Mistletoe preparations can also be administered into body cavities if liquid permeated by cancer cells has accumulated there and an effusion has formed (e.g. in the chest), or if the tumour grows in a body cavity, e.g. in the bladder. As mistletoe preparations have not yet been approved for this form of application, they are an off label use and therefore after information and with the consent of the patient (informed consent) on the responsibility of the treating physician.
In some types of cancer, e.g. breast cancer at an advanced stage, an effusion can form in the cavity between the lung and pleura. It often contains cancer cells and can considerably impair respiration. During a puncture in which the fluid (exudate) is removed, part of this fluid can be mixed with a higher concentration of mistletoe extract and then returned to the pleural cavity.