Economic Evaluation of Positron Emission Tomography (PET) in Non Small Cell Lung Cancer (NSCLC), CHERE Working Paper 2007/6

The results for the CT positive patients also show that PET marginally identifies more
patients correctly for surgery and has a lower number of missed operations; this is again,
because of CWU patients undergoing more mediastinoscopy with its risk of death than PET
patients. There are substantial numbers of futile thoractomies occurring in both CWU and PET
patients with 5.93 and 4.23 respectively. The reason the number of thoractomies is so high is
because of the low sensitivity of mediastinoscopy at only 72% due to it being unable to reach
some lymph nodes and with more mediastinal lymph metastasis patients in the section of the
model this causes an increase in numbers of futile thoractomies proportionally when compared
to the CT negative patients. The small difference in the number of futile thoractomies between
the CWU and PET strategies is because of better PET staging. Furthermore, the PET strategy
also reduces the number of futile radiotherapies that that would occur in the CWU cases due
PET correctly identifying more of the N2/3 M1 patients. However, there are only small gains
for improving the correctly staging more radiotherapy patients because N2/3 M0 patients only
gain around 0.15 QALYs per patient. The difference in costs and QALYS are even closer
between the two strategies and suggest that the results will be even more sensitive to changes
in model inputs and variables.

An ICER examines the additional cost of one strategy compared to another against the
additional benefits the strategy offers. The ICER is calculated by dividing the differences in
costs by the difference in patient’s benefit, to give an incremental cost per QALY.⁴⁰ The
incremental costs and QALYs and the resulting ICERS were calculated and presented in table
8.

Table 8: Totals costs, QALYs and incremental cost effectiveness ratios.

The results show that PET strategy is cost effective compared to just using the CWU
strategy for both CT negative and CT positive patients with an ICER of $A 14,581 and $A
52,039 per QALY respectively. The ICER for CT positive patient is expensive and it would be
down to a decision maker to decide whether this would be an acceptable cost worth paying for
an additional QALY.

The difference in results between the CT negative and CT positive results in terms of
their ICERs is due mostly to PET reducing the number of futile operations in non N0/1 M0

⁴⁰ Drummond et al Economic evaluation in Health care: Merging theory and practice. (Oxford, O.U.P, 2001) pp.
11-12.

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