A new study of nearly 8,800 women with early-stage breast cancer found that fewer than half – approximately 49 percent – completed their full regimen of hormone therapy according to the prescribed schedule. Investigators found that younger women were particularly likely to discontinue treatment. The findings underscore the need to both better understand the reasons behind such treatment non-compliance and also develop interventions to reduce it.

"We were surprised to see that so many young women stopped treatment early, despite the fact that the therapy has a proven track record of reducing breast cancer recurrence," said Dr. Dawn Hershman, associate professor of medicine and epidemiology at Columbia University Medical Center, who led the study. "Perhaps we need to do a better job of making patients aware that to get the full benefit of treatment, they need to take their medications on time and for the full duration."

While up to five years of oral hormone therapy (such as tamoxifen and aromatase inhibitors) for hormone-sensitive breast cancers is frequently prescribed to reduce the risk of cancer recurrence and death, some previous small studies indicated that only approximately 40 to 60 percent of women finish their recommended course of therapy. In order to provide a more comprehensive perspective, Dr. Hershman and her colleagues examined automated pharmacy records of 8,769 women diagnosed with stage I, II or III, hormone-sensitive breast cancer between 1996 and 2007. They used the records to identify hormonal therapy prescriptions and refill dates. Each woman filled at least one prescription for hormonal therapy within one year of diagnosis. Women used tamoxifen (43 percent), aromatase inhibitors (26 percent) or both (30 percent).

The researchers found that women under age 40 had the highest risk of discontinuing therapy early. By 4.5 years, 32 percent of all patients in the study had stopped taking their hormone therapy, and of those who did not stop, only 72 percent finished on schedule (meaning they took their medication more than 80 percent of the time).

They found that in women younger than 40 and older than 75, those who had lumpectomy as opposed to mastectomy and those with other medical illnesses were more likely to discontinue hormonal therapy early. Asian/Pacific Islander ethnicity, a history of prior chemotherapy, being married and longer prescription refill intervals were associated with completing 4.5 years of hormonal therapy. Longer refill intervals meant fewer chances to not refill prescriptions.

"Physicians are often unaware of patient compliance, and this is becoming an increasingly important issue in cancer," Dr. Hershman said. "It's very disturbing that patients under 40 had the highest discontinuation and non-adherence rates, because those patients have the longest life expectancy. If we can better understand the issues surrounding compliance with hormonal therapy, this might help us understand why patients don't adhere to other treatments that are moving out of the clinic and into the home, such as oral chemotherapy, as often as we would like."

She added that there are several possible reasons for halting therapy early, noting that 13 percent of the women delayed getting their first prescription refilled. These factors can include the side effects of the therapy, such as joint pain, hot flashes or fatigue, a lack of understanding of the benefit of the therapy, and high costs of medications and/or insurance co-payments.

Source: Journal of Clinical Oncology