POLAR aims to test the safety and efficacy of palbociclib given in combination with the standard endocrine therapy after surgery, in comparison to endocrine therapy alone, for patients with hormone-receptor positive, HER2-negative resected isolated locoregional recurrence (ILRR) of breast cancer.

Local or regional recurrence of breast cancer after a mastectomy or lumpectomy indicates a poor prognosis and, for a high proportion of patients, it also accompanies or precedes the development of metastasis in other organs and parts of the body. Patients with isolated locoregional recurrences (ILRR) and without evidence of distant metastasis are more at risk of developing subsequent distant metastasis and have a 5-year survival rate ranging between 45% and 80% after locoregional recurrence. These outcomes show the powerful negative prognostic importance of ILRR events and the need for treatments beyond surgical removal of the ILRR.

Chemotherapies and endocrine therapies given after surgery (adjuvant) reduce the risk of relapse and death in patients with primary breast cancer. However, few data are available about the optimal treatment in case of locoregional recurrence.

Palbociclib is used to treat patients with hormone receptor-positive, HER2-negative breast cancer that has spread beyond the original tumour and/or to other organs.

The aim of POLAR is to determine whether treatment with 3 years of palbociclib plus standard endocrine therapy for at least 3 years prolongs invasive disease-free survival (iDFS, the time during or after cancer treatment when there is no sign of cancer relapse) compared to treatment with standard endocrine therapy alone for at least 3 years in patients with hormone receptor-positive, HER2-negative resected isolated locoregional recurrence (ILRR) of breast cancer.

The study will also assess the tolerability of the drug combination palbociclib and endocrine treatment for 3 years, compared to endocrine treatment alone.

POLAR is a two-arm study. Patients will be randomly assigned to one of the following treatment arms:

• Arm A: patients will receive palbociclib for 3 years, in combination with a standard endocrine therapy for at least 3 years
• Arm B: patients will receive standard endocrine therapy for at least 3 years

The study is open to 400 patients (women and men) with histologically confirmed HR-positive, HER2-negative resected isolated locoregional recurrence (ILRR) of breast cancer.

The POLAR trial (IBCSG 59-19 / BIG 18-02) is sponsored and coordinated by the IBCSG (International Breast Cancer Study Group) and conducted under the BIG umbrella, in collaboration with GEICAM (Spanish Breast Cancer Group), SOLTI (Breast Cancer Research Group, Spain), SAKK (Swiss Group for Clinical Cancer Research), UCBG (Unicancer Breast Group, France) and the ABCSG (Austrian Breast & Colorectal Cancer Study Group).

Pfizer is the pharmaceutical partner of the study, providing funding and study drugs.

Recruitment opened in August 2019 and is still ongoing.

Approximately 35 centres in 6 countries are taking part in the study (Austria, France, Hungary, Italy, Spain and Switzerland).

Not at present

POLAR is made possible by a research grant and drugs provided by Pfizer and is run according to BIG’s Principles of Research Conduct.

NCT03820830