Predicting aggressive outcome in T1N0M0 breast cancer.

Despite the excellent overall prognosis, unpredictable breast cancer recurrences and deaths also occur among T1N0M0 patients. We have evaluated clinically applicable methods for identifying aggressive outcome in T1N0M0 breast cancer. The material is based on aggressive T1N0M0 invasive ductal and lobular carcinomas diagnosed in Turku University Hospital and Jyväskylä Central Hospital, Finland, during 1987-1997. We studied all the T1N0M0 breast cancers that had led to recurrency or death (n=21, 95% T1cN0M0) during the follow-up period (4-14 years). The study is based on statistical analyses of matched case-control data in which the prognostic factors of each individual patient with aggressive disease were compared with control patients (n=45) individually matched by tumour size, age at diagnosis, histological type of tumour and length of follow-up. The cancer cases were examined for clinically applicable conventional and immunohistochemical pathologic prognostic factors. High Ki-67 immunopositivity was the strongest prognosticator of breast cancer death or recurrence in T1N0M0 breast cancer. Also, high p53 immunopositivity, low oestrogen receptor immunopositivity and Her-2/neu oncogene amplification by chromogen in situ hybridisation were reliable indicators of unfavourable outcome. Our statistical methods also allowed us to determine for the present material a range of clinical significance for each immunohistochemical prognostic feature with the associated relative risk for breast cancer death and recurrence. The paper suggests guidelines for predicting aggressive outcome in T1N0M0 breast cancer.