The researchers examined trials of older chemotherapy techniques from the 1980s and discovered that these regimens resulted in a reduction of nearly a fourth of breast cancer mortality. While examining more recent trial regimens compared with the older regimens, the researchers found a further decrease of approximately one-sixth in breast cancer mortality.
The researchers claim that modern chemotherapy reduces breast cancer mortality by approximately one third amongst a large number of patients, in comparison to patients who received no chemotherapy. They also discovered that the CMF and 4AC chemotherapy regimens used in the 1980’s were more or less equal in effectiveness, reducing annual breast cancer mortality rates by 20-25%.
In addition, the researchers found that other treatments with lower chemotherapy doses were slightly less effective. Modern treatments with significantly more chemotherapy than standard 4AC, yet not so intensive as to require stem-cell rescue, were found to be slightly more effective.
The researchers found that, irrespective of factors such as tumor size and spread, the one-third reduction in breast cancer mortality appeared to apply to all women. The reduction in mortality also seemed to be unaffected by age, though only several women in these trials were older than 70 years of age.
The mortality risk associated with ER-positive breast cancer can be greatly reduced with a 5-year treatment of endocrine therapy. Endocrine therapy is found to be less toxic than chemotherapy, although a combination of chemotherapy and endocrine therapy was found to be more effective than endocrine therapy alone.
The researchers discovered than an overall reduction of one-third breast cancer mortality is dependent on the overall risk without chemotherapy. In cases of ER-positive disease, this means the risk remaining without appropriate endocrine treatment.
According to a study author, Sir Richard Peto, “Most breast cancers are ER-positive, and for ER-positive disease that appears to have been completely removed by surgery, the 10 year risk of recurrence and death from breast cancer can be reduced by at least half by giving a few months of modern chemotherapy plus 5 years endocrine therapy.”