HSC Exam Practice

Sample response. Tertiary prevention refers to the management of established disease to reduce complications, disability, and further deterioration — it does not prevent the disease or detect it early. A named example for CVD is cardiac rehabilitation programs (supervised exercise + dietary counselling + psychological support) offered to eligible Australian patients following myocardial infarction or CABG, funded through Medicare.

Marking notes. 1 mark for defining tertiary prevention as management of established disease to reduce complications/disability (must distinguish from primary and secondary prevention). 1 mark for a valid named example linked to CVD in Australia (cardiac rehabilitation is ideal; accept also: diabetes education services post-T2D diagnosis, statin therapy post-MI for secondary risk reduction).

Sample response. The molecular target of statins is HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis (mevalonate pathway). Statins competitively inhibit this enzyme, reducing the amount of cholesterol synthesised in liver cells. This causes hepatocytes to upregulate LDL receptor expression on their surface, increasing clearance of LDL-cholesterol from the bloodstream. Lower serum LDL reduces the lipid available for deposition in arterial walls, slowing atherosclerotic plaque formation and therefore reducing the risk of plaque rupture, thrombus formation, and myocardial infarction.

Marking notes. 1 mark for identifying HMG-CoA reductase (accept also: mevalonate pathway enzyme or hepatic cholesterol synthesis enzyme). 1 mark for the mechanism chain: statins inhibit enzyme → reduced hepatic cholesterol → upregulation of LDL receptors → increased LDL clearance. 1 mark for linking lower LDL to reduced atherosclerotic plaque formation and reduced MI risk.

Sample response. Conventional chemotherapy agents (e.g. cisplatin, taxanes) are cytotoxic — they disrupt DNA replication or mitotic spindle assembly in any rapidly dividing cell, regardless of whether the cell is cancerous. This lack of specificity means chemotherapy also damages rapidly dividing normal cells (bone marrow stem cells, gut epithelium, hair follicles), causing severe side effects: immunosuppression, hair loss, mucositis, and nausea. Targeted therapy (e.g. imatinib for CML) acts on a specific molecular driver present only in cancer cells — imatinib binds to the ATP-binding site of BCR-ABL tyrosine kinase, which is exclusively produced by CML cells carrying the Philadelphia chromosome translocation. Because normal cells lack BCR-ABL, imatinib selectively kills CML cells with minimal off-target damage.

Marking notes. Mechanism: 1 mark for chemotherapy (cytotoxic; disrupts DNA/mitosis in all rapidly dividing cells); 1 mark for targeted therapy (inhibits specific cancer-expressed protein — BCR-ABL or equivalent). Specificity: 1 mark for identifying that chemotherapy has low specificity (damages all dividing cells). 1 mark for targeted therapy having high specificity (BCR-ABL only in CML cells / cancer-specific molecular target absent in normal cells).

Sample response. CABG surgery bypasses the blocked section of the coronary artery by grafting a new blood vessel around the obstruction, restoring myocardial blood flow. However, CABG does not remove the atherosclerotic plaques from other coronary arteries, nor does it treat the underlying lipid metabolism disorder (elevated LDL-cholesterol) driving atherosclerosis. Without ongoing statin therapy, LDL remains elevated and atherosclerotic plaque continues to form in other arteries and potentially in the bypass graft itself. Lifestyle management (dietary modification, physical activity) addresses ongoing risk factors — visceral adiposity, insulin resistance (given T2D) — that would otherwise accelerate both CVD and T2D progression. Both interventions are needed to manage the disease that CABG cannot address.

Marking notes. 1 mark for correctly stating that CABG bypasses the blockage but does not remove plaques or treat the underlying atherosclerotic disease mechanism. 1 mark for explaining why statins are still needed post-CABG (LDL remains elevated; plaque progression continues in other arteries / the graft). 1 mark for explaining why lifestyle management is still needed — addresses risk factors (T2D-related insulin resistance, visceral adiposity) that CABG surgery does not treat.

Sample response. Mechanism 1: Aerobic exercise activates AMPK (AMP-activated protein kinase) in skeletal muscle cells. AMPK activation triggers the translocation of GLUT4 transporter vesicles to the plasma membrane, allowing glucose uptake from the blood into muscle cells independently of insulin receptor signalling. This directly lowers blood glucose during and after exercise. Mechanism 2: Sustained aerobic exercise and associated weight loss reduce the mass of visceral adipose tissue. Adipose tissue produces adipokines (e.g. TNF-alpha, IL-6) and free fatty acids that impair insulin receptor signalling in peripheral tissues. With less visceral fat, these inhibitory signals decrease and insulin receptor sensitivity is restored — meaning the body responds more effectively to existing insulin, improving glucose clearance from the blood.

