Patients will be visited every 6 weeks. In the training step, patients will remain under observation for a minimum of 6 weeks, until change of therapy (due to progression of disease, unacceptable toxicity, death, discontinuation) or for a maximum of 12 weeks. Patients enrolled in the validation step will remain under observation until change of therapy (due to progression of disease, unacceptable toxicity, death, discontinuation) or for a maximum of 24 weeks.