Chronic Myeloid Leukaemia with Comorbidity — Clinical Case

DCE Long Case

Patient profile

Mr T is a 58-year-old man who presents to his general practitioner with a three-month history of fatigue, early satiety and night sweats. A routine blood count reveals a markedly elevated white cell count, and he is referred urgently to the haematology service. He has a significant cardiac history, and the multidisciplinary team must integrate his leukaemia management with his cardiovascular risk. [1]

Presenting concern: Mr T describes three months of progressive exertional fatigue, a dragging sensation and fullness in the left upper quadrant after small meals (early satiety), and drenching night sweats requiring a change of nightclothes. He has lost 3 kg. His general practitioner found a white cell count of 168 and referred him urgently. He has had no chest pain, palpitations or bleeding. [1]

Past medical history: An ST-elevation myocardial infarction four years ago, treated with primary percutaneous coronary intervention to the left anterior descending artery, with a drug-eluting stent. He has hypertension and dyslipidaemia. He has no history of heart failure, with a recent echocardiogram showing a left ventricular ejection fraction of 50 percent with mild anterior wall hypokinesia. No diabetes. No prior thromboembolic disease. [1]

Medications: Aspirin 100 mg daily, atorvastatin 80 mg daily, ramipril 10 mg daily, bisoprolol 5 mg daily. He takes these reliably. No recent antibiotics. [1]

Family history: His father had coronary artery disease and died of a stroke at 74. No family history of leukaemia. [1]

Social: Married, two adult children. Former heavy smoker (40 pack-years), stopped after his myocardial infarction. Drinks 10 to 15 units of alcohol per week. Works as a school principal. He is anxious about the leukaemia diagnosis and about whether the treatment will interact with his heart condition. [1]

Examination:

• Comfortable at rest. ECOG performance status 1. No pallor, no bruising, no jaundice.
• Pulse 72, blood pressure 138 over 84. No cardiac murmurs. JVP not elevated.
• Spleen palpable 10 cm below the left costal margin, firm, smooth and non-tender.
• No palpable lymphadenopathy. No hepatomegaly. No peripheral oedema. [1]

Investigations:

• Haemoglobin 118 g/L, white cell count 168 (neutrophils 42 per cent, myelocytes 18 per cent, metamyelocytes 12 per cent, basophils 9 per cent, eosinophils 4 per cent, blasts 2 per cent), platelets 620.
• Blood film: leucocytosis with the full spectrum of myeloid maturation, basophilia, and a low leucocyte alkaline phosphatase score.
• Renal and hepatic function normal. Lactate dehydrogenase mildly elevated. Uric acid mildly elevated.
• Bone marrow aspirate and trephine: hypercellular marrow with marked granulocytic hyperplasia, fewer than 5 per cent blasts, no dysplasia. Conventional cytogenetics show the Philadelphia chromosome t(9;22) in all 20 metaphases.
• BCR-ABL1 transcript (quantitative RT-PCR on the International Scale): 45 per cent at baseline.
• 12-lead ECG: sinus rhythm, Q waves in V1 to V3 (old anterior infarct), QTc 430 ms. [1]

Candidate's opening statement (SASPOP)

"This is Mr T, a 58-year-old school principal presenting with symptomatic, newly diagnosed chronic-phase chronic myeloid leukaemia, confirmed by the Philadelphia chromosome t(9;22) and a BCR-ABL1 transcript of 45 per cent. He has bulky splenomegaly and B-symptoms, fewer than 5 per cent marrow blasts (chronic phase), and a low leucocyte alkaline phosphatase score excluding a leukaemoid reaction. The key feature that shapes his management is his significant cardiovascular comorbidity — a prior myocardial infarction with a drug-eluting stent, hypertension and a former heavy smoking history — which constrains the choice of tyrosine kinase inhibitor, because nilotinib carries a vascular risk and dasatinib carries pleural and pulmonary risk. His main problems are: the chronic-phase CML requiring a first-line tyrosine kinase inhibitor chosen with his cardiac risk in mind; the cardiovascular risk management, which must be integrated with the tyrosine kinase inhibitor choice; the BCR-ABL1 monitoring commitment on the International Scale at 3, 6, 12 and 18 months; the long-term question of treatment-free remission if he achieves a deep molecular response; and the psychosocial impact of a leukaemia diagnosis superimposed on established cardiac disease. My priorities are to start imatinib (the cardiovascular-safest option for him), to optimise his secondary prevention, to monitor the BCR-ABL1 transcript to the milestone schedule, and to counsel him honestly about prognosis and the long monitoring course ahead." [1]

