Using low-dose chemotherapy to keep cancer at bay may be more effective than trying to kill it completely, a new study revealed.
Current cancer treatments such as radiation, surgery and chemotherapy are aggressively designed to get rid of as many cancer cells as possible.
Oncologists, however, provided evidence that cancer patients may have a better chance of surviving while keeping the disease under control.
Controlling Cancer Cells
Total eradication of cancer is rare, experts said, and the toxic side effects of chemotherapy can be extremely destructive. It leads to hair loss, nausea and severe fatigue, as well as cripples the immune system and triggers anemia.
The research team said that aggressive chemotherapy treatments go against basic evolutionary principles that even tumor cells follow.
"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," said Dr. Robert Gatenby of the Moffitt Cancer Center and Research Institute, who led the research.
The cancer cells that make up the tumor are not equal. A tumor can comprise different types of malignant cells.
Researchers said this is supported by the fact that when chemotherapy is performed, some cancer cells wither, while some will start to bloom again after weeks or months. These are the cancer cells that, by a quirk of their mutations, are resistant to the chemo.
Because of this natural selection pressure, high-dose chemo may actually make the cancer worse, researchers said.
Gatenby and his team studied whether it would be plausible to find the perfect balance of chemo that would destroy enough tumors but not strong enough to encourage the resistant cells to emerge. They took cells from two different types of breast cancers, grew them in mice and treated the animals with standard chemo and modified chemo.
The first group of mice received low-dose chemo and then skipped sessions when the tumors shrunk, while the other group received incessant but gradually lower doses of chemo.
The second group exhibited the best response in terms of slowing tumor growth. In about 80 percent of the mice, the tumors continued to get smaller to the point that the animals did not need any additional chemo.
On the other hand, the first group of mice didn't see their tumors shrink at all. Gatenby said he was surprised with the results because he was concerned that despite the benefits, the new treatment may not have an impact on the tumor because it was growing quickly at the beginning.
But the new method did prove to be effective, although the tumor remained. Gatenby said the cancer cells became less active and grew more slowly than before.
Hopes For The Future
The novel method is called "adaptive therapy" (AT) and it is designed to oppose the natural responses of resistant cancer cells by controlling them.
Gatenby hopes that with enough patients taking advantage of the AT strategy in clinical trials, an algorithm may someday be developed so doctors can monitor individual cancer conditions to calculate the proper chemotherapy dose.
Meanwhile, the team plans to test the new therapy among men with prostate cancer. The findings of the new study are featured in the journal Science Translational Medicine.
Photo: Phil and Pam Gradwell | Flickr
