Table 1. Quality rating of included studies.

	Grunfeld (1996)	Gulliford et al (1997)	Brown et al (2002)	Koinberg et al (2004)	Baildam et al (2004)	Kokko et al (2005)	Grunfeld et al (2006)
Is the population under study defined (with inclusion and exclusion criteria)?	Yes	Yes	No (exclusion criteria omitted)	Yes	No	Yes	Yes
Are the main prognostic factors defined (at least age of patient and stage of tumour)?	Yes	Yes	Yes	Yes	No	Yes	Yes
Is treatment of first tumour specified?	Yes	Yes	Yes	Yes	No	Yes	Yes
Has a power calculation been carried out to assess the required cohort size?	Yes	No	No	Yes	No	No	Yes
Is cohort size sufficient for primary outcome measure (i.e. greater than any calculated sample size or of sufficient size to detect clinically significant difference)?	Yes	Yes	No	Yes	Yes	Yes	No
Is a comparison made of baseline characteristics (age and stage) between participants and those who refuse to participate?	Yes	Yes	Yes	No	No	No	No
Is mean or median follow up greater than 5 years?	No	No	No	Yes	Not given	No	No
Is loss during follow up specified?	Yes	No	Yes	No	No	No	No
Is the follow up schedule (including mammographic interval) specified?	Yes	Yes	No	Yes	No	Yes	Yes
Is mammographic frequency identical between follow-up groups?	Yes	Yes	Yes	Yes	Not given	Yes	Yes
Are mostly objective or validated outcomes used?	Yes	No	Yes	Yes	Yes	Yes	Yes
Were outcomes prospectively assessed?	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Was the article published in peer reviewed journal?	Yes	Yes	Yes	Yes	No	Yes	Yes
Total score	12	9	8	11	3	9	9