, spaghetti-like strands that grow in only two directions. Dendrimer molecules grow three-dimensionally by the addition of shells of branched molecules to a central core. The cores are also spacious and have “sticky” points on the outside to which various chemical units can be attached. By adjusting chemical properties of the core, the shells, and especially the surface layer, dendrimers can be tailored to fit the needs of specific applications.
Because you can easily attach an array of tailored molecules to a dendrimer - such as the drugs you have just designed to detect, interact with or kill cancer cells - it allows considerable efficiency in the development process. Knowing you have a safe way to hook together a cancer detector, a key to get inside the cancer cell, and the payload that will kill the cell, you can focus on making the best possible component parts of your new cancer therapy. Researchers are doing just this, and some of them are getting pretty good at it.
On the whole, I am optimistic on the prospects for the defeat of cancer. Resources are pouring into the field, and the trend in supporting and enabling technologies is towards accelerating progress. The long term solution will be tougher - but then, we'll be much, much better at this biotechnology business by the time that comes around to being next in the queue.