Immunotherapy has meaningfully improved survival for lung cancer patients, but the degree of success varies widely depending on the type of lung cancer, how advanced it is, and individual biological factors. In advanced non-small cell lung cancer (NSCLC), about 18% to 22% of patients treated with immunotherapy plus chemotherapy are alive at five years. That’s a significant improvement over the pre-immunotherapy era, when long-term survival was closer to 5%. Still, roughly 70% to 85% of patients either don’t respond to immunotherapy at all or eventually stop responding after an initial benefit.
Five-Year Survival Numbers
The clearest picture of immunotherapy’s success comes from five-year survival data. For patients with metastatic NSCLC whose tumors have high levels of a protein called PD-L1 (a marker that predicts how well immunotherapy will work), treatment with pembrolizumab nearly doubled the five-year survival rate compared to chemotherapy alone: 31.9% versus 16.3%. Median overall survival, the point at which half of patients are still alive, was about 26 months with immunotherapy compared to 13 months with chemotherapy.
For the broader population of advanced NSCLC patients (including those with lower PD-L1 levels), the numbers are more modest. Real-world data show five-year survival rates of roughly 18% to 22% when immunotherapy is combined with chemotherapy, depending on the specific subtype. When immunotherapy was used alone as a second-line treatment in earlier trials, the five-year survival rate was about 13.4%, compared to just 2.6% for chemotherapy alone. These aren’t cure rates, but they represent a genuine shift: a meaningful minority of patients with advanced disease are now living years longer than was previously possible.
How PD-L1 Levels Shape Your Odds
Not all lung cancers respond equally to immunotherapy, and PD-L1 expression is one of the strongest predictors. PD-L1 is a protein that tumors use to hide from the immune system. Immunotherapy drugs block this protein, exposing the cancer to immune attack. The more PD-L1 a tumor produces, the better immunotherapy tends to work.
When immunotherapy is used as a first treatment, about 40% of patients with high PD-L1 expression (50% or greater) see their tumors shrink. For patients with moderate PD-L1 (1% to 49%), that number drops to roughly 17%. And for patients with little to no PD-L1 (less than 1%), only about 8% see a measurable tumor response. These response rates explain why doctors test PD-L1 levels before starting treatment. They help set expectations and guide decisions about whether immunotherapy should be used alone or paired with chemotherapy.
Combination Therapy Results
Combining two different immunotherapy drugs can improve outcomes, particularly for patients whose tumors have low PD-L1. In a major clinical trial, patients who received nivolumab plus ipilimumab (which target two different immune checkpoints) lived a median of 17.1 months, compared to 13.9 months with chemotherapy alone. The two-year survival rate was 40% versus about 33%.
One of the most striking findings was how long responses lasted. When patients did respond to the combination, their response lasted a median of 23.2 months, compared to just 6.2 months with chemotherapy. This durability is one of immunotherapy’s most important advantages. Chemotherapy responses tend to fade quickly, while immunotherapy can produce lasting remissions in a subset of patients. Patients who remained progression-free at two years had an 82% chance of still being alive at five years, and those who reached four years without progression had a 100% survival rate at five years.
Early-Stage Lung Cancer
Immunotherapy isn’t only for advanced disease. When given before surgery (called neoadjuvant therapy), immunotherapy combined with chemotherapy can eliminate all detectable cancer cells in the surgical specimen. A large meta-analysis found this complete pathological response occurred in about 34% of patients. That’s a meaningful number, because patients who achieve this kind of response tend to have significantly lower rates of recurrence. This approach is changing how operable lung cancer is treated, giving patients with earlier-stage disease access to immunotherapy’s benefits before their cancer has a chance to spread further.
Small Cell Lung Cancer
Small cell lung cancer (SCLC) is less common but far more aggressive than NSCLC. Immunotherapy’s impact here has been more modest. For extensive-stage SCLC (cancer that has spread beyond the chest), adding immunotherapy to chemotherapy extends median survival to approximately 12 to 13 months. For limited-stage SCLC (confined to one side of the chest), the addition of durvalumab has pushed median survival up to nearly 56 months, a substantial improvement. While SCLC remains difficult to treat, immunotherapy has become part of standard first-line therapy for both stages.
Why Most Patients Don’t Respond
Despite the progress, the majority of lung cancer patients don’t experience lasting benefit from immunotherapy. Approximately 70% to 85% of patients either show no response from the start (primary resistance) or respond initially but then relapse as their cancer finds new ways to evade the immune system (acquired resistance). The reasons are complex and vary from person to person. Some tumors create an environment around themselves that suppresses immune cells. Others have very few genetic mutations, which means the immune system has fewer abnormal targets to recognize. Still others may lack the right immune cells in and around the tumor to mount an effective attack.
PD-L1 testing helps predict who will respond, but it’s imperfect. Some patients with low PD-L1 do respond, and some with high PD-L1 don’t. Researchers are working on better ways to identify who will benefit, including testing for tumor mutation burden and analyzing the types of immune cells present in tumor tissue.
Side Effects and Tolerability
Immunotherapy is generally better tolerated than traditional chemotherapy, but it comes with its own set of side effects. Because these drugs activate the immune system, they can cause the immune system to attack healthy tissues. These immune-related side effects occur in roughly 22% of patients across all severity levels, with about 4% experiencing serious (high-grade) reactions. The most commonly affected organs include the skin, lungs, liver, thyroid, and intestines.
In a real-world study of patients who had been on immunotherapy for at least 18 months, about 22% eventually stopped treatment due to side effects, often because of chronic effects that patients found disabling rather than acute emergencies. Another 46% stopped because their doctors felt there was no proven benefit to continuing beyond two years, and 20% chose to stop on their own. This points to an ongoing question in the field: how long patients should continue immunotherapy once their cancer is controlled, since the optimal treatment duration remains unclear.