Background
Phase 3 RCT. 498 patients with extensive-stage SCLC who had responded to chemotherapy AND who all received prophylactic cranial irradiation (PCI). Enrolled at 42 hospitals in Netherlands, UK, Norway, and Belgium (Feb 2009–Dec 2012). Patients had confirmed disease response to ≥4 cycles of chemotherapy before randomization.
Interventions and follow up
Arm A: Thoracic RT 30 Gy in 10 fractions + PCI (N=247)
Arm B: No thoracic RT + PCI (N=248)
Primary endpoint: 1-year OS
mFollow up: Median 24 month
Arm B: No thoracic RT + PCI (N=248)
Primary endpoint: 1-year OS
mFollow up: Median 24 month
Results
1-yr OS: 33% (thoracic RT) vs 28% (control), HR 0.84 (95% CI 0.69–1.01), P=.066 — not significant
2-yr OS: 13% vs 3%, P=.004
PFS: HR 0.73 (95% CI 0.61–0.87), P=.001 — significantly improved
6-mo PFS: 24% vs 7%
2-yr OS: 13% vs 3%, P=.004
PFS: HR 0.73 (95% CI 0.61–0.87), P=.001 — significantly improved
6-mo PFS: 24% vs 7%
Adverse events
Main adverse events: No severe toxic effects specifically attributable to thoracic RT. Most common grade ≥3 events: fatigue (11 thoracic RT vs 9 control) and dyspnea (3 vs 4). Thoracic RT was well tolerated in this patient population.
Conclusions
Thoracic RT did not significantly improve the primary endpoint of 1-year OS in extensive SCLC after chemoresponse (HR 0.84, p=0.066), but significantly improved 2-year OS (13% vs 3%) and PFS. The trial was borderline for its primary endpoint; the 2-year OS benefit may represent a meaningful advantage in a subset of long-term survivors.
Key Limitations
Key Limitations: Primary endpoint (1-year OS) was not met (p=0.066 — borderline). The 2-year OS benefit is a secondary endpoint, susceptible to false-positive concerns. All patients received PCI — results may not be generalizable to PCI-omission strategies (particularly after Takahashi 2017 challenged PCI utility). Context has shifted: CASPIAN/IMPOWER133 IO + chemo regimens may change the role of thoracic RT in extensive SCLC. The 30 Gy/10 fx dose is palliative in intent; higher doses may potentially produce different results.
Clinical Context
This trial provides the strongest evidence that thoracic RT in extensive SCLC after chemoresponse improves PFS and possibly long-term OS. Thoracic consolidation RT (30 Gy/10 fx) is now considered for extensive SCLC patients with good response to chemotherapy and residual thoracic disease, per NCCN guidelines. However, the Takahashi 2017 trial suggesting PCI may not benefit ES-SCLC patients with MRI surveillance complicates the "all patients receive PCI" context of this trial. The role of thoracic RT in the modern era of immunotherapy + chemotherapy (atezolizumab, durvalumab) for ES-SCLC is under investigation.
References