Participation in adjuvant clinical breast cancer trials: does study participation improve survival compared to guideline adherent adjuvant treatment? A retrospective multi-centre cohort study of 9,433 patients

Adjuvant clinical trials (CTs) usually compare a standard treatment regime versus an innovative new substance or regimen. Participation in CT however, is available for only few patients and exclusion criteria are usually very strict. Therefore we used an unselected patient cohort to investigate the following questions:

Material and methods: This German retrospective multi-centre cohort study included 9433 patients with primary breast cancer recruited from 1992 to 2008.

Results: One thousand two hundred and fifty-five (13.3%) patients participated in adjuvant clinical trials (PA) and 8178 (86.7%) did not (NPA). RFS was higher among participants (PA) than among non-participants (NPA) [p=0.006], but differences in overall survival (OAS) were not significant [p=0.15]. When stratified for guideline adherence, the outcome was not different for guideline conform NPA [RFS: p=0.88] [OAS: p=0.37] compared to PA. Survival parameters however, were significantly poorer in non-guideline conform PA [RFS: p<0.001] [OAS: p<0.001] and non-guideline conform NPA [RFS: p<0.001] [OAS: p<0.001] as compared to guideline adherent PA.

Discussion: There is a strong association between guideline adherence in adjuvant treatment in BC and survival. PA in clinical trials tended to higher survival rates, but only if guideline-adherent treatment was applied. Patients who do not have access to clinical trials may profit substantially from guideline-adherent adjuvant treatment.