Prognostic value of post treatment PET scan in small cell lung cancer.

Abstract

e20013 Background: In most lymphomas, improving patient outcome rely on an assessment of response to therapy. Functional imaging with 18-fluoro-deoxyglucose (FDG) positron emission tomography (PET) increases sensitivity and specificity of disease assessment, predicts outcome and directs future therapies. Lately, PET-scan is more utilized in small cell lung cancer (SCLC) both for initial staging and to assess response to therapy. However, limited data in the literature have evaluated the prognostic value of post-therapy response on PET-scan in SCLC. Methods: This is a retrospective chart-review of SCLC patients who received their first-line chemotherapy between January-2007 and December-2013. Inclusion criteria included complete data on age, sex, race, cancer stage, histologic grade, chemotherapy, radiotherapy, and PET images pre- and post-therapy. CR was defined as either 100% drop in FDG uptake on post-therapy PET-scan. Results: Fifty patients met the inclusion criteria, and served as the basis for this study. 46% had Limited Stage Small Cell Lung Cancer (LS-SCLC), and 54% had Extensive stage small cell lung cancer (ES-SCLC). All were treated with platinum-based chemotherapy in addition to concurrently radiation therapy for the LS-SCLC group. Eleven patients out of the whole cohort achieved CR. Using COX regression model, we evaluated the correlation between achieving CR on post-therapy PET-scan and survival outcome. We found that achieving CR was significantly correlated with worse outcome in ES-SCLC group (HR = 2.70; 95%CI: 1.26-5.81; p = 0.01). While, in the whole cohort and LS-SCLC group, P-value was not statistically significant, nevertheless achieving CR indicated unfavorable outcome (HR = 1.18; 95%CI: 0.51-2.69; p = 0.49) and (HR = 1.99; 95%CI: 0.77-5.13; p = 0.15) respectively. Conclusions: Unlike lymphomas, achieving CR on post-therapy PET-scan in SCLC was associated with worse survival outcome. This might indicate that in aggressive small cell lung cancer, despite excellent response to first-line therapy, the prognosis is still dismal. These results suggest that further prospective studies are warranted to identify the prognostic rule of post-therapy PET-scan in SCLC patients particularly those with ES-SCLC.