Using information from the Surveillance, Epidemiology, and End Results (SEER) database, which is the gold standard for data quality among cancer registries, investigators analyzed distant metastasis patterns and prognosis in three groups of patients: older group (i.e., >80 years), middle-aged group (i.e., 60-79 years), and younger group (i.e., <60 years). To be eligible for inclusion in the study, participants had to be aged >18 years at the time of diagnosis, have confirmed primary BC, have only one malignant primary tumor, and have been diagnosed between 2010 and 2016.
The primary outcome was overall survival (OS) and BC-specific survival (CSS). OS was defined as the time from the diagnosis of BC to death due to any cause or the date of the last follow up. CSS was calculated from the time of diagnosis of BC to death due to BC.
A total of 36,203 BC patients were included in the study, of which 12% (N = 4,359) were diagnosed at age >80 years, 54% (N = 19,688) were diagnosed at age 60 to 79 years, and 34% (N = 12,156) were diagnosed when they were aged <60 years. Clinicopathologic characteristics differed significantly among the age groups. There were more Caucasian in the older groups compared with the middle-aged and younger groups (87.8%, 83.8%, and 73.8%, respectively).
The older group was less likely to have aggressive luminal A BC than the middle-aged group, luminal B BC than the younger and middle-age groups, and less likely to have triple-negative and HER2-positive BC than the younger subtypes. A similar pattern was seen when examining treatment patterns, with older patients having a lower rate of surgery compared with the middle-age and young groups (86.6%, 91.6%, and 87.3%, respectively), radiation therapy (80.1%, 89.3%, and 89.1%, respectively), and chemotherapy (10.8%, 36.5%, and 67.4%, respectively).
Not surprisingly, the older group had reduced median survival (32, 36, and 34 months, respectively) and significantly worse CSS (odds ratio [OR] 1.402, P <.001) and OS (OR 1.136, P <.001).
Examining data on the correlation between age and metastasis, the researchers found that the older group had fewer occurrences of brain-only metastasis (0.85%, 3.23%, 1.83%, respectively with an OR 0.329, CI: 0.153-0.706) and multiple metastatic sites (2.64%, 3,86%, 6.28%, respectively with an OR 0.361, CI 0.284-0.458) than the other age groups. However, older BC patients had higher odds of lung-only metastasis (OR 1.274, CI 1.163-2.674). Bone metastasis was the most common type of metastasis in all BC subtypes, yet the odds were significantly reduced for bone-only metastasis in the >80-year age group (OR 0.704, CI 0.583-0.851).
Analysis of survival outcomes of different metastasis sites based on age revealed that the older group with liver-only metastasis had a significantly worse CSS and OS than other metastatic patterns.
This study provides insight for pharmacists working with older BC patients about the utilization of BC treatment modalities in this population as well as the prognosis of older adults with BC.
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