Precursor T-lymphoblastic lymphoma/leukaemia refractory

When T-cell acute lymphoblastic leukaemia or lymphoblastic lymphoma does not respond to treatment, patients face one of the most challenging situations in blood cancer care, with survival rates remaining below 30%.

Table of contents

• What is T-cell acute lymphoblastic leukaemia and lymphoblastic lymphoma?
• Understanding refractory disease
• Survival outcomes
• Treatment approaches
• Emerging therapies

What is T-cell acute lymphoblastic leukaemia and lymphoblastic lymphoma?

T-cell acute lymphoblastic leukaemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) are aggressive blood and bone marrow cancers that disrupt normal T-cell development in the thymus. These diseases are closely related and are treated similarly, though recent evidence shows they may respond differently to some treatments.^[1]

T-ALL represents approximately 15% of acute lymphoblastic leukaemia cases in children and about 25% in adults.^[2][3] T-LBL accounts for approximately 30% of pediatric non-Hodgkin lymphoma.^[2] The diseases occur rarely, with a yearly incidence of approximately 5-6 new cases per million people aged under 20 years in the United States.^[1]

The World Health Organization classifies T-LBL as the same disease as T-ALL. The main difference between them is the degree of bone marrow involvement, using a historical cutoff of 25%.^[1] When cancer develops during the normal T-cell development process in the thymus, it often spreads to the central nervous system. About 75% of cases develop masses behind the breastbone called mediastinal masses.^[4]

Understanding refractory disease

Refractory disease means that the cancer did not respond to treatment. In these cases, previous treatments did not kill enough cancer cells (called blasts) to reach a complete remission.^[2] This is different from relapsed disease, where the cancer returns after initially responding to treatment and achieving remission.

Patients with refractory T-ALL or T-LBL face particularly difficult circumstances. The disease has proven resistant to the initial intensive treatment, which typically involves multiple chemotherapy drugs given over an extended period.^[2]

Survival outcomes

While outcomes for newly diagnosed T-ALL and T-LBL have improved dramatically over recent decades, with long-term overall survival rates approaching 90% in children and adolescents, the situation for refractory disease remains challenging.^[1]

Patients with relapsed and refractory disease have historically faced a dismal prognosis. The survival rate for relapsed or refractory T-ALL and T-LBL remains poor, with overall survival rates below 30%.^[1][8] This stands in sharp contrast to improvements seen in B-cell acute lymphoblastic leukaemia, where novel immunotherapies have transformed treatment outcomes in recent years.^[1]

Treatment approaches

When T-ALL or T-LBL proves refractory to initial treatment, several options may be considered, though success rates remain limited.

Chemotherapy remains a primary treatment approach. When given for refractory disease, it is called reinduction chemotherapy. If the disease did not fully respond to initial treatment and only a partial remission was reached, doctors may use different drugs or more intense doses of medications already given.^[2]

A stem cell transplant may be offered if another remission is reached after the disease initially proved refractory. This complex treatment with many risks must be done in a special transplant centre or hospital. The transplant replaces damaged stem cells found in bone marrow, blood, and umbilical cords with healthy ones.^[11]

Patients may also receive treatment to prevent or treat cancer spread to the brain and spinal cord, known as the central nervous system. This is important because leukaemia cells can spread to these areas.^[11]

Emerging therapies

Recent advances in understanding the biology and genetics of T-ALL and T-LBL have identified novel targets for treatment. Researchers have comprehensively profiled the genomics of these diseases, enhancing the ability to identify high-risk patients at diagnosis and discovering new targets for precision medicines.^[2]

Immunotherapy represents a promising new direction. Novel immunotherapies have transformed treatment for patients with B-cell leukaemia, and many are now under investigation in clinical trials for T-ALL and T-LBL with promising early results.^[1][2]

One type of immunotherapy called CAR T-cell therapy is particularly noteworthy. This treatment takes millions of T cells from a person with cancer and changes them in the laboratory so they have special receptors on their surface. These receptors recognize a specific protein found on leukaemia cells. The modified T cells are then given back to the person where they multiply, attack, and destroy the cancer cells.^[11]

Clinical trials are investigating allogeneic anti-CD7 CAR-T cells for patients with relapsed or refractory T-ALL or T-LBL. These trials offer hope that improved patient outcomes may be achievable, though significant challenges remain.^[4]

Small molecule inhibitors targeting specific pathways involved in T-ALL biology are also under investigation. Recent insights into disease biology have identified recurrent genetic changes that can be grouped into several targetable pathways, offering potential new treatment approaches for patients who do not respond to standard therapy.^[1][2]