Using the 70-gene signature to predict cancer outcome

This paper studied whether adding the 70-gene signature (MammaPrint) to clinical guidelines could improve prediction of cancer outcome in early breast cancer patients.  

It is important to identify patients who are at high risk of breast cancer recurrence (return of cancer) and are eligible to receive adjuvant systemic treatment (treatment given after main therapy) so as to improve their health outcome. Calculation of patients' risk is traditionally based on clinical factors such as age and tumor size.

Recently, the presence of hormone receptors (proteins found on cell) have been used. Additionally, genes can also be used to predict risk. The 70-gene signature (group of genes) has previously been found to be a good predictor of cancer outcome after 5 years. 

427 female patients with invasive adenocarcinoma (cancer originating from glands) of the breast were included in the study. A 70-gene signature was obtained (classifying the tumor based on this group of genes). Patients' risk was assessed through several clinical guidelines. These guidelines calculated the 10 year survival probabilities based on age, tumor size, tumor grade (how abnormal cancer cells look under a microscope), presence of hormone receptors (including estrogen and progesterone) and number of lymph nodes affected. The results from these guidelines identified patients who were at high or low risk. High risk patients were advised to undergo adjuvant treatment. 

After an average follow-up time of 61.6 months, there were 24 cases of distant-recurrence free intervals (no cancer returning to another part of the body). 9 patients died due to breast cancer.

Based on the 70-gene signature, the 5-year distant-recurrence free interval was 97% in low risk patients and 91.7% in high risk patients.

The results found that adding the 70-gene signature to risk prediction algorithms improved the prediction of cancer outcome across the various guidelines. Untreated patients with a high clinical guideline risk but a low risk 70-gene signature had an excellent 5-year distant recurrence free interval varying between 97.1% and 100%. 

The authors concluded that adding the 70-gene signature to clinical guidelines may help to identify those patients in early breast cancer who would most benefit from extra treatment.

This study was short term and had a small number of untreated patients. There were some conflicting results between clinical risk assessment and the 70-gene signature.