Validity of the online prognostication tool “PREDICT” for young Japanese breast cancer patients

Background: “PREDICT” is increasingly being used as an online prediction tool in clinical practice, even in Japan. Especially for young breast cancer patients, we sometimes need more detailed data on an individual level about how much adjuvant treatment can reduce the patients’ mortality so that they can decide whether to undergo adjuvant treatment based on their various background characteristics, such as social activities, role in the family, or desire to maintain fertility. However, the validity of “PREDICT” has not been clarified for young Japanese breast cancer patients.