With the final goal to provide useful information for improving the oncofertility counselling of premenopausal women with HER2-positive early breast cancer, we have recently performed an exploratory analysis within the Adjuvant Lapatinib and/or Trastuzumab Treatment Optimization (ALTTO; BIG 2-06) trial aiming to address these unmet medical issues [4]. This evidence concerns the gene ERBB2 and breast cancer.