Residual cancer burden (RCB)
A score for how much cancer is left after pre-surgery treatment, from 0 (none) to III (a lot).
MD Anderson index combining tumour bed size, cellularity, and nodal involvement. RCB-II/III after neoadjuvant therapy predicts high relapse risk and defines populations for escalation trials (e.g., ctDNA-guided or ADC-based post-neoadjuvant therapy).
For stage II-III triple-negative breast cancer, chemotherapy plus pembrolizumab before surgery and pembrolizumab alone afterwards is now the standard approach worldwide, and the survival gain is real, not just a surrogate. It does not apply to stage I disease or to hormone-receptor-positive or HER2-positive cancers. The price is a year of immunotherapy with a meaningful chance of a permanent endocrine side effect such as hypothyroidism or adrenal insufficiency.
Everyone with HER2-negative early breast cancer that meets high-risk criteria should be offered germline BRCA testing, because a positive result now changes treatment: a year of olaparib after chemotherapy reduces relapse and death. It does not apply to low-risk tumours, HER2-positive disease, or somatic-only BRCA mutations.
HER2-positive breast cancer is now routinely treated before surgery so that the pathology result can guide what comes after: patients with no residual cancer continue trastuzumab (with or without pertuzumab), while those with residual disease switch to T-DM1. This model of using the tumour's response as a test has since been copied in triple-negative and other cancers.