Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are two related blood cancers. CLL leads to cancer cells in the blood and bone marrow (the spongy tissue found inside certain bones). SLL causes tumors in the lymph nodes (structures that help fight infection and filter out waste from the body). People can live with these two similar slow-growing diseases for many years.
Researchers estimate how long people with SLL live using statistics called survival rates. You may do better or worse than these predicted rates depending on whether you have certain prognostic factors that raise or lower your risk of severe disease.
The five-year survival rate for SLL in the United States is 86.9 percent. This means that, for every 100 people diagnosed with SLL now, about 87 people are expected to be alive in five years. This survival rate also applies to people with CLL.
Treatment options for SLL are constantly improving. Because the five-year survival rate is based on past information, it may not reflect newer, better methods. People being diagnosed with CLL now may have an even better prognosis than is reflected in these statistics.
Survival rates don’t tell you what your outcome will be. They are estimates based on large numbers of people. Your individual outlook depends on your prognostic factors — characteristics of you or your disease that increase or decrease your chance of having a good outlook. Talk to your doctor to learn more about how your personal factors affect your prognosis.
Younger people tend to have a better prognosis when they are diagnosed with SLL or CLL:
Older adults often have a worse outlook because they can’t undergo certain therapies. Some cancer treatments lead to better outcomes for young people but cause too many side effects in older people.
One of the factors in determining SLL outlook is the lymphoma stage. The stage describes where in the body lymphoma cells can be found and whether these cells have spread.
Doctors often stage SLL using the Lugano system, although they may also use Rai or Binet staging systems if SLL affects the blood or bone marrow. Under the Lugano system, the higher the stage is, the more advanced the lymphoma and the farther cancer cells have spread:
Advanced-stage SLL is more likely to lead to a poor prognosis. People with stage 3 or stage 4 SLL need more aggressive treatments than those with early-stage disease.
Cancer develops when a cell’s genes become damaged and undergo changes. Doctors can find gene changes in more than 80 percent of people with SLL and CLL. Some of these changes lead to more aggressive leukemia, and others are linked to slower-growing SLL.
Some people with SLL have mutations in a gene called immunoglobulin heavy chain variable region (IGHV). People with mutations often have a better outlook — treatment is more effective, and they have longer survival rates. IGHV mutations also affect how likely a person is to experience complete remission or the absence of disease signs and symptoms. In one study, 82 percent of people with mutated IGHV were in complete remission after six years. However, only 47 percent of people with normal IGHV were in complete remission at this time.
Additional gene mutations are also linked with a poor prognosis. People with changes in the TP53, NOTCH1, ATM, BIRC3, and SF3B1 genes are more likely to be resistant to treatment. Some studies have found that these changes can lead to worse outcomes, although this is still being studied.
Cytogenetic tests can show chromosome changes. Chromosomes are large pieces of DNA that contain genes. Sometimes, chromosomes within cancer cells contain deletions. Some of these abnormalities serve as prognostic factors in SLL. Changes called del(17p) and del(11q) — deletions in chromosomes 17 or 11 — are linked with a worse prognosis. On the other hand, deletion of part of chromosome 13 can be a sign of a favorable prognosis.
Newer SLL/CLL treatments may be more effective at treating people with SLL who have some of these high-risk gene changes. For example, the targeted therapy drug Imbruvica (ibrutinib) is effective at treating lymphoma and leukemia cells that contain del(17p) and del(11q).
Gene changes within cancer cells sometimes cause these cells to have different proteins on their outer surface. A person with SLL may have a worse prognosis if many of their lymphoma cells contain the proteins ZAP-70 or CD38. These proteins can be “read” with a test called flow cytometry.
Doctors may use blood tests to measure the levels of certain proteins. High levels of a protein called beta-2 microglobulin can indicate a poor prognosis.
As a person’s lymphoma is treated and monitored, doctors will measure levels of cancerous lymphocytes (white blood cells). If lymphocytes grow slowly, this may be a sign that the SLL will lead to a better prognosis. However, rapidly rising lymphocyte levels often signal more aggressive disease. A person may have a worse prognosis if their lymphocyte count doubles in less than a year.
Blood tests show that some people with SLL have high levels of certain types of lymphocytes, such as prolymphocytes. People with these cells are more likely to have their SLL transform into another more severe type of cancer such as prolymphocytic leukemia or diffuse large B-cell lymphoma.
Doctors sometimes predict outcomes for SLL and CLL with a tool called the CLL International Prognostic Index (CLL-IPI). The CLL-IPI takes into account individual risk factors and divides people with SLL into four risk groups. The prognostic index considers age, stage, changes in the TP53 and IGHV genes and levels of beta-2-microglobulin. Each of these prognostic factors is given a certain number of points, and then the points are added up into one final score. This calculation leads to the following groups:
These risk groups give you a clue about not only your prognosis but also about what treatment options may be best. People in the lowest-risk group may not need any treatment at all, whereas people in the highest-risk group may want to try newer therapies or take part in clinical trials.
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