In describing cancer disparities by racial have been progressed in the past several years. The focus of racial disparities has been shifted from single dimension models to complex frameworks. Several domains which contain biological, sociocultural, environment, education, and healthcare systems have been incorporated. These frameworks attempt to provide a deep structure which integrates both biology and social dimensions to explore the racial disparities in couples with health problems.(24–26) However, the considerable progress in understanding the mechanisms affecting racial disparities has been relatively slow. Indeed, the incidence, BCR and survival of racial disparities in breast cancer patients who received BCS are continuing to have been variety. In the current study, based on the large multirace dataset, we found great racial disparities in the incidence, BCR and survival of breast cancer patients after BCS. Compared with blacks and APIs, the white race is the race with the consistent highest incidence of breast cancer in the past decade. In addition, white breast cancer patients have the highest acceptance rate of BCS. The breast cancer incidence in blacks increased fastest than other races. In addition, minorities had a significantly higher increased BCR than whites. After adjusted the imbalance baselines of different races by stepwise IPW, we found white patients have the best prognosis than those of minorities.
The overall cancer incidence rate in women has remained generally stable over the past several decades. However, as the incidence of lung cancer and colorectal cancer declined, breast cancer has become the first leading cancer affecting women health worldwide.(2) Our study found in the age-adjusted breast cancer incidence data, the levels of breast cancer incidence in different races are unequally. Neither 2000–2004 or 2013–2017, white women had the consistent highest risk to suffer from breast cancer in their lifetimes. Moreover, although breast cancer incidence has historically been relatively low among minorities, the breast cancer incidence of minorities women raised rapidly in the past decade. The reason of the racial disparities in breast cancer incidence was complexed.(19, 27) Previous studies identified possible differences in biological properties in different races, such as the levels of hormones and growth factors, reproductive factors, susceptibility loci, BMI, socioeconomic status, breastfeeding and obesity.(20, 28–32) Those above possible differences may have the potential influence on the racial disparities of breast cancer incidence.
In the past century, Halsted’s radical mastectomy was regarded as the standard operation for no organ distant metastatic breast cancer patients.(33) However, this operation was too aggressive and low quality of life to patients.(34) This conception was ended in several large randomized clinical trials and the evolution toward less harm had been evidence based.(4, 5, 11) One of most noted study was termed as NSABP B-06.(35) Initial reports of the trial at five, eight, twelve and twenty years follow-up included 1843 enrolled patients, researchers indicated that breast cancer patients received segmental mastectomy regardless of breast irradiation performed, which resulted in BCSS and OS were no worse than that of patients after total mastectomy.(4, 35–37) More surprisingly, BCS plus radiation even exhibited better survival that total mastectomy in a 20-years follow up data.(4) Since then, a lot of clinical trials and long-term follow-up analyses have repeated demonstrated no worse survival outcomes between BCS and total mastectomy.(38–41) In fact, these findings recommend BCS to be a standard treatment option for early-stage breast cancer in the past two decades. Indeed, our findings also demonstrated raised trends of BCS in the population of American, which was consistent with previous studies. Patients select the surgery type can be influenced by several clinical or nonclinical factors, including clinicopathologic factors, physician factors, and individual factors with subgroups of sociodemographic, geographic, and personal beliefs and preferences.(22) This increased BCS rate may contribute to the early breast cancer screening program, which increases the rate of BC patients diagnosed at an early stage.(3) In addition, increasingly locally advanced breast cancer undergoes BCS after neoadjuvant therapy, which further increases the rate of BCS. Several studies have demonstrated that black women were less likely to choose mastectomy procedures than whites, which was consistent with our study, however, our findings point to the situation being changed in the last decade. In fact, blacks have a significant increase of BCS rates, which get increasingly closer to whites.
Although our findings were consistent with previous research, we confirmed that the rising trend of BCS in breast cancer surgery. However, patients after BCS in different races still have a large wide variation in survival regardless of tumor stage and Luminal type. Thus, the racial heterogeneity cannot be ignored. The possible racial heterogeneity affecting the worse prognosis of minorities included younger age at diagnosis, later stage of breast cancer at diagnosis, worse biologic and genetic factors, difficult access to health care and lower socioeconomic status.(42) In current study, after adjusting those imbalance characteristics including age, grade, stage and Luminal subtype, we found the prognosis of black breast cancer patients was still worse than that of white patients. We assumed that biologic and genetic factors, access to health care, and socioeconomic status as racial traits beyond the adjusted factors may play key roles in affect breast cancer patients’ survival. Indeed, it was observed that black women were less likely to obtain adequate treatment compared to white women. For example, black women were less likely to receive surgical treatment in tertiary hospitals and were more likely to have delays in receiving adjuvant therapy.(42) Interestingly, since API patients had more strict indications for BCS in the real world, we found their prognosis was better than that of other races in the unadjusted data. This result suggested that, to get a better prognosis, BCS should be only performed in blacks or APIs with more strictly indications.
We acknowledge the inherent limitations in this cancer registry dataset. Firstly, owing to the data availability, we could not collect other important information from the SEER program, such as surgical margins, income, premenopausal endogenous level hormones, breastfeeding, and susceptibility genetic factors, it is hard to adjust all potential bias in the current study.(20, 28–30, 43, 44) Secondly, although our study demonstrated the survival advantage in whites, it may be due to the receipt of adjuvant chemotherapy and radiation therapy after surgery. However, cancer registries do not systematically collect treatment regimens after surgery. In our study, we found the rates of radiotherapy were received similar in those three races. Moreover, the blacks with the worst survival even received the highest rate of adjuvant chemotherapy than other races. Despite the above limitations, our study included substantial samples, which could offer a deep insight into the racial disparities of breast cancer. Moreover, we have cumulative survival disparities using Fine-Gray regression models in the pairwise IPW adjusted dataset. These methods could reduce the potential cohort bias in a retrospective study, thereby providing more reliable and stable results.
To the best of our knowledge, we first based on a large individual patient-level dataset, which confirmed a comprehensive analysis of racial disparities in the incidence, BCR and survival of breast cancer after BCS. Our study revealed the increased of BCS rate in breast cancer, especially in minorities. However, after adjusting the imbalance between baseline characteristics by IPW, we found that minorities have performed worse survival than that of whites. This survival benefit may be attributed to the special genetic characteristics and socio-economic status of whites. In addition, our study points out that API breast cancer patients after BCS had the best survival in the real world. This survival benefit may be attributed to only API patients with more strict indications receiving BCS. We hypothesized that BCS should be more cautious for minorities for better survival. This significantly increased rate of BCS and worse survival in minorities should be alerted by health management departments and clinicals.