Study	Reason for exclusion
Aass 2005	Irrelevant interventions (interferon alfa‐2a with/without 13‐cis‐retinoic acid).
Abdel 2018	Wrong study design (single‐arm) and wrong patient population (recurrent/refractory).
Adler 1987	Irrelevant interventions (hormono‐immuno‐ versus hormonotherapy).
Amin 2018	CheckMate 016 study. Wrong study design (non‐randomised).
Amin 2018a	CheckMate 016 study. Wrong study design (non‐randomised).
Atkins 1991	Irrelevant comparison (interferon vs. interleukin).
Atkins 1993	Irrelevant comparison (interferon vs. interleukin).
Atzpodien 1997	Irrelevant comparison (interleukin vs. interferon and 5‐fluorouracil).
Atzpodien 1997a	Irrelevant comparison (interleukin vs. interferon and 5‐fluorouracil).
Atzpodien 1999	Irrelevant comparison (13‐cis‐retinoic acid, IFN‐alpha, IL‐2 and chemotherapy).
Atzpodien 2001	Irrelevant comparison (interferon+interleuking and 5‐FU versus tamoxifen).
Atzpodien 2004	Irrelevant comparison (interleukin vs. interferon).
Atzpodien 2006	Irrelevant comparison (interleukin‐2/interferon‐alpha2a/13‐retinoic acid‐based chemoimmunotherapy).
Barrios 2009	Wrong study design (single‐group assignment).
Beaumont 2009	RECORD‐1 study. Second‐line treatment.
Beaumont 2011	RECORD‐1 study. Second‐line treatment.
Berg 1998	Irrelevant comparison (interleukin versus interferon alpha‐2A).
Bex 2017	Irrelevant intervention (nephrectomy).
Boccardo 1998	Irrelevant comparison (interleukin versus interferon alpha‐2A).
Bracarda 2007	Wrong study design (same intervention, different schedules).
Buckley 2019	PRISM study. Dose‐finding study.
Cella 2016	Checkmate025 study. Second‐line treatment.
Choueiri 2017	Prior therapy allowed (more than 10% of patients).
Choueiri 2020	Prior therapy allowed (more than 10% of patients).
Choueiri 2020a	Prior therapy allowed (more than 10% of patients).
Cirkel 2016	Wrong study design (rotating treatments).
Cirkel 2017	ROPETAR study. Wrong study design (rotating treatments).
Climent 2020	ROPETAR study. Wrong study design (rotating treatments).
Cole 2003	Irrelevant comparison (interleukin versus interferon alpha‐2A).
Collinson 2012	STAR Trial. Irrelevant comparison (sunitinib; temporary cessation versus continuation).
Collinson 2018	PRISM. Dose‐finding study.
Colomba 2021	Wrong study design (single‐group assignment).
Conter 2013	Wrong study design (dose‐finding study).
de Mulder 1991	Irrelevant comparison (interferon versus interleukin).
Demirci 1999	Irrelevant interventions (vinblastine and interferon alpha with 5‐flourouracil).
Dexeus 1988	Irrelevant comparison (chemotherapy versus interferon).
Dexeus 1989	Irrelevant comparison (chemotherapy versus interferon).
DRKS00010309 2016	TAURUS. Terminated study.
Dubois 1997	Irrelevant comparator (p75 tumour necrosis factor receptor immunoglobulin G chimera).
Eisen 2019	Irrelevant intervention (adjuvant therapy).
Elhilali 2000	Irrelevant comparison (interferon vs. placebo).
Epaillard 2020	Wrong study design (biomarker‐driven trial).
Escudier 2005	Irrelevant comparator.
Euctr 2006‐003429‐95‐ES	Wrong study design (non‐randomised).
Euctr2006‐002851‐33‐AT	Ended prematurely.
Euctr2006‐005751‐16‐NL	Study ended prematurely.
