Metastatic Breast Cancer as a Chronic Disease: Evidence-Based Data on a Theoretical Concept.

Background: We challenge the concept of metastatic breast cancer (MBC) as a chronic disease.

Methods: We analyzed an unselected cohort of 367 patients who were diagnosed with MBC over a 22-year period (1990-2011).

Results: In order to create a "chronic disease subgroup", we separated those patients from the entire cohort in whom systemic therapy was not applied after the diagnosis of MBC ( = 53; 14.4%). Three hundred fourteen patients (85.6%) comprised the "chronic disease subgroup". The vast majority of those patients (89.8%) died of progressive disease after a median metastatic disease survival (MDS) of 25 months. Twenty patients (6.4%) died of non-MBC-related causes (MDS 38.5 months). Approximately 1 in 4 patients (26.8%) died within the first year after the MBC diagnosis. The 3- and 5-year MDS rates were 35.4 and 16.2%, respectively. Only 12 patients (3.8%) were exceptional survivors (MDS >10 years).

Conclusion: The term "chronic disease" might be appropriate in selected MBC cases, bringing MBC into alignment with "classical" chronic diseases such as diabetes and hypertension. However, most cases display fundamental differences with regard to temporal progression and above all the case fatality rate. More than 90% of patients in the "chronic disease subgroup" died of the disease with a MDS of 2-3 years (even those who underwent systemic palliative therapies). Doctors and patients might understand the term "chronic disease" differently. The term must be used sparingly and explained carefully in order to create a common level of communication based on a shared understanding which avoids awakening false hopes and fostering misleading expectations.