Risk factors of distant metastasis after surgery among different breast cancer subtypes: a hospital-based study in Indonesia

Background: More than one third of breast cancer patients including those that are diagnosed in early stages will
develop distant metastasis. Patterns of distant metastasis and the associated risks according to the molecular
subtypes are not completely revealed particularly in populations of patients with delayed diagnosis and advanced
stages.
Methods: Breast cancer patients (n = 1304) admitted to our institute (2014–2017) were evaluated to identify the
metastatic patterns and the associated risks. Metastatic breast cancers at diagnosis were found in 245 patients
(18.7%), and 1059 patients were then grouped into non-metastatic and metastatic groups after a median follow-up
of 3.8 years.
Results: Infiltration of the tumor to the skin and chest wall prevailed as the most powerful predictor for distant
metastasis (OR 2.115, 95% CI 1.544–2.898) particularly in the luminal A-like subtype (OR 2.685, 95% CI 1.649–4.371).
Nodal involvement was also significantly associated with the risk of distant metastasis (OR 1.855, 95% CI 1.319–
2.611), and the risk was higher in the Luminal A-like subtype (OR 2.572, 95% CI 1.547–4.278). Luminal A-like subtype had a significant higher risk of bone metastasis (OR 1.601, 95% CI 1.106–2.358). In respect to treatment, a
combination of anthracyclines and taxanes-based chemotherapy was significantly associated with lower distant organ spread in comparison with anthracycline-based chemotherapy (OR 0.510, 95% CI 0.355–0.766) and the effect was stronger in Luminal A-like subtype (OR 0.417, 95% CI 0.226–0.769). Classification into Luminal and non-Luminal subtypes revealed significant higher risks of bone metastasis in the Luminal subtype (OR 1.793, 95% CI 1.209–2.660) and pulmonary metastasis in non-Luminal breast cancer (OR 1.445, 95% CI 1.003–2.083).
Conclusion: In addition to guiding the treatment plan, a comprehensive analysis of clinicopathological variables
including the molecular subtypes could assist in the determination of distant metastasis risks of breast cancer
patients. Our study offers new perspectives concerning the risks of distant metastasis in breast cancer subtypes in
order to plan intensive surveillance or escalation of treatment particularly in a setting where patients are
predominantly diagnosed in late stages.