Reply to Durand Free

We read with great interest the comment of Durand [1] whom we thank for giving us the opportunity to focus further on some topics of our article [2].

First of all, we would like to stress that we routinely perform lobectomy with radical lymphadenectomy as a standard treatment for early-stage lung cancer for both staging and treatment purposes. For this very reason, we were able to retrospectively analyze our patients, all of whom underwent the same radical surgery, identifying a homogeneous group of cases with ‘very small’ non-small-cell lung cancer (NSCLC), <1 cm in size and pathological N0 status. In addition, all our patients were preoperatively staged by computed tomography (CT) and (not or) positron emission tomography/CT (PET/CT) with fluorodeoxyglucose.

Considering that in the 7th edition TNM the definitions of the TNM descriptors and the stage groups were based on the outcome measure of the overall survival [3], we focused our attention on NSCLC <1 cm in size, that in our opinion was not studied enough in detail and in which survival was probably underestimated, in order to highlight how the size of the tumor could be an important predictor of lymph node involvement and survival.

All our patients with ‘very small’ NSCLC had different lymph node involvement and a 5-year survival rate when compared with staging group of origin (T1a) which had a 5-year survival rate of 77% after radical excision [3]. Specifically, none of these patients had any pathological lymph node involvement and their 5-year overall survival was 100%. Besides, all of them had nodule size >8 mm in diameter, which was above the spatial resolution of the PET device.

In 2011, Fischer et al. demonstrated in their prospective randomized study that sensitivity and specificity of PET/CT were the same both for lymph nodes <1 cm and for enlarged nodes (>1 cm) [4]. In particular, they showed that the negative predictive value was significantly higher in the group with small nodules (96% vs 70%) and the positive predictive value was lower (43% vs 71%). This means that a negative PET/CT was highly valid in patients with normal-sized lymph nodes, considering ‘normal size lymph nodes’, as defined by Silvestri et al., the lymph nodes with short-axis diameter of ≤1 cm on a CT scan image [5].

In detail, we used CT as an anatomical tool for thorax imaging, and PET/CT as a functional tool offering information about metabolic activity of structures identified with fusion images of a low-resolution CT in order to have a complete preoperative staging.

In conclusion, our study confirms the literature reports suggesting that tumor size, measured by CT and intra-operatively confirmed by the pathologist, and standardized uptake value (SUV), measured by PET/CT, could be reliable independent predictors of tumor aggressiveness and lymph node involvement. Radical lymphadenectomy could be omitted in patients with stage I NSCLC tumors <1 cm in diameter or SUV <2.0, considering the complete absence of lymph node involvement and the demonstrated 100% 5-year survival rate.

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