Structured problem list (numbered, prioritised)

1. Chronic-phase CML, BCR-ABL1 positive, newly diagnosed — the central problem; needs a first-line tyrosine kinase inhibitor.
2. Cardiovascular comorbidity (prior MI, stent, hypertension, ex-smoker) — constrains the tyrosine kinase inhibitor choice; favours imatinib over nilotinib (vascular) and over dasatinib (pleural).
3. BCR-ABL1 monitoring commitment — serial quantitative RT-PCR at 3, 6, 12 and 18 months against the response milestones.
4. Secondary prevention optimisation — aspirin, statin, ACE inhibitor, beta-blocker, blood pressure and lipid control, all continued.
5. Long-term treatment-free remission candidacy — if he reaches a sustained deep molecular response, a future option to discuss.
6. Psychosocial support — the burden of a leukaemia diagnosis superimposed on established cardiac disease. [1]

Integrated management plan

Step 1 — Confirming chronic phase and the molecular diagnosis: [1]

Mr T has the classic presentation of chronic-phase CML: a markedly elevated white cell count with the full myeloid maturation spectrum and basophilia on the blood film, a low leucocyte alkaline phosphatase score (excluding a leukaemoid reaction), massive splenomegaly, fewer than 5 per cent marrow blasts, and the Philadelphia chromosome t(9;22) with a BCR-ABL1 transcript. The fewer than 5 per cent blasts, the absence of basophilia over 20 per cent, and the absence of clonal evolution place him firmly in chronic phase, which is the phase that responds excellently to tyrosine kinase inhibitor therapy. [1]

Step 2 — The tyrosine kinase inhibitor choice, constrained by cardiovascular comorbidity: [1]

The five tyrosine kinase inhibitors all inhibit BCR-ABL1, but they differ in efficacy depth and, critically, in toxicity. The second-generation tyrosine kinase inhibitors (dasatinib, nilotinib, bosutinib) achieve faster and deeper molecular responses than imatinib (the DASISION and ENESTnd trials) [1][3], but without a clear overall survival advantage, and at the cost of different toxicities. For Mr T, the toxicity profile is decisive:

• Nilotinib carries a significant risk of vascular events (myocardial infarction, stroke, peripheral arterial disease), QT prolongation and metabolic effects (hyperglycaemia, hyperlipidaemia). Given his prior myocardial infarction and vascular risk, nilotinib is the wrong choice [1].
• Dasatinib carries a risk of pleural effusion and pulmonary hypertension, which would be poorly tolerated in a man with cardiac disease, and an added bleeding tendency that matters with his aspirin [3].
• Imatinib 400 mg daily — the original tyrosine kinase inhibitor, with the longest safety track record — is the cardiovascular-safest option. Its toxicities (fluid retention, periorbital oedema, nausea, cytopenias, musculoskeletal aches) are manageable and do not include vascular or pleural events to the same degree. The IRIS trial established its long-term efficacy, with a complete cytogenetic response rate of 87 per cent at 5 years and an overall survival of 89 per cent [1][2].

I would therefore recommend imatinib 400 mg daily as first-line therapy, with the explicit rationale that it is the cardiovascular-safest option for this patient. I would accept a slightly lower probability of a deep molecular response (and thus a lower future treatment-free-remission candidacy) in exchange for a markedly lower vascular risk, which is the dominant threat to his life. If he had a high Sokal risk score and were young and cardiovascularly well, I might favour a second-generation tyrosine kinase inhibitor; here, the comorbidity reverses that calculus. [1]

Step 3 — Secondary prevention and drug interactions: [1]

I would continue all his cardiac medications — aspirin, atorvastatin, ramipril and bisoprolol — and confirm there are no major cytochrome P450 interactions. Imatinib is metabolised by CYP3A4; I would review his medication list for strong CYP3A4 inhibitors or inducers, and caution against grapefruit juice. I would aim for a blood pressure under 130 over 80 and an LDL cholesterol under 1.8 mmol per litre, and reinforce smoking cessation (already achieved) and alcohol moderation. [1]

Step 4 — BCR-ABL1 monitoring on the International Scale: [1]

The cornerstone of management is serial quantitative RT-PCR for BCR-ABL1 on the International Scale, measured at 3, 6, 12 and 18 months and then periodically. The milestones are: the early molecular response (under 10 per cent at 3 months), the major molecular response (under 0.1 per cent, typically by 12 months), and the deep molecular response (MR4 or MR4.5). If a transcript level rises by one log with loss of a major molecular response, I would first check adherence and drug interactions, then test for a BCR-ABL1 kinase domain mutation. If the T315I mutation is found, the answer is ponatinib (the only routinely available tyrosine kinase inhibitor active against it), with careful cardiovascular risk assessment given ponatinib's own thrombotic risk [4].

