Combination of drugs vs single drug – Which is more effective in metastatic breast cancer?

This paper compared the effect of combination chemotherapy with single drug chemotherapy in women with metastatic breast cancer.

Metastatic breast cancer is cancer that has spread to other parts of the body. Treatment can help to improve survival and quality of life of patients. Treatment can be given in different ways.

Combination chemotherapy (giving more than 1 drug at the same time) can kill more cancer cells if the drug dose is not reduced. It can also delay the development of drug resistance (cancer not responding to drug). However, the drug dose may be reduced to decrease toxicity. On the other hand, single agent chemotherapy (a single drug administered repeatedly) might be less toxic and be given in larger doses. However, it is not known whether this might compromise survival time. 

The paper compared combination chemotherapy with single drug chemotherapy.

The authors reviewed 12 studies with 2,317 women and analyzed their results. There were a total of 1,023 deaths. There was no difference in overall survival between the two treatment methods. 678 out of 886 women had disease progression (worsening of disease). Combination chemotherapy gave a 16% increased risk of disease progression than single agent chemotherapy. However, combination chemotherapy gave a 13% higher likelihood of overall tumour response (tumour shrinkage) compared to single agent chemotherapy.

There were 24 treatment-related deaths, of which 16 occurred among those receiving combination treatment and 8 among those receiving single agent treatment. There was no difference in the risk of neutropenia (low levels of the white blood cell neutrophil) or leukopenia (low levels of the white blood cell leukocyte) amongst the two treatment types. However, combination chemotherapy was associated with 32% higher risk of febrile neutropenia (development of fever with neutropenia).

3 studies looked at quality of life and found no difference in the quality of life between the two treatment types. 

The authors concluded that combination chemotherapy does not provide significant benefit to survival compared to single agent chemotherapy and supports current guidelines to use a single agent repeatedly unless rapid disease progression is seen.