Therefore, we propose that breast cancers with low levels of CtIP/RBBP8 might respond worse to tamoxifen treatment, but that once those tumors were resected, the probability of tumor relapse for those patients treated with tamoxifen was the same, irrespective of the level of CtIP/RBBP8 expression detected in the biopsy. The gene discussed is RBBP8; the disease is breast cancer.