Euctr2007‐002556‐41‐AT	Irrelevant comparison (trivax (cancer vaccine) with sunitinib versus sunitinib alone).
EUCTR2008‐002667‐13‐DE 2008	Adjuvant setting.
Euctr2012‐001730‐33‐ES	Study ended prematurely.
Euctr2015‐002133‐22‐FR	Irrelevant intervention(s).
Euctr2018‐001495‐38‐FR	Study ended prematurely.
Feldman 2020	Wrong study design (cohort study).
Feldman 2020a	Wrong study design (cohort study).
Figlin 1998	Irrelevant comparison (CD8(+) tumour‐infiltrating lymphocytes in combination with recombinant interleukin‐2).
Figlin 1999	Irrelevant comparison (CD8(+) tumor‐infiltrating lymphocytes in combination with recombinant interleukin‐2).
Figlin 2014	ADAPT trial. Terminated (no results).
Figlin 2014a	ADAPT trial. Terminated (no results).
Figlin 2017	ADAPT trial. Terminated (no results).
Figlin 2018	ADAPT trial. Terminated (no results).
Figlin 2020	ADAPT trial. Terminated (no results).
Flaherty 2015	Prior therapy allowed.
Foon 1988	Irrelevant comparison (interferon alpha(2B)‐interferon/gamma‐ interferon or the combination).
Fossa 1989	Irrelevant comparison (recombinant interferon‐alpha with or without vinblastine).
Fossa 1992	Irrelevant comparison (recombinant interferon‐alpha with or without vinblastine).
Gao 2017	Prior therapy allowed.
Gao 2019	Prior therapy allowed.
Gedye 2021	Wrong study design (single‐group assignment).
Ghiorghiu 2018	More than 10% received prior therapy.
Gleave 1997	Irrelevant comparison (interferon gamma‐1b injection versus placebo).
Gleave 1997a	Irrelevant comparison (interferon gamma‐1b injection versus placebo).
Gleave 1998	Irrelevant comparison (interferon gamma‐1b injection versus placebo).
Gore 2008	Irrelevant comparison (interferon‐a (IFN), interleukin‐2 (IL2) and 5‐fluorouracil (5FU) vs IFN alone).
Gore 2010	Irrelevant comparison (interferon‐a (IFN), interleukin‐2 (IL2) and 5‐fluorouracil (5FU) vs IFN alone).
Gruenwald 2020	Irrelevant intervention (behavioral intervention, concomitant coaching).
Haas 2016	Wrong intervention (adjuvant therapy).
Hainsworth 2015	Irrelevant comparator (CXCR4 inhibitor LY2510924).
Hainsworth 2016	Irrelevant comparator (CXCR4 inhibitor LY2510924).
Han 2002	Irrelevant comparison (interleukin‐2 versus subcutaneous interleukin‐2/interferon).
Harima 1990	Irrelevant comparison (interferon‐alpha (IFN) plus fluoropyrimidine (FP) and IFN alone).
Henriksson 1998	Irrelevant comparison (tamoxifen vs interleukin 2, alpha‐interferon (leucocyte) and tamoxifen).
Hutson 2006	Wrong study design (discontinuation design) and wrong patient population (recurrent).
Hutson 2021	CheckMate 920 trial. Wrong study design (non‐randomised).
ISRCTN95351638	PRISM. Dose‐finding study.
Jager 2005	Second‐line therapy.
Jayson 1998	Irrelevant comparison (interleukin 2 and interleukin 2‐interferon alpha).
Jeon 1999	Wrong study design (cohort study).
JPRN‐JapicCTI‐122014	Prior therapy allowed.
JPRN‐jRCTs031180024	Irrelevant comparison (nivolumab combined with image‐guided three dimensional beam‐convergent and extremely hypofractionated radiotherapy).
JPRN‐UMIN000001995	Prior therapy allowed.
Kinouchi 2004	Irrelevant comparison (interferon‐alpha (IFN) versus IFN + cimetidine).
