Immunotherapy for Cancer: Advances & Challenges

For decades, we have focused all our efforts on treating cancer by directly attacking tumor cells. Today we know that one of the most valuable and powerful tools to combat it was already in our own body: the immune system. Turning it into our ally is an interesting option in the fight against cancer.

What is immunotherapy?

Unlike treatments such as chemotherapy or targeted therapies, immunotherapy does not directly attack the tumor. Its objective is another: to reactivate the patient’s immune system so that it “does the job” and eliminates tumor cells.

Our immune system is designed to detect and eliminate threats, such as bacteria, viruses or damaged cells. And in theory, it should also be able to recognize and eliminate tumor cells. The problem is that cancer learns to stop, deceive or deactivate these defenses, managing to go unnoticed and progress.

That’s where immunotherapy comes in: instead of acting directly on the tumor, it removes those brakes and reinforces the immune response. This allows the body itself to recover its natural ability to fight the disease.

An old idea, a recent revolution

The idea of ​​using the immune system to fight cancer is not new. At the end of the 19th century, the American doctor William Coley observed that some cancer patients improved after suffering serious infections. Based on that observation, he attempted to provoke intense immune responses by injecting inactivated bacteria, known as Coley’s toxins.

The results were variable and the technique was eventually abandoned, but it left a fundamental idea: activating the immune system could become a very effective anti-tumor strategy.

Over time, and thanks to advances in biology and immunology, it was no longer necessary to resort to bacteria to activate defenses. Research identified much more precise and effective ways to activate the immune system, and it was then that immunotherapy began to show its full clinical potential.

There is no single immunotherapy

We usually talk about immunotherapy as if it were a single treatment, but in reality it encompasses very different strategies.

Among the most used are immune checkpoint inhibitors, which remove the “brakes” that prevent the immune system from attacking tumor cells. There are also monoclonal antibodies, which specifically recognize these cells and allow their elimination. As for adoptive cell therapies, such as CAR-T and TCR-T, they are based on modifying the patient’s own T lymphocytes so that they recognize and destroy malignant cells.

Added to this are therapeutic vaccines and other drugs in development whose objective is to stimulate the immune response.

The greatest hits: why immunotherapy was a revolution

The impact of immunotherapy became especially evident in tumors such as metastatic melanoma or lung cancer. In some patients, treatments that previously barely managed to gain a few months of life gave way to something unexpected: responses that are maintained over time.

This concept of “durable response” is the key to the revolution. It is not only about the tumor decreasing in size, but about it remaining controlled in the long term, something unusual with classic therapies. Therefore, with immunotherapy in our arsenal, we can speak of a paradigm shift in oncology.

So why aren’t all cancers treated with immunotherapy?

Here the big question arises. If it works so well in some cases, why not treat all patients with immunotherapy?

To understand it, it is necessary to distinguish between “hot” tumors and “cold” tumors. Hot tumors have the immune system “awake”: they present infiltration of T lymphocytes and inflammation. In these cases, immunotherapy is more likely to work. Cold tumors, on the other hand, lack immune activity and do not respond to these treatments.

Added to this is the enormous capacity for adaptation that some tumors have. Tumor cells can “hide” from the immune system, and become less visible. Others prevent the entry of immune cells into the tumor or block their activity.

Additionally, some tumors “modify” their environment to create an environment hostile to the immune response. In these cases, immunotherapy has little room for action, because there is no effective immune response to act on.

What if the immune system is activated excessively?

Activating the immune system has a price. In some patients, the immune response can also be directed against healthy tissues, causing side effects such as inflammation of the skin, intestine or thyroid gland.

In some cases, these side effects can be serious and appear even months after finishing treatment. Therefore, immunotherapy requires close medical follow-up and continuous surveillance.

It is not a universal cure, but it is a profound change

Immunotherapy has not replaced classic oncological treatments nor does it work in all patients. But it has shown something key: cancer can be treated differently.

Today we know that its success is not accidental and depends on several factors. First, research continues to understand why it works in some tumors and fails in others, and how cancer cells manage to escape the immune system. Second, better patient selection, based on biomarkers that help predict who can benefit from the treatment.

Third, long-term follow-up is essential, necessary both to control the disease and to monitor possible side effects.

Looking to the future of oncology research

Immunotherapy is not a “magic” solution, but it has represented a true revolution in oncology. It has shown that the immune system can become a very powerful therapeutic ally.

Its future does not lie in applying it indiscriminately, but in better understanding which patients it works for, why, and in combination with which treatments. In this way, oncology is moving towards precision medicine. Because true progress is not in trying more, but in treating better.