Could Residual Disease Irradiation be Better than Involved Field Irradiation for Limited-Stage Small Cell Lung Cancer? A Failure Pattern Analysis

Abstract

For limited-stage small cell lung cancer (LS-SCLC), the thoracic radiotherapy (TRT) plays a vital role. Previous clinical research showed that for the TRT could be limited to the postchemotherapy tumor volume and the positive prechemotherapy lymph node regions. Involved field irradiation (IFI) could be routinely applied. However, the optimum radiation field design remains controversial. In the present study, we retrospectively analyzed the patterns of failure in LS-SCLC patients receiving residual disease irradiation (RDI) in radiotherapy. A total of 47 patients with LS-SCLC treated with RDI with sequent or concurrent chemotherapy were enrolled in this study. The gross tumor volume (GTV) defined as residual volumes of positive node and primary tumor of the post-chemotherapy. The clinical target volume (CTV) included GTV with a margin 0.5 cm. Planning target volume (PTV) involved CTV with a margin 0.5 cm. RFI consisted of 1.5 grays (Gy) twice daily in 30 fractions up to a total dose of 45 Gy or 2.0 Gy daily up to 60 Gy. Treatment failures were divided into local and distant failures, and local recurrences were classified into inside RDI(IN-RDI), between RDI and IFI(RDI-IFI), and outside IFI(OUT-IFI). Among the 46 patients with detailed follow-up data for recurrences, 36 (78.3%) experienced recurrences, with 16 (34.8%) being local recurrence, and 29 (63.0%) being distant failure. For the 16 patients with local recurrences, 10, 5, and 1 were IN-RDI, OUT-IFI, and RDI-IFI recurrences, respectively. Residual disease irradiation (RDI) is feasible for LS-SCLC treated with sequent or concurrent chemotherapy and does not compromise failure inside the involved region.