When farmers try to manage insects in their crops, they figure out what dose of pesticide yields the best results. They do this based on understanding which bugs are the most harmful to their crops and what level of poison best combats them. This analogy may send shivers up the spines of organic eaters out there, but it does have relevance to the way chemotherapy is used in treating cancer.
It turns out that not all cancer cells (i.e. insects in the crops) are equally harmful within a tumor. Some are much more aggressive. When a broad-based chemo is used to kill all the cancer cells, it often leaves behind the most resistant ones, allowing them an opportunity to take over the tumor.
A quick look at evolution explains this phenomenon. Dr. Robert Gatenby, chair of radiology and co-director of the cancer biology and evolution program at Moffitt Cancer Center and Research Institute, says “We tend to think of cancers as a competition between the tumor and the host, but at the level of the cancer cell, cancer cells are mostly competing with each other,” he says. Competition within a tumor reflects a basic evolutionary principle, one which cancer cells utilize as well as normal cells.
Given this theory, Gatenby and his team wondered about the perfect level of chemotherapy that would repress the more aggressive cells, rather than encourage them to overtake the less aggressive cells. In the experiment, they took cells from two different breast cancers and grew them in mice. The mice were then treated to two separate chemo protocols. Group One mice were given lower-dose chemo and then skipped sessions if their tumors shrunk. Group Two mice were given continuous but gradually lower doses of chemo.
The researchers were surprised that 80% of the Group Two mice showed better response in reducing cancer growth. Some of the tumors disappeared completely.
This research is in its early stages and requires quite a bit of personalized chemotherapy analysis. One fly in the ointment – patients have to overcome the mindset that cancer treatment kills all cancer cells. They have to be content with the knowledge that not all cancer cells need to leave the body in order for a treatment to be successful.
In other words, leave the ladybugs and kill the locusts.