KEYNOTE-522 Updated Results: Pembrolizumab Plus Chemotherapy Followed by Pembrolizumab or Placebo for Early-Stage TNBC
Dr. Tolaney: At ESMO this year, we also saw updated data from KEYNOTE-522. This was the trial that really established the role of pembrolizumab in the setting of early-stage triple-negative breast cancer, where we had previously seen that adding pembro to an anthracycline–platinum–taxane backbone improved pathologic complete response rates and actually improved event-free survival. The data that we've previously seen represent 3 years of follow-up, and now we have data that came out at ESMO with 5 years of follow-up.
Continued improvement in event-free survival
In fact, what we see is continued improvement in event-free survival from the addition of pembrolizumab to chemotherapy, with a hazard ratio that was quite consistent with the original presentation. The new things in my mind that are quite relevant are that the events do seem to plateau at this 5-year mark. And, I think, that's consistent with what we would expect because most recurrences of triple-negative disease do occur early, and these data are really reflective of what we will see for events in this trial. And, the fact that the data continue to show this robust benefit, I think, is very reassuring.
Ongoing benefit in the adjuvant setting from pembrolizumab
I think the other thing that is of interest is that, when we looked at outcomes by patients who achieved pathologic complete response compared to those who had residual disease, we started to see more separation of the curves between the patients who had PCR who had received pembro compared to not. Before, it had seemed like the curves were overlapping; but, now, again we see this separation. And, in fact, they showed a hazard ratio between the two curves suggesting that it was around 0.66. To me, that suggests that achieving a PCR doesn't always mean the same thing. So, if someone got a PCR with pembro and we compare outcomes to someone who got a PCR with just chemo, we are seeing that people are having fewer events if they had the PCR with pembro, suggesting that the relationship between PCR and event-free survival is a little different when someone's had immunotherapy, that there continues to be benefit in that adjuvant setting from having received that pembrolizumab. And it is really helping prevent further events.
So, I think these are really interesting data, and, again, really just confirming that pembrolizumab does remain standard of care for early-stage II to III triple-negative breast cancer patients.
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