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First Reported Benefit of Immunotherapy in Triple Negative Breast Cancer
November 21, 2018
For the first time, researchers have an exciting new option for the treatment of triple negative breast cancer (TNBC), that thus far has lacked effective therapy.
TNBC refers to invasive breast cancers that lack expression of estrogen and progesterone receptors and are negative for the HER2 protein. TNBC accounts for about 10-15% of all breast cancers. It is typically more aggressive than estrogen receptor positive breast cancer and HER2 positive breast cancer. TNBC often occurs in younger women (under 40 years old), frequently of African American or Hispanic background. It can be associated with a BRCA1 gene mutation.
Typically, treatment of TNBC consists of conventional chemotherapy. Hormonal options and HER2 targeted agents are not effective. Numerous trials are underway to assess novel therapies.
At the recent European Society for Medical Oncology meeting, results of the IMpassion 130 study revealed the immunotherapy agent, Atezolizumab [Tecentriq], in combination with [nanoparticle albumin-bound (nab)]-paclitaxel [Abraxane] resulted in:
A reduced risk of disease worsening or death by 20% in all patients and 38% in the subgroup expressing PD-L1.
In patients with PD-L1–positive tumors, the median overall survival was 25.0 months with the combination compared to 15.5 months with standard chemotherapy alone.
The objective response rate was higher with the combination compared to chemotherapy alone for all patients (56% vs 46%) and those with PD-L1–positive tumors (59% vs 43%).
The study is soon to be published in the New England Journal of Medicine. From the study, it can be seen that overall survival was significantly improved in the patient arm receiving immunotherapy.
Implications for Pathologists
Pathologists are key to assessing the status of PD-L1 expression of tumors. However, unlike other tumors where PD-L1 expression is assessed by quantitation of tumor cell staining, in TNBC it is the tumor associated immune cells that are scored. These include the scoring of lymphocytes, macrophages and neutrophils, which make up the tumor microenvironment. Tumor cell staining is not taken into account.
H&E stain of a poorly differentiated TNBC
PD-L1 staining of immune cells in a TNBC (SP142 immunostain)