Biological factors and therapeutic modulation in breast cancer radiotherapy

The natural history and survival of breast cancer are extremely variable although the advances and improvement in treatment in recent years led to a lower mortality. In fact, in spite of the administration of systemic adjuvant therapy, women with metastatic lymph nodes at diagnosis have a risk of disease progression at 5 years of 40-50%. The disease heterogeneity and the intrinsic tumor cell resistance to therapies are determining factors of the problem. The role of parameters as tumor size, grading, vascular spread, axillary lymph node status, are well defined. However the increasingly early diagnosis and changes in clinical practice have led to the need for non morphologic parameters as estrogen and progesteron receptors, cell proliferation index, labelling index, growth factors tumor-dependent genes (p53, HER2), cell cycle regulators (cyclins). Specific cellular and molecular alterations are studied to identify diagnosticoinstrumental images (MRI) of tumor angiogenesis, the cause of the different tumor aggressiveness. In the surgical and consequently clinico-oncologic approach there is the problem of the interpretation and prognostic role of sentinel lymph node when it is positive for micrometastasis only, if diagnosed by immunohistochemistry.