Introduction: Programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC) assessment is mandatory for the single agent pembrolizumab treatment of patients with advanced non-small cell lung cancer (NSCLC). PD-L1 testing has been validated and is currently certified only on formalin-fixed paraffin-embedded materials but not on cytological smears. Unfortunately, a significant proportion of patients, having only cytological material available, cannot be tested for PD-L1 and treated with pembrolizumab. In this study, we aimed to validate PD-L1 IHC on cytological smears prospectively by comparing clone SP263 staining in 150 paired histological samples and cytological smears of NSCLC patients. Methods: We prospectively enrolled 150 consecutive advanced NSCLC patients. The clone SP263 was selected as, in a previous study of our group, it showed higher accuracy compared with clones 28-8 and 22-C3, with good cyto-histological agreement using a cut-off of 50%. For cyto-histological concordance, we calculated the kappa coefficient using two different cut-offs according to the percentage of PD-L1 positive neoplastic cells (<1%, 1–49% and ⩾50%; <50%, ⩾50%). Results: The overall agreement between histological samples and cytological smears was moderate (kappa = 0.537). However, when the cyto-histological concordance was calculated using the cut-off of 50%, the agreement was good (kappa = 0.740). With the same cut-off, and assuming as gold-standard the results on formalin-fixed paraffin-embedded materials, PD-L1 evaluation on smears showed specificity and negative predictive values of 98.1% and 93.9%, respectively. Conclusion: Cytological smears can be used in routine clinical practice for PD-L1 assessment with a cut-off of 50%, expanding the potential pool of NSCLC patients as candidates for first-line single agent pembrolizumab therapy.
ObjectiveA growing number of studies have suggested that non‐pathologists can reliably assess the adequacy and malignancy in rapid on‐site evaluation (ROSE) smears prepared during endoscopic sampling procedures. However, no study has verified whether they can also consistently estimate the tumour burden, which is critical for the molecular profiling of lung cancer. We aimed to assess the interobserver agreement (IOA) between a pathologist, a pulmonologist (previously trained in lung and lymph node cytopathology) and a molecular pathologist for the tumour burden in ROSE smears.MethodsThe ROSE smears of consecutive patients with suspected lung cancer undergoing endosonography or guided bronchoscopy were assessed independently by a pathologist, a pulmonologist and a molecular pathologist (gold standard). The IOA for the tumour burden, assessed through k‐statistics, was the primary outcome.ResultsA total of 322 ROSE smears obtained from 162 patients were evaluated. The IOA between the molecular pathologist and pulmonologist was very good (moderate to substantial), although slightly inferior to the IOA between the molecular pathologist and pathologist in the whole slide set (k: 0.707, 95% confidence interval [CI]: 0.677‐0.739 vs 0.793, 95% CI: 0.762‐0.815), as well as in smears prepared from lymphadenopathy (k: 0.783, 95% CI: 0.760‐0.855 vs 0.827, 95% CI: 0.728‐0.892) or from pulmonary nodules/masses (k: 0.558, 95% CI: 0.416‐0.686 vs 0.715, 95% CI: 0.621‐0.767).ConclusionsA professionally trained pulmonologist can reliably estimate the tumour burden in bronchoscopically derived ROSE smears, especially in the setting of lymphadenopathy. This can be particularly useful in institutions where a cytopathologist is not available regularly.
Preliminary results obtained with the dedicated Flex 19G needle are promising, as sample size/quality is satisfactory and the needle influence on scope flexibility is minimal.
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