SABCS 2024: Harnessing the Power of Tumor-Infiltrating Lymphocytes to Revolutionize Breast Cancer Treatment

In an interview with Pharmacy Times®, Roberto Salgado MD, PhD, Division of Research from the Peter MacCallum Cancer Centre in Melbourne, Australia, discussed the role of tumor-infiltrating lymphocytes (TILs) in breast cancer treatment. TILs are a measure of the immune system's activity in breast cancer tissues, which can be easily assessed by pathologists. Salgado shared that the presence and strength of TILs is associated with better patient outcomes and survival and may indicate which patients can safely forgo chemotherapy. Additionally, TIL levels can help predict response to immunotherapy, as the immune system's existing activity in the tumor can be amplified by these treatments.

Pharmacy Times

What are the latest advancements in our understanding of tumor-infiltrating lymphocytes (TILs) and their role in breast cancer prognosis and treatment?

Roberto Salgado MD, PhD

Tumor infiltrating lymphocytes, or generally called the TILs, is a measure of the immune system. It is a measure on how strong the immune system is active in the tissues of our patients. This is something that pathologists can easily find just by looking through the microscope. So, you don't need a genomic essay, you don't need a very expensive or complicated technology. The pathologist, who is the person in hospitals who makes the diagnosis, analyzing the tissues of their patients, is able to quantify the amount of immune cells and the amount of immune cells are called the TILS — tumor infiltrating lymphocytes, just based on an H&E. Now we do know, based on a lot of evidence, that the strength of the immune system in our patients with breast cancer is associated with the extent of outcome, so how good they survive. So, the more immune cells you have, the stronger the immune system is active in your cancer, and the longer the patients live. Recent evidence indicates that for a subset of those patients, the outcome is so excellent that they may not need chemotherapy, because we have found that the subset of those patients will have a very strong immune system, that they have such an accurate outcome that the clinician can discuss together with the patient whether they want or need additional chemotherapy, because nobody likes to have chemotherapy just for their pleasure, because it's very toxic. If a patient, together with his clinician or her clinician, can discuss on the immune system, they may take any more informed decision on what type of treatment they would like to get. So that's one element.

The second element is that we start to understand, also, based on a lot of evidence, that the strength of the immune is also important to predict response to immunotherapy. So, immunotherapy is actually a treatment that triggers the amount of immune cells, and those immune cells then attack the cancer cells. The more immune cells you have already in your cancer, the stronger the anti-cancer response is by that same immune system. So, immunotherapy only amplifies an existing signal. That's a very important element these days, is that the TILs may help to find those patients who may benefit from immunotherapy.

Pharmacy Times

How can TIL assessment be incorporated into clinical practice to guide treatment decisions and improve patient outcomes?

Salgado

When a pathologist analyzes the tissue, he determines on that same tissue of the patient a set of variables that the clinician needs to determine the treatment options. In that same analysis, the pathologist can easily incorporate an analysis of the extent of the immune system, so that the clinician gets a set of variables, like tumor size, a strong the tumor is proliferating. But in the same analysis, it can provide information the extent of the immune system. It doesn't cost anything, it's free —it's inexpensive. It's extremely powerful in terms of the information that it can give to the clinician. What type of information? It can determine together with the patient, whether the patients going to get chemotherapy or not. Or the clinician can discuss with the patient, based on that information, the extent of the therapy that the patient will get. All these tiny bits of information is extremely useful for clinicians, because they need the best information possible on the cancer of their patients to determine the best treatment options possible.

Pharmacy Times

What are the future directions of TIL research, and how might TIL-based therapies revolutionize the treatment of breast cancer?

Salgado

Well, there are 2 different ways to answer that question. TIL based therapies means that you characterize what determines whether the immune cells are attacking the cancer cells. They use that information to develop specific therapies using the immune cells themselves back again, injecting it back into the cancer or into the patient, so that it attacks specifically the cancer. What do we know? First, environment where the cancer is, is very important for the success of that type of therapies. The environment around the cancer cells is hostile to the immune system and immunotherapy or T cell therapies will fail. The pathologist may potentially have role in the future to inform clinical trial designs and inclusion of patients based on his assessment whether the environment of the cancer is hostile to the immune system or not.

Pharmacy Times

Is there anything you would like to add?

Salgado

Well, the only thing that I would like to add is that this biomarker called the TILs, has been developed by the community. It has been developed by pathologists from all over the world who have put a lot of efforts to develop a standardized method so that every pathologist globally can evaluate the extent of the immune system. It's actually very easy to incorporate methods in daily practice globally. It provides an enormous amount of information to the clinician. The caveat is, is that clinicians, as they do with every biomarker, needs to evaluate this method and this information very carefully and discuss together with the patient what the added value might be of that information for the patient.