Influence of timing of initiation of adjuvant chemotherapy over survival in breast cancer: a negative outcome study by the Spanish Breast Cancer Research Group (GEICAM).

PURPOSE: This retrospective trial evaluates whether the timing of initiation of the adjuvant chemotherapy has any influence over survival in early-stage breast cancer. PATIENTS AND METHODS: A total of 2782 patients from El Alamo project (from 1990 to 1997; n = 15,400) were selected with stages I-III, surgery and adjuvant chemotherapy. Data were gathered about prognostic factors such as age, tumor size, vessel permeation (vascular or lymphatic), histological grade, and number of involved nodes, hormonal receptor status and administration of hormone therapy. The time interval between surgery and initiation of chemotherapy, and dates of relapse, second primary breast tumor and death were recorded. Patients were assigned in four groups according to the surgery-chemotherapy interval: <3 weeks (group A), 3-6 weeks (group B), 6-9 weeks (group C) and >9 weeks (group D).
RESULTS: There were no differences in disease-free survival (DFS), nor in 5-year overall survival (OS), according to the timing of initiation of adjuvant chemotherapy. Cox proportional hazards model was used to adjust analysis for known prognostic factors but the effect of surgery-chemotherapy interval remained non-significant. The variable timing of initiation of adjuvant chemotherapy has also been assessed as a continuous variable and no differences have been detected.
CONCLUSION: The optimum time of initiation of adjuvant chemotherapy in early stages of breast cancer is unknown. The delay in the initiation of adjuvant chemotherapy has no influence over survival in the analyzed time intervals. Retrospective analysis like this one with enough statistical power would be necessary to detect differences among groups.