Transcript

The transcript has been lightly edited for grammatical purposes.

What’s the difference between duration of response and progression-survival in cancer care?

Dr. Stephen Liu: We often use terms like duration of response and progression-free survival. These are clinical trial terms that essentially try to answer, how long does this drug work?

When we say “response,” you might think it means the tumor gets smaller, and that’s true. In a clinical trial, a response has a specific definition: the tumor must decrease in volume by at least 30%, measured on two consecutive scans. Now, I don’t think it’s important for patients to memorize the exact definition, but it’s helpful to know that a response means we’ve seen a significant reduction in tumor size.

Then we look at how long that response lasts. Does the cancer shrink temporarily and then quickly grow back? Or does that reduction last for years? Obviously, the longer the duration of response, the better.

Progression-free survival is a little different. It measures how long it takes until the cancer starts to grow again. Duration of response only applies to people who meet that 30% reduction threshold. For example, if someone’s tumor shrinks by 10% and that smaller size is maintained for five years, that’s still incredibly valuable, but it wouldn’t count as a “response” in the clinical trial sense. Instead, that benefit is captured under progression-free survival.

So, progression-free survival looks at all patients in a trial and measures the average time until their cancer grows or spreads significantly. I think it’s often the better general measure. But in the end, both terms really speak to the same question: How long will this treatment help before we need to consider something else?

Chapter 2 of Precision Minute with Dr. Stephen Liu is now live. You can view the full video here.