Bevacizumab biosimilar (MB02) and reference bevacizumab in patients with stage IIIB/IV non-squamous non-small cell lung cancer (NSCLC) (STELLA study): Multiple Imputation analysis.
Authors: Trukhin Dmytro , Poddubskaya Elena , Zoran Andric , Bondarenko Igor , Shevnia Serhii , Zaric Bojan , Bellala Ravishankar , Charoentum Chaiyut , Perez Luis , Bullo Felicitas , Garcia Fernanda 
Published: June 2021

e15003 Background: Stella Trial is a phase III, multinational, double-blind and randomized study to confirm clinical similarity between MB02 and EU-bevacizumab in patients with stage IIIB/IV no squamous NSCLC. 627 subjects with newly diagnosed or recurrent stage IIIb/IV NSCLC were randomized 1:1 to receive either MB02 or EU-bevacizumab plus chemotherapy (paclitaxel and carboplatin) every 3-week cycle for six cycles (week 18) followed by MB02/bevacizumab in blinded monotherapy until disease progression, treatment intolerance, death, patient withdrawal or end of study (w52). An approach targeting the MI of the continuous sum of target diameters (mm), and subsequent categorization of Overall Response (OR) was performed as sensitivity analysis for the assessment of the primary endpoint. Multiple Imputation (MI) has emerged as a credible method to assess the effects of missing data (MD), an inescapable problem with a potential ability to undermine research results' strength and validity in a clinical study, providing the user with a valuable toolset to sufficiently account for the varying types of MD and appropriately adjust the assumptions. Methods: The primary endpoint of the study was Objective Response Rate (ORR) at week 18 per an Independent Radiological Committee (IRC) in the Intention to treat set (ITT). The ORR was analysed with a Cochran-Mantel-Haenszel model, including the stratification factors of sex, smoking status, disease diagnosis and disease stage, comparing the stratified estimates risk difference (RD). In addition, these results were analysed implementing a pattern-mixture MI process accounting for missing at random (MAR) and missing not at random (MNAR) data based on the sum of target diameters in subjects without tumour response data or falling into the categories NonCR/NonPD or non-evaluable (NE). Results: The clinical equivalence of MB02 with EU-bevacizumab is demonstrated by the efficacy data provided through the primary endpoint and the MI sensitive analysis applied. The MI (MAR and MNAR) represents an added value that supports the biosimilarity of MB02 and EU-bevacizumab. The results for the primary analysis of the RD in ORR at w18 in the ITT set were entirely contained within the boundaries of predefined margins (±12): -4.02 [95% CI: -11.76 to 3.71]). Under MI, the ORR RD showed similarity at 95% CIs (-1.92; 95% CI: -10.02 to 6.19) and using the multiple imputations for subjects without tumour response data (missing, NonCR/NonPD or NE), the ORR RD was -2.22 with 95% CI of (-10.54 to 6.10) at w18 in the ITT. Conclusions: The clinical equivalence of MB02 with EU-bevacizumab is demonstrated by the efficacy data provided through the primary endpoint and the MI sensitive analysis applied. The MI (MAR and MNAR) represent an added value that supports the biosimilarity of MB02 and EU-bevacizumab. Clinical trial information: NCT03296163.