New research shows women who have breast tumours removed during the first part of the cycle - called the follicular phase from days three to 12 - have a survival rate after 10 years of 45 per cent. The survival rate rises to 75 per cent for women who have the operation in the latter part of the month, the luteal phase.
The results, from a study of 112 women who underwent surgery at Guy's Hospital in London and published today in the journal Cancer, confirms evidence that has been accumulating for a decade on the importance of timing in breast cancer surgery. All breast cancer surgery is now performed in the luteal phase at Guy's but few other surgeons have followed suit. Professor Ian Fentiman, the head of the Imperial Cancer Research Fund's breast unit at Guy's, who led the research, said: "It has had no impact whatsoever. Surgeons are very happy to try out new technologies. But when it comes to something as simple as the timing of an operation - it just hasn't caught on."
The findings of the Guy's study apply to pre-menopausal women but other research by the team suggests postmenopausal women could also be affected. In the UK, where there are 13,000 deaths from breast cancer a year, it is estimated the change could save 300-400 lives. In the United States, where there are 30,000 deaths it could save 2,000 lives.
The Guy's team has finished a second, prospective study of 200 women allocated for surgery in the luteal phase whom it has followed since 1991. Those results are awaiting publication. Professor Fentiman said: "I hope that will be the definitive study in terms of convincing the rest of the world."
The importance of timing is linked with the effects of the hormones oestrogen and progesterone on the cancer. The patients who do best have hormonally sensitive cancers.
Professor Fentiman said: "The simplest way to think of it is if you take out the tumour in the second half of the cycle, it is like a hard-boiled egg whereas if you take it out in the first half of the cycle, it is like a raw egg and the chances of spilling the tumour cells are very much greater."
Hormone levels may also be important in encouragingspilled tumour cells to become established elsewhere.Reuse content