Dormancy and Minimal Residual Disease

Relapse, even after many years of disease-free survival, is a common and potentially life threatening complication of tumors. Two major causes for this are the presence of dormant tumor cells in the body and the existence of minimal residual disease after therapy.

Dormancy is a state, in which tumor cells are present, but do not proliferate for extended periods of time. In early stage tumors and consecutive to clinically successful treatment of carcinomata, there is presence of tumor cells in the blood and bone marrow of the patients. Many of them do not develop into metastatic lesions, rather a large proportion of solitary cells disseminates throughout the body but remains dormant [Naumov et al. 2001]. Tumors or their metastases may sustain dormancy for years to decades, and metastases can arise long after the removal of a primary tumor [Meltzer 1990;Karrison et al. 1999]. Dormancy is likely to be a fairly common occurrence. Nearly one third of women between the ages of 40 and 50 have small in situ breast tumors, whereas only about 1% of women in this age group encounter breast cancer [Nielsen et al. 1987]. This suggests that the vast majority of these tumors stay dormant.