News > Palbociclib failed to improve outcomes in early-stage disease

Palbociclib failed to improve outcomes in early-stage disease

Researchers confused, disappointed at results of much-anticipated phase III trial

general_content

Presented on December 7 at the San Antonio Breast Cancer Symposium, the findings show that palbociclib does not improve outcomes for people with early-stage hormone-positive (HR+) HER2- breast cancer.  

Preliminary findings of the trial were published in Lancet in July. The results were released concurrent with this week’s presentation in the Journal of Clinical Oncology.  

Background 

Now that researchers have seen how effective CDK inhibitors can be in metastatic breast cancer, they wanted to explore whether these medicines could work at preventing people with early-stage disease from a breast cancer recurrence. Palbociclib Collaborative Adjuvant Study (PALLAS) is among several studies asking that question.  

CDK inhibitors are a form of targeted therapy used to treat metastatic breast cancer. Many people prefer targeted therapy medicines because they cause fewer side effects than chemotherapy and often can be taken in pill form.  

CDK 4/6 inhibitors work by stopping cells from growing and dividing. The introduction of CDK 4/6 drugs in 2015 filled a gap in treatment options for HR+/HER2- breast cancer, particularly metastatic breast cancer.  

Endocrine (or hormone) therapy is a standard treatment after surgery for hormone-positive breast cancer. Different medicines of this type are available.  

Results 

The PALLAS phase III trial randomized participants to two groups – one that received palbociclib along with hormone (endocrine therapy). The other (control) group received endocrine therapy on its own.  

The average age of people in the trial was 52. Most had stage IIB or stage III breast cancer. All had ER+/HER2- breast cancer. Eighty-five percent were previously treated with chemotherapy. Fifty-nine percent were considered high risk. The average time at follow up was 31 months.  

After two years, the people in both groups had nearly the same results across all endpoints. 

Some participants appeared to improve initially but the data did not hold up. There were no differences in subgroups. No new side effects were identified.  

The clinical trial itself drew praise for its size and organization. Within three years, investigators exceeded trial goals by recruiting 5,800 participants at 406 centers in 21 countries. 

What it means for people with early-stage disease 

Based on these results, there is no reason to prescribe palbociclib in combination with endocrine therapy after surgery for early-stage HR+ breast cancer. Endocrine therapy alone is still recommended.  

The results of this study were both confusing and disappointing to the research community. It is unclear why these findings differed from the results of other trials of CDK inhibitors, particularly the monarchE trial, which reported favorable preliminary results this year. 

The phase III monarchE trial tests the CDK 4/6 inhibitor abemaciclib with endocrine therapy for early-stage HR+/HER2- disease. It is similar in size and scope to the PALLAS trial. The drugs themselves work similarly.

Looking for differences, the study team noted that the dose schedule is not the same. Abemaciclib in the monarchE trial is taken without a break, whereas palbociclib was given on a three weeks on/one week off schedule. The lead investigator was not prepared to say the differences in outcomes were due to this but suggested it bears further study. 

The PALLAS results do not have implications for metastatic breast cancer although it was noted that no new or worsening side effects were observed.  

Look for further studies to address unanswered questions.  

related_resources_article_carousel

Related resources

Abemaciclib

07/25/22 | BY: Tiffany Avery

Abemaciclib (Verzenio) is a targeted therapy approved by the Food and Drug Administration to treat hormone receptor-positive breast cancer.

Read More | 8 Min. Read

Targeted therapy for hormone-receptor positive breast cancer

07/25/22 | BY: Tiffany Avery

Targeted therapies are treatments that target specific proteins or markers on or within cancer cells that help cancer cells grow. There are many different kinds of targeted therapy. Hormonal therapy is a type of targeted therapy because it targets hormones that are active in cancer growth.

Read More | 6 Min. Read

Olaparib

05/22/22 | BY: Debu Tripathy

Olaparib (Lynparza) is a targeted therapy approved by the Food and Drug Administration that is used to treat early-stage or metastatic breast cancer that is either hormone receptor-positive and HER2-negative, or triple-negative, in people with an inherited BRCA gene mutation who have already been treated with chemotherapy.

Read More | 8 Min. Read

PARP inhibitors for BRCA-positive breast cancer

05/22/22 | BY: Debu Tripathy

Read More | 8 Min. Read

Neratinib

03/25/21 | BY: Tiffany Avery

Neratinib (Nerlynx) is a targeted therapy for people with HER2-positive breast cancer. It is the first medicine for people with HER2-positive breast cancer approved as extended therapy, meaning that for early-stage disease, it is given after primary treatment ends to lower the risk of cancer coming back.

Read More | 6 Min. Read

Pertuzumab

03/25/21 | BY: Tiffany Avery

Pertuzumab (Perjeta) is a targeted therapy used to treat early-stage and metastatic HER2-positive breast cancer. Pertuzumab is a monoclonal antibody, a type of medicine made in a lab that targets a specific protein, HER2, produced on the outside of a cell. It falls in a class of medicines called targeted therapies.

Read More | 6 Min. Read

Trastuzumab

03/25/21 | BY: Tiffany Avery

The medicine trastuzumab (Herceptin and biosimilars) is the most common medicine used to treat HER2-positive breast cancer. It is a monoclonal antibody, a medicine made in a lab that attacks a specific protein produced on the outside of a cell. It falls in a class of medicines called targeted therapies.

Read More | 7 Min. Read

Trastuzumab deruxtecan

03/25/21 | BY: Tiffany Avery

Trastuzumab deruxtecan (Enhertu) is an antibody drug conjugate approved to treat people with metastatic, HER2-positive, hormone receptor-negative breast cancer that has grown after at least two past treatments.

Read More | 2 Min. Read

Tucatinib

03/25/21 | BY: Tiffany Avery

Tucatinib (Tukysa) is a tyrosine kinase inhibitor used to treat metastatic, HER2-postive breast cancer. It is given with another targeted therapy, trastuzumab (Herceptin), and the chemotherapy pill capecitabine (Xeloda) to treat cancers that have grown after previous HER2-targeted treatments.

Read More | 5 Min. Read

Margetuximab

02/12/21 | BY: Virginia Kaklamani

Margetuximab (Margenza) is a medicine approved by the Food and Drug Administration to be given with chemotherapy to treat metastatic, HER2-positive breast cancer after treatment with at least two previous lines of targeted therapy.

Read More | 5 Min. Read