EDITOR,—Ciaran B J Woodman and colleagues' paper reporting the high rate of interval cancers in the North Western Regional Health Authority1 and the accompanying editorial2 will help to increase awareness that successful breast screening has several facets. Two view mammography at the first screen is a simple and effective way of improving the yield at prevalence screens, thus reducing the potential for “false negative” interval cancers. One of the principles behind mammographic breast screening is that the earlier in the detectable preclinical phase that this (or any) modality can achieve detection the longer the delay before …