Keytruda’s success rate varies significantly depending on the type of cancer, how advanced it is, and specific biological markers on the tumor. In advanced lung cancer, roughly 62% of patients see their tumors shrink when Keytruda is combined with chemotherapy. In melanoma, about 38% of patients are still alive seven years after starting treatment. These numbers represent a meaningful improvement over older therapies, but they also make clear that Keytruda works far better for some patients than others.
Lung Cancer Response Rates
Non-small cell lung cancer is the most common use for Keytruda, and the data here is the most mature. In the KEYNOTE-407 trial, which studied patients with advanced squamous lung cancer, 62.2% of patients treated with Keytruda plus chemotherapy saw their tumors shrink measurably, compared to 38.8% with chemotherapy alone. That’s a substantial difference in initial response.
Long-term survival tells a more sobering but still encouraging story. Five-year survival for the Keytruda combination group was 18.4%, versus 9.7% for chemotherapy alone. While fewer than one in five patients were alive at five years, Keytruda nearly doubled the odds of getting there. In patients whose tumors had high levels of a protein called PD-L1 (50% or more of tumor cells), survival was even better. A separate five-year study found that Keytruda reduced the risk of death by 32% compared to chemotherapy in patients with at least some PD-L1 expression on their tumors.
Why PD-L1 Levels Matter So Much
Keytruda works by blocking a protein that tumors use to hide from the immune system. Tumors that rely heavily on this cloaking mechanism, measured by something called a PD-L1 score, tend to respond much better. When PD-L1 expression is 50% or higher, roughly 45% of lung cancer patients respond to Keytruda alone, without needing chemotherapy at all. As PD-L1 levels drop, so does the likelihood of a strong response, which is why oncologists test for this marker before recommending treatment.
This biomarker testing is one of the most important factors in predicting whether Keytruda will work for a given patient. A high PD-L1 score doesn’t guarantee success, and a low score doesn’t rule it out, but it shifts the odds considerably.
Melanoma: The Longest Track Record
Keytruda was first approved for advanced melanoma, so the long-term data here stretches further than for any other cancer type. In the landmark KEYNOTE-006 trial, 37.8% of patients treated with Keytruda were alive at seven years, compared to 25.3% of those treated with ipilimumab, an older immunotherapy drug. For a cancer that was once considered a rapid death sentence once it spread, these numbers represent a genuine shift in prognosis.
Melanoma also tends to be one of the more immunotherapy-responsive cancers, which is why the numbers here are higher than in many other tumor types. Some melanoma patients who respond to Keytruda remain in remission for years after stopping treatment, though this isn’t universal.
Triple-Negative Breast Cancer
In triple-negative breast cancer, an aggressive subtype with historically limited treatment options, Keytruda is used before surgery to shrink tumors. The FDA approved it based on data showing a pathologic complete response rate of 63% when combined with chemotherapy, meaning nearly two-thirds of patients had no detectable cancer remaining in their surgical tissue. Chemotherapy alone achieved this in 56% of patients. The 7-percentage-point improvement may sound modest, but in a cancer this aggressive, it translates to meaningfully better long-term outcomes.
Colorectal Cancer With Specific Genetic Features
Keytruda is approved for colorectal cancers that have a specific genetic feature: microsatellite instability-high (MSI-H) or mismatch repair deficiency. Only about 5% to 15% of colorectal cancers have this characteristic, but for those that do, Keytruda can be remarkably effective. In the KEYNOTE-177 trial, the median duration of response was 75.4 months (over six years) with Keytruda, compared to just 10.6 months with chemotherapy. When Keytruda works in these patients, it tends to work for a very long time.
For colorectal cancers without this genetic feature, Keytruda is not effective. This is one of the clearest examples of how the drug’s success depends entirely on tumor biology.
Kidney and Bladder Cancer
In advanced kidney cancer, Keytruda combined with a targeted therapy called axitinib produced a 12-month survival rate of 90%, compared to 78% with the previous standard treatment. This combination is now a first-line option for advanced renal cell carcinoma.
The most recent FDA approval, granted in November 2025, added muscle-invasive bladder cancer to Keytruda’s list of uses. In patients who couldn’t receive standard cisplatin chemotherapy, combining Keytruda with another drug cut the risk of disease progression or death by 60% compared to surgery alone, and halved the risk of death overall. Median survival in the Keytruda group hadn’t even been reached at the time of analysis, meaning more than half the patients were still alive when results were published.
How Many Cancers Keytruda Now Covers
Keytruda is approved for more cancer types than any other single drug. Its indications span lung, melanoma, head and neck, bladder, breast, colorectal, cervical, liver, stomach, esophageal, kidney, and endometrial cancers, among others. Two dosing schedules are available: one administered every three weeks and another every six weeks. The FDA approved the less frequent schedule based on modeling data showing equivalent drug exposure, giving patients flexibility without sacrificing effectiveness.
Side Effects and Tolerability
Because Keytruda activates 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. Lung inflammation led to treatment discontinuation in 1.3% of patients in a large safety analysis of nearly 2,800 people. Colon inflammation caused 0.5% to stop, and liver inflammation caused 0.2% to stop. Thyroid problems are relatively common but rarely serious enough to require stopping treatment.
Overall, the rate of permanent discontinuation due to any single immune-related side effect is low, generally under 2%. Most patients tolerate Keytruda well enough to continue their full course of treatment, and many side effects are manageable with temporary use of steroids or hormone replacement. This tolerability profile is one reason Keytruda has replaced chemotherapy as a first-line option in several cancer types.