2024 SABCS Meeting: What’s New in Early & Metastatic Breast Cancer?

The researchers attending the 2024 San Antonio Breast Cancer Symposium will present various studies on early and metastatic breast cancer. This roundup includes a selection of abstracts about genetic testing, the impact of comorbidities, and lymph node metastasis detection.

Genetic Tests Not Interchangeable in Early Breast Cancer

Brigitte Schober and colleagues wrote that estimating recurrence risk in early-stage ER+, HER2- breast cancer is critical to identifying patients who may safely avoid adjuvant chemotherapy. The researchers compared the results of three gene expression assays: Prosigna (PAM50), MammaPrint (MP), and EndoPredict (EP).

• The authors conducted a retrospective analysis of 48 primary tumors using MP and EP, with corresponding formalin-fixed paraffin-embedded tissue analyzed by PAM50.

• Valid results were obtained for all three tests in 82% (39 of 48) of cases. Only 42% (20 cases) had identical risk classifications across all tests.
• Discrepancies in risk classification occurred in 40% (19 cases), and 9 cases had missing data.
• PAM50 versus EP: 57% concordance; 33% rate of intermediate risk with potential for differing treatment recommendations.
• PAM50 versus MP: 56% concordance; similar rate of intermediate-risk (33%) and discrepancies (11%).
• PAM50 results would have altered therapeutic recommendations in 21% (10 of 48) of cases, including intermediate risk cases, which could lead to over- or undertreatment.
• Follow-up data showed metastases or recurrence in five patients, with varied risk classification across assays (e.g., intermediate in PAM50, high in MP/EP).

Main Takeaways: The assays yielded inconsistent risk classifications, with implications for treatment decisions in 10% of cases. Each test provided distinct, supplementary data and could not be used interchangeably. The researchers called for further comparative studies to reduce misclassification and improve breast cancer risk stratification.

Obesity & Sarcopenia Impact Chemotherapy Outcomes

Building on existing research, Jasmine Hundal, MD, and colleagues sought to clarify the relationship between specific comorbidities and chemotherapy outcomes in early breast cancer.

• The study was a retrospective analysis of 323 patients receiving chemotherapy for early breast cancer.
• The researchers measured sarcopenia using the skeletal muscle index (SMI < 6.75 kg/m²).
• Using multivariate logistic regression, the researchers analyzed the association of sarcopenia and 16 comorbidities with chemotherapy toxicity endpoints, adjusting for age and obesity.
• Sarcopenia was strongly associated with chemotherapy toxicity (OR, 6.94; P<0.0001), as were obesity (OR, 3.58; P=0.02) and hypertension (OR, 1.98; P=0.048).
• Sarcopenia (OR = 2.48, p=0.03) and renal disease (OR = 4.41, p=0.03) were significant predictors of dose delays.
• Early termination occurred more frequently in patients with obesity (OR = 4.67, P=0.006) or osteoporosis (OR = 3.46, P=0.02).
• Hospitalizations rates were higher rates among patients with obesity (OR = 8.00, P=0.003), sarcopenia (OR = 8.70, P=0.0006), diabetes (OR = 3.22, P=0.04), renal disease (OR = 7.09, P=0.01), or osteoarthritis (OR = 4.34, P=0.01).
• Obesity (OR = 3.62, P=0.006) and sarcopenia (OR = 5.92, P=0.0003) were significantly associated with increased neuropathy risk.

Main Takeaways: Obesity and sarcopenia were major predictors of chemotherapy intolerance in patients with early breast cancer. Specific comorbidities, including hypertension, renal disease, diabetes, and osteoarthritis, played distinct roles in predicting adverse outcomes. The authors concluded that comprehensive, personalized management addressing these factors is crucial to improving treatment tolerance and patient QOL.

A New Kit to Detect Lymph Node Metastases

Yuki Hara and colleagues evaluated a novel semi-dry dot-blot detection kit that identifies cancer cells using cytokeratin-19 (CK-19). While its efficacy was previously confirmed in non-neoadjuvant chemotherapy settings, its reliability in post-neoadjuvant chemotherapy, which can alter cancer cell morphology, remained unclear.

• The authors conducted a retrospective study of 60 patients with breast cancer and 101 lymph nodes from Nagasaki University Hospital.
• Lymph nodes included sentinel lymph nodes excised in node-negative patients and dissected axillary lymph nodes in node-positive patients.
• Permanent histological diagnoses served as the standard, categorizing metastases into macrometastases (>2.0 mm), micrometastases (0.2–2.0 mm), and isolated tumor cells (ITCs, <0.2 mm).

• Patient subtypes: luminal (25%), HER2+ (48.3%), and triple-negative (26.7%).
• Among 101 lymph nodes, 12 had macrometastases (11.9%), while 89 were non-macrometastases (88.1%), including three micrometastases and one ITC.

• The kit achieved 91.7% sensitivity, 100% specificity, and 99.0% accuracy.

Main Takeaways: The kit demonstrated high accuracy in detecting lymph node metastases, including in patients treated with neoadjuvant chemotherapy. A multicenter prospective study is planned to validate these findings and broaden the clinical application of the kit in breast cancer care.