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

straight to surgery and virtually doubled the number of futile surgeries. While the increase in
the number of false positive patients causes more of the patients to undergo a mediastinoscopy
with its accompanied risk of death causing some patients to miss out on potentially curable
surgery. This, therefore, reduces the number of QALYs gained and at the same time increases
the costs in the PET strategy due to more futile surgeries. The effect of moving from CWU to
the PET strategy in both CT negative and CT positive patients is a increase in the ICER from
$A 14,581 to $A18,003 and $A 52,038 to $A 131,065 per QALY.

On the other hand, increasing the sensitivity and specificity of PET has the opposite
outcome of correctly staging more patients reducing the number of futile operations and
reducing the number of missed operations. This increases the number of QALYs and reduces
the cost of the treatments with the predictable result of the ICER falling to $A 11,841 in CT
negative patients and $A 29,730 and CT positive patients.

The overall effects in the movement of the ICER are smaller when using the higher
confidence interval because the confidence intervals around the point estimates are not
symmetrical. The large changes in the CT positive patients ICER can be attributed to the small
incremental change in the QALYs between the two strategies making the results more
sensitive. This gives much more uncertainty around the PET strategy in the CT positive
patients, because it is unlikely from a decision maker’s perspective they will accept an ICER of
$A 131,065 per QALY if the sensitivity and specificity of PET were found to be lower in
reality

Surgical morbidity rate

The base case assumed that the surgical morbidity rate caused a reduction in utility of
0.15 for every operation undergone. This parameter was only an estimation given in the HTBS
study and so no firm value was attached to it other than what seemed reasonable. The loss of
utility was therefore decreased to 0.1 and increased to 0.2 to take account of this uncertainty.

Table 11: Sensitivity analysis of the surgical morbidity rate

Surgical morbidity decreased to 0.1

The results for decreasing the surgical morbidity to 0.1 shows that for CT negative
patients the QALYs for both the CWU and PET patients increase. Nevertheless, there are more
patients who are undergoing surgery whether they are correct operations or futile operations in

21

<<   <   18   19   20   21   22   23   24   >   >>