Cancer is a complex, multi-headed beast, an umbrella of over 200 different afflictions. Thankfully, from using artificial viruses on the one hand to wielding CRISPR on the other, science is going full-out to defeat this ancient biological malevolent malfunction.

A new study, courtesy of a team led by Stanford Medicine (SM), places its bets on immunotherapy, a rapidly growing field that – unlike conventional chemotherapy – triggers the patient’s own immune system to deal with the cancer itself. Generally speaking, immunotherapy is more precise, whereas chemotherapy targets cells somewhat indiscriminately.

For this work, the team used two immune-stimulating agents, injected in small quantities directly into the tumors of mice. They found that it not only completely destroyed these tumors, but it also eliminated all elements of the cancer in the mice, even in parts of the body that the cancer had metastasized (spread) to long ago.

Writing in the journal Science Translational Medicine, the authors note that “it has recently become apparent that the immune system can cure cancer.” Clearly, great advances are being made: they conclude that, at least in mice, their new technique can “cure multiple types of cancer and prevent spontaneous genetically driven cancers.”

So what exactly are these two agents of which they speak, and what do they do?

As with plenty of immunotherapy investigations, the focus here was on stimulating the body’s T cells. These are lymphocytes, a type of white blood cell that plays a huge role in dealing with infections. They come in two flavors, helpers and killers, with the former assisting in the development of antibodies – the “handcuffs” that pin pathogens down – and the latter actually annihilating damaged or infected cells.

These T cells are excellent at spotting and dealing with abnormal cells, but they have some difficulty when it comes to cancerous cells. As they’re corrupted versions of our own cells, this means that they’re somewhat camouflaged. Even when the T cells do recognize the growing threat, they are often unable to destroy it as it proliferates through the body.

This new technique tries to tackle both the identification and the eradication problem in one fell swoop.

One agent, a short component of DNA, boosts the expression of a receptor on the surface of the T cells. The second agent is an antibody that attaches itself to this surface receptor, which activates the T cells and triggers them to attack the tumor.

As these agents are directly emplaced within the tumor, only T cells inside it are activated in this way. That way, they’re trained to recognize what the threat is immediately, and – after destroying the tumor – they swim through the body and obliterate its remnants elsewhere.

Clearly, the trial has been remarkably successful. In 90 mice infected with lymphoma – a cancer of the immune system – 87 of them were completely cured. The cancer did return in three of the cured mice, but a second round of treatment put that insurrection to an end.

Additional work on treating other cancers in mice, including breast cancer and colon cancer, has had somewhat more mixed results. Although the breast cancer mice responded well and often remained in remission, colon cancer seemed to be unaffected in experiments.

“The results of this study are very exciting, although there are some caveats,” Aimee Eckert, a doctoral research student focusing on cancer biology at University of Sussex – and who wasn’t involved in the study – told IFLScience.

“Studies that work well in mice do not guarantee success in human patients, though the fact that each of the two individual treatments used in this study are currently in clinical trials – and that they are now recruiting for the first human trials – is encouraging.”

Additionally, “not all tumors will be accessible for injection – many tumors require surgery first,” Eckert added. However, she suggests that “if this treatment is used alongside surgery and this can prevent secondary tumors or metastases from forming, then we could greatly improve life expectancy and/or cure rates for patients.”

Update: The use of the word "vaccine" in the study stems from the injection's ability to use the immune system to prevent the occurrence of future tumors.