A reverse transcriptase inhibitor, a type of drug often used to treat HIV, has been found to stop disease progression in one-quarter of patients with fourth-line metastatic colorectal cancer.
Researchers from Massachusetts General Hospital published their findings in the medical journal Cancer Discovery.
Colorectal cancer is responsible for approximately 10.2 per cent of all cancer cases worldwide, according to Targeted Oncology.
During the study, 32 patients with advanced metastatic colon cancer were monitored — nine were provided with lamivudine, an antiretroviral medication used to prevent or treat HIV and AIDS.
“After giving them only this one drug — nothing else — we saw signs of disease stability,” co-senior author David T. Ting said in a statement.
The other 23 patients were later given an adjusted dose of lamivudine, and researchers saw a high tolerance to the drug.
Another nine of the 32 patients, 28 per cent, had either disease stability or a mixed response when the trial ended — and though that doesn’t mean the tumours decreased in size, the researchers said the results were encouraging.
“If we see this kind of response with just one HIV drug, the next obvious trial is to see what else we can achieve with HAART, or highly active anti-retroviral therapy,” Ting said.
Ting and the team had found signs that the HIV drug could have potential in cancer treatment nearly a decade ago. As much as half of a tumour’s DNA was made of “repetitive elements,” which, at the time, were considered to be “junk DNA” — a term used for DNA that is non-coding. Since DNA contains instructions to create protein, this DNA is considered “junk” since it does not carry any such instruction.
Only cancer cells produced the repetitive element, Ting explained. Colorectal cancers produce a significant amount of those repetitive elements, which exude RNA that can replicate in a viral-like life cycle, which Ting called the “repeatome.”
“It’s a way for cancers to change their genome to adapt to stress,” Ting says.
Lower rate of colon, breast and prostate cancer
Previous research suggests that HIV patients receiving a three-drug anti-retroviral therapy for the rest of their lives see a significantly lower rate of colon, breast, and prostate cancer when compared to the rest of the general population.
“We did the trial to see if we could learn something new about the biology of cancer cells and in the process found this unexpected, very encouraging result,” Ting said. “Disease stability in a cancer patient population this advanced, with just one single agent, is highly unusual and we are hoping we can soon initiate a larger Phase III study with a three-drug reverse transcriptase inhibitor combination.”
Researchers suggest that this therapy may prevent cancer, or be able to turn a potentially lethal disease into a chronic one like HIV.
According to the Canadian Cancer Society, the survival rate for someone with stage 4 colorectal cancer is about 12 per cent.
Chris Arnold is a Toronto-based writer.