You don’t need to kill cancer.
You just need to keep it under control.
That’s the theory behind a new study published today in Science Translational Medicine.
Researchers say managing cancer with limited, lower doses of treatment can reduce toxic side effects as well as prevent drug-resistant cancer cells from taking over an infected part of the body.
The study results were greeted with interest within the cancer community.
William Phelps, PhD, the American Cancer Society’s director of preclinical and translational cancer research program, said the research is an “interesting idea” that needs more study.
“Anything one can do to limit toxicity in cancer treatment is a good thing,” Phelps told Healthline.
Dr. Giannoula Klement, a pediatric hematologist/oncologist at Tufts Medical Center who has used this type of treatment at her children’s clinic, was more emphatic.
“The study is a validation of an evolutionary concept,” Klement told Healthline. “I believe this is a tipping point.”
Lower Doses for Smaller Tumors
In their experiments, researchers led by Pedro M. Enriquez-Navas, PhD, of the Moffitt Cancer Center in Florida used different treatments on a small sampling of mice that had one of two forms of breast cancer.
In the experiments, standard chemotherapy reduced the mice’s breast tumors, but those malignancies grew back after treatment was stopped.
Another treatment regimen involved skipping doses whenever the tumors had shrunk. In this experiment, the tumors also grew back.
The so-called adaptive therapy regimen involved initial high doses of treatment followed by progressively lower doses as the tumors shrank. In these groups, 60 to 80 percent of the mice were slowly weaned off the treatments without any significant relapses.
In aggressive chemotherapy, the researchers said, drug-sensitive tumor cells are destroyed, but drug-resistant tumors are left behind. Those cells then take over and propel uncontrolled tumor growth.
Adaptive therapy, they argued, stabilizes the cancer by maintaining a small population of drug-sensitive tumors that suppress the growth of the resistant cells.
The lower doses also reduce the amount of toxic side effects of heavy chemotherapy.
Klement, who wrote an accompanying editorial supporting the research, said the technique is a “formidable change in cancer therapy approach.”
She said you can “truly never reach the amount of chemotherapy” needed to eliminate every single cancer cell.
She added that adaptive therapy should be combined with treatments that boost a patient’s cancer-fighting immune system.
Phelps noted the adaptive therapy does involve an “intensive treatment and diagnosis schedule” that takes place over a long period of time.
“We need some way to validate that this process works,” he said.
What Happens Next?
The study had its limitations.
It involved small groups of mice and it was used only on two strains of breast cancer.
The report authors acknowledged these factors in their study and said follow-up investigations and experiments are needed.
Phelps said the therapy needs to be explored in a patient setting and perhaps with other cancers to see how effective it can be.
He noted there is a precedent of early high dose and later low dose therapy when treating cancers such as chronic lymphocytic leukemia.
Phelps said there may be some hesitation to use adaptive therapy simply because many patients as well as medical professionals may be reluctant to leave cancer cells inside a body.
“They will have to prove that this therapy is better,” he said.
He said if researchers can do that, then “it will be easier for cancer patients to say it’s OK.”
Klement agrees there has been some reluctance.
However, she notes adaptive therapy has been getting attention since at least 2000. Some HIV treatments, in fact, employ this strategy.
It usually takes 15 to 20 years for a change in technique to take hold, Klement added.
“I think we’re there now,” she said.