These can usually be treated in much the same way as other publications/ebooks on the Internet.
Author. If no author can be found, start with the title.
Title: subtitle [Internet].
Place of publication:
Year of publication [cited Year Month Day].
National Health Service, Cancer Research UK. Cancer registration – what it is, the benefits of being on the register, and your options [Internet]. [London]: Public Health England; 2016 [cited 2017 Jan 12]. Available from: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/565221/cancer_registration_information_leaflet.pdf