Can timing breast cancer surgery to a woman’s menstrual cycle impact her long-term outcome?
This is a question that we’ve explored previously on this blog. There has been research suggesting that the optimal timing of breast cancer surgery as it relates to the phase of a woman’s menstrual cycle may reduce her risk of recurrence. Specifically, the research suggested that premenopausal women who undergo a surgery – either a lumpectomy or a mastectomy – during the second half of their menstrual cycle (counting the first day of bleeding as day 1, the second half is typically days 15 through 28), appear to have a lower risk of recurrence and better survival than women who have surgery during the first half of their cycle. This possibility makes biological sense. During the first half of the cycle there is an increase in levels of hormones and growth factors that might speed the progression of breast cancer. These can be present at high levels in the bloodstream. Surgery to remove the tumor can release malignant cells into the blood, where the hormones may spur them to proliferate. In contrast, these growth-promoting hormones are at lower levels during the second half of the monthly cycle. In addition, studies show that biochemicals that promote angiogenesis, the growth of blood vessels that feed tumors, are also at higher levels during the first half of the cycle, while ones that discourage angiogenesis are higher during the second half.
There have also been several studies looking at how significant an effect a woman’s menstrual cycle might actually have on long-term outcomes in breast cancer. A 2011 analysis that reviewed all of the available trials found conflicting results among different studies. However, it’s worth noting that there were problems in the trials. For one, there were no randomized trials of mastectomy or lumpectomy patients available for analysis at that time (randomized trials are a more accurate way to assess a scientific theory than studies that look back at a patient population). In addition, some studies had a small number of patients.
Another problem is that different studies classified menstrual cycles differently. For example, some have used a “clinical” definition, based on the number of days since Day 1 of the menstrual period. Others have used the levels of hormones in the blood on the day of the surgery. A recent study, with 90 patients (not considered very large) found that the phase of the menstrual cycle affected disease-free survival, but only if it was assessed by counting days since Day 1 of the cycle – not by hormones or other methods. This study found that surgery in the latter half of the menstrual cycle had better results. Another interesting study published in 2011 was based on a randomized trial. It observed that breast cancer patients whose ovaries were removed in order to control their breast cancer also had a better long-term outcome if their surgery occurred in the latter half of the menstrual cycle.
So at this point, we cannot make the recommendation that surgery should be scheduled in the latter half of the menstrual cycle quite as strongly as we did before, which was prior to seeing the negative results of some of the more recently published studies. However, if possible, it probably still makes some sense to schedule surgery later in the menstrual cycle. However, if your situation is urgent – the tumor is large or growing at an accelerated pace – it’s important to discuss this research realistically with your doctor. The urgency of removing the tumor may very well outweigh the potential influence of timing it to your menstrual cycle.
Otherwise, and if scheduling surgery during the second half of the cycle means waiting only a few days longer, we advise patients that there could be a benefit to waiting. Specifically, if the tumor is small (less than one centimeter) and shows no signs of growing rapidly (a grade 1 tumor with low Ki- 67, low S- phase fraction, or low number of necrotic cells), it may be advantageous to schedule surgery during the second half of your cycle. With the new data on this topic, there may be less justification in waiting, but if your tumor is small and slow-growing, there is no downside. So if this is an important factor to you in scheduling your surgery, by all means plan for a date in the second half of your cycle.