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Table 1 Criteria for judgment risk of bias for each study
| Domains | Judgment criteria for responses to each domain | ||
|---|---|---|---|
| Yes | No | Unclear | |
| Selection bias | |||
| Selection | |||
| Any criteria descriptions for the patients | Any different radiotherapy plan,tumor stage,local recurrence,distant metastasis,follow duration etc. | Not mentioned | |
| The representativeness of the postoperative radiotherapy group | truly representative of the average, elderly, community-dwelling resident | somewhat or selected group of patients, e.g. only certain socio-economic groups/areas | no description of the derivation of the cohort |
| The representativeness of the surgery only group | drawn from the same community as the intervention cohort | drawn from a different source | no description of the derivation of the non intervention cohort |
| Comparability | |||
| Group comparable for:a.average age b.negative margin c patinet status | All the three variables were comparable between the groups | at least one of these was not reported even if others were comparable | Not mentioned |
| Group comparable for:a.tumor stite b.radiotherapy plan c.tumor stage | All the three variables were comparable between the groups | At least one of those was not comparable even if others were not reported | Not mentioned |
| Control for confounding at each outcome | Appropriate methods are used to control the potential confounders (e.g. matching, modeling, etc.) | No method was applied to control the potential confounders | Insufficient description |
| Design or Analysis bias | |||
| Blinding of participants at each outcome | 1.Blinding of participants at each outcome | 1. No blinding or incomplete blinding, the outcome is likely to be influenced by lack of blinding | Insufficient description |
| 2.No blinding or incomplete blinding, but the reviewers judge that the outcome is not likely to be influenced by lack of blinding | 2. Blinding of key study participants and likely that the blinding could been broken, and the outcome is likely to be influenced by lack of blinding | ||
| 3. Blinding of key study participants and unlikely that the blinding could been broken | |||
| Ascertainment of intervention exposure | Medical records or structured interview | Written self report | Insufficient description |
| Outcomes | |||
| Blinding of outcome assessment at each outcome | 1. Blinding of outcome assessment at each outcome | 1. No blinding of outcome assessment, the outcome measurement is likely to be influenced by lack of blinding. | Insufficient description |
| 2. No blinding of outcome assessment, but the reviewers judge that the outcome measurement is not likely to be influenced by lack of blinding. | |||
| 2. Blinding of outcome assessment ensured, and likely that the blinding could have been broken and the outcome assessment is likely to be influenced by lack of blinding. | |||
| 3. Blinding of outcome assessment ensured, and unlikely that the blinding could have been broken. | |||
| Ascertainment of outcome data | Record linkage | Self report | Insufficient description |
| Was follow up long enough for outcomes to occur | The follow-up was long enough for outcomes to occur, if median duration of follow-up > = 6 month | if median duration of follow-up < 6 months | Insufficient description |
| Adequacy of follow up of cohorts | 1. complete follow up: all subjects accounted for | follow up rate < 80 % (select an adequate %) and no description of those lost | Insufficient description |
| 2. subjects lost to follow up unlikely to introduce bias: number lost < = 20 %, or description of those lost suggesting no different from those followed | |||
