What is the effect of adding carboplatin before main cancer therapy?

This paper studied the effect of adding carboplatin (Paraplatin) to neoadjuvant therapy (given before main treatment)  in patients with triple negative breast cancer and HER2-positive breast cancer. 

HER2 positive breast cancer is associated with over-expression of the human epidermal growth factor receptor 2 (HER2) protein. Triple negative breast cancer is defined as the absence of the progesterone receptor (protein), estrogen receptor and HER2 in cancer cells.

Neoadjuvant therapy is usually given before main treatment to shrink the tumor. Carboplatin is a type of platinum drug that adds further activity to neoadjuvant treatments. Previous studies have suggested that patients with triple negative breast cancer have a higher response to platinum drugs. It was suggested that also adding platinum drugs to treatment of HER2 positive patients might improve patient response. 

315 women with triple-negative breast cancer and 273 women with HER2-positive breast cancer were evaluated. All patients received paclitaxel (Taxol) as well as doxorubicin (Doxil, Adriamycin) once a week for 18 weeks. Triple negative breast cancer patients also received bevacizumab (Avastin) simultaneously. HER2 positive patients received trastuzumab (Herceptin) and lapatinib (Tyverb) simultaneously. 299 patients were randomly assigned to not receive carboplatin while 296 patients were assigned to receive carboplatin every week for 18 weeks.  

36.9% of patients who did not receive carboplatin and 43.7% of patients who received carboplatin had a complete response (absence of disease in breast). Patients who received carboplatin were 39% more likely to have a complete response.

In patients with triple negative breast cancer, 36.9% who did not receive carboplatin and 53.2% who did receive carboplatin had a complete response.

In HER2-positive tumours, 36.8% who did not receive carboplatin and 32.8% who did receive carboplatin had a complete response.

39% of patients who did not receive carboplatin and 48% of patients who received carboplatin did not complete treatment due to adverse events. Anaemia (low red blood cells), neutropenia (low white blood cells associated with the immune system), thrombocytopenia (low platelet levels), and nausea were more common in those given carboplatin. Addition of carboplatin was also associated with a higher rate of diarrhoea and anorexia. There were 4 deaths and 115 adverse events among patients not given carboplatin and 1 death and 130 adverse events among patients who were given carboplatin.  

The authors concluded that adding carboplatin to neoadjuvant treatment significantly increased the response of patients with triple negative breast cancer but not of patients with HER2-positive breast cancer.