Impact of FDG PET in small-cell lung cancer patients treated with curative intent chemoradiotherapy

Abstract

Purpose or Objective The role of staging 18F-fludeoxyglucose PET/CT in small-cell lung cancer (SCLC) is uncertain (not mandated in the CONVERT trial with discrepancy in clinical guidelines). We investigated the impact of 18F-fludeoxyglucose PET/CT on survival in SCLC patients treated with curative-intent chemoradiotherapy. Materials and Methods Patients with limited-disease (TNM stage 1-3) histologically confirmed SCLC who received curative-intent chemoradiotherapy in a single UK institution between 2015 and 2018 were retrospectively analysed. Patients were divided into 2 groups: those staged with conventional imaging (contrast-enhanced thorax and abdomen CT and brain imaging with or without bone scintigraphy) and those staged with 18F-fludeoxyglucose PET/CT in addition. The primary endpoint was overall survival. Univariable and multivariable Cox analyses were conducted to evaluate the following variables for association with survival: age, gender, baseline comorbidities, Eastern Cooperative Oncology Group performance status (ECOG PS), TNM stage, planning target volume (PTV), use of staging 18F-fludeoxyglucose PET/CT and treatment approach (sequential vs concurrent chemoradiotherapy). The study was approved locally and complied with UK research governance (ethics reference: 17/NW/0060). Results Data from 203 patients with limited-disease SCLC were analysed. Median overall survival in the whole cohort was 19.1 months (range: 1.8-78.1). Median overall survival was 14.9 months (range: 1.8-77.6) and 37.7 months (range: 1.9-78.1) in patients treated with sequential (radiotherapy dose: 50-55Gy in 20 once daily fractions; 140 (69%) patients) and concurrent chemoradiotherapy (radiotherapy dose: 45Gy in 30 twice daily fractions; 63 (31%) patients), respectively. The two staging groups were well balanced (including treatment approach) except for a higher percentage of patients with ECOG PS2, a lower percentage of patients with N3 stage and slightly smaller PTV volume in patients staged with 18F-fludeoxyglucose PET/CT (p<0.05; Table 1A). Variables associated with overall survival on multivariable analysis were male gender (HR=1.49; 95% CI: 1.05-2.10, p=0.025), N2 stage (HR=2.00; 95% CI: 1.10-3.65, p=0.024), sequential chemoradiotherapy (HR=1.94, 95% CI: 1.30-2.90, p=0.001) and staging 18F-fludeoxyglucose PET/CT (HR=0.59, 95% CI: 0.41-0.86, p=0.006) as seen in Table 1b. Median overall survival was 23.6 months (range: 1.8-78.1) and 15.0 months (range: 3.1-77.6) in patients staged with or without 18F-fludeoxyglucose PET/CT, respectively (Kaplan Meier survival curves adjusted for variables in the multivariable model are shown. Conclusion We report longer overall survival in limited-stage SCLC patients who were staged with 18F-Fludeoxyglucose PET/CT. While prospective trials are needed for confirmation, our results provide indirect evidence supporting the use of staging 18F Fludeoxyglucose PET/CT in SCLC patients considered for curative intent chemoradiotherapy.