Minimal residual disease in breast cancer

The incidence of breast cancer is increasing dramatically in the developed countries. Although attention is being paid to diagnose breast cancer early through screening programs, still a significant number of patients classif ied to have a localised disease at diagnosis, later experience a systemic r ecurrence. Therefore, more sensitive and reliable methods to detect the ear ly spread of the disease, permitting the early use of additional systemic t herapy, seem justified. New treatment strategies, such as immunotherapy emp loying monoclonal antibodies against breast cancer cells, is promising. Sin ce such a treatment is most efficient on patients with limited disease, sen sitive methods to monitor the therapeutic effect are needed. Immunocytochem istry using tumour associated monoclonal antibodies and reverse transcripti on polymerase chain reaction assays (RT-PCR), that screen for carcinoma-spe cific expression of mRNA in bone marrow and blood, have been developed. Man y standardisation problems with the detection methods currently in use are unsolved. Despite this, we discuss here recent data showing that the presen ce of occult tumour cells in the bone marrow is a prognostic factor in pati ents with breast cancer.