The probability of nodal metastasis in novel T-factor: the applicability of sublobar resection.

Abstract

Recently sublobar resection is often indicated for small-sized peripheral lung cancer according to size or the consolidation/tumor ratio on CT; however, the T-factor classification drastically changed in the 8th version. We investigated the relationship between a novel clinical T-factor classification, which includes other clinical information and the pathologic N-factor, to evaluate the applicability of the novel T-factor classification to sublobar resection. From January 2013 to October 2017, 545 patients with cTis or cT1 lung cancer underwent surgery. Patients with non-peripheral type, induction treatment, cN≥1, cM1, and those without nodal dissection, preoperative evaluation by thin-sliced CT or FDG-PET were excluded. Finally, 325 patients were eligible for inclusion. All clinical parameters were prospectively collected and retrospectively analyzed. The 8th edition of TNM classification was utilized. Nodal metastasis was detected in 38 (11.7%) patients. Among cTis/1mi/1a/1b/1c patients (n=10/11/51/146/107), pN1 and pN2 were observed in 0/0/2/9/10 and 0/0/1/8/8, respectively. cT1b/c patients showed a significantly higher rate of nodal metastasis (P=0.024). Among 253 cT1b/c patients, solid-type tumors (n=177) were more frequently associated with nodal metastasis. A ROC curve analysis revealed that SUVmax 1.9 was the cutoff value (AUC=0.827) for the presence of nodal metastasis. Using the 2 parameters of solid-type or SUVmax ≥1.9, we could successfully exclude patients with nodal metastasis, for whom sublobar resection is not indicated. In terms of nodal metastasis, sublobar resection can be applicable for all cTis/1mi tumors; patients with cT1a/b/c tumors with mixed GGO and low SUVmax are candidates for sublobar resection.