Kinouchi 2006	Irrelevant comparison (interferon‐alpha (IFN) versus IFN + cimetidine).
Larkin 2019	KEYNOTE‐427. Wrong study design (non‐randomised).
Law 1995	Irrelevant comparison (interleukin‐2 with or without lymphokine‐ activated killer cells).
Lee 2020	KEYNOTE‐427. Wrong study design (non‐randomised).
Lee 2021	Wrong study design (cohort study).
Lindskog 2020	Irrelevant comparison (ilixadencel plus sunitinib versus sunitinib alone).
Lissoni 1993	Irrelevant comparison (interleukin‐2 subcutaneous immunotherapy versus interleukin‐2 plus interferon‐alpha).
Liu 2012	Irrelevant comparison (autologous CIK cell immunotherapy versus interleukin‐2 treatment combination with IFN‐α‐2a).
Lummen 1996	Irrelevant comparison (interferon‐gamma versus interleukin‐2 and interferon‐alpha2b).
Madhusudan 2004	Irrelevant comparison (interferon alpha alone or in combination with thalidomide).
McDermott 2001	Irrelevant comparison (interleukin‐2 versus interleuking + interferon).
McDermott 2005	Irrelevant comparison (interleukin‐2 versus interleukin + interferon).
McDermott 2013	BEST trial. Prior therapy allowed.
McDermott 2020	KEYNOTE‐427. Wrong study design (non‐randomised).
Mickisch 2001	Irrelevant comparison (radical nephrectomy plus interferon‐alfa‐based immunotherapy compared with interferon alfa alone).
Minasian 1993	Wrong study design (cohort study).
Molina 2009	RECORD‐1 study. Prior therapy allowed.
Motzer 2001	Irrelevant comparison (interleukin‐12 versus interferon‐alpha2a).
Mulders 2012	Prior therapy (50% of patients).
Naglieri 1998	Irrelevant comparison (interleukin‐2 (IL‐2) and interferon‐alpha immunotherapy versus an IL‐2 and 4‐epirubicin immuno‐chemotherapy).
NCT00002737	Irrelevant comparison (interferon alfa plus isotretinoin versus interferon alfa alone).
NCT00005966	Irrelevant comparison (interferon‐alfa2b alone versus interferon‐alfa2b plus thalidomide).
NCT00019539	Irrelvant comparison (bevacizumab versus thalidomide) and prior therapy allowed.
NCT00027664	Irrelevant comparison (interferon alfa with thalidomide versus interferon alfa alone).
NCT00053820	Irrelevant comparison (interleukin‐2 and fluorouracil versus interferon alfa alone).
NCT00073307	Second‐line therapy.
NCT00100906	Irrelevant interventions and dose‐finding study.
NCT00378703	One line of prior therapy was allowed.
NCT00416871	Irrelevant comparison (interleukin infusion versus interleukin by injection).
NCT00467025	Irrelevant intervention (AMG386).
NCT00491738	SABRE‐R study. Terminated (no results).
NCT00709995	Phase II not conducted.
NCT00835978	Dose‐finding study.
NCT00873236	Study ended prematurely.
NCT01164228	Irrelevant comparison (sunitinib with or without gemcitabine hydrochloride).
NCT01223027	Second‐line treatment.
NCT01408004	Wrong study design (efficacy of rotating regimen).
NCT01444807	Wrong study design (single‐group assignment).
NCT01616186	Study withdrawn.
NCT01664182	Second‐line therapy.
NCT01673386	Study terminated (no results).
NCT01727089	Second‐line therapy.
NCT01727336	Second‐line therapy.
NCT01793636	Second‐line therapy.
NCT02014636	Phase II (randomised part) not conducted.
NCT02127710	Wrong study design (single‐group assignment).
NCT02667886	Second‐line therapy.
NCT02724020	Second‐line therapy.
NCT02960906	Wrong‐study design (BIOmarker‐driven trial).
