There's an extremely interesting article at io9.com about the progress being made in the fight against cancer. Having lost more than one friend to this disease, it's a subject of great importance to me. Here's an extract.
You probably already know that cancer is not just one disease — it's many diseases, gathered under a single umbrella. But in the past, we thought there were types of cancer called "breast cancer" or "prostate cancer," which were basically site specific — and now we've found that cancer is much more varied.
"Cancer is hundreds if not thousands of different diseases," says David Weinstock, an assistant professor with the Dana-Farber Cancer Institute and Harvard Medical School. "Saying, 'Why don't we have a cure to cancer,' is like saying, 'Why don't we have a cure to infection.'"
There are multiple levels of complexity, adds Weinstock: You have different basic types, like colon cancer versus lymphoma. Then you have hundreds of different types of lymphomas, and then every single person's lymphoma is different at a molecular level. And even though you think of cancer cells as all identical, in fact "not every cancer is the same, [and] there are many differences within a tumor." When you attack a tumor, "you're killing a diverse population" of cells, some of which will be resistant.
Most cancers under treatment have 100 different mutations within a single tumor, says Agus. "It's very hard to model that."
Meanwhile, you have to kill the tumor without killing the person who has it. People talk about the "therapeutic index," says Weinstock — which is the chances of killing the tumor, versus the chances of killing a normal cell.
Another wrinkle: cancer cells are bi-directional, meaning that stem cells can differentiate into mature tumor cells — but mature tumor cells can also turn back into stem cells, says Agus. Thus, treatments that have involved just killing the stem cells in the hopes that this would keep the cancer from recurring have failed, because the tumor can always repopulate with more stem cells.
There's more at the link.
The article points out that major advances in the treatment of cancer have occurred, and are ongoing. Still, it's going to be a long, hard battle to beat this disease.