What is immunotherapy for cancer? 

Immunotherapy is an infusion-based treatment that trains your own immune system to attack, control and destroy cancer cells. It’s been used as a treatment for certain types of cancer — primarily lung cancer and melanoma — since the 2010s. And, since 2020, it’s been used for triple negative breast cancer.

The results from immunotherapy trials and treatment have quickly moved it into a standard of care for these cancers, with or without chemotherapy, and it is continuing to show incredible promise in clinical trials for treating other types of cancer as well.

How immunotherapy works

Immunotherapy is effective against cancer by training your own immune system to find and destroy cancer cells. There are different types of products which fall under immunotherapy treatment, but they all generally work to optimize immune function.

Infusions of immunotherapy through an IV upregulate your body’s own immune function so that your body is not attacking all cells, just cancerous ones. It’s very effective, and compared with chemotherapy, minimally toxic to most patients.

The data we’ve accrued from immunotherapy’s first uses in melanoma and lung cancer, as well as many other subsequent cancer types used with or without chemo and/or radiation, is that in almost any arena in which immunotherapy has been studied it has demonstrated remarkable benefits almost entirely across the board, with few exceptions. That is rare in cancer research, and extraordinarily unique.

Good candidates for immunotherapy

In my practice, immunotherapy is being used currently primarily for triple negative breast cancer, which is very aggressive and accounts for about 15 to 20 percent of breast cancer cases. It tends to show up more in younger patients, Black women, Ashkenazi Jewish women and those with the BRCA 1 or 2 gene mutation.

However, this is just the beginning for immunotherapy for patients who have breast cancer. We have trials open right now incorporating immunotherapy for those who have hormone receptor-positive, HER2- negative cancer, which is a very common type, and the results so far are very exciting. There were also two phase two studies presented in 2025 that demonstrated a novel way to treat BRCA + patients with triple negative breast cancer: incorporating immunotherapy combined with a pill effective in BRCA + patients that offers a treatment with the intent to cure that is entirely free of chemotherapy use.  

We talk with each patient who might be a candidate for the treatment. If a patient meets all the criteria for possible treatment, we make sure to discuss it with them as an option. In certain cases — like with autoimmune conditions, where the immune system is already too active — we sometimes must withhold immunotherapy, but we work with patients and other specialists to try to ensure access and tolerability.  

What to expect with immunotherapy

Immunotherapy is given as an IV infusion. Sometimes this is given with chemotherapy. It can be given prior to, after, or in lieu of surgery and/or radiation. In triple negative breast cancer, it is given before surgery and combined with chemotherapy. This way, we can evaluate if the therapy is working: If the tumor has shrunk — or is gone — by the time of surgery, we will know if the immunotherapy is working.

Generally, we infuse immunotherapy medication over the course of a half hour to two hours, and we can also give this alongside other infusions, too, which may lengthen that time. Many cancer patients receive three or more drugs, including different types of chemotherapy, to help combat their cancer.   During the infusion, most people don’t tend to have reactions specifically to immunotherapy. So, for example, in cases of lung cancer, melanoma, or others- where it’s the only treatment being infused, patients rarely experience much of a reaction during treatment. If providers are also infusing chemotherapy at the same session, there likely is a slightly higher chance of reactions or side effects from the chemo.

Immunotherapy is a very good way of minimizing toxicity and maximizing efficacy — and that is a true strength of the therapy.

Benefits of immunotherapy

The benefits of immunotherapy are vast and showing promise for the future. Because immunotherapy doesn’t attack all dividing cells like chemotherapy does, it is not apt to cause the same damage. That’s why patients undergoing chemo experience a vast array of side effects, such as losing their hair, but those undergoing a regimen of only immunotherapy would not.   For many people, immunotherapy has no side effects and often feels like taking nothing at all. People can and do get these infusions for long periods of time without a complaint.

