Risk Stratification for HR+ HER2- Early Breast Cancer

Clinical-Pathological Risk Categories

• The European Society for Medical Oncology (ESMO) guidelines suggest that tumor size ≤2 cm with node-negative disease is associated with low risk 3
• The American Joint Committee on Cancer (AJCC) defines low risk features as Grade 1 (low histologic grade) indicating well-differentiated tumors 3
• High ER/PR expression (strongly positive hormone receptors) is a low risk feature, according to the National Comprehensive Cancer Network (NCCN) guidelines 2
• A low Ki-67 proliferation index (<15-20%) suggests lower proliferative activity, as stated by the NCCN guidelines 2
• The absence of lymphovascular invasion (LVI) is a low risk feature, according to the ESMO guidelines 2
• Special histological subtypes, such as tubular, cribriform, or mucinous carcinomas, are associated with low risk, as defined by the World Health Organization (WHO) classification 3
• Tumor size >2 cm but ≤5 cm with limited nodal involvement (1-3 positive nodes) is considered an intermediate risk feature, according to the ESMO guidelines 1
• Grade 2 tumors with mixed clinical-pathological features are associated with intermediate risk, as stated by the NCCN guidelines 2
• Moderate Ki-67 levels (15-30%) are considered an intermediate risk feature, according to the NCCN guidelines 2
• Clinical-genomic discordance, where clinical and genomic risk assessments diverge, requires careful interpretation, as emphasized by the British Journal of Cancer guidelines 5
• Four or more positive lymph nodes, regardless of other factors, is a high risk feature, according to the ESMO guidelines 1
• Grade 3 (high histologic grade) indicating poorly differentiated tumors is a high risk feature, as defined by the AJCC 2
• Large tumor size (T3 or higher) is associated with high risk, according to the ESMO guidelines 3
• High Ki-67 (>30%) suggesting aggressive biology is a high risk feature, as stated by the NCCN guidelines 2
• Presence of lymphovascular invasion is a high risk feature, according to the ESMO guidelines 2
• Young age (<40 years) is associated with more aggressive disease, as emphasized by the NCCN guidelines 2

Genomic Risk Stratification

• The 21-Gene Recurrence Score (Oncotype DX) is supported by the ESMO 2024 guidelines and European Commission recommendations for use in node-negative disease, with a low genomic risk generally defined as RS <26 1
• The European Commission guidelines provide specific recommendations for the 70-Gene Signature (MammaPrint), with low genomic risk defined as patients classified as low by 70-GS 5
• High genomic risk is defined as RS >30 for the 21-Gene Recurrence Score, indicating potential chemotherapy benefit, as stated by the British Journal of Cancer guidelines 5
• The 70-Gene Signature should be used only in women at high clinical risk, with a conditional recommendation and low certainty, as emphasized by the British Journal of Cancer guidelines 5

Integrated Risk Assessment Algorithm

• The NCCN framework stratifies patients into very low risk, low-intermediate risk, and high risk categories, with treatment decisions guided by genomic testing and clinical risk factors, as stated by the NCCN guidelines 2
• Very low risk patients may be considered for endocrine therapy alone, according to the NCCN guidelines 4
• Low-intermediate risk patients require genomic testing to guide chemotherapy decisions, as emphasized by the British Journal of Cancer guidelines 5
• High risk patients typically require systemic chemotherapy, according to the NCCN guidelines 4

Critical Nuances and Pitfalls

• Clinical-genomic discordance requires careful interpretation, with women with high clinical risk but low genomic risk showing potential benefit from avoiding chemotherapy, as demonstrated by the MINDACT trial 6
• The Luminal A-like versus Luminal B-like distinction is important, with endocrine therapy alone sufficient for majority of Luminal A-like patients, and chemotherapy followed by endocrine therapy for majority of Luminal B-like patients, as stated by the ESMO guidelines 1
• The persistent risk of late relapse (>5-8 years) in HR+ disease means risk assessment must account for both early and late recurrence patterns, as emphasized by the NCCN guidelines 2