Although a study showed that a new immunotherapy drug combined with traditional chemotherapy showed promise against an aggressive form of breast cancer, it may not be enough to justify its use.

The results, published in the New England Journal of Medicine, question if the expense and side effects of the combined treatment were worth the expense because the benefits for most women appeared to be small.

The drug is called Tecentriq from Roche.  The study tested Tecentriq plus chemo versus chemo alone in 902 women with advanced triple-negative breast cancer.  The women in the combined therapy group went two months longer on average without their cancer worsening compared with those on chemo alone.  That's a modest benefit.  What's more, the combined therapy didn't significantly improve survival in an early look before long-term follow-up is complete.

Advanced triple-negative breast cancer accounts for 15 percent of all breast cancer cases.  It's difficult to treat because the tumor's growth is not fuelled by the hormones oestrogen or progesterone, nor by the HER2 gene which is targeted by the drug Herceptin.