The Ministry of Health and Welfare and the National Cancer Center in South Korea announced that the incidence rate of breast cancer was 62.6 per 100,000 women in 2016, up 14.4% from 54.7 per 100,000 in 2014. While the rates for most cancers, such as thyroid cancer, stomach cancer, and colorectal cancer, are decreasing, breast cancer rates are increasing every year in Korea. In all cases of breast cancer, the proportion of those aged 65 and older increased from 12.04% in 2007 to 16.29% in 2016. This increase is attributed to the growth in the elderly population. As a convention, a person aged 65 years or more is referred to as “elderly” [1,2]. Based on these data, we defined a person aged 65 years or more as “elderly” in this study. Elderly patients with breast cancer, however, tend to be reluctant to undergo treatments due to comorbidities and deterioration in quality of life and socioeconomic status. In addition, elderly patients often miss optimal treatment due to delay while seeking alternative medicine. Therefore, we assessed the tumor characteristics and long-term clinical outcomes of breast cancer patients over the age of 65 to provide evidenced-based data for the treatment and prognosis of elderly patients.

There were 286 patients aged 65 or older diagnosed with invasive breast cancer between 2008 and 2014 in this study, including 212 patients from Pusan National University Hospital and 74 from Pusan National University Yangsan Hospital.

The median age of the patients was 70 years (range, 65–92 years). Among these patients, 43 (15.0%) had a local recurrence or distant metastasis with a median follow-up period of 61 months (range, 14–134 months). Loco-regional recurrences occurred in 15 patients: one in ipsilateral axillary lymph node, five in supraclavicular lymph nodes, and nine involving breast and chest wall. There were 37 patients with distant metastasis: 15 involving lung, 13 involving bone, 10 related to liver, and four cases of brain metastasis.

Two of the 286 patients were male patients and two patients underwent surgery, followed by neoadjuvant chemotherapy. Hypertension was diagnosed in 172 patients, and 73 were diagnosed with diabetes mellitus. During the follow-up period, 32 patients were diagnosed with cancers involving other organs.

We found that pathologic node stage, the final stage, and the status of endocrine therapy varied significantly between patients with and without local recurrence or distant metastasis (Tables 1, 2). However, there were no differences in the pathologic tumor stage, grade, lymphovascular invasion, and intrinsic subtype (Table 1). Also, no differences were found between treatments with different types of surgery, chemotherapy, or radiotherapy (Table 2).

In multivariate Cox-regression analysis, pathologic nodal stage and the status of endocrine therapy were identified as prognostic factors for DFS. Stage and status of endocrine therapy were significant risk factors for OS and BCSS (Table 3).

Although obesity was not a risk factor for DFS, OS, or BCSS, it was related to luminal A and B type tumors. The chi-square test showed that overweight and obesity were correlated with positive hormone receptors, with a P-value of 0.003 (Table 4).

Fig. 1 shows the Kaplan-Meier curves for DFS, OS, and BCSS according endocrine therapy status. Patients who received endocrine therapy had a better 5-year DFS rate than those who did not receive endocrine therapy (91.9% vs. 80.1%, endocrine therapy vs. no endocrine therapy, respectively; P=0.007). In addition, the group, which was treated with endocrine therapy, had superior 5-year OS and BCSS rates compared with the group, which was not exposed to endocrine therapy (92.1% vs. 80.9%, P=0.005; 93.7% vs. 81.8%, P=0.005, respectively).

Korean women in their forties have a high breast cancer incidence rate unlike the rate in Western countries [3,4]. As mentioned earlier, however, the proportion of patients over the age of 65 is gradually increasing. Of all breast cancer patients, 16.29% were aged 65 or older in 2016, more than double since 2007. The increase in elderly breast cancer patients is significantly correlated with overweight status and obesity, especially in hormone receptor-positive cancers [5–8]. Mammographies are performed in women over 40 years old every 2 years in Korea. Mammography alone is highly sensitive in patients over 65 years of age due to the age-related reduction in breast density and may be responsible for the higher rates of breast cancer diagnosis. In this study, advanced stage was a significant risk factor for OS and BCSS. Therefore, appropriate examination should be conducted to increase early detection of breast cancer. We performed breast conservation surgery in 107 patients (37.4%) and found that the type of surgery was not related to DFS, OS, or BCSS. Early detection of breast cancer increases the possibility of breast-conserving surgery, which could lead to improved quality of life in elderly patients.

The pathologic nodal stage was a significant risk factor for local recurrence or distant metastasis in this study. When metastasis is detected in axillary lymph nodes, chemotherapy must be considered, followed by surgery. In general, patients over 65 years of age are more likely to manifest adverse events than younger patients [9–11]. Dose-reduction chemotherapy is common in elderly patients and may reduce treatment efficacy [12,13]. When administering chemotherapy, the effectiveness of treatment must be balanced against the possible side effects.

In our study, 65.6% of HER2-positive patients were treated with adjuvant trastuzumab. Elderly patients are often excluded from targeted therapy because they cannot withstand chemotherapy before adjuvant trastuzumab can be administered. Patients also discontinue with targeted therapy in the middle of treatment due to cardiotoxicity, which is a common side effect of trastuzumab.

Our findings are consistent with other studies that recommend endocrine therapy for elderly patients with luminal A or B type breast cancer [9,14–17].

The group treated with endocrine therapy showed longer survival and prevention of local recurrence or distant metastasis, suggesting that 66.1% of these patients have been diagnosed with luminal A or B type and were treated with endocrine therapy.

A limitation of this study was that all intrinsic subtypes of breast cancer were included. Chemotherapy, targeted therapy, and radiotherapy might be underestimated because optimal treatment varies according to the intrinsic subtype. Despite this limitation, our results were similar to previous studies. Therefore, tailored therapy is indicated for elderly patients based on their individual situation.

In conclusion, elderly patients manifested favorable intrinsic subtypes of breast cancer. Therefore, endocrine therapy is recommended elderly patients with breast cancer carrying luminal A or B type tumors. Advanced stages of breast cancer are related to poor prognosis in elderly patients with breast cancer. Elderly patients tend to stop treatment more easily than younger patients with advanced stage breast cancers. Therefore, early detection of breast cancer is especially beneficial in elderly patients.