Step 5 — Treatment-free remission as a future option: [1]

If Mr T achieves a sustained deep molecular response (MR4 or deeper for over 2 years) on at least 3 years of imatinib, he would become a candidate for treatment-free remission — the carefully selected discontinuation of imatinib under rigorous molecular monitoring, established by the STIM trial [5]. Around 40 to 60 per cent of well-selected patients maintain a molecular remission off therapy, with relapse usually within 6 months and reliably regained on restarting. This is a future discussion, not a first-line plan, and the slower and less deep responses with imatinib (compared with second-generation tyrosine kinase inhibitors) make this less likely than in a younger patient on dasatinib or nilotinib — but it remains a real goal worth mentioning.

Step 6 — Communication and psychosocial support: [1]

I would be honest and hopeful: chronic-phase CML is one of the great success stories of modern oncology, with a near-normal life expectancy on tyrosine kinase inhibitor therapy, and his cardiac disease (not the leukaemia) is the dominant threat to his survival. I would explain the imatinib rationale (cardiovascular safety), the monitoring commitment, the manageable side effects, and the long horizon. I would address his anxiety directly, provide written information, introduce a cancer nurse coordinator, and integrate his haematology and cardiology care. [1]

Probing questions the examiner would ask

Q: Why imatinib rather than a second-generation tyrosine kinase inhibitor for this patient? [1]

A: "The second-generation tyrosine kinase inhibitors — dasatinib (DASISION) and nilotinib (ENESTnd) — achieve faster and deeper molecular responses than imatinib, but without a clear overall survival advantage [1][3]. The choice is therefore individualised by toxicity and comorbidity. For Mr T, nilotinib carries a significant risk of arterial vascular events (myocardial infarction, stroke, peripheral arterial disease) and QT prolongation, which is unacceptable given his prior infarction. Dasatinib carries a risk of pleural effusion and pulmonary hypertension, poorly tolerated in cardiac disease, plus a bleeding tendency that matters with his aspirin. Imatinib has the longest safety track record and the most favourable cardiovascular profile, and its efficacy in chronic-phase CML is excellent (IRIS: 87 per cent complete cytogenetic response at 5 years, 89 per cent overall survival) [1][2]. I would accept a lower probability of deep molecular response and future treatment-free remission in exchange for a markedly lower vascular risk, which is the dominant threat. This is a textbook example of comorbidity constraining the therapeutic choice."

Q: How do you interpret a rising BCR-ABL1 transcript on imatinib? [1]

A: "A confirmed rise (a one-log rise with loss of a previously achieved major molecular response) is loss of response. The first steps are to confirm adherence — non-adherence is the single commonest cause of loss of response — and to review drug interactions, particularly CYP3A4 inhibitors and inducers that affect imatinib levels. After excluding these, the next step is BCR-ABL1 kinase domain mutation testing to identify the resistance mechanism and guide the switch. Most mutations respond to a second-generation tyrosine kinase inhibitor; the T315I gatekeeper mutation is the exception and requires ponatinib. I would never simply increase the imatinib dose without this structured assessment." [1]

Q: What is the T315I mutation, and how is it managed? [1]

A: "The T315I is a threonine-to-isoleucine substitution at codon 315 of ABL1 — the gatekeeper residue — which sterically blocks the binding of all first- and second-generation tyrosine kinase inhibitors (imatinib, dasatinib, nilotinib, bosutinib). It is the most clinically important resistance mutation in CML. The PACE trial established that ponatinib, a third-generation tyrosine kinase inhibitor designed to overcome T315I, has significant activity in T315I-positive disease [4]. Ponatinib carries an important risk of arterial and venous thromboembolism, which is a particular concern in this patient with his cardiac history, so cardiovascular risk assessment and dose optimisation are essential. If ponatinib fails, allogeneic stem cell transplant is the salvage option."

