Survival Outcomes Based on Axillary Surgery in Ductal Carcinoma In Situ: A Nationwide Study From the Korean Breast Cancer Society.

PURPOSE: In total mastectomy (TM), sentinel lymph node biopsy (SLNB) is recommended but can be omitted for breast-conserving surgery (BCS) in patients with ductal carcinoma in situ (DCIS). However, concerns regarding SLNB-related complications and their impact on quality of life exist. Consequently, further research is required to evaluate the role of axillary surgeries, including SLNB, in the treatment of TM. We aimed to explore the clinicopathological factors and outcomes associated with axillary surgery in patients with a final diagnosis of pure DCIS who underwent BCS or TM. METHODS: We retrospectively analyzed large-scale data from the Korean Breast Cancer Society registration database, highlighting on patients diagnosed with pure DCIS who underwent surgery and were categorized into two groups: BCS and TM. Patients were further categorized into surgery and non-surgery groups according to their axillary surgery status. The analysis compared clinicopathological factors and outcomes according to axillary surgery status between the BCS and TM groups. RESULTS: Among 18,196 patients who underwent surgery for DCIS between 1981 and 2022, 11,872 underwent BCS and 6,324 underwent TM. Both groups leaned towards axillary surgery more frequently for large tumors. In the BCS group, clinical lymph node status was associated with axillary surgery (odds ratio, 11.101; p = 0.003). However, in the TM group, no significant differences in these factors were observed. Survival rates did not vary between groups according to axillary surgery performance. CONCLUSION: The decision to perform axillary surgery in patients with a final diagnosis of pure DCIS does not affect the prognosis, regardless of the breast surgical method. Furthermore, regardless of the breast surgical method, axillary surgery, including SLNB, should be considered for high-risk patients, such as those with large tumors. This may reduce unnecessary axillary surgery and enhance the patients' quality of life.

Clinical characteristics and prognosis of postpartum breast cancer.

PURPOSE: Postpartum breast cancer (PPBC) is a not well-established subset of breast cancer, and only few studies address its poorer prognosis. However, previous studies show that PPBC is associated with worse outcome with higher rates of metastasis than in young women's breast cancer (YWBC). We aimed to analyze the clinical characteristics and prognosis of PPBC based on the diagnosis period of PPBC. METHODS: We retrospectively reviewed 208,780 patients with breast cancer from the Korean Breast Cancer Society registry (KBCSR) database between January 2000 and December 2014. We included premenopausal women aged 20-50 years who underwent breast cancer surgery. The patients were classified by 5-year intervals according to the diagnosis period of breast cancer, from the first birth to the breast cancer diagnosis. RESULTS: Compared with patients in the other groups, patients diagnosed within postpartum 5 years (PPBC < 5 years) group were younger, had a more advanced stage, had lower estrogen receptor (ER) and progesterone receptor (PR) expression, and had a higher human epidermal growth factor receptor 2 (HER2) positive rate. Further, PPBC < 5 years group had a worse survival rate than the nulliparous and other groups (5-year cumulative survival: PPBC < 5 years group, 89%; nulliparous group, 97.3%; 5 ≤ PPBC < 10 years group, 93%). In the multivariate analysis, the PPBC < 5 years group was associated with a worse survival rate (hazard ratio 1.55, 95% confidence interval [CI] 1.148-2.094, p 0.004) after adjustment for age at diagnosis, breast cancer stage, ER and HER2 status, Ki-67 level, and chemotherapy. CONCLUSION: Our findings indicated that patients diagnosed with breast cancer within the first 5 years after delivery had aggressive characteristics and a poor survival rate. It is important to elucidate the pathophysiology of PPBC and establish novel therapeutic strategies to improve the survival rate.

Clinicopathological features and prognosis associated with breast cancer laterality: a nationwide study from the Korean Breast Cancer Society.

