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IMpower133

First-line atezolizumab plus carboplatin and etoposide versus placebo plus carboplatin and etoposide in extensive-stage small-cell lung cancer

Phase 3NCT02763579

Population
Patients with previously untreated extensive-stage small-cell lung cancer
Design
Double-blind, placebo-controlled phase 3 trial; randomisation 1:1 to carboplatin and etoposide with atezolizumab or placebo for four 21-day cycles (induction), then atezolizumab or placebo maintenance until unacceptable toxic effects, RECIST 1.1 progression or no additional clinical benefit. Two primary endpoints: investigator-assessed PFS and OS in the ITT population. The registry lists 503 enrolled; the paper's abstract reports 201 and 202 randomised.
Primary endpoint
PFS, OS
Arms
  • Atezolizumab plus carboplatin-etoposide (experimental, n = 201): Carboplatin and etoposide with atezolizumab for four 21-day cycles, then atezolizumab maintenance
  • Placebo plus carboplatin-etoposide (control, n = 202): Carboplatin and etoposide with placebo for four 21-day cycles, then placebo maintenance
People
Horn L, IMpower133 Study Group
OSHR 0.70 (95% CI 0.54–0.91)Δ median OS+2 monthsPFSHR 0.77 (95% CI 0.62–0.96)Δ median PFS+0.9 months
Show the numbers
Results reported for IMpower133
EndpointAnalysisAtezolizumab plus carboplatin-etoposidePlacebo plus carboplatin-etoposideEffect
OSprimarymedian follow-up 13.9 monthsHorn 2018median 12.3 monthsmedian 10.3 monthsHR 0.70 (95% CI 0.54–0.91)P=0.007Hazard ratio for death. The abstract does not label this analysis as interim or final.
PFSInvestigator-assessedprimarymedian follow-up 13.9 monthsHorn 2018median 5.2 monthsmedian 4.3 monthsHR 0.77 (95% CI 0.62–0.96)P=0.02Hazard ratio for disease progression or death; progression assessed by the investigators per the abstract.
Results reported for IMpower133
EndpointAnalysisAtezolizumab plus carboplatin-etoposidePlacebo plus carboplatin-etoposideEffect
OSprimarymedian follow-up 13.9 monthsHorn 2018median 12.3 monthsmedian 10.3 monthsHR 0.70 (95% CI 0.54–0.91)P=0.007Hazard ratio for death. The abstract does not label this analysis as interim or final.
PFSInvestigator-assessedprimarymedian follow-up 13.9 monthsHorn 2018median 5.2 monthsmedian 4.3 monthsHR 0.77 (95% CI 0.62–0.96)P=0.02Hazard ratio for disease progression or death; progression assessed by the investigators per the abstract.
Hazard ratio (95% CI) by endpoint. Values below 1 favour the experimental arm.
OSPFS0.512◀ experimentalcontrol ▶
Data table
EndpointHR95% CI
OS0.70.54–0.91
PFS0.770.62–0.96
Illustrative — modelled from reported values, not trial data. OS, primary.
0%25%50%75%100%051015202530Months (modelled)
  • Atezolizumab plus carboplatin-etoposide (experimental)
  • Placebo plus carboplatin-etoposide (control)

Median-only curves assume a constant hazard (exponential) and fit plateaus, as seen with some immunotherapies, poorly.

Data table (modelled values)
MonthsAtezolizumab plus carboplatin-etoposidePlacebo plus carboplatin-etoposide
0100.0%100.0%
863.7%58.4%
1542.9%36.4%
2327.4%21.3%
3117.4%12.4%
Illustrative — modelled from reported values, not trial data. PFS, primary.
0%25%50%75%100%024681012Months (modelled)
  • Atezolizumab plus carboplatin-etoposide (experimental)
  • Placebo plus carboplatin-etoposide (control)

Median-only curves assume a constant hazard (exponential) and fit plateaus, as seen with some immunotherapies, poorly.

Data table (modelled values)
MonthsAtezolizumab plus carboplatin-etoposidePlacebo plus carboplatin-etoposide
0100.0%100.0%
367.0%61.7%
739.3%32.4%
1026.4%19.9%
1317.7%12.3%
Primary publication: Horn L, Mansfield AS, Szczęsna A, Havel L, Krzakowski M, Hochmair MJ, et al. First-Line Atezolizumab plus Chemotherapy in Extensive-Stage Small-Cell Lung Cancer. N Engl J Med. 2018;379(23):2220-2229. PubMedDOI

Appears in

Sources

  1. Horn L, Mansfield AS, Szczęsna A, Havel L, Krzakowski M, Hochmair MJ, et al. First-Line Atezolizumab plus Chemotherapy in Extensive-Stage Small-Cell Lung Cancer. N Engl J Med. 2018;379(23):2220-2229.

    PubMedDOI