Can leeches treat swelling and pain?

Can leeches be used to reduce the swelling and pain my wife has in her arm after breast cancer treatment?

It sounds as if your wife has lymphoedema. The swelling is caused by tissue fluid build up in her arm. Normally this would drain away through the lymphatic vessels and lymph nodes. But it cannot drain away if the lymphatics or nodes are blocked if

A cancer is growing in the lymph nodes
The lymph nodes have been removed
The lymph nodes have been affected by radiotherapy

Leeches would not help because they are used to relieve swelling and congestion caused by a build up of blood. In lymphoedema this is not the problem. Leeches are sometimes used in cancer treatment. Some plastic surgeons use them after surgery for mouth cancer to help the healing of skin and muscle flaps used to recreate the lip or tongue.

There are many ways to treat lymphoedema. It is most often treated with compression bandages and specialist massage to reduce the swelling. There is information in our breast cancer section about lymphoedema and its treatment.