Immunotherapy is a type of cancer treatment that helps your immune system recognize and attack lung cancer cells. Unlike chemotherapy, which directly kills fast-growing cells, immunotherapy works by removing the “brakes” that cancer puts on your immune response. It has become a standard part of treatment for most stages of lung cancer, and in advanced non-small cell lung cancer, it has nearly doubled five-year survival rates compared to chemotherapy alone.
How Immunotherapy Works Against Lung Cancer
Your immune system is already capable of destroying cancer cells, but tumors have evolved ways to hide. The most common strategy lung cancer cells use is hijacking a set of molecular signals called immune checkpoints. These checkpoints normally prevent your immune system from attacking healthy tissue, but cancer cells exploit them to avoid detection.
The main checkpoint that lung cancer exploits involves a protein called PD-L1. About half of non-small cell lung cancers produce PD-L1 on their surface. When PD-L1 on a tumor cell connects with PD-1 on an immune cell, it sends a “stand down” signal that shuts the immune cell off. Immunotherapy drugs called checkpoint inhibitors block this handshake, allowing immune cells to stay active and attack the tumor.
A second checkpoint, CTLA-4, works earlier in the immune response. CTLA-4 sits on immune cells and acts as a brake during the initial activation phase, before those cells ever reach the tumor. Drugs that block CTLA-4 release this early brake, producing a broader and more aggressive immune response. Some treatment plans combine both types of checkpoint inhibitors to hit cancer’s defenses at two different points.
Who Is Eligible for Immunotherapy
Not every lung cancer patient responds equally to immunotherapy, and the treatment plan depends heavily on a biomarker test called PD-L1 expression. This test measures what percentage of tumor cells display the PD-L1 protein. A biopsy sample is scored, and the result falls into rough categories that guide treatment decisions.
Patients whose tumors have PD-L1 expression of 50% or higher are the strongest candidates for immunotherapy on its own, without chemotherapy. At 1% or above, immunotherapy is still an option but is more commonly paired with chemotherapy. Even patients whose tumors have no detectable PD-L1 can benefit from certain immunotherapy combinations, though the benefit tends to be smaller. In the CheckMate 227 trial, five-year survival for patients with low or absent PD-L1 was 19% with a dual immunotherapy combination, compared to just 7% with chemotherapy alone.
Immunotherapy Alone vs. Combined With Chemotherapy
For advanced non-small cell lung cancer, the two main approaches are immunotherapy by itself or immunotherapy paired with platinum-based chemotherapy. The choice comes down to a few practical factors: how much cancer is present, how quickly it’s growing, how symptomatic you are, and your PD-L1 score.
Many oncologists lean toward immunotherapy alone for patients with high PD-L1 expression (50% or above) and relatively slow-growing disease. The side effect profile is more favorable, tolerability is better, and quality of life tends to be higher compared to adding chemotherapy. For patients with a heavy disease burden, aggressive tumor growth, or significant symptoms, the combination with chemotherapy is often preferred because it can shrink tumors faster while the immune response builds. There are no head-to-head trials definitively settling this question, so the decision is typically a conversation between you and your oncologist about your specific situation.
Five-Year Survival With Immunotherapy
Before immunotherapy became available, the five-year survival rate for metastatic non-small cell lung cancer in the United States was about 7%. Immunotherapy has changed that picture significantly. In the CheckMate 227 trial, which followed patients for at least five years, the combination of two checkpoint inhibitors produced a five-year survival rate of 24% in patients whose tumors had PD-L1 of 1% or higher. That’s nearly triple the chemotherapy rate of 14% in the same group.
Even a single checkpoint inhibitor improved outcomes, with a 17% five-year survival rate in that population. For patients with tumors showing less than 1% PD-L1, the dual combination still reached 19% at five years versus 7% for chemotherapy. These numbers represent a meaningful shift: while most patients with advanced disease still face a difficult prognosis, a substantially larger fraction are now living years rather than months.
