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William D. Travis



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    ES12 - Lung Cancer Pathology in the Age of Genomics (ID 15)

    • Event: WCLC 2019
    • Type: Educational Session
    • Track: Pathology
    • Presentations: 1
    • Now Available
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      ES12.05 - Impact of STAS in Lung Cancer Staging (Now Available) (ID 3222)

      15:15 - 16:45  |  Presenting Author(s): William D. Travis

      • Abstract
      • Presentation
      • Slides

      Abstract

      Spread through air spaces (STAS) is an established histologic marker of poor prognosis found in 15-60% of lung cancers. The association with poor prognosis is supported by data from over 3500 patients from multiple multidisciplinary investigative groups worldwide. This prognostic significance has been demonstrated in all major types of lung cancer including adenocarcinoma,1 squamous cell carcinoma,2 small cell carcinoma,3 large cell neuroendocrine carcinoma,3, atypical carcinoid3 and pleomorphic carcinoma.4, 5

      As this large volume of clinical data has accumulated some important issues that have arisen. 1) Importance of processing, 2) Role in Staging? 3) Limited resection vs lobectomy and 4) Frozen section.

      Criteria for STAS

      The original definition of STAS by Kadota et al and the 2015 WHO consisted of tumor cells within the first alveolar air spaces in the lung parenchyma beyond the edge of the main tumor. In adenocarcinoma it can occur as one of three morphologic patterns including 1) micropapillary structures within air spaces; 2) solid nests or tumor islands and 3) scattered discohesive single cells.1, 6 In a recent paper we also proposed to require the presence of more than a single STAS cluster.3 The solid nest pattern is characteristic in other lung cancer histologies such as squamous cell carcinoma and neuroendocrine tumors. 3-dimensional studies with serial histologic sectioning and microCT whole block imaging suggest that there may be two mechanisms of spread into the adjacent lung: 1) detachment, migration through air spaces and reattachment with vessel co-option and 2) tumor islands of continuous tumor spread into adjacent air spaces.

      An important component of the diagnostic criteria is the distinction from artifacts: 1) mechanically induced tumor floaters that are randomly situated often at the edge of the tissue section or out of the plane of section; 2) jagged edges of tumor cell clusters suggesting fragmentation or edges of a knife cut during specimen processing; 3) isolated tumor clusters at a distance from the tumor rather than spreading in a continuous manner from the tumor edge and 4) linear strips of cells lifted off alveolar walls.

      Importance of Processing

      To assess for STAS histologic sections need to be taken in such a way to maximize the interface between the tumor and adjacent non-neoplastic lung parenchyma. For example, sections of subpleural tumors that maximize assessment of the visceral pleura or the interface with dense fibrotic scars or post-obstructive organizing are not well suited for assessment of STAS. This applies to both frozen and permanent sections.

      Role of STAS in Staging?

      Although the prognostic significance of STAS, has led some to suggest it might be included as a factor in staging,7, 8 there is insufficient data at this time to make such a recommendation. Tumor size should continue to be measured according to the gross and/or microscopically recognized edge of lung cancers rather than according to the maximum distance of furthest STAS. Although vascular (V) and lymphatic (L) invasion are recognized in TNM staging, only visceral pleural invasion (VPI) is officially incorporated as a T-factor in the 8th Edition. STAS is regarded as a sign of invasion similar to V, L and VPI, however, more data is needed before introducing this as a T-factor for staging.

      Limited resection vs lobectomy

      Evidence is accumulating that indicates an increased risk of recurrence and worse survival associated with STAS positive tumors treated by limited resection compared to lobectomy.5, 9

      Role of Frozen Sections in Assessing STAS

      There is limited data evaluating pathologist’s ability to recognize STAS in frozen section. Eguchi et al found the sensitivity and specificity of frozen section for prediction of STAS were 71% and 92%. respectively and interrater reliability across 5 pathologists was 0.67.9

      Walts AE et al studied frozen section for evaluation of STAS and recommended that current evidence did not warrant frozen section evaluation for STAS.10 However, frozen section sensitivity to detect STAS positivity was 50%, with a 100% positive predictive value and an 8% negative predictive value. These studies suggest if a pathologist sees STAS on a frozen section there is a 92-100% likelihood it will be present on permanent sections. Both studies were retrospective so attention was not always given to including the tumor edge and adjacent lung. More studies are needed to evaluate the potential role of frozen section in detecting STAS and guiding intraoperative decisions by surgeons.

      REFERENCES

      1. Kadota K, et al. Tumor Spread through Air Spaces is an Important Pattern of Invasion and Impacts the Frequency and Location of Recurrences after Limited Resection for Small Stage I Lung Adenocarcinomas. J Thorac Oncol 2015;10:806-14.

