Help me make sense of this?

AnniebNJ, The good news for you and me was that Grade 1 Luminal B is quite unusual had a very good prognosis even without chemo, according to that study. Figure 4 shows the hazard ratios for each grade by subtype. The discussion is particularly interesting:

"Despite being increased in number by our proposal, only a small proportion of luminal A–like tumors were defined as poorly differentiated (2.5%). Reciprocally, a small proportion of our redefined luminal B–like tumors were well-differentiated (4.6%). Such a pattern was observed in a previous study in which the intrinsic subtype assignment was based on gene expression profiling. Bastien et al. reported 14.1% poorly differentiated luminal A tumors and 9.4% well-differentiated luminal B tumors among women with locally advanced primary invasive breast cancer studied using the PAM50 gene set [8]. Interestingly, an accurate assessment of tumor grade remains a powerful prognostic parameter, though it is not included in any of the surrogate definitions for luminal tumors. In our present series, patients with G1 tumors belonging to the luminal B class had significantly better outcomes than patients with G2 and G3 tumors of the same class, despite the fact that almost 80% of the former group of patients did not receive any chemotherapy in addition to endocrine therapy. Conversely, patients with G3 tumors of the luminal A class had worse outcomes than those with G1 and G2 tumors of the same class, with HRs not different from the HR for patients with G3 tumors of the luminal B class, despite the fact that >40% of the former patient group did receive adjuvant chemotherapy. It is tempting to speculate that a more comprehensive surrogate definition of the luminal classes of tumors for clinical purposes could incorporate grade as a first discriminator (G1 for luminal A and G3 for luminal and biological features to define the luminal classes among the G2 tumors only."