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Thread: What is Lung Cancer Stage "4a" and "4b"?

  1. #1

    What is Lung Cancer Stage "4a" and "4b"?

    Another thread brought up a diagnosis of Stage 4a NSCLC . I have found many online sites about lung cancer staging, but cannot locate info on Stage 4a or 4b.

    Does anyone have help on what is the difference between IVa (4a) and IVb (4b) in lung cancer? A site?

  2. #2
    Senior User
    Join Date
    Feb 2012
    I don't believe there is a type of a or b when staging lung cancer stage 4. There is however, and a or b when determining the size of the tumor. For my dad he was stage IV T2BN1 M1M1B. the T2B portion of this indicated the size of his tumor in his lung. I got the below information from a site when I did a google on stage IV Lung cancer staging.

    T2a = Tumor >3 cm but ≤5 cm in greatest dimension.

    T2b = Tumor >5 cm but ≤7 cm in greatest dimension.

    I've never seen or heard though of just Stage IV A or B lung cancer.
    71 year old Father diagnosed 2/2/2012 with Stage IV Lung Cancer NSCS with METS to the Brain, spine, bones, Adrenal Glands, Lymph Nodes, Liver, Pancreas, omentum.

    Heart Attack 2/19/2012
    Whole Brain Radiation and Radiation to the Spine 2/27/2012 completed 15 sessions on 3/16/2012
    Heart Attack 3/10/2012

    Passed away 3/26/2012[/B] I love you dad, you will be missed.


  3. #3
    I've finally come across some info on Stage IVA and StageIVB lung cancer. It is based upon the TNM [Tumor/Nodes/Metastasis] classification of lung cancer (specifically, the "M" classification):

    Metastasis (M)
    MI = distant metastasis.
    MIa = Separate tumor nodule(s) in a lobe of the lung on the opposite side from the lung with the primary tumor, tumor with pleural nodules or malignant pleural or peridardial effusion.
    MIb = Distant metastasis

    From that, IVa or IVb is determined:
    Stage IVA = any T, any N, M1a
    Stage IVB = Any t, any N, M1b

    Source - "Staging": http://www.patientresource.com/Lung_Cancer_Staging.aspx

    It only took me 9 months to find this info. But I've been watching for it, and finally, bingo.

  4. #4
    Yes, HOS1, Stage IV has a "M1", and that can be even more specific as to M1a [Stage IVa] or M1b [Stage IVb].


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