      2. Lu S, et al. Spread through Air Spaces (STAS) Is an Independent Predictor of Recurrence and Lung Cancer-Specific Death in Squamous Cell Carcinoma. J Thorac Oncol 2017;12:223-34.

      3. Aly RG, et al. Spread Through Air Spaces (STAS) Is Prognostic in Atypical Carcinoid, Large Cell Neuroendocrine Carcinoma, and Small Cell Carcinoma of the Lung. J Thorac Oncol 2019.

      4. Yokoyama S, et al. Tumor Spread Through Air Spaces Identifies a Distinct Subgroup With Poor Prognosis in Surgically Resected Lung Pleomorphic Carcinoma. Chest 2018;154:838-47.

      5. Liu H, et al. Prognostic Impact of Tumor Spread Through Air Spaces in Non-small Cell Lung Cancers: a Meta-Analysis Including 3564 Patients. Pathol Oncol Res 2019.

      6. Travis WD, et al. WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart. 4th ed. Lyon: International Agency for Research on Cancer; 2015.

      7. Uruga H, et al. Will spread through air spaces be a staging parameter in lung cancer? Journal of thoracic disease 2018;10:593-6.

      8. Dai C, et al. Tumor Spread through Air Spaces Affects the Recurrence and Overall Survival in Patients with Lung Adenocarcinoma >2 to 3 cm. J Thorac Oncol 2017;12:1052-60.

      9. Eguchi T, et al. Lobectomy Is Associated with Better Outcomes than Sublobar Resection in Spread through Air Spaces (STAS)-Positive T1 Lung Adenocarcinoma: A Propensity Score-Matched Analysis. J Thorac Oncol 2019;14:87-98.

      10. Walts AE, et al. Current Evidence Does Not Warrant Frozen Section Evaluation for the Presence of Tumor Spread Through Alveolar Spaces. Arch Pathol Lab Med 2018;142:59-63.

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    P2.09 - Pathology (ID 174)

    • Event: WCLC 2019
    • Type: Poster Viewing in the Exhibit Hall
    • Track: Pathology
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/09/2019, 10:15 - 18:15, Exhibit Hall
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      P2.09-24 - IASLC Global Survey for Pathologists on PD-L1 Testing for Non-Small Cell Lung Cancer (ID 906)

      10:15 - 18:15  |  Author(s): William D. Travis

      • Abstract
      • Slides

      Background

      PD-L1 immunohistochemistry (IHC) is now performed for advanced non-small cell lung cancer (NSCLC) patients to examine their eligibility for pembrolizumab treatment, as well as in Europe for durvalumab therapy after chemoradiation for stage III NSCLC patients. Four PD-L1 clinical trial validated assays (commercial assays) have been FDA/EMA approved or are in vitro diagnostic tests in multiple countries, but high running costs have limited their use; thus, many laboratories utilize laboratory-developed tests (LDTs). Overall, the PD-L1 testing seems to be diversely implemented across different countries as well as across different laboratories.

      Method

      The Immune biomarker working group of the IASLC international pathology panel conducted an international online survey for pathologists on PD-L1 IHC testing for NSCLC patients from 2/1/2019 to 5/31/2019. The goal of the survey was to assess the current prevalence and practice of the PD-L1 testing and to identify issues to improve the practice globally. The survey included more than 20 questions on pre-analytical, analytical and post-analytical aspects of the PDL1 IHC testing, including the availability/type of PD-L1 IHC assay(s) as well as the attendance at a training course(s) and participation in a quality assurance program(s).

      Result

      344 pathologists from 310 institutions in 64 countries participated in the survey. Of those, 38% were from Europe (France 13%), 23% from North America (US 17%) and 17% from Asia. 53% practice thoracic pathology and 36%, cytopathology. 11 pathologists from 10 countries do not perform PD-L1 IHC and 7.6% send out to outside facility. Cell blocks are used by 75% of the participants and cytology smear by 9.9% along with biopsies and surgical specimens. Pre-analytical conditions are not recorded in 45% of the institutions. Clone 22C3 is the most frequently used (61.5%) (59% with the commercial assay; 41% with LDT) followed by clone SP263 (45%) (71% with the commercial assay; 29% with LDT). Overall, one or several LDTs are used by 57% of the participants. A half of the participants reported turnaround time as 2 days or less, while 13% reported it as 5 days or more. Importantly, 20% of the participants reported no quality assessment, 15%, no formal training session for PD-L1interpretation and 14%, no standardized reporting system.

      Conclusion

      There is marked heterogeneity in PD-L1 testing practice across individual laboratories. In addition, the significant minority reported a lack of quality assurance, formal training and/or standardized reporting system that need to be established to improve the PD-L1 testing practice globally.

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