Targeting chemotherapy and hormone therapy resistant breast cancer

The authors aimed to evaluate the effectiveness of lapatinib (Tyverb) as treatment for women with metastatic breast cancer (the tumor has spread to other organs) where previous treatment has proven ineffective.

Circulating tumor cells (CTC’s) are cells from a primary tumor that have migrated into the blood stream. They have been shown to resist therapy in both early and metastatic disease stages. Their presence is therefore predictive of tumor recurrence (the cancer returns).

New therapies need to be identified to effectively target CTC’s.

The aim of this study was to determine whether lapatinib could prove valuable as treatment for breast cancer that has previously shown resistance to prior treatment such as chemotherapy or hormone therapy.

A total of 22 patients were evaluated. While 90% of patients were human epidermal growth factor receptor 2 negative (HER2-) for their primary tumor,  93% had HER2+ CTC’s. 66% showed a decrease in the number of CTC’s following treatment with lapatinib. Furthermore, after only one cycle of treatment, 76% of women showed a decrease in the HER2+ CTC’s. 1500mg/day of lapatinib was allocated as the appropriate dosage.

This significant result was not extended to those with HER2- CTC’s, or to those who progressed during lapatinib treatment. 

A safety assessment on this drug showed common side-effects such as fatigue (extreme tiredness), diarrhoea and a rash. These toxicities were reported as manageable, however, with only one case of severe but not life-threatening gastritis (inflammation of the stomach lining).

The authors concluded that lapatinib was a successful treatment for women with HER2+ CTC’s in stable (not actively progressing) metastatic breast cancer, regardless of HER2 status in the primary tumor. 

This study contained a very small number of patients.

Discuss this drug with your doctor if you satisfy the criteria of HER2+ CTC’s in stable metastatic breast cancer.