Success predictors of adjuvant chemotherapy in node-negative breast cancer patients under 55 years.

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.