6. Quality criteria for the assessment of bias.

Quality criteria	positive	negative	unclear	Consequence of negative classification
RCT
Central randomisation	Performed with adequate methods described	Inadequate methods described	Not Reported (NR)	Confounding
Concealment of allocation	Performed with adequate methods described	Inadequate methods described	NR	Confounding
Statistical power	Powered for survival	Powered for response	NR	Underpowered for survival
Observational studies
Selection of patients	Based on transparent criteria; plausible matching criteria	Indicative of strong selection bias; resulting in incomparable groups	NR	Confounding
Study size	Justified	Fewer patients than planned	NR	Underpowered for OS
RCT and observational study
Confounding at baseline	Reporting of at least 5 key prognostic factors per arm allowing assessment of similarity of groups	Relevant difference in key prognostic factors obviously present clinically but not addressed	</= 5 factors reported or no information per arm	Confounding
Comparability of treatment	Treatment identical up to and including first ASCT	Notable difference with onset and duration of toxic treatment	Unclear	Lead‐time bias/ confounding
Subsequent treatment	Information available with type and outcome per arm	No information available	NR or no info per arm	Confounding
ITT analysis	Yes, including definition reported	No	Analysis or definition NR	Selection and attrition bias with loss of power1
Compliance with 2nd TASCT	High (> 85%)	Low (<70%)	70‐85% or NR	Attrition bias1 or loss of power2
Completeness of follow‐up	<15 % loss to follow‐up; censoring rules defined	Incomplete follow‐up (> 15%) with unknown consequence for analysis	Loss to follow‐up or censoring rules NR	Attrition bias1 or loss of power2
Cross‐over	Reported and < 15%	Reported and > 15%	NR	Null bias
Definition of endpoints	Comprehensive reporting of accepted/ established endpoint definitions	Use of biased endpoint (e.g. different period of observation for study arms)	Incomplete reporting*	Lack of scientific validity
Standardisation of diagnostic procedures or central review	Mentioning of standardisation efforts, use of accepted staging systems	Reporting of centre effects or major changes in diagnostic criteria over the course of the study	NR	Information bias (if systematically different between arms)
Data maturity (Tricot 2009)	> 4 years follow‐up (FU)	Less than 4 years FU	NR	Insufficient follow‐up
Publication type&	Peer‐reviewed full‐text	Conference presentations	Not Applicable (NA)	Error‐prone due to less proof‐reading (at the least)

NR not reported

¹ if informative censoring

2 if at random

* of endpoint definitions with major impact on denominator (e.g. so‐called TRM)