Scientists have discovered a genetic marker that may predict which breast cancer patients are at high risk of recurrence, potentially saving many women from undergoing unnecessary chemotherapy.

Between 60 and 70 percent of women with breast cancer that has not spread to the lymph nodes are cured by local surgery or radiotherapy. But 85-90 percent of them still receive additional chemotherapy because doctors fear their cancer will recur.

John Foekens and colleagues from Erasmus MC Rotterdam, Netherlands, said on Friday they had found patterns of gene expressions across 76 genes which could successfully predict relapse.

The discovery, which was reported in the Lancet medical journal, might allow clinicians to avoid unnecessary treatment or choose less aggressive therapies in future.

However, Tor-Kristian Jenssen, from database organization PubGene in Norway, sounded a note of caution, since other researchers had identified gene “signatures” relating to different genes in the past.

Although the latest study was the largest of its type, it might still be too small to provide a final selection of the right genes for analysis, Jenssen wrote in an accompanying commentary.