Purpose: Although breast cancer is known to show a left predominance, the clinical characteristics and causes underlying this finding remain unclear. In addition, no related studies on breast cancer laterality have been conducted in patients with breast cancer in Korea. Therefore, we aimed to analyze differences in breast cancer laterality and the associated clinicopathological characteristics and prognosis among Korean patients with breast cancer. Methods: We conducted a retrospective analysis using large-scale data on clinicopathological factors and prognosis differences related to breast cancer laterality from the Korean Breast Cancer Society Registration system. The left-to-right ratio (LRR) of breast cancer was calculated through binomial distribution, and factors related to breast cancer laterality were identified through logistic regression analysis. In addition, the differences in the survival rates for left and right breast cancers were analyzed using the Kaplan-Meier method and Cox proportional hazards model. Results: In 171,500 patients, the LRR was 1.031 (95% confidence interval, 1.022-1.041; P < 0.001). Multivariate analysis showed that the ratio of left breast cancer was related to age, body mass index (BMI), location, and human epidermal growth factor receptor 2 (HER2) status. The survival rate of patients with left and right breast cancers showed no significant difference. Conclusion: A large-scale analysis revealed a left predominance in breast cancer laterality in Korean patients. Over time, this predominance gradually decreased. Age, BMI, location, and HER2 status affected breast cancer laterality. However, while left breast cancer showed relatively aggressive characteristics, it was not associated with a difference in the survival rate.

Survival of Breast-Conserving Surgery Plus Radiotherapy versus Total Mastectomy in Early Breast Cancer.

BACKGROUND: Breast-conserving surgery (BCS) has been reported to have better survival rates when compared with total mastectomy (TM) in early breast cancer. We evaluated the long-term outcomes of Korean women with early breast cancer who underwent either BCS plus radiotherapy (RT) or TM. METHODS: In this population-based study, we evaluated 45,770 patients from the Korean Breast Cancer Registry (KBCR) who were diagnosed with early breast cancer, and divided them into the BCS + RT and TM groups. To minimize bias caused by factors other than the surgical method, we used exact match pairing of prognostic factors. We compared the 10-year overall survival (OS) and breast cancer-specific survival (BCSS) before and after exact matching. As the KBCR is a multicenter, online-based registry program, we used the Asan Medical Center (AMC) database, a single-center database, to validate the results from the KBCR database. RESULTS: In both the KBCR and AMC cohorts, the BCS + RT group showed better OS and BCSS than the TM group, before and after exact matching. For the KBCR cohort after exact matching, the hazard ratios for OS and BCSS were 1.541 (95% confidence interval [CI] 1.392-1.707, p < 0.001) and 1.405 (95% CI 1.183-1.668, p < 0.001), respectively, favoring the BCS + RT group. For the AMC cohort after exact matching, the hazard ratios for OS and BCSS were 1.854 (95% CI 1.476-2.328, p < 0.001) and 1.807 (95% CI 1.186-2.752, p = 0.006), respectively. CONCLUSIONS: Our results suggest that BCS + RT is at least equivalent to TM in terms of OS and may affect treatment decisions in early breast cancer patients.

Omission of axillary lymph node dissection in patients who underwent total mastectomy with 1 or 2 metastatic lymph nodes.

PURPOSE: Sentinel lymph node biopsy (SLNB) is the standard axillary procedure in early breast cancer patients. In a randomized trial, the survival rates were not different when axillary lymph node dissection (ALND) was omitted in patients with 1 or 2 lymph node metastases who underwent breast conserving surgery. This study aimed to compare the outcomes in patients who underwent total mastectomy (TM) with 1 or 2 metastatic nodes according to the types of axillary surgery. METHODS: In total, 79,058 patients registered in the Korean Breast Cancer Society database who underwent TM were included in the analysis. The inclusion criteria were history of TM and SLNB, pathologic T stage 1 or 2, clinically negative axillary lymph nodes, 1 or 2 metastatic axillary lymph nodes, no radiation therapy, and no neoadjuvant therapy. We divided the patients into the SLNB only and SLNB + ALND groups. The groups were matched by propensity scores. We retrospectively analyzed the differences in the overall survival (OS) between the 2 groups. RESULTS: A total of 883 patients were matched in a 1:4 ratio for the SLNB only and SLNB + ALND groups in the cohort from 1999 to 2014. There were no significant differences in OS between the 2 groups (P = 0.413). Subgroup analysis revealed a significant survival benefit in the SLNB + ALND group in the T2 subgroup (P = 0.013). CONCLUSION: OS did not differ between the 2 groups in early breast cancer patients with 1 or 2 metastatic axillary lymph nodes who underwent TM. Omission of ALND may be considered in selected patients.

