Modern imaging technique assessment of small cell lung cancer doubling time.

e17561 Background: Doubling time in non-SCLC tumors has been well studied, but this is less so in SCLC. We aim to study in vivo doubling time in SCLC using modern imaging techniques. Methods: Patients (pts) with SCLC with both diagnostic computed tomography (CT) and subsequent staging Positron Emission Tomography (PET)/CT were identified from institutional database. Primary lesion and nodal disease on the initial CT scan and on the CT component of PET/CT scan was measured. Diameter Doubling Time (D-DT) = [(dt)*log 2] / [3(log D2 – log D1)], where dt was time interval between scans, D2 and D1 are diameters of lesion on second and first scan respectively. Volume Doubling Time (V-DT) = [(dt)*log 2] / (log V2 – log V1), where V2 and V1 are volume of 2nd and 1st CT. Results: 18 eligible pts were identified. 61% were males, median age 63. Primary lesion was assessable in 14 pts and nodal disease in 17. Mean interval between scans was 19.7 days (range: 6 – 67). Mean diameter of primary lesion on 1st and 2nd scan...