Please note that this summary only contains information from the full scientific abstract: View ESMO Scientific Abstract

Long-term effectiveness of palbociclib plus letrozole in post-menopausal women with metastatic breast cancer

Date of summary: September 2019

Review of medical records


Study date: February 2015


End date: February 2019


The full title of this abstract is: Real-world effectiveness of first-line palbociclib + letrozole for metastatic breast cancer 4 years post approval in the US

The study drugs are approved to treat the condition under study that is discussed in this summary.


Researchers must look at the results of many types of studies to understand whether a study drug works, how it works, and whether it is safe to prescribe to patients.

This summary reports the results of only one study. The results of this study might be different from the results of other studies that the researchers look at.


More information can be found in the scientific
abstract of this study, which you can access here:
View ESMO Scientific Abstract

What did this study look at?

  • People can have diferent types of breast cancer. Knowing which type of breast cancer a person has can help the doctor and patient choose the most appropriate treatment option.
  • Advanced breast cancer is cancer that has spread within or beyond the breast. If the cancer has spread beyond the breast, it is also called metastatic breast cancer.
    • Some breast cancers are sensitive to hormones such as estrogen, which cause the cancers to grow. People with this type of breast cancer have hormone receptor positive (HR+) cancer; people without it have hormone receptor negative (HR−) cancer.
    • Changes to genes within some breast cancers cause cells to make too much of a protein that stimulates their growth. This protein is called human epidermal growth factor receptor 2 (HER2 for short). People with this type of breast cancer have HER2+ cancer; people without it have HER2− cancer.
  • Palbociclib + hormone therapy is an approved treatment in Europe for women with HR+/HER2− advanced or metastatic breast cancer.
    • Palbociclib + hormone therapy may stop cancer cells from multiplying, which can help slow down or stop the spread of the cancer.
    • Letrozole is a hormone therapy used with palbociclib. Letrozole lowers the amount of estrogen the body produces, which helps slow or stop cancer growth.
  • In this study, researchers looked at information from the medical records of post-menopausal women in the United States with metastatic HR+/HER2− breast cancer.
  • This study is a ‘real-world’ study, not a clinical trial.
    • In clinical trials, the treatments that people receive are often tightly controlled so that researchers can test the effect of a new drug.
    • In real-world studies, people receive approved drugs in a normal clinical practice This helps researchers understand how drugs are used in real life.
  • This summary describes how well treatment with palbociclib + letrozole worked in these women over a 4-year period.

Who took part in this study?

What were the results of the study?

More results from this study can be found here:
View ESMO Scientific Abstract

What were the main conclusions reported by the researchers?

  • This study provides real-world insights into palbociclib + letrozole as a treatment for women with metastatic HR+/HER2− breast cancer.
  • The majority of women in the study benefited from this treatment in the long term.
  • These results support the findings of previous clinical trials.
  • This is a small real-world study. More research is needed.

Who sponsored this study?

Pfizer Inc.
235 East 42nd Street NY,
NY 10017
Phone (United States): +1 212-733-2323

Pfizer would like to thank all of the women who took part in this study.

Click to show further information on the study and clinical trials in general