Relative Survival Benefit by Hormonal Receptor Status of Adding Trastuzumab to Neoadjuvant Chemotherapy in Breast Cancer Patients.

PURPOSE: Neoadjuvant chemotherapy (NAC) involving trastuzumab markedly increases pathologic complete response (pCR) rates in patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer. Despite increasing pCR rates, long-term survival gains are controversial owing to distinctive biologic behavior mediated by the presence of hormonal receptors (HRs) that may interact with HER2 receptors. We, therefore, investigated the differences in relative survival gain provided by neoadjuvant trastuzumab-based chemotherapy on HR positive (HR+) status of patients. METHODS: We retrospectively analyzed women with stage II or III HER2+ breast cancer who underwent NAC followed by a breast cancer surgery between 2008 and 2013. The survival benefits of adding trastuzumab to NAC were analyzed by classifying patients into HR+ and HR negative (HR-) groups. RESULTS: Of 666 patients included in the study, 374 (52.1%) were HR+ and 319 (47.9%) were HR-. In the HR+ group, trastuzumab treatment led to higher pCR rates and significantly better breast cancer specific survival (BCSS) and overall survival (OS) than no trastuzumab treatment. However, among patients with HR- breast cancer, trastuzumab treatment showed no statistically significant difference between BCSS and OS following multivariate analysis. CONCLUSION: We found that the addition of trastuzumab to NAC improved relative survival benefit in HER2+/HR+ patients than in HER2+/HR- patients, even though the pCR rate increases were lower. Although pCR has been regarded as a surrogate marker for estimating long-term survival benefits after NAC, it alone may not translate into real long-term oncologic outcomes in particular cancer subtypes after trastuzumab-based NAC. Further longer-term evaluation of the objective survival benefit after NAC driven by a dual HER2 block according to HR status is warranted.

Survival benefit of postoperative radiotherapy for ductal carcinoma in situ after breast-conserving surgery: a Korean population-based cohort study.

PURPOSE: It has been accepted that radiation therapy (RT) for ductal carcinoma in situ (DCIS) has no survival benefit despite increasing local control. However, a recent large database study reported a small but significant benefit. Using a Korean population-based large database, we examined the survival benefit of RT for DCIS after breast-conserving surgery (BCS) and analyzed which subgroup might derive benefit from it. METHODS: Data from 6038 female DCIS patients who underwent BCS with or without RT between 1993 and 2012 were included in this study. We used propensity score analysis to control for differences in baseline characteristics. RESULTS: Before adjusting, patients who received RT were more likely to have a large-sized tumor, poor histologic grade, poor nuclear grade, and less hormone receptor positivity. Ten-year overall survival (OS) rates were 95.0% in the non-RT group and 97.1% in the RT group (p < 0.001). After adjusting, previously noted differences of characteristics were substantially reduced, and then ten-year OS rates were 94.3% in the non-RT group and 97.6% in the RT group (p = 0.001). When examining the benefit of RT according to proposed prognostic scores, patients with a score of 0 showed no difference in OS by adding RT after BCS, whereas those with high scores demonstrated a significant benefit. CONCLUSIONS: We demonstrated the significant OS benefit of postoperative RT after BCS based on a large database, and for the first time beyond the western population. The omission of RT for selected patients to prevent overtreatment needs to be more elaborately studied.

The effect of adjuvant chemotherapy on survival in Korean patients with node negative T1c, triple negative breast cancer.

