TOP LINE:
Patients with pure mucinous breast cancer (PMBC) have better recurrence-free interval (RFI), recurrence-free survival (RFS), and overall survival (OS) compared with patients with invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC). Patients with PMBC had a 5-year RFI of 96.1%, RFS of 94.9%, and OS of 98.1%.
METHODOLOGY:
- The researchers analyzed data from 23,102 women diagnosed with hormone receptor-positive, HER2-negative stage I-III breast cancer, including 20,684 with IDC, 1,475 with ILC, and 943 with PMBC.
- The multicenter cohort study included patients who underwent primary breast surgery between January 2000 and December 2015 at six academic institutions in Singapore, Taiwan, Korea and Japan.
- The current NCCN clinical practice guidelines “recommend considering adjuvant chemotherapy only for lymph node-positive tumors,” while adjuvant endocrine therapy is recommended for estrogen receptor-positive and/or progesterone receptor-positive, lymph node-positive tumors, or tumors ≥ 3 cm. Previous studies have found no significant association between adjuvant chemotherapy and breast cancer-specific survival or OS in patients with early-stage mucinous breast cancer.
- The aim of the study was to compare the recurrence and survival outcomes of PMBC with those of IDC and ILC, to determine clinicopathological prognostic factors of PMBC, and to investigate the association between adjuvant systemic therapy and outcomes in different subgroups of PMBC.
- Information extracted included patient demographics, tumor characteristics, treatment administered, and staging according to the AJCC TNM classification.
TAKE AWAY:
- Patients with PMBC had better RFI (hazard ratio (HR), 0.59; 95% CI, 0.43–0.80), RFS (HR, 0.70; 95% CI, 0.56–0.89), and OS (HR, 0.71; 95% CI, 0.53–0.96) than patients with IDC in multivariable Cox regression analyses.
- Less than half (48.7%) of the recurrences in patients with PMBC were distant recurrences, which is a lower rate than in patients with IDC (67.3%) and ILC (80.6%).
- Significant prognostic factors for RFI in PMBC included positive lymph nodes (HR 2.42; 95% CI 1.08–5.40), radiotherapy (HR 0.44; 95% CI 0.23–0.85), and endocrine therapy (HR 0.25; 95% CI 0.09–0.70).
- No differential associations were found between chemotherapy and outcomes in PMBC subgroups by nodal stage, tumor size, and age.
IN PRACTICE:
“This international multicenter cohort study of PMBC evaluated one of the largest current real-world data sets for clinical prognostic factors, which also includes valuable data on relapse events, associations with adjuvant systemic therapy, and a comparison with the SEER database,” the study authors wrote. “In our cohort, as expected, PMBC showed superior RFI, RFS, and OS compared to IDC and ILC, both of which had comparatively similar survival outcomes.”
SOURCE:
The study was led by Yoon-Sim Yap, MBBS, PhD, of the National Cancer Centre Singapore in Singapore. It was published online on May 14 in the Journal of the National Comprehensive Cancer Network.
RESTRICTIONS:
Limitations of this study include its long-term retrospective nature and the lack of central pathology review. The high proportion of missing values for tumor grade in PMBC in the multicenter cohort might influence the identified prognostic factors. Due to the specific geographic location of the participating institutions, the results of the study may not be generalizable to all populations.
DISCLOSURE:
Study author Yeon Hee Park, MD, PhD, disclosed that he serves on a data safety monitoring board and an advisory board for AstraZeneca, Pfizer, Roche, Menarini, Novartis, and Daiichi Sankyo, and serves as a consultant for AstraZeneca, Pfizer, Eli Lilly and Company, Gilead Sciences, Merck & Co., Inc., Eisai, Roche, Daiichi Sankyo, Menarini, Everest Pharmaceuticals, and Novartis. Additional information is provided in the original article.
Several editorial tools, including AI, were used to create this article. Human editors reviewed the content before publication.