NCT03035630	Study terminated (no results).
NCT03092856	Second‐line therapy.
NCT03095040	Second‐line therapy.
NCT03173560	Dose‐finding study.
NCT03501381	Second‐line therapy.
NCT03595124	Second‐line therapy.
NCT03829111	Irrelevant intervention (probiotics in addition to nivolumab and ipilimumab).
NCT04195750	Second‐line therapy.
NCT04300140	Second‐line therapy.
Negrier 1996	Irrelevant comparison (interleukin‐2 versus interferon alfa).
Negrier 1997	Irrelevant comparison (interleukin‐2 and interferon with or without fluorouracil).
Negrier 1998	Irrelevant comparison (interleukin‐2 versus interferon alfa).
Negrier 2000	Irrelevant comparison (interleukin‐2 and interferon with or without fluorouracil).
Negrier 2006	Irrelevant comparison (intravenous interleukin versus subcutaneous interleukin).
Negrier 2007	Irrelevant comparison (medroxyprogesterone with interferon alfa‐2a or interleukin 2 versus a combination of both).
Negrier 2008	Irrelevant comparison (intravenous interleukin versus subcutaneous interleukin).
Nosov 2010	Wrong study design (randomised discontinuation trial).
Nosov 2012	Wrong study design (randomised discontinuation trial).
Pal 2015	Second‐line therapy.
Pal 2021a	Second‐line therapy.
Passalacqua 2010	Irrelevant comparison (interleukin‐2 versus interferon‐alpha).
Plimack 2015	Wrong study design (dose‐finding study).
Pyrhonen 1995	Irrelevant comparison (interferon alfa‐2a with vinblastine versus vinblastine alone).
Pyrhonen 1996	Irrelevant comparison (interferon alfa‐2a with vinblastine versus vinblastine alone).
Pyrhonen 1999	Irrelevant comparison (interferon alfa‐2a with vinblastine versus vinblastine alone).
Ravaud 2006	Full‐text not available; inclusion criteria unclear.
Ravaud 2016	Adjuvant therapy.
Rexer 2017	Terminated study.
Richards 1977	Irrelevant interventions (chemotherapy).
Rini 2011	Irrelevant comparator (AMG 386).
Rini 2012	Irrelevant comparator (AMG 386).
Rodriguez‐Vida 2020	Terminated study (no results).
Rpcec 2017	Irrelevant comparison (HeberFERON intravenous versus HeberFERON subcutaneous).
Sternberg 2013	Wrong study design (cohort study) and wrong study population (refractory).
Szarek 2021	Second‐line treatment.
Tannir 2016	Terminated study.
Taylor 2020	Wrong study design (single‐group assignment) and wrong patient population (selected solid Tumours).
Taylor 2020a	Wrong study design (single‐group assignment) and wrong patient population (selected solid Tumours).
Thiam 2010	RECORD‐1 study. Second‐line treatment.
Trump 2004	Irrelevant comparison (subcutaneous interferon alfa‐2a, subcutaneous interleukin‐2 and intravenous fluorouracil versus oral 13‐cis‐retinoic acid versus IFN‐alpha‐2a and vinblastine.).
Twardowski 2015	Prior therapy allowed (more than 10% with prior therapy).
Twardowski 2017	Prior therapy allowed (more than 10% with prior therapy).
Verzoni 2018	Irrelevant comparator (cytoreductive nephrectomy).
Voss 2015	Wrong study design (single‐group assignment).
Voss 2019	Second‐line therapy (1–3 prior therapy lines).
Witte 1995	Irrelevant comparison (interleukin versus interferon).
Wood 2013	ADAPT study. Terminated (no results).
Wright 2020	Second‐line therapy.
Yang 2002	Prior therapy (majority of patients).
Yang 2003	Prior therapy (majority of patients).
Zhou 2016	Prior chemotherapy (13% of patients).
Zhou 2019	Prior chemotherapy (13% of patients).