The invention relates to a gaseous composition containing xenon as active ingredient for use in preventing or limiting tumour cell migration and/or limiting or preventing metastasis formation in an individual suffering from cancer. The prevention or limitation of tumour cell migration is obtained through the action of the xenon on free cancer cells. The xenon acts on the free cancer cells carried by the blood. The effective volume proportion of xenon is between 5% and 79%, it is preferably at least 50%. The gaseous composition also contains a volume proportion of oxygen (O2) of at least 21%. It is administered by inhalation or insufflation.
