Large population-based study identifies that tumor size and lymph node involvement are associated with risk of death in metastatic breast cancer
Despite significant advances in breast cancer treatment, 5-year survival rate remains low in patients with metastatic breast cancer (1-3). The data prompt us to identify clinicopathologic and treatment factors that predict risks in cancer patients with metastatic disease.
We studied the overall survival or risk of all-cause death in de novo metastatic breast cancer population with 35812 patients from the Surveillance, Epidemiology, and End Results (SEER) database in the United States enrolled between January 1, 2004, and December 31, 2015. We also estimated independent performance of nodal status and T-stage adjusting for clinicopathological features and treatment factors bymultivariable Cox proportional hazards regression analysis.
We found that death was significantly higher in metastatic breast cancer patients with 1 to 3 nodes, 4 to 9 nodes, ≥10 lymph node involvements, and node status unknown, respectively, than node-negative patients (Figure image). Importantly, the association of nodal involvements with death was independent of age, race, tumor grade, estrogen-receptor status and HER2 status as well as chemotherapy, radiotherapy and surgery. In addition, death was significantly higher in patients with T stage (T) 2, T3, T0, T4, and Tx, respectively, than T1 patients (Figure image). They all but T0 are independent of other clinicopathologic and treatment factors. We also demonstrated the association between T stage or axillary lymph nodes and the death risk in HR+/HER2–, HR+/HER2+, HR–/HER2+ and triple-negative metastatic breast cancer subtypes.
Furthermore, I’d discuss the potential impact of our results and role of surgery in the management of metastatic breast cancer. Surgery is currently not a standard of care to manage patients with metastatic breast cancer. The surgical procedure is for salvage purpose, e.g., resection of a few numbers of metastases in the brain, lung, liver or other areas or treating open wound in the chest. Nonetheless, we found that patients who underwent surgery despite with palliative intent had a significantly reduced death rate, consistent with many previous studies. In a meta-analysis including 15 studies, surgical removal of the primary tumor in metastatic breast cancer was associated with better survival, with a 31% decreased risk of death (5). This was confirmed by an updated meta-analysis with 19 reports including randomized clinical trials in metastatic breast cancer (6). A randomized phase III (MF07-01) study compared the local treatment followed by systemic therapy to the systemic therapy alone for treatment naive stage IV breast cancer patients at diagnosis (7). This metastatic breast cancer trial demonstrated a significant improvement for 5-year survival rate of 41.6% versus 24.4%.
Mounting evidence revealed that proportions of cancer stem cells and cancer cells resistant to treatment propagated as the tumors grew larger (8, 9); it is conceivable and calculable that bulky tumors increase the treatment burdens (10, 11). Anticancer drugs were likely to be more accessible to cancer cells, and systemic therapies were much more effective after surgical removal of bulky tumors including necrotic and avascular tumor areas (12).
In summary, the risk of all-cause mortality was significantly higher in patients with distant metastasis at diagnosis and exhibited node involvement and larger breast tumors. This is an unbiased population-based study in the context of the SEER data that included all patients who had a survival time one month or greater. It is important to recognize and integrate the tumor size and nodal status, in addition to metastatic cancer sites, into the risk assessment and clinical management in metastatic breast cancer. Our findings may have an impact on other metastatic cancer types, ultimately to substantially reduce the cancer death in the years to come.
- SEER 18 2011–2017, All Races, Females by SEER Summary Stage 2000 at https://seer.cancer.gov/statfacts/html/breast.html. Accessed on March 12, 2022.
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- DeSantis CE, Ma J, Gaudet MM, Newman LA, Miller KD, Goding Sauer A et al. Breast cancer statistics, 2019. CA Cancer J Clin 2019; 69: 438-451.
- Press DJ, Miller ME, Liederbach E, Yao K, Huo D. De novo metastasis in breast cancer: occurrence and overall survival stratified by molecular subtype. Clin Exp Metastasis 2017; 34: 457-465.
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- Lu S, Wu J, Fang Y, Wang W, Zong Y, Chen X et al. The impact of surgical excision of the primary tumor in stage IV breast cancer on survival: a meta-analysis. Oncotarget 2018; 9: 11816-11823.
- Soran A, Ozmen V, Ozbas S, Karanlik H, Muslumanoglu M, Igci A et al. Randomized Trial Comparing Resection of Primary Tumor with No Surgery in Stage IV Breast Cancer at Presentation: Protocol MF07-01. Ann Surg Oncol 2018; 25: 3141-3149.
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