TABLE 1.

Grading criteria for evidence on diet, nutrition, physical activity and survival in women with breast cancer

Evidence grades	Grading criteria for evidence on diet, nutrition, physical activity and survival in women with breast cancer	Het	PB	Mec
Strong evidence
Convincing	Evidence of an effect from a meta‐analysis of RCTs or at least two well‐designed independent RCTs	No	No	Desirable
Probable	Evidence of an effect from a meta‐analysis of RCTs or two well‐designed RCTs	Some	No	Desirable
	OR Evidence of an effect from one well‐designed RCT and one well‐designed cohort study	No	No	Required
	OR Evidence from at least one well‐designed pooled analysis of follow‐up studies	No	No	Required
	OR Evidence from at least two independent well‐designed follow‐up studies	No	No	Required
Limited evidence
Limited suggestive	Evidence from a meta‐analysis of RCTs or at least two well‐designed RCTs but the confidence interval may include the null	Some	No	Not required
	OR Evidence from one well‐designed RCT but the confidence interval may include the null	No	No	Required
	OR Evidence of an effect from a pooled analysis of follow‐up studies	Some	No	Not required
	OR Evidence from a pooled analysis of follow‐up studies but the confidence interval may include the null	Some	No	Required
	OR Evidence of an effect from at least one follow‐up study	No	No	Required
	OR Evidence of an effect from at least two follow‐up studies	No	No	Not required
	OR Evidence from at least two follow‐up studies but the confidence interval may include the null	Some	No	Required
Limited—no conclusion	Any of the following reasons: Too few studies available Inconsistency of direction of effect Poor quality of studies	—	—	—
Strong evidence
Substantial effect on risk unlikely	Evidence of the absence of an effect (a summary estimate close to 1.0) from any of the following: a. A meta‐analysis of RCTs b. At least two well‐designed independent RCTs c. A well‐designed pooled analysis of follow‐up studies d. At least two well‐designed follow‐up studies • Absence of a dose‐response relationship (in follow‐up studies)	No	—	Absence

Note: Special upgrading factors: (a) Presence of a plausible biological gradient (‘dose response’) in the association. Such a gradient need not be linear or even in the same direction across the different levels of exposure, so long as this can be explained plausibly. (b) A particularly large summary effect size (a relative risk of 2.0 or more, or 0.5 or less, depending on the unit of exposure), after appropriate control for confounders. (c) Evidence from appropriately controlled experiments demonstrating one or more plausible and specific mechanisms. (d) All plausible known residual confounders or biases including reverse causation would reduce a demonstrated effect, or suggest a spurious effect when results show no effect. Special considerations important for evidence for breast cancer survivors including the following potential confounding variables—the type of tumour, type of treatment, amount of treatment received and the dissemination of the disease.

Abbreviations: Het, substantial unexplained heterogeneity or some unexplained heterogeneity; PB, publication bias; Mec, strong and plausible mechanistic evidence is required, desirable but not required, not required or absent.