ASCO 2020: Early-Stage Breast Cancer Treatment Updates

This year’s virtual meeting included a number of clinical trial presentations focused on these cancers

Treatment optimization–balancing efficacy with toxicity–remains a clinical challenge in early-stage breast cancer and was a major focus of clinical trials featured at this year’s virtual annual meeting of the American Society of Clinical Oncology (ASCO). Below are key highlights:

HER2-positive breast cancer

Early-stage HER2-positive breast cancer is an aggressive disease. Neoadjuvant (pre-surgical) therapy with anthracycline-based chemotherapy and HER2-directed therapy, followed by continued HER2-targeted therapy, is standard treatment. In spite of its efficacy, patients remain at risk of recurrence and systemic chemotherapy-induced side effects. The key to treatment optimization is being able to effectively identify the most appropriate targeted treatment for each patient. Two studies demonstrate progress in personalizing treatment for patients with this form of the disease.

The phase II TRAIN-2 study compares two neoadjuvant chemotherapy regimens in patients with high-risk HER2-positive breast cancer. All patients receive dual HER2-targeted therapy with trastuzumab (Herceptin®) or pertuzumab (Perjeta®), and either an anthracycline-based chemotherapy or non-anthracycline-containing chemotherapy. After three years of follow-up in 438 patients, investigators reported excellent pathological complete response (no residual tumor at time of surgery) with both chemotherapy options, but an increased risk of severe side effects, including cardiac toxicity, in patients receiving the anthracycline-based chemotherapy. These findings confirm earlier reports that anthracyclines provide no added benefit—and indicate that many patients may be spared their potential toxicity.

The PHERGAIN study is evaluating the use of positron emission tomography (PET) imaging during neoadjuvant therapy to monitor tumor response in patients with HER2-positive breast cancer. In preliminary results, investigators reported that patients whose PET scan showed positive response to the treatment had pathological complete response. The study is ongoing, but results suggest that PET imaging during neoadjuvant therapy may help identify patients who can forego adjuvant chemotherapy.

Read more about TRAIN-2 and PHERGAIN here.

ER-positive, HER2-negative breast cancer

In patients with locally advanced ER-positive, HER2-negative breast cancer, neoadjuvant (pre-surgical) endocrine (hormone-directed) therapy reduces the need for chemotherapy and allows for less invasive breast-conserving surgery, but patients rarely achieve pathological complete response. Results from the TAILORx study proved that women with an Oncotype Dx Breast Recurrence Score® between 11 and 21, representing about 70 percent of early-stage ER-positive breast cancers, could safely forego chemotherapy.

A similar study, MINDACT assessed risk of recurrence by a different genomic assay (MammaPrint) and clinical tumor characteristics. Reporting on long-term follow up from the MINDACT trial, BCRF investigator Dr. Fatima Cardoso reported that patients whose tumors were characterized as high risk by clinical characteristics but low risk by MammaPrint, did not benefit from chemotherapy. After more than eight years of follow-up, Dr. Cardoso reported that 95 percent of patients were free of distant metastasis (cancer that has spread to organs or lymph nodes away from the original site)  at five years, affirming the clinical utility of MammaPrint as a prognostic test in high risk breast cancer. One caveat was found for women under 50 years old. As reported in the TAILORx study, chemotherapy did add benefit in these patients. Further studies are needed to understand whether this is due to chemotherapy’s cancer-killing effects or ovarian suppression effects. Read more about the MINDACT study here.

Read the rest of BCRF’s 2020 ASCO annual meeting coverage here.