Marking notes. Mechanism 1: 1 mark for GLUT4 translocation to plasma membrane (named protein required); 1 mark for insulin-independent glucose uptake causing reduced blood glucose. Mechanism 2: 1 mark for a second distinct mechanism (visceral fat reduction + improved insulin sensitivity via reduced adipokines/free fatty acids; or resistance training + increased muscle mass as glucose sink). 1 mark for naming the specific cellular protein in mechanism 2 (e.g. adipokines, TNF-alpha; or AMPK as the shared activator if mechanism 1 is GLUT4 only). Accept any two well-mechanised pathways — GLUT4/AMPK and adipokine/insulin sensitivity are the lesson examples.

Sample response. Conventional chemotherapy (e.g. cisplatin) causes severe side effects including immunosuppression, alopecia (hair loss), mucositis, and nausea because it damages all rapidly dividing cells — including normal bone marrow progenitor cells, gut epithelial cells, and hair follicles. Imatinib produces a much milder side effect profile (typically mild nausea, fluid retention, and fatigue) because its molecular target, BCR-ABL tyrosine kinase, is only expressed in CML cells carrying the Philadelphia chromosome translocation. Normal haematopoietic cells do not express BCR-ABL and are therefore not affected by imatinib — bone marrow is not suppressed, hair follicles are not damaged, and the gut epithelium is not harmed.

Marking notes. 1 mark for identifying that conventional chemotherapy damages all rapidly dividing cells (including normal bone marrow/gut/hair follicles), causing severe side effects. 1 mark for stating that imatinib specifically targets BCR-ABL, which is absent from normal cells. 1 mark for explaining the consequence: imatinib does not damage normal rapidly dividing cells, so bone marrow suppression, alopecia, and gut toxicity are absent or minimal.

Sample response (a). The imatinib group maintains high overall survival throughout the 10-year period, declining gently from 100% at baseline to approximately 83% at year 10. The interferon-alpha (prior chemotherapy) group declines more steeply, from 100% at baseline to approximately 42% at year 10. The approximate difference in 10-year survival between the two groups is therefore approximately 40 percentage points in favour of imatinib.

Marking notes (a). 1 mark for correctly describing imatinib group trend (gradual decline, approximately 80–85% survival at year 10). 1 mark for correctly describing interferon-alpha group trend (steeper decline, approximately 40–45% survival at year 10). 1 mark for quantifying the approximate difference (~40 percentage points; accept ±5 points).

Sample response (b). Imatinib is a targeted therapy that specifically inhibits BCR-ABL tyrosine kinase — the constitutively active oncoprotein produced by the Philadelphia chromosome translocation in CML cells. By binding to the ATP-binding site of BCR-ABL, imatinib prevents it from phosphorylating downstream proliferative signalling proteins, stopping the continuous division signal in CML cells. Because normal cells do not express BCR-ABL, imatinib selectively suppresses the CML clone without the severe off-target bone marrow toxicity that limits chemotherapy dosing. This sustained, targeted suppression of the CML-driving oncoprotein allows most patients to maintain long-term remission, explaining the high 10-year survival. Interferon-alpha, by contrast, has less specificity and is associated with greater toxicity and inferior molecular remission rates, leading to faster disease progression and lower long-term survival.

Marking notes (b). 1 mark for identifying BCR-ABL as the target and describing imatinib's mechanism (inhibits kinase activity, blocks proliferative signalling). 1 mark for explaining why imatinib spares normal cells (BCR-ABL absent from normal cells). 1 mark for linking this specificity to long-term sustained remission (higher survival maintained over 10 years vs interferon-alpha). 1 mark for comparing with interferon-alpha (less specific, greater toxicity, inferior molecular remission = lower long-term survival).

Sample response (c). A key limitation is that the two treatment groups were likely treated in different time periods (interferon-alpha was the pre-imatinib standard of care), meaning differences in supportive care, disease staging practices, and diagnostic criteria may confound the survival comparison. This is not a concurrent randomised controlled trial; historical controls may be systematically different from the imatinib-era patients.

