Zaucha 2017.

Study characteristics
Methods	Secondary citation(s) NA Language of publication English Study design Prospective, observational, multi‐centre study (11 centres) Study centre(s) 11 haemato‐oncology centres Country Poland Median follow‐up time (range) 44.7 months (12.7–90.2)* *Data for surviving participants only
Participants	Number of included participants 310 registered participants, out of which 24 were excluded from analysis due to treatment intensification based on PET1 and/or clinical symptoms of active HL Inclusion criteria Newly diagnosed with classic HL Exclusion criteria Absent/poor‐quality PET‐CT images Consent Yes; written informed consent Recruitment period January 2008 to October 2014 Age (range, in years) 30.8 (median, 18–80) Ethnic group(s) Not reported Stages of disease All stages Comorbidities Not reported Therapy regimen ABVD dependent on disease stage: stages I‐IIA 2‐4x ABVD with radiotherapy or 6x ABVD; stages IIB‐IV 6‐8x ABVD with or without radiotherapy
Prognostic factor(s)	Prognostic factor(s) Interim PET Definition of prognostic factor(s) Whole‐body scan (mandibular angle to one third upper femur) Timing of prognostic factor measurement 11‐13 days after end of ABVD cycle 1 (PET1) Additional scan after ABVD cycle 2 for participants with a PET1 score of 3‐5 (PET2) Method for measurement (use of specific scale and cut‐off) Deauville 5‐point scoring system Scores 1‐3 considered negative, scores 4‐5 considered positive 6 reviewers interpreted all scans using the blinded independent central review method, disagreements were resolved in a joint session Was the same definition and method for measurement used in all participants? No; PET2 only administered to participants with a PET1 score of 3‐5 Were prognostic factor(s) assessed blinded for outcome(s), and for each other (if relevant)? Yes
Outcome(s)	Primary outcome(s) and definition(s) Progression‐free survival (PFS), not defined Secondary outcome(s) and definition(s) Kinetics of response Timing of outcome measurement At 3 years Was the same definition and method for measurement used in all participants? Yes Was/were outcome(s) assessed blinded for prognostic factor(s), and for each other (if relevant)? Yes
Missing data	Participants with any missing value? Yes; only 198 participants had PET2 scans If yes, how were missing data handled? Not reported
Analysis	Univariable analysis: Yes Total number of participants included in univariable analysis for each outcome 286 (PET1) / 198 (PET2) Statistical method Kaplan‐Meier (survival analysis) Cox proportional hazard regression analysis (HR between treatment groups) How was the prognostic factor treated? Binary Multivariable analysis: No
Risk of bias (QUIPS)	Study participation Low risk Clear description of participants and study characteristics. Study attrition Low risk Prognostic factor measurement Moderate risk Adequate measurement and description. Prognostic factor measured the same way for all participants. However, while PET1 scans were available for all participants, the availability of PET2 scans was dependent on the result of PET1. No further scans were performed if PET1 was negative Outcome: Overall survival Not reported as a primary endpoint in the publication. IPD data were available and used to calculate the HR and SE for this outcome. Outcome: Progression‐free survival Outcome measurement High risk No definition of outcome. 'Other prognostic factors (covariates)' High risk Disease stage not accounted for. Statistical analysis and reporting High risk No detailed description of analysis. Outcome: Adverse events Not reported
Notes	Conflict of interest The authors have declared no conflicts of interest. Funding No funders to report.