in actual clinical practice than younger counterparts.
After 46 months of treatment, the survival rate was only 25%, according to a study presented in June at the annual meeting of the American Society of Clinical Oncology. The finding suggests that older age is an important prognostic factor for breast cancer survival, said study author Zhonghui Jenny Ou, a doctoral candidate at the Massachusetts College of Pharmacy and Health Sciences in Boston.
For comparison, Ms. Ou cited the CLEOPATRA trial which showed a median overall survival of 57.1 months for patients who were treated with pertuzumab, docetaxel and trastuzumab versus 40.8 months for placebo with docetaxel plus trastuzumab.
The Ou study is based on an analysis of data between 2012 and 2016 from the SEER-Medicare database. The final analysis included 73 women (average age 75 years at diagnosis) with early-stage HER2-positive/HR-negative metastatic breast cancer. Fifty-six women were treated with trastuzumab with pertuzumab and chemotherapy as first-line treatment, and 17 were treated with chemotherapy only. The longest length of treatment with trastuzumab was over 44 months. And, the median follow-up for overall survival was 13 months (95% confidence interval, 12.7-18.7).
Between 2012 and 2016, five patients died from other causes, including lung cancer, cerebrovascular diseases, aortic aneurysm and dissection, pneumonia and influenza, and heart disease.
“While there are many clinical trials about HER2-positive metastatic breast cancer, these trials were all performed in younger and relatively healthier patients. Few studies included elderly patients 65 years or older,” Ms. Ou said.
According to the American Cancer Society, 31% of all newly diagnosed breast cancer cases are in women who are 70 years old or older, yet 47% of all breast cancer deaths each year are in women in this age group.
Undertreatment and lower treatment intensity have been cited by other studies as possible contributing factors to lower overall survival rates, but breast cancer in elderly women is a complex and understudied subject. Why the mortality rates for elderly women are disproportionately higher than those of younger women is attributable to a number of reasons, write the authors of one of the most recent studies on the subject.
“It is well established that receipt of adjuvant chemotherapy, trastuzumab, and hormonal therapy reduces risk of recurrence and death across all age groups, yet multiple studies document suboptimal systemic treatment and adherence for older patients, including omission of efficacious treatments, receipt of lower intensity and/or nonguideline treatment, or poor adherence to hormonal therapy,” Freedman et al. wrote in the May 15, 2018, issue of the journal Cancer.
While the Ou study sample size was small, the study’s real-world analysis is telling, Ms. Ou said.
“The major limitation of this study is that it has – after applying all the eligibility criteria to the 170,516 breast cancer patients from the SEER-Medicare database between 2012 and 2016 – a study population of just 73 patients. The number is sufficient to do survival analysis,” she said.