Breast cancer

07 April 2014

Pfizer drug increases breast cancer survival time

A study found that women treated with hormone drug letrozole plus Pfizer's new palbociclib lived almost twice as long as women treated with letrozole alone.

Pfizer Inc's experimental breast cancer drug in a clinical trial nearly doubled the amount of time patients lived without their disease getting worse, but overall survival was not yet shown to be statistically significant, researchers said.

The Phase 2 study, which involved women with the most common form of breast cancer, found that those treated with hormone drug letrozole plus Pfizer's palbociclib lived for an average of 20.2 months before their cancer progressed, compared with 10.2 months for patients given letrozole alone.

The US Food and Drug Administration has granted "breakthrough" status for palbociclib. Pfizer is still discussing a regulatory pathway for the drug and has not decided whether to seek accelerated approval based on Phase 2 trial results, said Mace Rothenberg, chief medical officer for Pfizer's oncology unit.

Read: Breast cancer: a single mom's journey to recovery

Important experimental drug

Palbociclib is viewed as one of the company's most important experimental drugs that some analysts believe could eventually claim annual sales of more than $5 billion, if approved by regulators.

The trial tested the pill, which targets proteins involved in cell division, in post-menopausal women with locally advanced or newly diagnosed breast cancer that had spread to other parts of the body.

The women had cancer that was both oestrogens receptor positive – meaning tumours grow in response to oestrogens – and HER2-negative, meaning that the HER2 protein is not causing the cancer. Such patients make up about 60 percent of advanced breast cancer cases.

Read: Living with breast cancer

Still too early

The initial data showed overall survival of 37.5 months for the combination treatment, compared with 33.3 months for patients given just letrozole, an oestrogens blocker sold by Novartis AG under the brand name Femara.

Researchers said that because only about 30 patients in each arm of the 165-patient trial had died it was still too early to define the drug's impact on survival.

Read: Treating breast cancer with surgery

"The curves are starting to separate ... It hasn't reached statistical significance, but patients are still being followed," said Dr. Richard Finn, associate professor of medicine at the University of California, Los Angeles, and a lead author of the study.

Side effects seen in the trial, including low blood cell counts and fatigue, were manageable, he said in a telephone interview ahead of the study's presentation in San Diego at a meeting of the American Association for Cancer Research.

Drug really shows promise

Hormonal agents, like Femara, have extended survival for women with oestrogens-positive, HER2 negative breast cancer, but there have been no big advances in treatment for nearly two decades, said Dr Judy Garber, a breast cancer specialist at Boston's Dana-Farber Cancer Institute and AACR representative not involved in the palbociclib trial.

"This is garden variety breast cancer," she said. "When it recurs, all we really have are other hormonal agents ... This is the first new drug to really show promise."

Read: Breast cancer: myths and facts

Pfizer is conducting Phase 3 trials in breast cancer patients as well as earlier-stage trials in other types of cancer.

Companies trying to develop treatments similar to palbociclib include Novartis and Eli Lilly & Co, which presented Phase 1 data at the AACR meeting.

The small trial found that Lilly's drug, LY2835219, used on its own, shrank tumours in 25% of women with metastatic oestrogen-positive breast cancer, and stabilized the cancer in 55% of the same group of women.

Breast from Shutterstock

Read more:

Drug keeps breast cancer at bay
Experimental drug fights breast cancer
Breast cancer drug switch found



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Breast cancer expert

Dr Gudgeon qualified in Birmingham, England, in 1968. She has more than 40 years experience in oncology, and in 1994 she founded her practice, Cape Breast Care, where she treats benign and malignant breast cancers. Dr Boeddinghaus obtained her qualification at UCT Medical School in 1994 and her MRCP in London in 1998. She has worked extensively in the field of oncology and has a special interest in the hormonal management of breast cancer. She now works with Dr Gudgeon at Cape Breast Care. Read more.

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