Women being treated for breast cancer may be unaware of the side effects to expect
In a study 99% of women said they had experienced side effects as a result of taking the hormonal therapies tamoxifen and goserline.
But only 89% have side effects recorded in their medical notes.
The study, by the Cancer Research Campaign, said women's lack of knowledge meant they were unable to make informed choices about the treatment recommended to them.
Professor Lesley Fallowfield of the Royal Free and University College Medical School, one of the researchers, said: "We need to train our doctors in communication skills, and make sure that cancer patients aren't suffering in silence."
Women's experiences
Specific symptoms were examined.
Ninety-one per cent of women said they thought their treatment had caused hot flushes, though this was only noted in 47% of medical notes.
Eighty per cent said they had gained weight, although just 21% of notes recorded this.
The researchers said there may be a "self-fulfilling prophecy" about rarer side effects, such as vaginal dryness or a loss of libido - which women may only mention when asked.
The CRC said previous research had focussed on individual's specific, but possible uncommon symptoms, rather than looking at how a wide group had been affected by side effects.
Prof Fallowfield said: "Clearly some of the side effects are being overlooked. And that could well be because our over-stretched cancer doctors simply don't have the time to spend listening to their patients about how they are feeling."
She said many women were unaware of what their effects might be, sometimes because of the terminology used.
"In at least one case the interviewee told us she hadn't had any side effects, but when we showed her a list of symptoms she found she had several of them.
"While a patient might say that she felt 'weepy' or 'irritable', a doctor would probably describe this as 'anxiety' or 'depression'."
Communication 'the key'
Jean King, director of education funding for the CRC, said it was important the hundreds of thousands of women across the world who were taking hormone therapies had a clear picture of the side effects they may experience.
"This study's findings have implications for the treatment of all cancers."
Delyth Morgan, chief executive of Breakthrough Breast Cancer said: "Good communication between doctor and patient at all levels is key.
"Women must be fully informed of the benefits and all possible side effects of treatments.
"It is essential that patients can be confident about the information they receive from their doctors before deciding what is right for them."