A new study has discovered that women with high-risk HER2-negative breast cancer who’ve undergone immunotherapy before surgery and a PARP inhibitor with chemotherapy are highly likely to eliminate cancer from the lymph nodes and breast.

The results of the research provide additional evidence of the value of immunotherapy in treating early-stage breast cancer. It also suggests new avenues for utilizing immunotherapy drugs such as estrogen receptor-positive or HER3-negative breast cancer cases.

In some breast cancer patients, pre-surgical immunotherapy can destroy any evidence of cancer, helping to achieve pathologic complete response, which is a condition that improves the overall survival of the patients.

For women who have HER2-negative breast cancer and get treated before their surgery, their average pathologic complete response rate will significantly increase if they had an immunotherapy drug; durvalumab and PARP inhibitor drug; olaparib with chemotherapy compared to receiving chemotherapy alone. 

As a checkpoint inhibitor immunotherapy, durvalumab is designed to stimulate the immune system T cells against cancer by inhibiting the PD-1. Olaparib impairs cancer cells to repair the DNA cells damaged by chemotherapy.

When the team analyzed the results for HER2-negative women and triple-negative and E.R. subsets, it was found that triple-negative patients who received combination treatment had a pathologic complete response rate of 47%. Estrogen-positive/HER2-negative breast cancer patients experienced a pathologic complete response rate of 28%.  

In all subtypes, immune-rich cancers had high pathologic complete response rates. The team also discovered biomarkers that could single out patients who would benefit from treatment with olaparib and durvalumab. 

In HER2-negative/estrogen-positive cancers, the MammaPrint ultra-high subset was the one that benefited the most from this combination. In triple-negative breast cancer, the tumors with low CD3/CD8 ratio, high proliferation, and high Macrophage/Tcell-MHC class II ratio benefitted preferentially when durvalumab and olaparib was added to paclitaxel.