Scientists have expressed optimism for women with hard-to-treat breast cancer after a new chemotherapy regime proved it can shrink tumours twice as fast as normal methods.

Women with aggressive "triple-negative" disease fare much better on a non-standard chemotherapy drug if they have inherited BRCA gene mutations, the results of a trial showed.

Currently most patients with this type of breast cancer, which does not respond to hormone therapies or the targeted drug Herceptin, are treated with the chemotherapy agent docetaxel.

But the new trial findings show that those with defective versions of the genes BRCA 1 or BRCA 2 are much more likely to benefit from a different chemo drug, carboplatin.

A total of 376 women with advanced triple-negative breast cancer took part in the trial, including 43 who had BRCA gene faults.

Among the BRCA mutation carriers, carboplatin shrank tumours in 68 per cent of cases, while docetaxel only had a 33 per cent success rate.

Carboplatin also produced fewer side-effects and delayed tumour progression for months longer in women with BRCA mutations.

The results are likely to change international guidelines by introducing genetic testing for women with triple-negative breast cancer.

Lead researcher Andrew Tutt, Professor of Breast Oncology at The Institute of Cancer Research, said: "Our study has found that women with triple-negative breast cancer who have BRCA 1 or 2 mutations are twice as likely to respond to carboplatin as they are to standard treatment.