Ovarian cancer is often difficult to detect
Scientists have discovered why a treatment for ovarian cancer only works in half of the patients who have it.
Paclitaxel shrinks ovarian tumours - but Cambridge University researchers found that patients lacking a specific type of protein tend to be immune.
Cancer Research UK, who funded the survey along with the Medical Research Council, said it will help ensure drugs are given to those likely to benefit.
There are 7,000 cases of ovarian cancer diagnosed in the UK each year.
Paclitaxel is part of a family of drugs called taxanes - originally derived from yew trees.
The researchers, based at the Cambridge Research Institute, examined ovarian cancer cells and data from 20 patients.
They found those who did not respond to paclitaxel had lower levels of a protein called TGFBI in their pre-treatment samples.
And further analysis revealed that cancer cell death rate was higher following treatment where levels of TGFBI were high.
Lead researcher Dr James Brenton said: "TGFBI is lost in one third of primary ovarian cancers and it is possible that this protein could be used as a biomarker for selecting patients likely to respond to this class of drug.
"Our findings offer hope not only for improved ovarian cancer treatment, it may also lead to improvements in the success rate of other taxane drugs used to treat lung and breast cancer."
Dr Ahmed Ashour Ahmed, who also worked on the study, said: "Our work reveals that some proteins that surround cancer cells such as TGFBI send messages to microtubules, the backbone of the cell, sensitising them to paclitaxel.
"Deciphering the code by which these messages are sent will enable the discovery of new treatments that will simulate the coded messages leading to a significant improvement in paclitaxel response."
Professor Herbie Newell, of Cancer Research UK, said: "We are entering a period of cancer treatment where more drugs are targeted at those people who will benefit the most.
"This personalised medicine approach potentially means treatments will be more effective with fewer side effects.
"This is really important for diseases like ovarian cancer that can be challenging to treat."