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ORAL 24 - CT Detected Nodules - Predicting Biological Outcome (ID 122)
- Event: WCLC 2015
- Type: Oral Session
- Track: Screening and Early Detection
- Presentations: 1
ORAL24.07 - Behavior Differences of Screen-Detected Lung Cancers in the CT Arm of the National Lung Screening Trial (NLST) (ID 587)
10:45 - 12:15 | Author(s): Z.J. Thompson
Lung cancer screening identifies cancers with heterogeneous behaviors. In addition to screen-detected incidence lung cancers, screening also identifies prevalence cancers at the baseline screen and interval lung cancers diagnosed following a negative screen at any time point prior to the next screening round. To date, few studies have performed a comprehensive analyses comparing prevalence and interval lung cancers and screen-detected lung cancers based on sequence of screening results in the NLST.
The entire CT arm of the NLST was reconstructed according to baseline and follow-up screening results (positive vs. negative screen). Lung cancers immediately following a positive baseline (T0), and prior to the T1 screen, formed the prevalence cancers (PC); interval cancers (IC) were defined as lung cancers diagnosed following a negative screen at any point prior to the next screening round. Two screen-detected lung cancer (SDLC) cohorts were identified based on one (SDLC1) or two (SDLC2) prior positive screens and two screen-detected lung cancer cohorts following one (SDLC3) or two (SDLC4) prior negative screens. Differences in patient characteristics, progression-free survival (PFS), and overall survival (OS) were assessed.
Since there were no differences in patient characteristics and outcomes between SDLC1 and SDLC2 and between SDLC3 and SDLC4, the four screen-detected cancer case groups were combined into two combined SDLC case groups (SDLC1/SDLC2 and SDLC3/SDLC4). The lung cancer-specific death rate was higher for SDLC3/SDLC4 compared to SDLC1/SDLC2 lung cancers (136.6/1,000 person-years vs. 71.3/1,000 person-years, P < 0.001). PFS and OS were significantly lower for SDLC3/SDLC4 than SDLC1/SDLC2 (P < 0.004; P < 0.002, respectively). Overall, PFS and OS were highest in SDLC1/SDLC2 and lowest in the interval cancers (Figure 1); PFS and OS for the prevalence cancers were intermediate between SDLC1/SDLC2 and SDLC3/SDLC4. All findings were consistent when stratified by stage and histology. Multivariable Cox proportional models revealed that the SDLC3/SDLC4 case groups were associated with significantly poorer PFS (HR=1.72; 95% CI 1.19-2.48) and OS (HR=1.62; 95% CI 1.08-2.45) compared to SDLC1/2 lung cancers (HR=1.00). Figure 1
This post hoc analysis reveals novel insight to the heterogeneity of lung cancers diagnosed in a screening population. As with interval cancers diagnosed following a negative screen, lung tumors that arise in a lung environment ostensibly free of lung nodules are likely more rapidly growing and aggressive which results in significantly poorer outcomes. Additional research will be needed to understand the potential translational implications of these findings and to reveal biological differences of screen-detected tumors.
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