Determining Regional Recurrence Patterns by Breast Cancer Subtype

Breast cancer has become the most common cancer worldwide, with about 2.3 million new cases annually. Its different molecular subtypes lead to different treatment and follow-up strategies. A South Korean study sought to identify local and regional recurrence patterns across subtypes. This could help personalize treatment and monitoring, particularly for younger patients.

What Are Local and Regional Recurrence, and How Do They Differ?

• Local: “Local” concerns a particular point or very limited area—in other words, a very early stage. In medicine, a local condition or effect affects a specific part or organ. A local infection, for example, affects only a wound without spreading elsewhere. A local injection is given at one point or a few nearby points. In local breast cancer, the tumor remains in breast tissue without spreading to surrounding tissues or lymph nodes.

• Regional: “Regional” covers a wider area than “local.” A regional condition or effect may involve not only a particular organ or body area but adjacent or related areas too. A regional infection, for example, may affect an organ and spread to nearby tissues or lymph nodes. Regionally advanced breast cancer means that the tumor has spread from the breast to surrounding tissues, particularly the underarm lymph nodes. This indicates a more advanced stage and may require more extensive approaches, including surgery, radiation, chemotherapy, and targeted drugs. 

Local and Regional Recurrence Patterns Across Molecular Breast Cancer Subtypes

Study Scope

• Location: Seoul National University Hospital, South Korea
• Period: January 2000 - December 2018
• Participants: 16462 women who had undergone breast cancer surgery, meaning they had early-stage disease

Main Findings

• 10-Year Survival Rates:

  • Patients without ipsilateral breast cancer recurrence: 95.9%
  • Patients without regional recurrence: 96.1%
  • Patients without contralateral breast cancer: 96.5%

• Differences by Hormone Receptor and HER2 Status:

  • Hormone Receptor-Negative/HER2-Positive Subtype: This group had the lowest proportion of patients free from ipsilateral breast tumor recurrence (HR = 2.95, 95% CI = 2.15–4.06), meaning a greater risk of recurrence in the same breast. The HR (hazard ratio) indicates how much higher the risk is: in this case, approximately 3 times higher.
  • Triple-Negative (Hormone Receptor-Negative/HER2-Negative) Subtype: This group had the worst regional recurrence-free survival (HR = 2.95, 95% CI = 2.37–3.67), indicating a greater risk of spread to areas surrounding the breast. It also had the highest risk of contralateral breast cancer (HR = 2.12, 95% CI = 1.64–2.75), meaning a greater risk of spread to the opposite breast for this subtype.

The molecular subtypes of breast cancer are illustrated below to help explain the topic:

• Annual Recurrence Patterns:

  • In hormone receptor-negative/HER2-positive and hormone receptor-negative/HER2-negative subtypes, tumor recurrence in the same breast—the one in which cancer first appeared—peaks at about 2 years. It then declines before peaking again at about 9 years, forming a “double-peak” pattern.

• Differences by Age:

  • Women younger than 40 showed larger differences among breast cancer subtypes in ipsilateral breast tumor recurrence, regional recurrence, and contralateral breast cancer patterns.

Conclusion

The study shows that local and regional recurrence follows different patterns by breast cancer subtype, with larger differences in younger patients. The findings suggest tailoring monitoring strategies to subtype-specific local and regional recurrence patterns, particularly for younger patients.