Immunotherapy for Small Cell Lung Cancer
Small cell lung cancer, which accounts for about 15% of lung cancers, is aggressive and fast-growing. Immunotherapy plays a different role here. It is not used alone but rather added to standard chemotherapy (typically carboplatin and etoposide) as a first-line treatment for extensive-stage disease.
In the IMpower133 trial of 403 patients, adding the checkpoint inhibitor atezolizumab to chemotherapy extended median overall survival from 10.3 months to 12.3 months, with a 60% response rate. The CASPIAN trial showed similar results with durvalumab, pushing median survival from 10.5 to 12.9 months. More recent trials have shown even larger gains. The ETER701 trial, which combined a checkpoint inhibitor with an anti-blood-vessel drug and chemotherapy, reached a median survival of 19.3 months compared to 13.3 months with the control regimen. While these improvements are measured in months rather than years, they represent meaningful progress for a cancer type that had seen little advancement in decades.
Immunotherapy Before and After Surgery
Immunotherapy is no longer limited to advanced or metastatic disease. It is increasingly used in earlier-stage lung cancer, either before surgery (neoadjuvant) or after surgery (adjuvant), to reduce the chance of recurrence.
In the neoadjuvant setting, immunotherapy is given for a few cycles before the tumor is removed. The goal is to shrink the tumor and prime the immune system to hunt down any remaining cancer cells after surgery. Trials have enrolled patients with stages IB through IIIB disease. Higher PD-L1 expression on the tumor correlates with better responses to pre-surgery immunotherapy, though some patients with no PD-L1 expression still achieve significant tumor shrinkage.
After surgery, adjuvant immunotherapy aims to mop up microscopic disease that might otherwise cause a relapse. In the IMpower010 trial, patients with stage II to IIIA disease who received atezolizumab after surgery and standard chemotherapy had a 34% lower risk of their cancer returning, provided their tumors expressed PD-L1 on at least 1% of cells. Even across all patients regardless of PD-L1 status, the risk of recurrence or death dropped by 21%.
How Long Treatment Lasts
Most current treatment protocols set a maximum duration of two years (24 months) for immunotherapy, assuming the cancer hasn’t progressed and side effects remain manageable. This applies to the major checkpoint inhibitors used in first-line and later-line settings. Before this became standard, earlier trials simply continued treatment until the cancer grew or side effects became intolerable, with no upper limit.
The question of whether stopping at two years is safe remains an active discussion. Data from the CheckMate 153 study explored what happens when patients stop after just one year. Patients who continued treatment beyond one year had a median progression-free survival of 24.7 months, compared to 9.4 months for those who stopped. Overall survival was also longer in the group that continued. Based on these results, stopping at one year appears to be too early for most patients.
At the two-year mark, the picture is less clear. Lifelong immunotherapy appears unnecessary and carries ongoing cost and side effect burden. But stopping at two years in patients who are responding well is not yet universally accepted. Your oncologist will weigh your response, side effects, and individual risk when deciding whether to stop or continue.
Side Effects to Watch For
Because immunotherapy works by activating the immune system, its side effects are fundamentally different from chemotherapy. Instead of hair loss and nausea, the main risks involve the immune system attacking healthy tissues. These are called immune-related adverse events, and they can affect nearly any organ.
The most concerning side effect in lung cancer patients is pneumonitis, an inflammation of the lungs. In one study of 122 patients, about 20% experienced severe immune-related side effects, and pneumonitis accounted for nearly two-thirds of those cases. It was also responsible for the vast majority of treatment-related deaths: seven of eight fatal immune-related events in that study were caused by pneumonitis. Symptoms include new or worsening shortness of breath, cough, and chest pain. Early detection is critical because pneumonitis is treatable when caught early but can be fatal if it progresses.
Other immune-related side effects include inflammation of the colon (causing diarrhea and abdominal pain), thyroid problems (either overactive or underactive), skin rashes, liver inflammation, and joint pain. Most of these are manageable with temporary pauses in treatment and medications that calm the immune response. Mild side effects are common, but severe ones requiring treatment interruption occur in roughly one in five patients.