Reading cost-effectiveness evidence

What an ICER, a QALY, a threshold, a price year and a quality score actually mean.

Economic evaluation
A study that compares two treatments on both cost and health outcome. A paper that reports only what something costs — a budget impact, a facility's capital cost — is not one, and is not in the table.
QALY (quality-adjusted life year)
One year of life in full health. A year lived with a serious side effect counts as a fraction of one, so two treatments that extend life equally can still differ in QALYs if one is harder to live through. It is the unit that lets a late cardiac event and a hearing loss be weighed on the same scale.
ICER (incremental cost-effectiveness ratio)
The extra cost of a treatment divided by the extra health it buys, usually written as a cost per QALY gained. An ICER of US$50,000 per QALY means each additional quality-adjusted year costs that much more than the comparator.
Dominance
A treatment that is both cheaper and more effective. There is no ratio to quote, which is why some rows in the table say “cost saving” instead of a number.
Willingness-to-pay threshold
The most a health system will pay for a QALY. Below it, a treatment is usually called cost-effective. Thresholds differ by country and are sometimes not stated at all, which is why the same ICER can be cost-effective in one paper and not in another.
Perspective
Whose costs were counted. A payer perspective counts what the insurer or health service pays; a societal perspective also counts travel, time off work and productivity. The same treatment looks cheaper or dearer depending on which was chosen, so the table always shows it.
Price year
The year the money is expressed in. A cost in 2002 euro is not a cost in 2024 euro. Most studies in this field never state one — the table says not stated rather than guessing, and that is a real limitation of the literature, not of the table.
Discount rate
The rate at which future costs and health are counted as worth less than present ones, usually 3% a year. It matters most in paediatric studies, where the benefit arrives decades later.
QHES score
The Quality of Health Economic Studies instrument (Ofman 2003): 16 weighted items out of 100 covering the objective, the perspective, where each estimate came from, how uncertainty was handled, the horizon and discounting, how costs were measured, the model's transparency, the discussion of bias, and whether funding was disclosed. It scores how well a study was reported. A high score is not a verdict that the conclusion is right, and a low one does not make the study wrong — it makes it harder to check.

Why we do not convert currencies

It would be easy to turn every ICER into dollars and sort the lot. It would also be misleading. An ICER is a ratio in one currency, of one price year, judged against one payer's threshold, built on that country's own prices for a course of treatment. Converting it at today's exchange rate compares a Japanese carbon-ion study against a US proton study as though the two health systems paid the same way and valued a QALY the same amount, and most of these studies do not even state the price year a conversion would need. The studies themselves do not convert; neither do we. The table groups by currency, and sorting works inside a block, where the comparison means something.

Where these studies come from

A standing PubMed search runs over every paper entering our research library and flags anything that pairs a particle-therapy term with an economics term. Each candidate is then screened by hand: a full economic evaluation of proton, carbon-ion, helium or BNCT therapy goes into the table, a cost-only or budget-impact paper does not. Values are entered from the paper's own abstract first, and from its full text only for the fields the abstract left blank. Nothing is inferred: a field the paper does not report reads not stated.