Author of

• 15530

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  P3.06 - Poster Session/ Screening and Early Detection (ID 220)

  • Event: WCLC 2015
  • Type: Poster
  • Track: Screening and Early Detection
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/09/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)

  • 15536

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    P3.06-006 - Extent of Progression for Small Cancers in a Screening Program Even with Proper Follow-Up (ID 3096)

    09:30 - 09:30  |  Author(s): R.S. Avila
    • Abstract

    Background:
    Current guidelines for repeat CT imaging of small nodules detected during screening are a function of the size and consistency of the nodules and the round it was detected. They attempt to balance the frequency with which a change would genuinely occur (i.e. the frequency with which a nodule of a given size is a cancer) with the ability to actually measure the change should it have occurred. Recently the American College of Radiology has established a new set of guidelines for this purpose called LungRads. This study analyzes the change in nodule volumes and doubling times for small nodules if the LungRads guidelines are followed.
    
    Methods:
    The LungRads protocol focuses on providing categories for nodules based on their degree of suspiciousness and provides suggestions for follow-up. They also provide criteria so as to determine when growth is genuine —that is, the change in size is beyond what could have occurred solely as a result of measurement error. Genuine growth defined as increase in diameter of >1.5 mm. For purposes of estimating change in nodule volume and doubling times associated with them, we used the time intervals in LungRads for follow-up and derived the doubling times necessary for a nodule to reach the definitional growth threshold. We assumed a spherical model for the nodules and used a simple exponential growth rate. We focused on solid nodules where the range of growth rates is known to be large and they are most accurately measured.
    
    Results:
    For LungRads Category 2, where 6 month follow up CT is recommended, in order for a 4 mm nodule to grow sufficiently so as to pass the size threshold where change could be detected, it would need to have a doubling time faster than 129 days, anything slower would not achieve the necessary size change and it would only then be rescanned 6 months later at an annual repeat scan and it would then potentially reach a size of 8.0 mm. For category 4A, LungRads recommends repeat scanning in 3 months. According to the protocol, a 6 mm nodule would need a doubling time of 92 days for detection otherwise at one year it will reach a size of 15.1 mm.
    
    Conclusion:
    The change threshold for growth and time intervals between scans can have serious consequences downstream in terms of how large a tumor might become before it can reliably be diagnosed. The ability to better define the threshold for when change has occurred will always be beneficial as it will allow not only the very fast growing tumors to be diagnosed but those with more typical doubling times as well. The LungRads protocol keeps the smallest size category of tumors from growing beyond 15 mm when workup is initiated.