Just two cups of coffee a day could halve the risk of breast cancer returning in women recovering from the disease, a study has found. Researchers found coffee can stop the growth of tumours in women who have already been treated with the drug tamoxifen. Tamoxifen is the main hormonal therapy drug given to women who have not been through the menopause, and is usually taken for five years or longer after treatment for breast cancer. Just two cups of coffee a day can halve the risk of breast cancer returning and boosts the effect of the drug tamoxifen, researchers found . Most breast cancer tumours rely on the hormone oestrogen to grow, and tamoxifen blocks oestrogen from reaching the cancer cells. This means the cancer either grows more slowly or stops growing altogether. As part of the study, Swedish and British researchers looked at data from 1,090 breast cancer patients, in a follow up of a similar study carried out two years ago. They found that more than 500 women who had been treated with tamoxifen, and those that had drunk at least two cups of coffee a day, had only half the risk of their cancer returning than those who drank less coffee, or none at all. Ann Rosendahl, a researcher from Lund University who carried out the study, said: 'The study also shows that those who drank at least two cups of coffee a day had smaller tumours and a lower proportion of hormone-dependent tumours. 'We saw that this was already the case at the time of diagnosis.' Researchers also looked more closely at two substances that usually occur in coffee – caffeine and caffeic acid. They found the breast cancer cells reacted to these substances, especially caffeine. Caffeine caused the cells to divide less frequency, and die more often, especially when it was drunk in combination with tamoxifen. The study found  caffeine caused breast cancer cells to divide less frequently and die more often . Ms Rosendahl said: 'This shows that these substances have an effect on the breast cancer cells and turn off signalling pathways that the cancer cells require to grow.' The team demonstrated both in in breast cancer patients and at cell level that coffee can reinforce the effect of treatment with tamoxifen. However, they emphasise the importance of taking prescribed medication. Ms Rosenhal added: 'They are incredibly important, but if you like coffee and are also taking tamoxifen, there is no reason to stop drinking it. 'Just two cups a day is sufficient to make a difference.' This is not the first study to link coffee consumption with improved cancer prognosis. Drinking coffee may reduce the risk of cancer in heavy drinkers, research has found. A World Cancer Research Fund study shows the hot drink can protect against liver cancer, which is often associated with alcohol abuse. For each cup consumed a day, there is about a 14 per cent decreased risk of liver cancer, found the study by the World Cancer Research Fund. And scientists at Harvard Medical School have found that women who drink three or more cups of coffee a day have a 20 per cent lower risk of developing the most common form of skin cancer compared to those who had less than one cup per month. They also found that men who drank the same amount saw a nine per cent lower risk of the skin cancer, basal cell carcinoma.
Coffee can stop cancer returning in women treated with tamoxifen.
Tamoxifen stops oestrogen reaching tumour cells, so they do not grow.
Coffee drinkers had fewer cancers and their tumours were smaller.
Caffeine cuts of signalling pathways that the cancer cells require to grow.