This latest study scientifically proves that women over 50 with the most common type of breast cancer will not benefit from chemotherapy if they do not have cancer in the lymph nodes and score low for recurrence.
The study, which has been closely followed by many oncologists worldwide who have been using earlier findings to guide their treatment of patients since the study began in 2006, was praised by cancer research advocates as progress made possible by cutting-edge advances in genomics.
The researchers performed a prospective trial between 2006 and 2010 involving 10,273 women with hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, axillary node-negative breast cancer. However, most breast cancer occurs in older women.
The new treatment finds T-cells that are successfully killing the patient's tumours and manufactures billions of clones in the laboratory.
ACT has been shown to be effective in treating tumours with a high level of mutations such as melanoma, but has been less successful when tested in cancers with a lesser mutation load, such as stomach, oesophageal, ovarian, and breast cancers.
The patients' tumors were analyzed using a test called Oncotype DX, which examines the activity of 21 genes to predict the risk of a recurrence over 10 years. Nine years after the treatment 94 percent of the women were alive and 84 percent were free from the cancer. "Your body is trying to fight that cancer anyway, let alone having to put all of this other stuff in your system that isn't really necessary, I just feel so blessed that I got the right doctors, and they were just on top of everything", Tuttle said.
Now cancer scientists across the globe are looking at how this new research - which was published in Nature Medicine today - can be applied to any type of cancer. "Patients who had chemotherapy plus an anti- hormone pill versus an anti-hormone pill alone - they had no difference in terms of their survival or outcomes long-term".
The new results are on the 67 percent of women at intermediate risk.
The current study focused on those whose scores were in the middle range, from 11 to 25. "As an oncologist, on Monday in the clinic, I will offer less chemotherapy that will not be of benefit to patients and that is very reassuring to know that when I am offering patients chemotherapy, they are likely to benefit from it".
Although chemo does help extend life in many cancers, saving patients from the extra treatment could lessen the overall burden of the breast cancer.
The first patient to undergo the treatment, Judy Perkins, was diagnosed with incurable stage 4 breast cancer in 2013, ten years after undergoing a mastectomy for an earlier bout with the disease. Most women in this situation don't need treatment beyond surgery and hormone therapy, he said.
Doctors caring for Ms Perkins during her recovery described her return to health as "remarkable".
"Oncologists have been getting much smarter about dialing back treatment so that it doesn't do more harm than good", said Steven Katz, a University of MI researcher who examines medical decision-making.
Oncotype DX is becoming more standard. This will impact about 70,000 patients a year.
This work showed "we are now at the cusp of a major revolution in finally realizing the elusive goal of being able to target the plethora of mutations in cancer through immunotherapy", he wrote.