Marking notes (c). 1 mark for any valid methodological limitation: historical controls vs concurrent RCT; different time periods with different supportive care; possible differences in patient selection/staging; or patients in the imatinib era may have had better supportive care beyond the drug itself. Accept any scientifically valid limitation.

Sample response. Evaluating a treatment requires a balanced assessment of its biological effectiveness, financial cost, patient accessibility, and patient-specific appropriateness — not simply listing its properties.

For Type 2 diabetes, Australian Diabetes Society guidelines recommend lifestyle modification as the first-line treatment for early-stage disease. Dietary change (reducing refined carbohydrates and saturated fat, increasing fibre) lowers post-meal blood glucose and visceral adipose tissue; aerobic exercise activates AMPK in skeletal muscle, triggering GLUT4 translocation to the plasma membrane and enabling insulin-independent glucose uptake; resistance training increases muscle mass, expanding the body's glucose sink. Weight loss exceeding 15% has been associated with sustained T2D remission in some patients. The direct financial cost of lifestyle management is very low, but it demands substantial time, behavioural change, food security, access to safe exercise environments, and support from dietitians and diabetes educators — creating significant socioeconomic barriers for patients with low income, long working hours, or limited health literacy. Medicare's Chronic Disease Management Plan provides some allied health referral funding, improving accessibility.

When lifestyle intervention alone does not achieve target HbA1c (below 7.0% for most patients), metformin is the PBS-listed first-line pharmacological agent. Metformin activates AMPK in hepatocytes, reducing gluconeogenesis (synthesis of glucose from non-carbohydrate precursors) and improving GLUT4-mediated glucose uptake in peripheral tissues. This lowers fasting and post-meal blood glucose by approximately 1–2% HbA1c. Critically, metformin does not restore beta-cell function or reverse insulin resistance — it improves the response to existing insulin. The PBS co-payment is approximately $6/month, making metformin financially accessible to virtually all Australians. Side effects (initial gastrointestinal discomfort) can reduce adherence in the short term but typically resolve. Metformin is contraindicated in severe kidney disease.

The most biologically effective treatment for T2D may be bariatric surgery (achieving sustained remission in over 50% of severely obese patients) or semaglutide (a GLP-1 agonist achieving significant HbA1c reduction and weight loss) — but neither is appropriate for all patients. Bariatric surgery carries surgical risk, requires profound lifelong dietary compliance, and is not PBS-funded for T2D management (limiting accessibility). Semaglutide has higher cost without full PBS subsidy. For a newly diagnosed patient like Marcus (fasting blood glucose 8.2 mmol/L, limited time to exercise), lifestyle intervention + metformin is the most appropriate starting approach — it is evidence-based, safe, cheap, and accessible — even if bariatric surgery might produce a larger biological effect in a different patient profile.

Therefore, the most biologically effective treatment is not always the most appropriate: appropriateness requires integrating biological effectiveness with cost, accessibility (geographic, financial, time), patient safety, adherence capacity, and disease stage. The PBS and Medicare are critical in narrowing the gap between effectiveness and accessibility for subsidised treatments such as metformin, statins, and imatinib.

Marking criteria.

• 1 mark — Defines or correctly applies evaluation (balanced judgement of effectiveness + cost + accessibility + patient factors; not a simple list).
• 1 mark — Correctly describes mechanism of at least one pharmacological treatment for T2D with named protein/enzyme (metformin + AMPK + gluconeogenesis reduction; or GLP-1 agonist).
• 1 mark — Correctly describes mechanism of lifestyle management for T2D with at least one named cellular mechanism (GLUT4 translocation, AMPK, visceral fat reduction).
• 1 mark — Compares effectiveness of at least two T2D treatments with reference to HbA1c reduction, T2D remission data, or beta-cell function restoration.
• 1 mark — Addresses cost and accessibility of at least two treatments, including the role of PBS (metformin ~$6/month; bariatric surgery not PBS-listed; or equivalent specific examples).
• 1 mark — Explains why biological effectiveness alone does not determine appropriateness, using a patient-specific example (disease stage, adherence capacity, surgical risk, socioeconomic barriers).
• 1 mark — Reaches a coherent evidence-based overall judgement that links effectiveness, cost, accessibility, and patient context, using precise lesson terminology (AMPK, GLUT4, gluconeogenesis, PBS, HbA1c, visceral fat, or equivalent).