Abstract
e20683 Background: OPD represents limited extra-central nervous system (eCNS) progression. In oncogene-addicted NSCLC, OPD can be treated with local ablative therapy to prolong TKI control. The impact of PET/CT vs CT to detect OPD at first eCNS progression has not been assessed previously. Methods: Patients with metastatic EGFR-mutant (EGFR-MT), ALK or ROS-1 rearranged (ALK+, ROS-1+) NSCLC with eCNS progression on a relevant TKI (2010-2016) were identified. Scan methodology at first eCNS progression was noted and progression was categorized as OPD using 2 definitions (≤ 2 or ≤ 4 progressing lesions) or non-OPD. Median time-to-progression (MTTP) was calculated from start of TKI to first eCNS progression. Data was analyzed using Chi squared and log rank tests as appropriate using p < 0.05 as significant. Results: Sixty-seven patients (EGFR-MT = 37, ALK+ = 28, ROS-1 = 2) were analyzable. OPD (≤ 2 lesions) occurred in 62.5% (20/32) noted by PET/CT vs. 54.3 % (19/35) by CT (p = 0.496). OPD (≤ 4 lesions) occurred in 84.4 % (27/32) noted by PET/CT vs. 65.7 % (23/35) by CT (p = 0.080). MTTP in PET/CT-detected OPD (≤ 2) (N = 20) was 332.5 days vs. 143 days in CT-detected OPD (N = 19) (p = 0.0092). MTTP in PET/CT-detected non-OPD ( > 2) (N = 12) was 185 days vs. 109 days in CT-detected non-OPD (N = 17) (p = 0.0503). MTTP in PET/CT-detected OPD (≤ 4) (N = 27) was 298 days vs. 143 days in CT-detected OPD (N = 23) (p = 0.0128). MTTP in PET/CT-detected non-OPD ( > 4) (N = 5) was 167 days vs. 104.5 days in CT-detected non-OPD (N = 12) (p = 0.1090). Conclusions: In this non-randomized retrospective study the proportion of OPD (≤ 2 or ≤ 4 progressing lesions) at first eCNS progression did not differ significantly for PET/CT vs. CT. MTTP was significantly longer for PET/CT vs CT detected OPD, but not for non-OPD progression. Potentially longer MTTP in the PET/CT OPD subgroup may reflect preselecting patients with disease difficult to detect by CT (e.g., bone/lymph node) which is more indolent. A prospective randomized study is required to assess the true impact of PET/CT vs CT on detecting OPD in oncogene-addicted NSCLC on TKI therapy.
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