HTBS Study
The HTBS study is based on a decision analysis with seven possible strategies
analysed. They conducted their own meta-analysis to estimate the sensitivity and specificity of
PET. The majority of parameters used in the model were taken from the Dietlein study.18 The
costs were estimated from a detailed costing of a Scottish PET facility. All patients had a
definite diagnosis of NSCLC, were fit for surgery and had a conventional work up (CWU),
which usually consists of a chest x-ray, brochoscopy and a CT scan. If the CT scan was
positive then the patients had enlarge nodes and therefore a greater risk of mediastinal
metastasis or distant metastasis, whereas these risk was reduced if the results were CT
negative, in other words the nodes were normal. It was assumed that the rate of metastasis was
10% and could only be detected by PET.
The results for the CT positive patients found that two strategies which noticeably
outperformed the other strategies. These were Strategy 3 (mediastinoscopy all and no PET),
which had the second best outcome. Strategy 7 (mediastinoscopy after positive PET) had the
best outcome and had a higher number of QALYs compared to just giving a PET scan with no
further staging procedures to everyone mainly because of the relatively poor detection of
enlarged N2/3 patients compared to the 100% specificity of mediastinoscopy. The incremental
cost effectiveness ratio (ICER) was extremely high with a value of £59,000 per QALY relative
to the threshold implicitly used by NICE in the UK and therefore does not seem to be cost
effective at any current acceptable national healthcare threshold.
The results for CT negative patients found that strategies 1, 3 and 7 dominated the other
strategies. Strategy 1 (send all to surgery) was the third best outcome with Strategy 3 the
second best and Strategy 7 having the best incremental cost per QALY of £10,500. This
suggests that using PET for CT negative patients is a cost effective strategy in this model.
NICE Study
The NICE study was also based and built upon the HTBS and Dietlein studies. They
looked at two groups of patients who were expected to benefit most from PET. The first was
those patients with normal sized lymph nodes (i.e. negative) on CT being considered for PET,
they excluded positive patients because they felt that these patients would not benefit due to the
high ICER recorded in the HTBS study. The second group were patients that were being
considered for radical radiotherapy this consisted mainly of those patients with enlarged nodes
(i.e positive) on CT.
In the surgery model they considered three strategies. Under the first strategy patients
went straight to thoractomy. In the second, the patients have a mediastinoscopy and then either
receive radical radiotherapy (N2/3) or thoractomy (N0/1). In the third strategy patients have a
PET scan and then receive either active supportive care (M1), thoractomy (N0/1, M0) or
mediastinoscopy (N2/3, M0).They found that the mediastinoscopy strategy was dominated by
the PET strategy. The PET strategy compared to the thoractomy strategy resulted in 22% fewer
futile thoractomies, 1% fewer surgical deaths and a more appropriate selection of patients for
radical radiotherapy. This resulted in an increase in life expectancy of 0.04 per patient and an
18 Dietlein, M., K. Weber, et al. (2000). "Cost-effectiveness of FDG-PET for the management of potentially
operable non-small cell lung cancer: priority for a PET-based strategy after nodal-negative CT results." Eur J Nucl
Med 27(11): 1598-609