Cancer Genetics and Epigenetics 2018, Vol.6, No.2, 13-18
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shown that the visceral metastasis rate of TNBC patients is higher than that of non-TNBC patients, and the lung
and brain metastasis rate is also higher than that of non-TN patients. The rate of bone metastasis in BC patients
was higher than that in non-TNBC patients. In the imaging examination represented by ultrasound and MR, some
studies showed that the marginal burr like change and central necrosis rate of TNBC were lower than that of
non-TNBC, showing the characteristics of partial benign tumor (Xie et al., 2018).
1.3 Pathological features of negative breast cancer
The tumor diameter of tri-negative breast cancer is larger than that of non-triple-negative breast cancer, and it is a
kind of low-differentiated tumor. The cell proliferation activity, histological grade and mitotic count are
significantly higher in tri-negative breast cancer than in non-triple-negative breast cancer patients (Dang et al.,
2018). In TNBC, invasive ductal carcinoma was the main clinicopathologic classification, followed by medullary
carcinoma. In addition, it is easy to invade the vascular and has a strong invasive ability and metastasis ability,
which lead to the increase of recurrence rate.
2 Current Status of Treatment of Triple Negative Breast Cancer
2.1 Local treatment
Although TNBC has a high recurrence rate, surgery is still the first choice for local treatment (Grobmyer et al.,
2017). Clinical trials have shown that comparing with mastectomy, breast conserving surgery have similar a local
recurrence rates. Therefore, in TNBC, breast conserving surgery is the best procedure.
2.2 General treatment
Hormone receptor-positive breast cancer may have a good prognosis after endocrine therapy such as tamoxifen,
aromatase inhibitor or ovariectomy. However, due to the lack of hormone receptor and HER-2 expression in triple
negative breast cancer, endocrine therapy and targeted therapy are not the best treatment methods. At present,
chemotherapy is the only effective treatment for TNBC. Although chemotherapy can benefit the survival of
patients with triple negative breast cancer, the toxic reaction is heavy, some patients cannot tolerate, and once the
patients develop chemotherapeutic drug resistance, the consequences are generally disastrous, and the tumor will
quickly recur and metastasize (Wataru et al., 2018).
2.3 New research direction of tri-negative breast cancer
Due to the failure of traditional endocrine therapy and targeted therapy, triple negative breast cancer patients
sometimes metastasize early, which seriously affects the physical and mental health of patients. In recent years,
the main research directions of TNBC focus on three aspects: new targeted therapy, immunotherapy therapy and
new endocrine therapy.
3 New Targeted Therapy
In order to reduce toxicity, reduce the risk of disease progression, and promote individualized treatment of triple
negative breast cancer to improve the prognosis of patients, researchers have done a lot of research in the targeted
treatment direction. At present, a variety of targeted drugs have entered the stage of clinical trials. And the
research on targeted therapy of TNBC is divided into four categories.
3.1 Targeted therapy for DNA repair
The main research direction is that Poly-ADP-ribose polymerase (PARP), PAPR is a key enzyme involved in
DNA repair. It can recognize the breakpoint of DNA single strand and initiate repair. Its inhibitor resulted in cell
death by blocking the formation of adenosine ribose polymers (Ishitha et al., 2016). BRCA gene is a suppressor
gene that can repair the broken DNA double strand by homologous recombination repair pathway. Some studies
have shown that BRCA gene mutation was detected in 11.2% of TNBC patients. Blocking the repair of single
strand DNA breakpoint by PARP inhibitor resulted in DNA single strand break, BRCA gene mutation could not
initiate homologous recombination to repair DNA double strand, both existed in tumor cells which could produce
synergistic lethal effect. Therefore, BRCA gene mutants are sensitive to PARP inhibitors and have a significant
therapeutic effect.
