In a new study, 80% of mice with pancreatic cancer had their tumors disappear completely after treatment with a new "radioactive gel" therapy. A result also found in tumors that are difficult to treat.
The new approach, which combines traditional chemotherapy drugs with a new method of irradiating the tumor, is the most effective treatment for pancreatic cancer ever recorded in mouse model tests.
We think that constant radiation allows drugs to interact more strongly than current therapy allows. This new approach may work better for many other cancers as well.
Jeff Schaal, first author of the research, Duke University
Radiotherapy "from the inside"
In tests done so far on mice, stopping the growth of a tumor was already considered an excellent result. This new approach does not provide radiation from the outside, which passes through healthy tissues. It directly "delivers" radioactive iodine into the tumor, within a gelatinous envelope that protects healthy tissues and is absorbed by the body after the radiation subsides.
The study is published in the journal Nature Biomedical Engineering (I link it here).
"We have done a full immersion in the papers of over 1.100 treatments. We have never found results where the tumors have shrunk and disappeared like in this case," he says. Jeff Schaal, who conducted the research in the laboratory of Ashutosh Chilkoti, professor of biomedicine engineering at Duke University. "That's why we realized we have something extremely interesting".
Pancreatic cancer, enemy to be killed
Despite accounting for only 3,2% of all cancer cases, the pancreatic cancer is the third leading cause of death from this disease. It is very difficult to treat because it tends to develop aggressive genetic mutations that make it resistant to many drugs. Not only that: it is usually diagnosed very late, when it has already spread to other parts of the body.
The current flagship treatment combines chemotherapy, which keeps cells in a reproductive stage vulnerable to radiation for longer periods of time, with targeted radiation.
This approach, however, is ineffective unless a certain radiation threshold reaches the tumor. And despite recent advances in radiation beam modeling and targeting, that threshold is very difficult to achieve without risking serious side effects.
Another method involves implanting a radioactive sample encased in a titanium envelope and placed directly inside the tumor. Unfortunately, however, titanium blocks all radiation other than gamma rays, and the implant can only remain inside the body for a short time before the damage to surrounding tissues begins to defeat the purpose.
"There is no good way to cure pancreatic cancer right now," says Schaal. Hopefully it will exist, though.
How "radioactive" gel works
To get around the problems associated with current therapies, Schaal decided to try an implantation method that uses a substance composed of elastin-like polypeptides (ELPs). In summary, a gel-like substance with personalized properties.
At room temperature, ELPs exist in a liquid state: but they form a stable gelatinous substance inside the human body, which is warmer. When injected into a tumor along with a radioactive element, ELPs form a small deposit that encloses radioactive atoms. In this case, the researchers decided to use iodine-131, a radioactive isotope of iodine, because it has been used in medical treatments for decades: its biological effects are well known.
The gel packs iodine-131 and prevents it from escaping into the body, depositing almost all of its energy in the tumor without reaching the surrounding tissue. Over time, the gel degrades and is absorbed by the body, but not before the 131-iodine has decayed into a harmless form of xenon.
In the study, Schaal and colleagues tested this new treatment alongside paclitaxel, a commonly used chemotherapy drug, to treat various mouse models of pancreatic cancer. Overall, the tests have seen a 100% response rate in all models, with the tumors completely eliminated in three quarters of the models about 80% of the time. The tests also revealed no immediately noticeable side effects other than those caused by chemotherapy alone.
Radioactive gel, the next steps
The radioactive gel approach is still in its early preclinical stages and will not soon be available for human use. The next step is to test it in larger animals - if successful, a Phase 1 clinical trial in humans will follow.
"My lab has been developing new cancer treatments for nearly 20 years, and this work is perhaps the most exciting we have done in terms of its potential impact," says prof. Chilkoti.
Once again, always, we look forward to the turning point.
