Background: Even after successful radical treatment of lung cancer, patients in stages I and II of the TNM system very frequently suffer recurrence, which end lethally. Detection of subclinical residual disease after surgery is thus one of the most important emerging diagnostic methods. Minimal residual disease (MRD) is defined as the presence of isolated tumor cells or circulating cells in a patient after curative primary tumor removal and at the same time, no clinical signs of cancer. Conventional methods cannot detect minimal residual disease and hence there is a need for detection using new molecular biological methods.
Methods: We searched the PubMed database for original and review articles on minimal residual disease in lung cancer. Search words were "lung cancer", "minimal residual disease" and "detection of minimal residual disease". The publications we found were compared with the results of our own studies on the detection of minimal residual disease in lung cancer and the personal experiences are described. Examination of blood samples from 98 healthy volunteers and bone marrow from 12 patients with non inflammatory and non tumour illness, were used to determine cut-off values for specific markers in the compartments. Subsequently, expression of selected markers in tumor tissue was analysed in a pilot sample of 50 patients with lung cancer and the presence of MRD was measured as expression of values of the tested markers correlated with clinico-pathological characteristics.
Conclusions: Recent studies on other malignancies apart from lung cancer have shown the importance of MRD detection in the determination of disease progression and prognosis. The methods of MRD diagnostics are based on detection of specific tumor markers. Of these, the most specific for lung cancer, appears to be the LunX protein. The best method for determining MRD is probably RT-PCR. Further studies should expand knowledge in this area: to refine understanding of the importance of tumor markers for prognosis, as well as to confirm the significance of these findings in clinical practice.