Non-compliance with Tamoxifen and Recurrence Rate
This is quite a serious and important study. The rate of non-compliance among women who are taking Tamoxifen or any of the AIs is quite high. There are many suggested reasons for this problem: side effects or perceived side effects, cost of the drugs, denial or a sense that the medication may not be needed. Whatever the cause, we know that women who stop taking these medications sooner than five years have a higher recurrence rate than those who finish the course.
This is a report of a Scottish study looking at women's declining adherence to a prescribed five year course of tamoxifen. As time went on, more women stopped taking the drug, and the rate of recurrence increased. As you likely know, the current trend is taking anti-estrogen medications for even longer than five years. Many oncologists are keeping at least some of their patients on one or another of these drugs for ten years, and I hear lots of discussion about keeping some women on them indefinitely. Stay tuned.
And, for now, here is an excerpt from NHS Choices:
What were the basic results?
The researchers identified 3,361 women who started hormone treatment after surgery for breast cancer, 85% of whom started on tamoxifen and 15% on aromatase
inhibitors. These women were followed up for 4.37 years on average. Of these 3,361 women who received hormone treatment, 36% (1,194) died during the study
Overall adherence to hormone treatment was high, but declined with each year after surgery. Average adherence was:
90% in year one
82% in year two
77% in year three
59% in year four
By year five only 51% were still receiving prescriptions for hormone treatment.
When women with high adherence (those who received prescriptions for at least 80% of the five-year period after surgery) were compared with those with low
adherence (less than 80%), one-third of the 2,785 women with high adherence died from any cause during follow-up compared with 46% of the 576 women with low
adherence. After adjustment for other factors associated with mortality (for example age and tumour stage) the researchers calculated that women with low adherence
had a 20% increased risk of dying from any cause compared with women with high adherence (hazard ratio (HR) 1.20, 95% confidence interval (CI) 1.03 to 1.40).
However, interestingly, there was no significant difference in risk of dying specifically from breast cancer between women with high and low adherence, the only
difference was in all-cause mortality.
A similar pattern was seen in the risk of breast cancer recurrence – with no significant difference between groups.
The researchers found that women who had good adherence (at least 80%) for three years or less were at increased risk of death from any cause, death due to breast
cancer and recurrence compared with women who had good adherence for the total five years. This suggests that the longer a woman is adherent, the less her risk of
all-cause and breast-cancer-specific mortality and recurrence.