The Palace have clearly learned from the consternation which arose, over here when, following the death of The Late Queen, it emerged that those 'in the know' (some media figures, senior politicians and civil servants, etc) had known that she had cancer for over a year before her death, but that The Palace insisted that the story be suppressed. The official statement has to strike a balance between openness and personal medical confidentiality - it is being assumed that the 'regular treatment' will be chemotherapy but, in the absence of detail as to the type of cancer, no-one can be sure.
Opinions about HIs Majesty are being set aside - the general consensus is that we wish him (and all those facing cancer) a full recovery.