Evaluating the effectiveness and safety of sacituzumab govitecan versus chemotherapy in patients with HR+, HER2– metastatic breast cancer.

This study investigated the effectiveness and safety of sacituzumab govitecan (Trodelvy; SG) compared to chemotherapy in patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) metastatic breast cancer (BC). The data showed that SG significantly improved survival without cancer progression compared to chemotherapy in these patients with manageable side effects.

BC is classified into different subtypes depending on the presence or absence of certain receptors (proteins found on the surface of the cancer cells). HR+ and HER2- is a subtype of BC that tests positive for female sex hormone receptors (such as estrogen and progesterone) and negative for the HER2 protein. This type of cancer accounts for 70% of all BCs. Patients with this subtype of BC commonly receive hormone therapy (HT) like tamoxifen (Nolvadex) which acts by decreasing the female hormone estrogen. However, many patients with metastatic BC are resistant to HT. This can be challenging to treat.

SG is a biological treatment. Most BCs have on the surface of BC cells a protein called Trop-1. SG is made up of an antibody-drug that attaches to the Trop-2 protein on BC cells and a second drug that kills the cancer cells once it penetrates them. It may help patients who have not had success with other BC treatments and have developed metastatic cancer (cancer that has spread to other parts of the body). However, the effectiveness and safety of SG compared to chemotherapy in patients with HR+/HER2- metastatic BC are still unknown.

This study involved 543 patients with HR+/HER2- metastatic BC. Patients were randomly assigned into 2 groups. Group 1 involved 272 patients who received SG. Group 2 involved 271 patients who received one of the following chemotherapy treatments: eribulin (Halaven), vinorelbine (Navelbine), capecitabine (Xeloda), or gemcitabine (Gemzar). The average follow-up period was 10.2 months.

The average survival without cancer progression was 5.5 months with SG and 4 months with chemotherapy. Patients who received SG were 34% less likely to have cancer progression than those who received chemotherapy.

After 6 months, 46% of the patients who received SG were alive without cancer progression versus 30% of the patients who received chemotherapy. After 12 months, 21% of the patients who received SG were alive without cancer progression versus 7% of the patients who received chemotherapy.

Patients who received SG were 16% more likely to have a better overall survival compared to those who received chemotherapy.

The most common side effects were low white blood cell counts (51% in group 1 versus 38% in group 2) and diarrhea (9% in group 1 versus 1% in group 2).

This study concluded that SG significantly improved survival without cancer progression compared to chemotherapy in patients with HR+/HER2- metastatic BC with manageable side effects.

Immunomedics, the manufacturer of SG, sponsored this study. The follow-up period was very short. Longer-term studies are needed.