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K.S. Tan

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    MINI 01 - Pathology (ID 93)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI01.07 - Comparison of Grading Systems Based on Histologic Patterns and Mitotic Activity to Predict Recurrence in Stage I Lung Adenocarcinoma (ADC) (ID 3030)

      10:45 - 12:15  |  Author(s): K.S. Tan

      • Abstract
      • Presentation
      • Slides

      An established grading system for lung adenocarcinoma does not exist but is greatly needed. The histologic classification proposed by the International Association for the Study of Lung Cancer (IASLC), the American Thoracic Society (ATS) and the European Respiratory Society (ERS) has been shown to define prognostically significant subgroups of lung adenocarcinoma (ADC). Since then, various grading systems based on histologic patterns have emerged as promising methods to further discriminate patient risk of clinical outcomes. The aim of this work is to quantitatively assess the discrimination properties of a set of grading systems proposed in recent years to identify the best grading scale(s) independent of other clinical factors to predict recurrence.

      We considered five grading systems: (1) single predominant pattern as six subtypes; (2) as three grades of low (lepidic), intermediate (acinar, papillary) and high (micropapillary, solid); (3) two most predominant grades; (4) predominant grade with mitotic grade; and (5) predominant grade with cribriform pattern and mitotic activity criteria. We evaluated the performance of each grading system with the concordance predictive estimate (CPE). The CPE represents the probability that for any pair of patients, the patient with the better predicted outcome from the Cox model had the longer survival time. CPE > 0.80 demonstrates strong performance. To compare the performance of the grading systems, we determined the significance of the differences between the CPEs. Five-year recurrence-free probability (RFP) was derived using the Kaplan-Meier method.

      We applied the grading systems to a uniform large cohort of stage I lung ADC (N=909). The scale based on the single predominant pattern as five subtypes yielded a CPE of 0.63 (95% CI, 0.59-0.67), indicating moderate discrimination. Our analysis showed that grading systems (1), (2), and (3) were not significantly different from each other, suggesting that identifying finer subtypes and second predominant pattern may not improve discrimination. Grading system (4) [CPE, 0.67; 95% CI, 0.63-0.71] yielded a significantly higher CPE than (1), (2) and (3) [p<0.01]. Grading system (5) [CPE, 0.67; 95% CI, 0.63-0.71] was significantly better than (1), (2) and (3) but not (4) [p=0.776]. The lack of improvement in discrimination with the inclusion of cribriform between (4) and (5) can be attributed to the significant relationship between cribriform pattern and mitoses. As the proportion of cribriform pattern increased, the amount of mitotic activity also increased (p<0.001). Under (2), the 5-year RFP of the intermediate grade was 0.81. The addition of cribriform and mitotic counts further classified the intermediate (acinar, papillary) grade such that those with <10% cribriform and low mitotic count had 5-year RFP of 0.89, while the 5-year RFP for the other combinations are between 0.73-0.75.

      Grading systems based on histologic patterns and mitotic activity out-perform those with only histologic pattern. This comparison study suggests that proposed grading systems (4) or (5) provide valuable information in discriminating patients with different risks of disease-recurrence in patients with lung ADC.

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