Lymphoma is a type of cancer that originates in the lymphatic system, a network of tissues and organs. ALK positive lymphoma is a specific subtype, distinguished by a particular genetic alteration that influences its behavior and treatment response.
Understanding ALK Positive Lymphoma
The “ALK positive” designation refers to an abnormal rearrangement of the Anaplastic Lymphoma Kinase (ALK) gene. This gene normally produces a protein involved in cell growth. In ALK positive lymphoma, a portion of the ALK gene merges with another gene, forming a new “fusion” gene.
This genetic change results in an abnormal, constantly active ALK fusion protein. This leads to uncontrolled cell growth and division, a hallmark of cancer. While other rare lymphomas can be ALK positive, its most common manifestation is ALK-positive Anaplastic Large Cell Lymphoma (ALCL). ALK-positive ALCL is a type of T-cell non-Hodgkin lymphoma and is considered aggressive.
ALK-positive ALCL affects children, adolescents, and young adults, and is more common in males. It often presents with swollen lymph nodes but can also involve other parts of the body. It is rare in adults over 50 but is one of the more common pediatric lymphomas.
Identifying ALK Positive Lymphoma
Common signs of ALK positive lymphoma include swollen, painless lymph nodes. Patients may also experience B symptoms such as fever, night sweats, unexplained weight loss, and fatigue.
Medical evaluation begins with a physical examination. Imaging tests, such as CT and PET scans, assess the extent of the disease and identify abnormal masses or organ involvement.
Definitive diagnosis relies on a biopsy, typically of an affected lymph node or tissue. The sample is examined under a microscope to identify characteristic lymphoma cells. Specialized laboratory tests confirm ALK positivity. Immunohistochemistry (IHC) detects the ALK protein, while techniques like fluorescence in situ hybridization (FISH) or polymerase chain reaction (PCR) identify the specific ALK gene rearrangement.
Treatment Approaches
Treatment strategies for ALK positive lymphoma emphasize therapies that target the abnormal ALK protein. ALK inhibitors, such as crizotinib, alectinib, and brigatinib, are a significant part of treatment. These medications block the abnormal ALK fusion protein, inhibiting uncontrolled cancer cell growth. Crizotinib, a first-generation ALK inhibitor, is approved for pediatric and young adult patients with ALK-positive ALCL. Newer generation ALK inhibitors like brigatinib and alectinib have shown promising results, especially in patients who have not responded to earlier treatments.
Traditional chemotherapy regimens also play a role, often used as initial treatment or in combination with targeted therapies. The CHOP regimen, consisting of cyclophosphamide, doxorubicin, vincristine, and prednisone, is a commonly used chemotherapy approach. In some cases, etoposide may be added, forming the CHOEP regimen, or brentuximab vedotin may replace vincristine, creating the BV-CHP regimen.
Other potential treatments include radiation therapy, which may be used for localized disease, and stem cell transplantation, which can be an option for patients with relapsed or refractory cases. Treatment plans are individualized, taking into account factors like the stage of the disease, the patient’s age, and their overall health status. The selection of therapy depends on the specific characteristics of the lymphoma and the patient’s response to initial treatments.
Prognosis and Follow-Up
The prognosis for ALK positive lymphoma, particularly ALK-positive ALCL, is often considered favorable with appropriate treatment. It is generally regarded as one of the more treatable forms of systemic ALCL. For adults with ALK-positive ALCL, the 5-year overall survival rate typically ranges between 70% and 90%.
Several factors can influence the overall outcome, including the specific subtype of lymphoma, the stage at which it is diagnosed, and how well the patient responds to initial therapy. Younger patients generally have a better prognosis, partly because they may tolerate aggressive treatments more effectively. Age over 40 can have a negative impact on prognosis.
Following treatment, long-term follow-up care is important. This includes regular check-ups to monitor for any signs of recurrence and to manage potential long-term side effects that may arise from the therapies received. Ongoing monitoring helps ensure sustained remission and address any new health concerns promptly.