There was an abundance of promising new research that came out of the 2023 San Antonio Breast Cancer Symposium. Here are some highlights for metastatic breast cancer. Be sure to check out our early-stage highlights here.
Terms to note while reading:
Progression-free survival (PFS): the time a patient lives with their disease and it does not progress or continue to grow.
Overall survival: the time between diagnosis (or the start of treatment) to the time of death.
Clinical benefit rate: the percentage of patients who saw a reduction (either complete or partial) in tumour size or had stable disease due to treatment.
Median: when arranged in order from lowest to highest, the middle value in a data set.
Patient reported outcome (PRO): an assessment of a person’s health status directly from the patient’s perspective.
Elacestrant (Oserdu) improves progression-free survival (PFS) for ESR1-mutated advanced or metastatic breast cancer.
Results from the EMERALD trial showed that elacestrant significantly improved the time patients with an ESR1 mutation lived without cancer progressing (PFS) compared to the standard treatment. This benefit was consistent across different patient subgroups, including those with other specific mutations (PIK3CA and TP53), different metastatic sites (bones, liver, lungs), and for both HER2-low or negative. Patients had been previously treated with 1 to 2 lines of endocrine therapy and a CDK4/6 inhibitor. Side effects were manageable, and quality of life was maintained. The most common reported adverse events were musculoskeletal pain, nausea and fatigue.
Inavolisib shows better progression free survival (PFS) for patients with a PIK3CA mutation.
Adding inavolisib to palbociclib (Ibrance) and fulvestrant (Faslodex) improves PFS compared to palbociclib and fulvestrant alone. Median PFS for the inavolisib arm was 15 months, while only 7.3 months in the control arm. The Phase III INAVO120 trial also found the drug combination to be well tolerated, with similar side effects to those reported for each drug individually.
Health-related quality of life is positive for patients treated with capivasertib (Truqap) and fulvestrant (Faslodex).
Using patient reported outcomes from 3 questionnaires, patients with aromatase inhibitor-resistant HR+, HER2- mBC treated with this drug combination had improved side effects and quality of life than compared to the placebo arm of the trial. Reported side effects were generally manageable and there were low rates of patients needing to reduce the dose, pause treatment or stop altogether.
Tucatinib (Tukysa) slows disease progression including for those with brain metastases.
Phase III of the HER2CLIMB-02 trial shows continued improved progression free survival (PFS) for patients treated with tucatinib plus ado-trastuzumab emtansine (T-DM1, Kadcyla). Patients receiving tucatinib showed a median PFS of 9.5; median PFS was 7.4 months for patients receiving T-DM1 plus a placebo. Median PFS for patients with brain metastases was 7.8 months compared to 5.7 months in the placebo group.
Triple Negative (HR-, HER2-)
Combining pembrolizumab (Keytruda) with olaparib (Lynparza) does not improve progression free survival or overall survival.
In the Phase II KEYLYNK-009 trial, compared to pembrolizumab with chemotherapy, the olaparib combination showed similar median PFS and OS. The study did show an improvement in treatment related adverse effects for those treated with pembrolizumab and olaparib.
Triple Positive (HR+, HER2+)
A chemotherapy-free approach may be an option for patients with HR+ and HER2+ mBC.
Often triple positive breast cancers have the potential to become resistant to hormone therapies. Offering an approach combining anti-HER2, anti-estrogen, and a CDK4/6 inhibitor may help to overcome this resistance. Researchers from the ASPIRE trial treated patients with anastrozole (an anti-estrogen therapy), palbociclib (Ibrance, a CDK4/6 inhibitor), trastuzumab and pertuzumab (Herceptin & Perjeta, anti-HER2 therapies) and found a clinical benefit rate of 97% as well as significant improvement in progression free survival. The results indicated that most patients had stable disease for at least 6 months.
Combination of zanidatamab, palbociclib (Ibrance), and fulvestrant (Faslodex) shows promising progression free survival.
The study of another chemotherapy-free combination included 51 patients with a median age of 54 who received this treatment combination. After a median follow-up of 16 months, 67% of patients had at least 6 months of progression-free survival. This study was conducted with patients who have had multiple previous lines of therapy. The most common side effects reported include diarrhea, neutropenia, and nausea.
Quality of Life
Routine exercise may reduce fatigue and improve quality of life according to a promising study focusing specifically on metastatic breast cancer.
In the PREFERABLE-EFFECT study, participants with metastatic breast cancer participated in a 9-month structured exercise program. Patients were surveyed at 3, 6, and 9 months and saw positive health-related quality of life scores, improved fatigue levels and physical functioning over the course of the exercise program.
CBCN’s attendance at SABCS was made possible thanks to travel funding support provided by Pfizer Oncology.