Q: When can you stop the tyrosine kinase inhibitor? [1]

A: "Treatment-free remission is attempted only in chronic-phase CML, after at least 3 years of tyrosine kinase inhibitor therapy and a sustained deep molecular response (MR4 or deeper for over 2 years), in a motivated patient who will adhere to intensive monitoring. The STIM trial was the proof of concept: around 40 to 60 per cent of well-selected patients maintain a molecular remission off therapy, with relapse (when it occurs) usually within 6 months and reliably regained on restarting [5]. After stopping, BCR-ABL1 is monitored monthly for 6 months then less frequently, with re-initiation if loss of major molecular response. For Mr T on imatinib, with its slower and less deep responses, this is a future possibility to revisit, not a first-line plan."

Q: What is the role of allogeneic stem cell transplant in CML today? [1]

A: "In the pre-tyrosine kinase inhibitor era, allogeneic stem cell transplant was the only curative treatment for CML and was offered first-line. With tyrosine kinase inhibitors achieving near-normal life expectancy, transplant is now reserved for tyrosine kinase inhibitor failure — the T315I mutation without ponatinib response, progression to accelerated or blast phase, or intolerance of all available tyrosine kinase inhibitors. It carries substantial treatment-related mortality and chronic graft-versus-host disease, so it is never first-line. For Mr T, transplant is not part of the plan unless he fails multiple tyrosine kinase inhibitors." [1]

Communication and shared decision-making

"Mr T, you have a type of leukaemia called chronic myeloid leukaemia. The good news is that it is one of the great success stories of modern treatment — there is a tablet, taken once a day, that targets the exact genetic fault driving your leukaemia and controls it extremely well, to the point that your life expectancy is now very close to normal. The tablet is called imatinib. I am recommending imatinib specifically — rather than two newer, similar drugs — because those newer drugs can affect the blood vessels and the heart, and given your history of a heart attack, imatinib is the safest choice for you. Its side effects are mostly manageable — some fluid retention, a puffy feeling around the eyes, some muscle aches, and occasional nausea — and we will manage these with you. You will keep taking all your heart medicines exactly as before, because protecting your heart is just as important as treating the leukaemia. The leukaemia is measured by a blood test for the genetic signal — the BCR-ABL level — at 3 months, 6 months, 12 months and 18 months, and then periodically; the goal is for that level to fall very low. Most people with your condition live a full life on this tablet, and in a few years, if your response is deep and stable, we may even be able to talk about stopping it under careful monitoring. The most important thing for your long-term health is actually your heart, not the leukaemia — so please keep your cardiac appointments, your blood pressure and cholesterol under control, and never start smoking again. I will give you written information, introduce you to a cancer nurse coordinator, and review your blood tests closely. What questions do you have?" [1]

Outcome and follow-up

Mr T is discussed at the haematology multidisciplinary meeting, where the consensus is to start imatinib 400 mg daily, chosen for its cardiovascular safety in the context of his prior myocardial infarction. His cardiac medications are continued unchanged, and his cardiologist is informed. [1]

He tolerates imatinib well, with mild periorbital oedema and some muscle cramps managed with simple measures and adequate hydration. His white cell count normalises within 4 weeks, and his spleen becomes impalpable by 3 months. His BCR-ABL1 transcript falls to 6 per cent at 3 months (achieving the early molecular response milestone of under 10 per cent), to 0.8 per cent at 6 months, to 0.15 per cent at 12 months, and to 0.05 per cent at 18 months — a major molecular response sustained over the monitoring period, consistent with an optimal response on imatinib. [1]

His cardiac status remains stable, with no angina, a well-controlled blood pressure, and an LDL cholesterol of 1.4 mmol per litre on atorvastatin. A surveillance echocardiogram shows stable left ventricular function. He continues full-time work as a school principal. [1]

At the 24-month review, his BCR-ABL1 transcript is stable in major molecular response, and a conversation begins about the longer-term goal of a deep molecular response (MR4) and, if sustained for over 2 years, the possibility of a carefully monitored treatment-free remission trial in the future — with the explicit understanding that imatinib's slightly slower and shallower responses make this less likely than on a second-generation tyrosine kinase inhibitor, but that the trade-off against his cardiovascular safety was the right one for him. He remains under lifelong combined haematology and cardiology surveillance, with the clear understanding that his heart disease, not his leukaemia, is the dominant threat to his long-term survival. [1]