Five-Year Survival in Patients with ES-SCLC Treated with Atezolizumab in IMpower133: Imbrella a Extension Study Results .
Introduction : In the Phase III IMpower133 trial (NCT02763579), First-line treatment with atezolizumab + carboplatin/etoposide (A+CE) improved OS and PFS vs placebo + carboplatin/etoposide (P+CE) in patients with ES-SCLC. At the time of IMpower133 study closure, patients treated with A+CE were eligible to enrol in the Phase IV, single-arm IMbrella A extension and long-term observational study (NCT03148418). Given the interest in long-term OS data for immunotherapy in ES-SCLC, we report patient outcomes from IMbrella A as an extension of the IMpower133 results
Methods : Patients enrolled in IMpower133 were eligible for roll-over to the open-label, non-randomised, multicentre IMbrella A extension study if they continued to receive atezolizumab at the time of IMpower133 closure and did not have local access to the study treatment or if they discontinued atezolizumab in IMpower133 and were in survival follow-up. Patients in the P+CE arm were not eligible for enrolment. Survival, treatment status and safety were assessed in IMbrella A .
Results : Median follow-up was 59.4 months in the A+CE arm (IMpower133 and IMbrella A; clinical cutoff date [CCOD]: 16 Mar 2023) vs 26.4 months in the P+CE arm (IMpower133 only; CCOD: 24 Sep 2022). A total of 18 patients from the A+CE arm of IMpower133 were enrolled in IMbrella A. The 5-year OS rate in the A+CE arm was 12% (IMpower133 and IMbrella A) (Table). Of the 11 patients still alive at the data cutoff date, the median age at baseline was 59 years, 4 patients had an ECOG PS of 1, 2 patients had baseline brain metastases and none had baseline liver metastases. MD Anderson Cancer Center SCLC subtype information, based on expression of neuroendocrine (SCLC-A and SCLC-N), non-neuroendocrine (SCLC-P) and immune-infiltrated (SCLC-I) transcriptional signatures, was available for 7 of 11 patients who were alive at 5 years (SCLC-A, n=1; SCLC-I, n=2; SCLC-N, n=4) .
Conclusions : This long-term follow-up analysis of IMpower133 patients enrolled in the IMbrella A extension study provides the first report of 5-year survival outcomes for patients who received first-line cancer immunotherapy for ES-SCLC and demonstrates that durable survival benefit up to 5 years is possible with A+CE .
| OS Rates, % | A+CE (n=201) | P+CE (n=202) |
| IMpower133 (CCOD: 24 Sep 2022) | ||
| 1 year | 52 | 39 |
| 2 years | 22 | 16 |
| IMpower133 and IMbrella A (CCOD: 16 Mar 2023) | ||
| 3 years | 16 | NEa |
| 4 years | 13 | NEa |
| 5 years | 12 | NEa |
NE, not estimable. |
Clinical trial information: NCT03148418 .
Funding: F. Hoffmann-La Roche Ltd .