How much does Perjeta add to Herceptin postsurgery? Depends how you slice it

Adding Roche's Perjeta to Herceptin triggered a 19% lower chance of developing invasive breast cancer in some patients.

CHICAGO—Since March, when Roche announced that adding Perjeta to blockbuster Herceptin staved off postsurgery breast cancer progression in early-stage patients, the question has been “By how much?” As it turns out, the answer is, “Not a lot.”

At a three-year follow-up, 94.1% of those receiving both Perjeta and Herceptin hadn’t developed an invasive form of the HER2-positive disease, compared with 93.2% of women taking Herceptin solo—a difference of just one percentage point.

But thanks to an already-favorable prognosis for patients on Herceptin, that difference translated into a 19% lower chance of developing invasive breast cancer. And that's something Dietmar Berger, Roche’s global head of clinical development in hematology and oncology, called “really important.”

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“If you progress in the adjuvant, then you’re considered metastatic, and then it’s considered palliative, so this is a really important result that the risk is reduced by 19%,” he said in an interview.

The Perjeta-Herceptin combo is now approved to treat patients with HER2-positive breast cancer before surgery and also to treat patients with metastatic HER2-positive disease. The new data, by contrast, are for patients at earlier stages of the disease, but after surgery.

In the higher-risk subgroups—such as hormone-receptor negative patients—the combo performed even better. “[W]e see even more benefit now” in those higher-risk patients, Berger said. And higher-risk subgroups make up some 70% of the overall patient population.

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“That’s where the largest unmet medical need is, and that’s where the benefit of dual targeting will be the largest,” Berger pointed out. How the drugs are going to be used in the clinic is “really a discussion of risk” and how patients and their physicians talk about it, he added. “That’s really a very nuanced discussion.”

Meanwhile, it’s not a bad time for Roche to be getting some positive data—especially data that could potentially result in a new indication. The cancer giant’s older medications have proven prime targets for biosimilar drugmakers, and Herceptin is looking particularly vulnerable: Mylan and Biocon are hard at work on the leading candidate, and over the weekend, Celltrion reported that its version had stacked up to Roche’s product in a late-stage trial, too.