The breast cancer therapy Ibrance (palbociclib) offers no more benefits than treatments with which it was compared in clinical trials, according to an analysis by the German Institute for Quality and Efficiency in Health Care.

In addition, the institute’s dossier assessment, which covers a new therapy’s benefits once it reaches the market, concluded that data was inadequate or even missing for several treatment groups, including those receiving Ibrance as a second-line therapy. That makes an accurate assessment impossible, the institute said.

Ibrance is approved in the United States and Europe for women with HR-positive, HER2-negative locally advanced or metastatic breast cancer. The approvals are for a combination of Ibrance and either an aromatase inhibitor or Faslodex (fulvestrant) in women who received endocrine — or hormone — therapy earlier.

In examining possible benefits of the treatment, institute researchers looked at different patient groups, including both premenopausal and postmenopausal women, and women with previous treatments that were unsuccessful.

Pfizer, which manufactures Ibrance, had conducted two randomized clinical trials in postmenopausal women, who took it as a first-line treatment. The trials compared a combination of Ibrance and Femara (letrozole) with the use of Femara alone.

Researchers found no differences in benefits between the two groups when they compared the women’s health status, health-related quality of life, and discontinuation of treatment due to side effects. Women treated with the Ibrance combination had a longer progression-free survival, but overall survival was similar in the two groups.

Overall survival can be difficult to assess accurately in the short term, however, so cancer trials often use progression-free survival as a substitute measure.

But the institute noted that using progression-free survival as a substitute measure needs to be validated in order to prove that the drug provides additional benefits. “It is a good sign when the tumor does not continue to grow or even shrinks under a new treatment. It is not certain, however, that patients actually survive longer,” the researchers said in a press release.

Although Pfizer did a validation analysis, the institute pointed out that its researchers used studies that compared single treatments, while Ibrance is approved only as a combination therapy. Moreover, the validation analysis did not include studies of Ibrance, the institute said.

The institute decided to perform a new analysis that included data from the Ibrance trials. It concluded that progression-free survival was not a valid substitute for overall survival.

In addition, combination treatment with Ibrance produced more severe side effects than therapy with Femara only, according to the institute report. Since the increase in side effects was not accompanied by any advantages, the institute argued that Ibrance actually provides less benefit overall.

It also said Pfizer’s dossier did not include data on first-line treatment of premenopausal women or women in menopause. Finally, the institute said it was unable to assess Ibrance’s benefit as a second- or later-line treatment in women before, during, or after menopause because Pfizer’s researchers had failed to compare it with other therapies.