Certain breast cancers spread to the bones using an enzyme that drills "seed holes" for planting new tumours, research has shown.

The discovery could lead to treatments aimed at preventing secondary breast cancers in patients with non-hormone sensitive disease.

The enzyme lysyl oxidase (Lox) is released from the primary tumour in the breast. Scientists found that it produces holes in bone that provide fertile ground for the growth of spreading, or metastatic, cancer cells.

But the process could be blocked, at least in mice, with bisphosphonate drugs that prevent bone loss and are used to treat osteoporosis.

The drugs are already prescribed to men with advanced prostate cancer that has spread to the bones, to prevent pain and fractures.