The two major types of non-small cell lung cancer (NSCLC), adenocarcinomas and squamous cell carcinomas, have long been considered two distinct diseases. But researchers are now discovering that these tumor types may have a much more complicated, intertwined relationship.
As researchers gather for the 2018 American Society of Clinical Oncology meeting, we reviewed the implications of these discoveries for the future of lung cancer treatment with Christine Fillmore Brainson, PhD, assistant professor at the University of Kentucky Markey Cancer Center.
What are some of the unanswered questions that continue to drive research in NSCLC?
We still don’t know which cells are the culprits — the “cells of origin” for different subtypes of lung cancer. That’s something our lab is trying to parse out in mouse models. Understanding the cells of origin may help us to develop treatments that specifically target these NSCLC subtypes.
We’re also trying to personalize treatment for lung cancer patients. At the University of Kentucky, when lung cancer patients don’t respond to chemotherapy, we sequence their tumor biopsy. This lets us understand the unique genetic combinations that contribute to their lung cancer. Then we consider the approved and investigational therapies that target those mutations.
How has our understanding of different types of lung cancer evolved recently?
We’re beginning to understand that there may be more plasticity in NSCLC subtypes than we had thought. Sometimes, a patient is originally diagnosed with adenocarcinoma. Then a second biopsy after treatment may reveal that those tumors have qualities of both adenocarcinoma and squamous cell carcinomas. Having a tumor that looks like both, which we call adenosquamous lung cancer, complicates things, and it has a poor prognosis. This transformation could be a factor in resistance to therapy in NSCLC.
Do we know what drives this change in the tumor cells?
We typically only see second biopsies after a patient has been treated with epidermal growth factor receptor (EGFR) kinase inhibitors. So that treatment might be driving the transformation in patients. Or it might also happen after chemotherapy. We don’t know because we don’t take that second biopsy then to look at it.
In a previous study, we showed that we could force this transition in mice through specific genetic changes.
How might this finding affect how doctors diagnose patients?
In the future, a diagnosis of adenosquamous lung cancer, rather than just adenocarcinomas or squamous cell carcinomas, might be common. And it might justify taking a second biopsy after chemotherapy. Right now, that’s not recommended, because often the patient isn’t doing well at that point, and you don’t want to add a lung surgery unless there will be a clear benefit.
Understanding the cells of origin may help us to develop treatments that specifically target these NSCLC subtypes.
If one NSCLC subtype can change into another, how could that affect treatment?
We’ve seen that targeted immunotherapies work well in squamous cell carcinoma. My laboratory is studying whether the transition to squamous cell carcinoma can make the patient’s cancer more susceptible to immunotherapy. We’re studying this in a mouse model right now. If we can push the transition toward squamous cell carcinoma with a targeted therapy, maybe we can boost the response to immunotherapy.
What does the future of lung cancer treatment look like?
Cytotoxic therapy, such as chemotherapy, and immunotherapy combinations are potentially going to be the future of NSCLC treatment. At ASCO, researchers will present studies that show more data on chemotherapy and immunotherapy combinations to treat adenocarcinomas. Combinations are being tested in clinical trials, and the Food and Drug Administration have approved a few combinations for specific circumstances. We see that some patients do much better when treated with immunotherapy and chemotherapy. So we should continue exploring combinations of immunotherapies with our standard therapies. Combinations seem to be one clear way to go forward.
To learn more about how immunotherapies may be a new partner for chemotherapy, read “The Evolving Role of Chemotherapy in Lung Cancer.”