B-PLL is a rare subtype that’s more aggressive than other blood cancers and has a low survival rate. However, ongoing research and clinical trials may offer new treatment options to improve outcomes.

B-PLL is a cancer that affects immune system cells called prolymphocytes. The term “prolymphocytes” usually refers to immature cells that go on to become a type of white blood cell (WBC) called a lymphocyte, which helps protect your body against infections. However, in B-PLL, the prolymphocytes are actually mature B cells.

These mature B cells divide rapidly and eventually crowd out normal cells, leading to symptoms like fevers, night sweats, and weight loss.

B-PLL tends to be more aggressive than other types of leukemia and carries a less favorable outlook. Keep reading to learn more about what causes B-PLL, who’s likely to develop it, and how doctors approach treatment.

The symptoms of B-PLL are similar to other types of leukemia and may include:

Signs of B-PLL a doctor might detect include:

Researchers don’t fully understand the cause of B-PLL, but experts think a mutation (error) in the genes of bone marrow cells may be responsible. The mutation causes your body to produce abnormal mature WBCs that grow uncontrollably and crowd out healthy cells.

Some researchers suspect B-PLL occurs when a slow-growing B-cell cancer, like chronic lymphocytic leukemia (CLL), transforms or evolves into B-PLL.

Prolymphocytic leukemia: B-PLL vs. T-PLL

Prolymphocytic leukemia occurs when prolymphocytes grow out of control in the bone marrow. Doctors divide prolymphocytic leukemia into two types depending on which type of WBCs are affected.

  • B-PLL affects WBCs called B lymphocytes (B cells).
  • T-PLL affects WBCs called T lymphocytes (T cells).

B-PLL is more common than T-PLL, but both types are very rare.

Risk factors that may increase your chances of developing B-PLL include:

  • older age (median age of diagnosis is 69 years)
  • assigned male at birth
  • a family history of blood and bone marrow cancers

A doctor will ask about your symptoms and medical history and conduct a physical exam. But no single test can diagnose B-PLL, and a doctor can’t make a diagnosis on your symptoms alone.

B-PLL is very similar to other types of blood cancers, such as CLL and mantle cell lymphoma (MCL). Specialists called hematopathologists will need to conduct various lab tests to help differentiate it from other types of blood cancers.

Tests doctors use to diagnose B-PLL include:

Doctors usually diagnose B-PLL when at least 55% of the lymphocytes in the blood are prolymphocytes.

B-PLL is very rare, so there’s no standard treatment strategy. A doctor may recommend enrolling in a clinical trial involving new drugs or drug combinations.

Treatment for B-PLL may include:

  • Watch and wait: If you don’t have symptoms, a doctor may recommend waiting until signs and symptoms appear. Doctors refer to this as active surveillance or watchful waiting. You’ll have to undergo frequent blood tests during this time.
  • Chemotherapy: The most common treatment for B-PLL is a combination of chemotherapy agents, like FCR (fludarabine, cyclophosphamide, and rituximab) and BR (bendamustine and rituximab). However, B-PLL is often resistant to chemotherapy.
  • Targeted therapies: Alemtuzumab (Campath) is a targeted therapy that may be especially helpful for those with the TP53 gene mutation. Though not yet approved by the Food and Drug Administration (FDA) for B-PLL, a doctor may recommend newer therapies like ibrutinib (Imbruvica) and idelalisib (Zydelig). These treatments have shown promise in treating other B-cell cancers.
  • Hematopoietic stem cell transplantation: Doctors typically only recommend a stem cell transplant in younger, healthier people who have shown a response to initial treatments. A stem cell transplant may cure B-PLL, but not many people are eligible for this treatment.

B-PLL is an aggressive cancer with a typically less favorable outcome. Since it’s so rare, information on survival rates is limited.

In a 2022 study of 950 people with B-PLL who received diagnoses between 2004 and 2019, the median overall survival was 2.8 years. About 39% of people survived for 5 years after diagnosis, and 26% of people survived for 10 years after diagnosis. Older age was associated with a less favorable outlook.

B-PLL is a rare cancer that occurs when WBCs called B-prolymphocytes divide and grow uncontrollably. Since B-PLL is so rare and often resistant to chemotherapy, there’s a strong need for clinical research and new treatments. If you receive a B-PLL diagnosis, talk with your doctor about the possibility of joining a clinical trial.