Side effects from immunotherapy  

All medical treatments carry the risk of side effects, but we’re finding immunotherapy has fewer risks and side effects than other types of cancer treatments. This is in large part because, unlike other cancer therapies, immunotherapy does not target cells that are dividing indiscriminately like chemotherapy does. As such, immunotherapy is far less toxic when it is functioning optimally.   Because immunotherapy drugs are given as an IV infusion, patients may experience temporary local irritation or skin changes, but most patients undergoing immunotherapy don’t experience the traditional side effects from the infusions that patients and oncologists have encountered for decades with chemotherapy. Yes, you read that right: unlike chemotherapy, which can cause hair loss, nausea, diarrhea, anemia, low blood counts, painful neuropathy and many other troublesome symptoms, immunotherapy is extremely well tolerated in most cases.

There is one type of side effect to consider, though. In a minority of cases, the immune system can get confused and instead of properly following its training, it can attack healthy organs—by and large the thyroid is the most affected organ, but other organs can be affected as well, such as the intestines, skin, lungs, heart, liver, brain, eyes, etc. Theoretically, it can attack any cell in the body. But in practice, oncologists don’t typically see that happen. The thyroid is the most affected organ, and we can and do successfully manage those toxicities. Many of the events there and elsewhere are also quite minor and not harsh. This really is a therapy that maximizes efficacy and minimizes toxicity for the majority of people.

Success rates for immunotherapy

Determining success rate is tricky and highly dependent on each case.

When it comes to triple negative breast cancer specifically, we provide immunotherapy along with chemotherapy for six months prior to any surgery we perform. That’s because we want to know how the tumor responds, and that gives us information that we wouldn’t have if we performed surgery first. We start to determine possible success outcomes for the treatment by calculating how much of the tumor is left at the time of surgery. We then sort the tumor into one of four designations, called Residual Cancer Burden (RCB), based on how much cancer is left over.

The statistics for outcomes vary wildly based on the response to treatment. In triple negative breast cancer, if a patient’s tumor ranks at an RCB 0, meaning there isn’t any cancerous tissue left after immunotherapy at the time of surgery, there’s a very likely possibility that patient will never deal with this cancer again. Those who rank at an RCB 1 — meaning, they have microscopic levels of disease left over — do almost as well in the future as the zeros do. In triple negative breast cancer specifically, those who obtain an RCB 3, meaning there are large amounts of cancerous tissue left over, there is around an 80 percent chance of recurrence based on the most recent literature, in which patients did not receive immunotherapy. We do have new data to suggest that it may not be so high now with immunotherapy, but it is not clear how much that number is decreased by in the long term.

We now have evidence from the Keynote 522 trial — a monumental leap forward for triple negative disease — that immunotherapy, provided in concert with chemotherapy, is directly tied to increased “pathological complete response” results. This means there is zero cancerous tissue remaining — by as much as 20 percent over the control group who received chemotherapy alone. This is extremely important and optimistic news that immunotherapy provides significant benefits to cancer patients. It also means there’s more work to be done to increase these positive statistics.

Key differences between immunotherapy and chemotherapy

It's hard to compare chemotherapy to immunotherapy directly when you dig into the details: It’s not like comparing apples to apples. The biggest difference is that immunotherapy trains your own body to attack only cancer cells. Chemotherapy gets sent in to wipe out all dividing cells, cancerous or not.

Treatment also really depends on the subtype of cancer, and both chemotherapy and immunotherapy can be important treatments to eliminate cancer. In general, you don’t have the same degree of positive outlook with chemotherapy because almost all patients will experience some side effects. Immunotherapy may very well not cause any side effects at all.  

Is immunotherapy stronger than chemotherapy?

This is a complicated and nuanced question to answer, because it depends on the type of cancer and stage. 

However, we are seeing very promising results in non-chemotherapy immunotherapy drugs that, in some cases, represent a new definition of standard of care for many of our patients — one that doesn’t include chemotherapy, where it previously would have.

Minimizing toxicity and maximizing efficacy will always be our goal, and we look forward to future advances of immunotherapy for cancer.