ESR1 and acute lymphoblastic leukemia: Neo-ALL-IN study (56) showed that when patients with ER+/HER2+ EBC received neoadjuvant therapy with a chemo-free regimen (letrozole + lapatinib), high baseline TILs of over 20%, a decrease in the ER Allred score after neoadjuvant treatment, and SUVmax (maximum standardized uptake value, a measure of activity in PET imaging linked to cell viability and proliferation) in baseline FES-PET are to be considered potential biomarkers in these patients.