Success Predictors of Adjuvant Chemotherapy in Node-Negative Breast Cancer Patients Under 55 years1

BACKGROUND Adjuvant systemic chemotherapy (ASCT) in lymph node-negative breast (LN-) cancers improves survival. The majority of (LN-) patients receive ASCT when the St. Gallen criteria or its modifications are used, as accurate identifiers which patients benefit from ASCT are lacking. This may imply over-treatment in many patients. AIM To evaluate which patients or primary tumor factors predict ASCT success. MATERIAL AND METHOD Retrospective analysis by single and multivariate survival analysis of clinical and tumor characteristics in (LN-) breast cancers <55 years, related to ASCT (n=125) or-not (n=516). RESULTS The two patient groups did not differ in age, tumor diameter, grade, type, number of mitoses and other factors. Fourteen-year survival for the ASCT and non-ASCT patients was 83% and 74% (Hazard Ratio=HR=0.33; p<0.0001, 9% absolute=12% relative difference). Subgroup analysis showed that the recurrence-free survival=RFS of ASCT treated vs. non-treated patients differed in patients with grade 1 cancers (p=0.008), grade 2 cancers (p=0.004), grades 3 (p=0.02), tumors under and >or=2 cm (p=0.001 and 0.0002), oestrogen receptor-positive or -negative tumors (p=0.003,0.04), MAI < 10 and >or=10 (p=0.005,0.003) and fibrotic focus absent (p=0.002). With multivariate analysis the most important predictor of ASCT effect was the MAI. In patients with slowly proliferating tumors (MAI <3) no advantage was found between patients treated-or-not with adjuvant chemotherapy (RFS=92% and 91%, p=0.13, p=0.63 for overall survival), contrasting those with MAI >or=3 (p=0.0001; HR=0.32, 95% CI 0.18-0.58). CONCLUSION MAI is the strongest predictor of adjuvant systemic chemotherapy success. In patients with MAI < 3 (31% of all patients), ASCT does not improve survival.