The fight against B-cell and T-cell lymphoma
Haematology The fight against lymphoma now includes treatments which activate the body's own immunity — and others which interfere with the growth pathways of malignant cells and stop them from proliferating.
Treatments to fight lymphoma, or cancer of the lymphatic system, have progressed in recent years. But this is mainly because of antibody therapy and growth inhibitors — not the arrival of new drugs.
“There are various drugs that we use to the treat different kinds of lymphoma,” says Dr Robert Marcus, a consultant haematologist at King's College Hospital specialising in lymphoma therapy. “But we haven't seen any novel chemotherapy drugs in this area for many years.” Currently, chemotherapy is still the main treatment for virtually all lymphomas. “But now there are antibodies which bind to the surface of lymphoma cells and help to kill them; and inhibitors which interfere with the signalling pathways in malignant cells — especially in low-grade lymphomas — that stop them proliferating,” says Marcus.
Lymphomas occur when blood and lymph gland cells, known as lymphocytes, become abnormal and either proliferate out of control or fail to die when they have served their normal function. There are two main types of lymphocytes in the body: B-lymphocytes (B-cells) and T-lymphocytes (T-cells). Normal T-cells help process bacteria and augment or suppress immune responses; B-cells, meanwhile, secrete immunoglobulin which binds to — and helps kill — bacteria and viruses.
The two main types of lymphoma are Hodgkin lymphoma and non-Hodgkin lymphoma. According to figures from Macmillan, around 1700 people a year are diagnosed with Hodgkin lymphoma. In the young, treatment can be very successful; in older people, especially where disease is widespread, the cure rates fall to under 50 per cent.
Statistics from NHS Direct show that more than 12000 people in the UK are diagnosed with non-Hodgkin lymphoma each year.
There are a multiplicity of types: some are slow-growing and treatment may not be needed for months, years — or ever. Others, including Hodgkin lymphoma, the commonest subtype of B-cell lymphoma, and almost all T-cell lymphoma, are aggressive and need treatment immediately after diagnosis. PCR-based clonality testing is used in the diagnosis of B-cell and T-cell lymphomas, improving confidence in diagnosis. With the development of Next-Generation Sequencing (NGS) technologies, clonality analysis facilitates monitoring of patients, as it allows for testing of Minimal Residual Disease (MRD).
A major obstacle in the fight against lymphoma is that tumours secrete molecules which disguise them from tumour-destroying T-cells. Some novel agents are now being used to restore T-cell responses — the body's own immunity — to attack particular types of lymphoma. “These have been effective in treating Hodgkin lymphoma and are beginning to be used in other lymphomas, often in combination with other drugs,” says Marcus. “That, I think, is where the hope for future treatment lies.”