Should a letter with a General Practitioner's (GP) signature vs. a letter alone be used for inviting asymptomatic women to organised population-based breast cancer screening programmes?

The GDG made a conditional recommendation by consensus for the intervention based on the desirable anticipated effects, negligible costs and savings of the intervention, and varied feasibility and acceptability concerns.

The GDG noted that for women between the ages of 50 and 69, in whom screening is strongly recommended, the balance favours the intervention because participation rate is an appropriate outcome. Participation rate was not considered an appropriate outcome for the other age ranges. For women in the age groups, 45-49 and 70-74, outcomes such as confidence and satisfaction of the woman in making an informed decision are crucial and the GDG advises interpretation of this intervention in the context of the recommendations on screening age ranges (please see point 2 in the implementation considerations). As recommending for an intervention that increases participation may not be beneficial, but detrimental.

• The comparison evaluated for this recommendation needs to be interpreted in the context of the other comparisons of methods for inviting women to screening programmes evaluated by the GDG.
• It is noted that for age groups where the recommendation made by the GDG for screening is conditional (45-49 and 70-74 age groups) informed decision-making is crucial for implementation, and there would be concern about increasing inappropriate screening with this intervention. Where the GDG made a strong recommendation for screening in women between the ages of 50 and 69, this intervention is recommended as it is desirable to increase participation in screening.
• In certain countries there may be a difference in who is defined as a GP or what their status and relationship is with women.
• The GDG noted that extrapolation may be necessary to the signatures of other individuals on the letter, where GP signatures are not the most appropriate. No evidence on other signatures (e.g. screening programme directors) was identified.
• The GDG considered that the GP's consent for the use of their signature on the letters is essential for this intervention to be implemented.
• The GDG noted that the desirable benefits may vary depending on the relationship of women with the GP whose signature is on the letter.
• This intervention may only be possible in settings where the GP of women for screening programmes can be accessed or linked to the screening programme.

• The GDG recommends research on the effect of this intervention on other important outcomes such as informed decision-making, particularly for women where a conditional recommendation was made (45-49 and 70-74).
• Research on the best modality for inviting women in the age ranges where a conditional recommendation was made (45-49 and 70-74).
• Research evaluating the use of electronic messages including e-mail, social media and SMS as compared to paper letters for invitation to screening.