The predictive accuracy of the final nomogram system was determined by calculating Harrell’s Cindex and AIC index. For the nomogram system, the Cindex was 0.83, which is higher than the value of 0.7 expected for a system with accurate overall survival prediction. In addition, it was also higher than the Cindex for the traditional American Joint Committee on Cancer (AJCC) staging scheme (0.797). The calibration plot of the nomogram for cancer-specific survival is shown in Figure 2B. From the calibration curve, we found that predicted cancer-specific survival was closely associated with actual cancer-specific survival, with which it was always within a 10% margin of error. To avoid overfitting the nomogram-derived prognostic model, we also determined its AIC index. The AIC index of the nomogram scheme was 11112.85, which is lower than the AIC index for the AJCC breast cancer staging scheme (11393.13). This indicates that the nomogram system constructed in this study is a better prognostic predictor when estimating cancer-specific survival in elderly patients with breast cancer.
In the nomogram predictive system, we found that tumor size was a strong prognostic indicator of cancer-specific survival. A stratification analysis was performed to evaluate cancer-specific survival in groups that were treated using three surgical approaches according to differences in tumor size and the use of radiotherapy. The results indicated that a localized surgical approach resulted in better cancer-specific survival regardless of whether or not the patients were treated with radiotherapy. Moreover, localized surgery also resulted in better cancer-specific survival when the tumor size was <50 mm in diameter. In addition, in patients in whom the tumor size larger was <50 mm, cancer-specific survival was not worse in treatment using a localized surgical approach than an extended surgical approach (Figure 3).
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(To view a larger version of Figure 3 click here.)
In order to reduce the bias caused by the retrospective analysis, a propensity score analysis was performed. After patients who underwent local and radical surgical approaches were matched, 5068 pair patients were included in the validation set. Figure S2 shows a jitter plot of the data for matched and unmatched patients as well as the corresponding distributions of propensity score values. We used a matched data set for further analysis, and the results indicated that while localized surgery resulted in better cancer-specific survival when tumor size was <50 mm, radiotherapy was required to improve cancer-specific survival (Figure S3).
DISCUSSION
Patients with breast cancer who are older than 80 years represent a unique segment of the population. Which treatment strategies are best in this type of patient remains to be determined. When choosing a strategy, we should consider life expectancy, the potential benefits of treatment, the patient’s goals for treatment and the potential risks associated with treatment, including its effects on function and quality of life.1 Therefore, cancer-specific survival may be a more appropriate factor for evaluating treatment strategies and other prognostic indexes.
Other studies have found that patients who are 80 years or older tolerate surgery well with low complication rates.2,3 These data indicate that although complications occurred in 37.1% of this cohort, 31.4% of all complications were minor. In addition, in elderly patients with breast cancer who underwent surgery, perioperative mortality was zero. However, in our study, the results indicated that a localized surgical approach was not worse than extended surgery for estimating cancer-specific survival. At the same time, localized surgery did not substantially change the shape of the breast and resulted in fewer traumas. Therefore, patients were more likely to accept this type of surgical procedure. Furthermore, another study has supported the idea that most older women could be considered candidates for breast preservation.7
In patients with breast cancer tumors <3 cm in size and negative lymph nodes and who are ER and/or PR positive and HER-2 negative, breast-conserving therapy and endocrine therapy without breast radiation are viable options. No undergoing radiation had no effect on overall survival but may be associated with the rate of breast cancer recurrence.8,9 In our study, we found that radiotherapy improved cancer-specific survival and overall survival in elderly breast cancer patients. In elderly breast cancer patients who might not need radiotherapy (eg, those with a tumor size <2 cm, negative HER-2 expression and positive ER/PR expression), radiation also provided some benefits to cancer-specific survival and overall survival. However, we should acknowledge that radiotherapy might increase the risk of cardiovascular incidents, for which the HR increment ranged from 1.5 to 2.4.10 In patients with cardiovascular-related severe diseases, a strategy involving radiotherapy requires careful consideration. The HR quoted is for mediastinal radiation, which is rarely done these days. The heart dose is usually reduced with deep inspiration breath-holding technique.
