Multicenter real-world study of efficacy and safety of omitting the clinical target volume in limited-stage small cell lung cancer

Routine clinical target volume (CTV) coverage in limited-stage small cell lung cancer (LS-SCLC) aims to address microscopic extension but ofter increases toxicity without necessarily translating to improved disease control. A multicenter real-world study in China investigated whether omitting CTV coverage could preserve efficacy while reducing toxicity compared with conventional delineation. The study enrolled 946 LS-SCLC patients between February 2016 and February 2025. According to radiotherapy strategy, patients were classified into an Omit-CTV group (n=403) and a CTV group (n=543). Propensity score matching yielde 265 patients per group. Primary endpoints were progression-free survival (PFS) and overall survival (OS). With a median follow-up of 33.2 months, response rates were similar between groups (ORR 69.4% with CTV versus 72.8% with Omit-CTV); as were PFS (median 11.6 versus 11.8 months; p=0.500) and OS (median 30.7 versus 35.8 months; p=0.220). No statiscally significant difference was observed in local recurrence patterns (p=0.561). Omit-CTV was associated with lower rates of radiation pneumonitis (grade 1-2: 20.0% versus 27.7%; grade ≥ 3: 3.4% versus 8.3%; p=0.004) and esophagitis (grade 1-2 32.1% versus 39.2%; grade ≥ 3: 5.7% versus 9.1%; p=0.037). Among patients receiving immunotherapy, median PFS was not reached in the Omit-CTV groups and 15.2 months in the CTV group (HR 0.48; p=0.03) with median OS not reached and 26.9 moths (HR 0.31; p=0.018). The authors conclude that in this large-scale LS-SCLC cohort, Omit-CTV was associated with similar efficacy and lower rates of treatment-related toxicity, with a promising survival signal in patients receiving immunotherapy.