Statistical approach to mediastinal staging in NSCLC with M.E.S.S.i.a. Software. Preliminary data and multicenter prospective validation study framework

The exclusion of pathological involvement of mediastina lymph nodes in patients affected by NSCLC plays a central role i assessing their prognosis and operability. Ceron et al. developed software - called M.E.S.S.i.a (Mediastinal Evaluation wit Statistical Support; instan approach) - that allows the calculatio of the residual probability of lymph node involvement after certain number of tests has been done, by integrating every tes result with the pre-test prevalence. M.E.S.S.i.a. bridges a gap o current American College of Chest Physicians (ACCP) guidelines providing probability values of mediastinal metastasis for a correc clinical decision. We conducted a preliminary retrospective stud in a series of 108 patients affected by non small cell lung cance (NSCLC). Pathological staging was compared to the probability o nodal involvement calculated by M.E.S.S.i.a. software. Forty-two out of 108 subjects (39%) had a calculated post-test probability <8%; none of these had proven N2/N3 metastasis at surgical staging (negative predictive value, NPV: 100%). In 12/41 cases M.E.S.S.i.a. was able to avoid invasive procedures. The remaining 66 (61%) patients did not reach the surgical threshold; among these, 11 displayed N2 positivity at pathological staging. Receiving operator curve (ROC) analysis produced an area under curva (AUC) value of 0.773 (p<0.001). These preliminary data show a high accuracy of M.E.S.S.i.a. software in excluding N2/N3 lymph node involvement in NSCLC. We have therefore promoted a prospective multicenter study in order to to get a validation of the calculator at different levels of probability of lymph node involvement. The recruitable subjects are potentially operable NSCLC patients; the gold standard for detection of mediastinal disease is the surgical lymph node dissection.