SAN ANTONIO – captured in the National Cancer Database.
“Data for elderly patients in clinical trials is limited. The NCCN [National Comprehensive Cancer Network] guidelines note that there is limited data to make chemotherapy recommendations for those older than 70 years of age,” commented first author Shreya Sinha, MD, an oncology fellow at the State University of New York, Syracuse. Furthermore, the few studies assessing adjuvant chemotherapy benefit among geriatric breast cancer patients have had conflicting results.
In the new study, reported at the San Antonio Breast Cancer Symposium, older women with stage I-III breast cancer who received adjuvant chemotherapy had a nearly 40% reduction in the adjusted risk of death relative to counterparts who did not receive adjuvant chemotherapy. Benefit was seen across disease stages and across hormone receptor statuses.
Patients’ fitness to receive chemotherapy and their causes of death could not be determined, Dr. Sinha acknowledged. Therefore, chemotherapy’s role in the observed survival difference is not definitive.
“In general, when we are treating our elderly population, we have to take physiologic age into consideration when coming up with a treatment plan,” she said. However, “we also have to use chemotherapy toxicity prediction calculators,” such as the Cancer and Aging Research Group tool and the Chemotherapy Risk Assessment Scale for High-Age Patients.
In addition, gene-based assays, such as Oncotype DX and MammaPrint, which were not taken into account for the study, can be applied to estimate the likely benefit of chemotherapy and further inform the treatment decision.
“It can’t be that chemotherapy is making these patients live longer. It has to be that the doctors know not to give chemotherapy to those who are going to die soon,” speculated symposium attendee Steven E. Vogl, MD, an oncologist at Montefiore Medical Center, New York.
He therefore wondered if the amount of chemotherapy received was related to survival. “If it was a chemotherapy effect, then more is probably better, and if it’s a selection effect at the time of initiation, then more probably wouldn’t be better.”
“These are the issues we run into when we use the National Cancer Database or such large databases,” Dr. Sinha replied. “We don’t necessarily have the information on how much chemotherapy the patients received. It really is based on if they received chemotherapy or not.”
Study details
The 160,676 patients studied were treated for stage I-III breast cancer during 2004-2015 and were included regardless of hormone receptor status and HER2 status.
Overall, 60.45% received adjuvant chemotherapy, Dr. Sinha reported. Mean age was 70.7 years among chemotherapy recipients and 75.5 years among nonrecipients.
Women were more likely to receive adjuvant chemotherapy if they had a tumor grade of 2 or 3 (adjusted odds ratios, 1.88 and 3.51), had a tumor negative for both estrogen and progesterone receptors or just progesterone receptors (aOR, 2.72 and 1.70), had private insurance versus Medicaid or Medicare (aOR, 1.40 and 1.20), or received radiation therapy (aOR, 2.55).
Women were less likely to receive adjuvant chemotherapy if they had stage 1 or 2 disease (aOR, 0.23 and 0.56; P less than .0001 for each), were older than 80 years (aOR, 0.105; P less than .0001), had undergone lumpectomy versus mastectomy (aOR, 0.82; P = .0011), were treated in an academic versus community program (aOR, 0.93; P = .0007), or had a Charlson/Deyo comorbidity score of 3 or higher (aOR, 0.38; P less than .0001).
Median overall survival was 144.9 months with and 112.6 months without adjuvant chemotherapy. The difference translated to a significantly reduced risk of death for the women given adjuvant chemotherapy (adjusted hazard ratio, 0.617; P less than .0001). The corresponding 10-year overall survival rates were 59.5% and 46.7%.
The reduced risk of death with adjuvant chemotherapy was evident in women with stage 1 disease (aHR, 0.801), stage 2 disease (aHR, 0.608), and stage 3 disease (aHR, 0.666) (P less than .0001 for all). It was also evident in those with tumors positive for both estrogen and progesterone receptors (aHR, 0.649), negative for progesterone receptors only (aHR, 0.609), and negative for both (aHR, 0.547) (P less than .0001 for all).
“The HER2/neu patient unfortunately was not well defined since there was no data [on that marker] before 2010,” Dr. Sinha noted
Dr. Sinha reported no relevant conflicts of interest. The study received funding from the Research Foundation of SUNY.
SOURCE: Sinha S et al. SABCS 2018, Abstract GS2-02.