KEYNOTE-590: What the Esophageal Cancer Trial Found

The question this trial set out to answer

KEYNOTE-590 asked whether adding an immune drug to chemotherapy helps people with advanced esophageal cancer live longer. The short answer is yes. The longer answer is that the gain was small on average and much larger in one group. Which group a tumor falls into matters more than the headline.

Who joined, and the test that sorted them

Between July 2017 and June 2019, 1,020 people were screened and 749 joined. Of those, 373 got pembrolizumab plus chemotherapy. The other 376 got a placebo plus the same chemotherapy. All had advanced esophageal cancer, or a Siewert type 1 cancer where the esophagus meets the stomach. None had been treated for it yet.

People could join whatever their PD-L1 result. PD-L1 is a protein found on some tumor cells and nearby cells. The score used here is the combined positive score, or CPS. A higher score means immune drugs are more likely to work. The trial then compared the groups by score.

The chemotherapy was 5-fluorouracil plus cisplatin. Other hospitals and countries use other combinations.

Survival, group by group

Across everyone in the trial, half the pembrolizumab group were still alive at 12.4 months. With chemotherapy alone, that figure was 9.8 months. The hazard ratio was 0.73 (95% CI 0.62 to 0.86; p<0.0001). In plain terms, about a 27% lower risk of dying at any moment.

Squamous-cell tumors with a CPS of 10 or more did much better: 13.9 months against 8.8 months, hazard ratio 0.57 (95% CI 0.43 to 0.75; p<0.0001).

Time before the cancer grew barely moved. It was 6.3 months against 5.8 months across everyone, hazard ratio 0.65 (95% CI 0.55 to 0.76). In the high-score group it was 7.5 months against 5.5 months.

Why the average is the wrong number to carry away

The gain for the whole trial was 2.6 months on the median. In high-PD-L1 squamous tumors it was 5.1 months, close to double. An average of those two describes almost nobody.

That is why this trial helped push PD-L1 testing into everyday esophageal cancer care. The score does not just describe a tumor. It changes what the extra drug is likely to be worth.

What the side effects cost

Severe problems were common in both groups. Treatment-related events of grade 3 or worse hit 72% on the combination and 68% on chemotherapy alone. So the immune drug added little on top. But the starting burden was already heavy: nearly three in four people had a severe problem of some kind.

What this trial cannot tell you

• It cannot promise anyone 2.6 extra months. A median describes a group, not a person.
• It says nothing about pembrolizumab used alone, or used later in the illness.
• The chemotherapy underneath was fixed. Results could differ with a different backbone.
• Its strongest findings are in squamous-cell tumors. The evidence in adenocarcinoma is thinner.

Worth asking if this affects you

• Has my tumor been given a PD-L1 combined positive score, and what was it?
• Is my tumor squamous cell or adenocarcinoma?
• Which chemotherapy would sit underneath the immune drug here?
• How soon would we know whether it is working for me?

Sources

This article was written from the sources below, which were checked on the source-check date shown above.

• Lancet: Pembrolizumab plus chemotherapy vs chemotherapy for first-line advanced esophageal cancer (KEYNOTE-590) (primary)

How this article was prepared

Prepared by Cancer Explained's AI-assisted editorial system and checked against the sources listed below. This article has not been reviewed by a healthcare professional unless a named reviewer is specifically shown.

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