Study	Reason for exclusion
Arimoto 2003	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Awwad 1992	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Awwad 2002	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Baumann 2001	2 commentaries on Fu 2000; no additional data.
Catterall 1977	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
CHART 1997	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Cummings 2007	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
DAHANCA 2003	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Datta 1989	Abstract only. No subsequent publication identified. Unclear percentage of oral cavity and oropharyngeal cancer patients included.
Dieckmann 1990	Uncertain if truly randomised ‐ abstract only, no subsequent publication identified.
Dvivedi 1978	59% of patients have squamous cell carcinoma of the head and neck but not stated how many of these have oral cavity or oropharyngeal cancer. No longer possible to contact authors.
Flores 1996	Unclear how many of these have oral cavity or oropharyngeal cancer.
Garden 2004	3 treatment groups, each with different chemotherapy regimen, therefore results cannot be attributed to radiotherapy.
Giglio 1997	Comparison of radiotherapy regimen, but results confounded by use of chemotherapy in 1 arm.
Hansen 1997	Reanalysis of data from 2 DAHANCA studies.
Hering 1981	Randomisation not mentioned.
Hintz 1979	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Holsti 1988	Inadequate randomisation ‐ odd versus even birth dates.
Jackson 1997	Some trial participants are randomly allocated to treatment, and some are not. Minority of participants have oral cavity or oropharyngeal cancer. Attempts to contact author failed.
Janot 2008	Patients had recurrent disease.
Johnson 1995	Conference abstract. No information on proportion of included participants with oral cavity or oropharyngeal cancer. No subsequent publication identified.
Katori 2007	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Klima 1988	Patients with metastatic disease included.
Kokal 1988	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Kramer 1987	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Maor 1983	Includes recurrent cancer patients.
Mishra 1996	Only some of the patients are randomised but all are analysed together. "However some surgeons preferred to put more clinically node‐positive cases into the post‐operative radiotherapy group."
Nissenbaum 1984	Less than 6 months follow‐up.
Noel 1997	Unclear how many patients have oral cavity or oropharyngeal cancer.
Noel 1997a	Unclear how many patients have oral cavity or oropharyngeal cancer.
Noel 1997b	Unclear how many patients have oral cavity or oropharyngeal cancer.
Noel 2001	Commentary on 4 trials ‐ no data.
Rink 1989	3 groups but not randomised.
Robertson 1998	Comparison of 2 different radiotherapy regimens, 1 of which includes surgery. Results confounded.
Sanchiz 1990	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Singh 1984	Unclear if true RCT. Data presented as percentages; unclear denominator.
Snow 1981	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer. Authors have not responded to request for separate data.
Srivastava 2001	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Strong 1978	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Suwinski 2008	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.
Tupchong 1991	Less than 50% of participants in trial have oral cavity or oropharyngeal cancer.

RCT = randomised controlled trial.