BACKGROUND: The present study investigated the prognostic role of adjuvant systemic chemotherapy in patients with node negative, T1c triple negative breast cancer (TNBC) from a nationwide cohort. In addition, the prognostic effect between 3 different chemotherapy regimens were compared in node-negative T1c TNBC patients by subgroup analysis. METHODS: From the Korean breast cancer registry database, 1,151 T1c node negative TNBC patients were included in this study. Patients were categorized into four treatment groups according to chemotherapy regimen: (1) no chemotherapy, (2) adriamycin plus cyclophosphamide (AC), (3) adriamycin/epirubicin plus cyclophosphamide plus 5-FU (FAC/FEC), and (4) cyclophosphamide plus 5-FU plus methotrexate (CMF). Overall survival (OS) was evaluated between each patient group. RESULTS: Of the 1,151 T1c node negative TNBC patients, 1,006 received adjuvant chemotherapy, while 145 received no chemotherapy. Among the patients receiving adjuvant chemotherapy the distribution of regimens was: 586 AC, 168 FAC/FEC (126 FAC, 42 FEC), and 252 CMF. The mean follow-up time of the full study cohort was 87.98 ± 33.56 months (range = 6-192 months). Patients in the no chemotherapy group showed significantly worse OS compared to each chemotherapy regimen group. However, when OS was compared between each chemotherapy regimen, no significant difference was found. CONCLUSIONS: This study showed that adjuvant systemic chemotherapy improved OS in T1c node negative TNBC patients, regardless of chemotherapy between AC, FAC/FEC, and CMF regimens.

Neoadjuvant Chemotherapy and Prognosis of Pregnancy-Associated Breast Cancer: A Time-Trends Study of the Korean Breast Cancer Registry Database.

PURPOSE: Pregnancy-associated breast cancer (PABC) is rare, and its cause and prognosis are not well known. Additionally, treatment is limited with respect to the risk to the fetus. The purpose of this study was to investigate the characteristics and treatment trends of PABC and the survival rate according to the treatment. METHODS: In the Korean Breast Cancer Society Registry database, women younger than 50 years and who were diagnosed with breast cancer from 1996 to 2015 were included. PABC was defined as breast cancer diagnosed during pregnancy or within 1 year after delivery. RESULTS: We examined 411 patients with PABC and 83,381 patients with non-PABC. Over time, the proportions of patients undergoing breast-conserving surgery and sentinel lymph node biopsy increased, and neoadjuvant chemotherapy and radiation therapy administration rates also increased. In the past, the overall survival of patients with PABC was poorer than that of patients with non-PABC, but there was no difference in overall survival rates in more recent years. There was no difference in overall survival rates between patients who received neoadjuvant chemotherapy (hazard ratio [HR], 1.28; 95% confidence interval [CI], 0.66-2.49; p=0.459), but PABC conferred poorer prognosis than non-PABC in patients receiving adjuvant chemotherapy (HR, 1.63; 95% CI, 1.27-2.08; p<0.001). CONCLUSION: There was no difference in the prognosis between patients with PABC and those with non-PABC receiving neoadjuvant chemotherapy. The increase in neoadjuvant chemotherapy according to current treatment guidelines is expected to improve the survival rate of patients with PABC.

Poor Prognosis of Lower Inner Quadrant in Lymph Node-negative Breast Cancer Patients Who Received No Chemotherapy: A Study Based on Nationwide Korean Breast Cancer Registry Database.

BACKGROUND: We aimed to investigate the prognostic influence of primary tumor site on the survival of patients with breast cancer. PATIENTS AND METHODS: Data of 63,388 patients with primary breast cancer from the Korean Breast Cancer Registry were analyzed. Primary tumor sites were classified into 5 groups: upper outer quadrant, lower outer quadrant, upper inner quadrant, lower inner quadrant (LIQ), and central portion. We analyzed overall survival (OS) and breast cancer-specific survival (BCSS) according to primary tumor site. RESULTS: Central portion and LIQ showed lower survival rates regarding both OS and BCSS compared with the other 3 quadrants (all P < .05) and hazard ratios were 1.267 (95% CI, 1.180-1.360, P < .001) and 1.215 (95% CI, 1.097-1.345, P < .001), respectively. Although central portion showed more unfavorable clinicopathologic features, LIQ showed more favorable features than the other 3 quadrants. Primary tumor site was a significant factor in univariate and multivariate analyses for OS and BCSS (all P < .001). For lymph node-negative patients, LIQ showed a worse OS than the other primary tumor sites in the subgroup with no chemotherapy (P < .001), but that effect disappeared in the subgroup with chemotherapy (P = .058). CONCLUSION: LIQ showed a worse prognosis despite having more favorable clinicopathologic features than other tumor locations and it was more prominent for lymph node-negative patients who received no chemotherapy. The hypothesis of possible hidden internal mammary node metastasis could be suggested to play a key role in LIQ lesions.

