Introduction:
Comparable ipsilateral breast cancer recurrence rates have been shown for adjuvant radiotherapy (RT) and endocrine therapy (ET) in elderly patients (>70 years) with oestrogen-receptor positive, low risk, early breast cancer (T1, Grade I/II, node negative)1-6. On this basis, we conducted a CMA to evaluate the direct costs of treatment and their common toxicities.
Methods:
Costs for three adjuvant treatments were included in this analysis: (i) Conventional whole breast RT (15 fractions)7, (ii) Aromatase inhibitor (AI) therapy (Anastrazole 1mg/day for 5 years) and (iii) Tamoxifen (20mg/day for 5 years)8. Costs to the healthcare provider over a ten year period were compared. Total cost (C) included total treatment cost (TxC) and cost of toxicity management (CTox) where C=TxC+CTox. Costs of treatment/investigations were estimated from Medicare Benefits Schedule (MBS) and drug costs were taken from MIMS (Australia). Common toxicities (>10% - on MIMS/trials) and rare but serious side effects (with significant health burden) were included in this analysis. Sensitivity test was applied to incidence rates (clinically relevant rates), drug costs (alternative product costs on MIMS) and also total cost (C) (±50%, ±25%, ±10%). Differential timing of cost was accounted for using discount rates (DR) of 3% & 5%.
Results:
C for RT, AI and Tam are $3015 (sensitivity range: $3015-3038), $6374 ($2256-11243) and $1044 ($475-1617) respectively. Osteopenia/osteoporosis treatment is the main driver of cost in AI treatment. It is also the most sensitive to variation in drug cost and incidence rates. AI treatment, currently the standard of care, was identified as being six times more expensive than Tam and twice as expensive as RT.
Conclusion:
This CMA shows that Tam is the most cost effective adjuvant therapy. AI is the most expensive where C is very sensitive to cost of bone health management which is a significant problem in this patient group.