Being told you have chronic lymphocytic leukaemia (CLL) or small lymphocytic lymphoma (SLL) can be frightening, even if the doctor uses words like "slow-growing" or "indolent." This guide explains what these diagnoses mean in plain language, how treatment decisions are made, and how clinical research might be relevant to your situation.
CLL and SLL are the same disease at a biological level — they involve the same type of abnormal white blood cell (a B-lymphocyte that has become cancerous) — but they are described differently depending on where the disease is mainly found.
Both conditions are types of blood cancer (leukaemia / lymphoma). They tend to grow slowly, and many people live with them for years before treatment is needed. However, they are not curable with current standard treatments — and for some people, the disease does become active and require treatment.
CLL is often discovered incidentally on a routine blood test, when a high lymphocyte count triggers further investigation. The diagnosis is confirmed by a blood test called flow cytometry, which identifies the specific pattern of proteins on the surface of the abnormal cells — this pattern is characteristic of CLL/SLL. A bone marrow biopsy is not always needed for diagnosis, though it may be done to assess how extensively the marrow is involved.
If you were diagnosed with CLL and your doctor said you didn't need treatment yet, this can be confusing — especially if you feel anxious about having a cancer diagnosis. But early treatment in CLL has not been shown to improve survival compared to starting treatment when the disease becomes active or causes symptoms. "Watch and wait" (also called "active monitoring") means regular blood tests and clinic appointments to monitor your blood counts, symptoms, and any changes in your lymph nodes.
Treatment is started when the disease shows signs of progression — for example, rapidly rising lymphocyte counts, enlarging lymph nodes, anaemia, low platelets, or symptoms such as significant fatigue, night sweats, or weight loss.
Common concern: Many people feel that waiting to treat their cancer is risky. The research evidence does not support this — early treatment exposes patients to the side effects of therapy without improving outcomes. If this concerns you, it's a good question to raise directly with your haematologist.
When treatment is needed, the choice depends on your overall health, age, the genetic characteristics of your CLL, and whether this is your first treatment or a relapse after previous treatment.
BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib) are now a standard treatment for most patients with CLL. These are tablet-based treatments taken daily that work by blocking a protein called Bruton's tyrosine kinase, which CLL cells depend on for survival. They are generally well-tolerated, though side effects include an increased risk of bruising and bleeding, and some patients experience heart rhythm problems.
BCL-2 inhibitors (venetoclax, often combined with obinutuzumab) are another effective option, taken for a fixed duration rather than continuously. They are particularly effective in patients whose CLL has certain genetic features.
Chemoimmunotherapy — combinations of chemotherapy with a targeted antibody such as rituximab — was the standard treatment for many years and remains an option for some younger, fitter patients with favourable disease genetics.
CLL is not currently curable with standard treatments, which means it can come back (relapse) after a period of remission or become resistant to treatment (refractory). When this happens, different drugs from those used initially are usually tried. Our KCLG-HAEM-01 trial is specifically designed for patients with relapsed or refractory CLL who are receiving ibrutinib — if this applies to you, you may want to find out more about trial eligibility.
When you are diagnosed or when treatment decisions are being made, these questions can help you get the information you need:
For more information or to find out about trial eligibility, visit our patient information page or contact our team directly.
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