Education Level Is a Strong Prognosticator in the Subgroup Aged More Than 50 Years Regardless of the Molecular Subtype of Breast Cancer: A Study Based on the Nationwide Korean Breast Cancer Registry Database.

PURPOSE: This study investigated the role of the education level (EL) as a prognostic factor for breast cancer and analyzed the relationship between the EL and various confounding factors. MATERIALS AND METHODS: The data for 64,129 primary breast cancer patients from the Korean Breast Cancer Registry were analyzed. The EL was classified into two groups according to the education period; the high EL group (≥ 12 years) and low EL group (< 12 years). Survival analyses were performed with respect to the overall survival between the two groups. RESULTS: A high EL conferred a superior prognosis compared to a low EL in the subgroup aged > 50 years (hazard ratio, 0.626; 95% confidence interval [CI], 0.577 to 0.678) but not in the subgroup aged ≤ 50 years (hazard ratio, 0.941; 95% CI, 0.865 to 1.024). The EL was a significant independent factor in the subgroup aged > 50 years according to multivariate analyses. The high EL group showed more favorable clinicopathologic features and a higher proportion of patients in this group received lumpectomy, radiation therapy, and endocrine therapy. In the high EL group, a higher proportion of patients received chemotherapy in the subgroups with unfavorable clinicopathologic features. The EL was a significant prognosticator across all molecular subtypes of breast cancer. CONCLUSION: The EL is a strong independent prognostic factor for breast cancer in the subgroup aged > 50 years regardless of the molecular subtype, but not in the subgroup aged ≤ 50 years. Favorable clinicopathologic features and active treatments can explain the main causality of the superior prognosis in the high EL group.

Breast cancer-specific mortality in small-sized tumor with node-positive breast cancer: a nation-wide study in Korean breast cancer society.

Tumor size and number of lymph node (LN) metastases are well known as the most important prognostic factors of breast cancer. We hypothesized that very small breast cancers with LN metastasis represent a progressive biologic behavior and evaluated tumor size stratified by LN metastasis. Data between 1990 and 2010 were obtained retrospectively from the Korean Breast Cancer Society Registry with inclusion criteria of female, non-metastatic, unilateral, and T1/2 breast cancer. We collected the following variables: age at surgery, tumor size, number of LN metastases, nuclear grade (NG), lymphovascular invasion (LVI), estrogen receptor status, progesterone receptor status, and epidermal growth factor receptor-2 status. Patient characteristics were compared by means of independent t-tests for continuous variables and the Chi-square or Fisher's exact test for categorical variables. Kaplan-Meier curves, with corresponding results of log-rank tests, were constructed for breast cancer-specific survival (BCSS). Five- and eight-year breast cancer-specific mortality (BCSM) was obtained in groups of 300 patients, followed by smoothing according to the confidence interval using the lowess method. We identified 39,826 breast cancer patients who met the inclusion criteria. Among them, 1433 (3.6 %) patients died due to breast cancer. The median follow-up duration was 63.4 (3-255) months. In the multivariate analysis, age at surgery, NG, LVI, subtype, and tumor size-nodal interactions were independently associated with BCSM. The N1 group had lower BCSS for T1a than T1b. The N2+ group also had lower BCSS for T1b than T1c or T2. In the N1 group of tumors smaller than 10 mm, 5- and 8-year BCSM decreased with larger tumor size. Patients with very small tumors with LN metastasis have decreased BCSM according to increase tumor size. Small tumors with LN metastasis could have aggressive biological behavior.