Targeted therapy in Lung Cancer Care: What the Research Shows

Once the results of comprehensive biomarker testing come back, they do more than just provide information — they can fundamentally change the course of treatment. For patients whose tumors carry a specific targetable gene change, those results open the door to a class of medications designed to precisely block what is driving their cancer.

Three Types of Systemic Therapy — and Why They Are Not Interchangeable

Dr. Bruna Pellini, chief of thoracic medical oncology at Baptist Health Herbert Wertheim Cancer Institute, uses an analogy to explain the difference. Targeted therapy, she says, is like blocking a specific highway that the cancer uses to grow. "There is I-95 and there's maybe U.S. 41. We're going to block I-95 because your cancer likes to take I-95 to grow. So that's targeted therapy."

Chemotherapy works differently. It kills cells that grow fast — but it cannot distinguish between cancer cells and healthy cells. That is why it causes side effects like nausea, vomiting, and hair loss, Pellini explains. It does not know what is cancer and what is not.

Immunotherapy works by trying to wake up the body's immune system so it can find and kill cancer cells. But Pellini notes that this approach has a significant limitation in patients whose cancer is driven by a specific gene change: "You have to have good soldiers to shoot the cancer cells. And in a lot of the diseases that are driven by genetic alterations, we have blind soldiers. They don't know how to shoot. You need snipers, and the oncogene-driven tumors don't have snipers. So that's why immunotherapy shouldn't be given in that situation."

The Harm in Starting the Wrong Treatment

For patients with certain targetable mutations, starting with immunotherapy — either alone or in combination with chemotherapy — is not just less effective. It can be actively harmful. The reason is toxicity overlap: some of the targeted therapies that are most effective for these patients have side effects that overlap dangerously with those of immunotherapy drugs. If immunotherapy is given first and causes inflammation or organ effects, it may become impossible to safely give the targeted therapy at full dose later.

"If we hurry, we can give something that is not benefiting our patient, has a lot of side effects, and then when we find the biomarker that can drive the decisions, it can actually harm our patients," Pellini said. "Because the toxicities overlap, and then it becomes very difficult, because if you cannot give the right drug because of the side effects that are overlapping from something that you shouldn't even have given to begin with, you are harming your patient."

What If a Patient Is Already on the Wrong Treatment?

When a patient has already started immunotherapy or chemotherapy before a targetable mutation is found, the question becomes: What now? Can they switch to a targeted therapy?

The answer, Pellini says, is yes — but with careful timing and close monitoring. Chemotherapy clears the body relatively quickly. Immunotherapy, however, can remain active in the body for months — sometimes up to four months — which creates uncertainty about when it is safe to introduce a targeted drug.

"I would switch," Pellini said. "The question is the timing." In practice, she described waiting at least six to nine weeks after the last immunotherapy dose, continuing chemotherapy in the interim to control the disease, doing pulmonary function tests, providing close monitoring with more frequent scans, and instructing patients to track their oxygen levels at home with a pulse oximeter.

Leah Phillips, who now helps patients facing exactly this situation as an advocate with the Young Lung Cancer Initiative, approaches these conversations with care. "You're not the doctor. You're the patient. You were listening to what you were told to do by someone you trusted," she tells them. "Let's not focus on what happened. Let's focus on what we can do now."

She encourages patients in this situation to seek a second opinion and to connect with advocacy organizations that can help guide them toward centers with experience in their specific mutation.