Abstract Background In patients with node-positive early breast cancer (EBC), dose-dense adjuvant chemotherapy improves disease-free survival (DFS) compared with standard interval chemotherapy. The GIM2 trial supports the value of dose-dense chemotherapy and suggests that the benefit is present in patients with hormone receptor-negative or hormone receptor-positive tumours (Del Mastro et al. Lancet 2015). In order to individualize decision making, there is a need to examine the absolute treatment effects of dose dense chemotherapy according to patient and tumor characteristics. Patients and Methods The randomized phase III GIM2 trial enrolled 2091 patients. The primary endpoint was DFS. A continuous, composite measure of treatment benefit for each patient was determined from a Cox model incorporating potential predictive factors (age: 25-40/41-55/56-71; histological grade: 1+2/3; hormonal receptor status: positive/negative). Subpopulation treatment effect pattern plot methodology was used to reveal differential treatment effects on DFS according to composite index. The study focused on patients with HER2–negative disease (N=1287). Results On average, the magnitude of benefit with dose dense chemotherapy versus standard chemotherapy ranged widely across different subpopulations, as quantified by the composite measure of relevant variables. The highest benefit was observed in patients with high grade, hormone receptor-negative disease (hazard ratio for DFS 0.44, 95% CI 0.23-0.83). Of note, a relevant benefit was observed also in patients with high grade, hormone receptor-positive disease (hazard ratio for DFS 0.74, 95% CI 0.50-1.09). Conclusion The absolute improvement in DFS with dose dense adjuvant chemotherapy is substantial in some patients with node-positive HER2-negative breast cancer, particularly those regarded as having high index risk (hormone receptor-negative, high grade disease). Interestingly, a significant effect of dose dense chemotherapy was observed also in patients with hormone receptor-positive, high grade disease. Citation Format: Puglisi F, Ceppi M, Cognetti F, De Placido S, Bruzzi P, De Laurentiis M, Bisagni G, Cavazzini G, Durando A, Turletti A, Valle E, Montemurro F, Barni S, Ardizzoni A, Gamucci T, Colantuoni G, Del Mastro L. Dose dense adjuvant chemotherapy in patients with early breast cancer: Differential treatment effects according to composite index of benefit [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-09-12.