Figure 1

Overview of the case–control study designs. Legend: Thick circles, cases; Thin circles, controls; Full border, individuals with cancers; Dotted border, general population individuals, most of whom have not had cancer, but may have had DCIS or Early Stage Cancer²). ^ Match on date of birth within 1 month either side; 2 controls per case. * Match on date of birth within 1 month either side; 1 control per case. # Match on date of birth within 1 month either side, date of first diagnosis within 2 months prior to and including the case’s date of first diagnosis; 1 control per case. ¹Advanced stage is defined as lymph node positive or tumour size >20 mm or both. ²Early stage is defined as lymph node negative, and tumour size ≤20 mm.