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common situation) then the two curves will be very similar in shape.
Figure 1 shows a hypothetical five year survival curve for tumour X, and is used to show the usual
representation of this type of data. It includes percentage figures along the curve showing the recurrence
rates for each of the five years following treatment.
1 Restricted Class 2: For private flying, limitations in use in many Contracting States include “without passengers”,
“outside controlled airspace”, and “with safety pilot.”
2 TNM classification: staging of tumours according to three basic components – primary tumour (T), regional nodes
(N) and metastasis (M). Numbers denote size and degree of involvement, e.g. 0 means “undetectable”, and 1, 2, 3,
and 4 a progressive increase in size and involvement. Thus a tumour can be described as T1N2M0.
ICAO Preliminary Unedited Version — October 2008 III-15-4
Years since primary treatment
Figure 1.– Overall five year survival after primary treatment of tumour X.
The graph represents the recurrence rates for all cases of tumour X. These data, however, include a large
spectrum of recurrence rates from very low (early stage disease) to very high (late stage disease). To
illustrate the effect of different stages on prognosis, it is assumed that tumour X lesions can be divided
into three types, or stages, based on the pathological examination of the resected specimen.
Studies have shown that the prognosis following surgical treatment for tumour X is related positively to
the stage of the tumour at operation. Thus the previous overall five year survival curve of tumour X can
be broken down into three separate curves relating to the three separate stages as shown in Figure 2. As
would be expected, the more advanced stage tumours (stages 2 and 3) have a worse prognosis than early
lesions.
ICAO Preliminary Unedited Version — October 2008 III-15-5
Years since primary treatment
Figure 2.– Five year survival for tumour X divided into pathological stages
From the data in Figure 2 it is possible to derive a yearly percentage risk of recurrence for any stage of
tumour X. For instance, the risk of a recurrence between two and three years after surgery for a stage 2
tumour is nine per cent
Defining the site of recurrence
Each tumour has its own particular sites of recurrence, and these have been recorded in pathology
textbooks since they were first written. Although metastases can occur in any part of the body, the
majority are found in lymph nodes, lungs, bones, bone marrow and brain. For any particular tumour the
risk of first recurrence at each of these sites can be determined from available data sources. However,
these data are often difficult to find in the medical literature. Figures for the incidence of metastases in
various organs at post-mortem are more easily obtained, and in some tumours an extrapolation from such
data may be necessary to obtain a “first recurrence” incidence.
Table 3 provides an example of the percentage incidence figures of first recurrence at different sites for a
hypothetical tumour.
Site incidence Per cent
ICAO Preliminary Unedited Version — October 2008 III-15-6
Local and regional lymph nodes 60
Liver 20
Brain 10
Lung 5
Bone 5
Bone marrow 0
Table 3.– Incidence of metastasis by site for a hypothetical tumour
Defining the risk of a particular metastasis causing incapacitation
A first recurrence in a regional lymph node carries a very small risk of incapacitation. A brain metastasis,
on the other hand, as the first indication of recurrent disease, must be assumed to carry a 100 per cent
potential for sudden incapacitation in the form of a fit or seizure or another neurological event such as
paresis, sensory loss or headache. Metastatic disease in bone marrow can cause anaemia and bleeding
disorders. Rarely metastases erode major vessels with catastrophic consequences (lungs and liver).
The risk of subtle incapacitation is harder to quantify, but it must be assumed that any recurrence of any
tumour will degrade the operational abilities of aircrew to some extent. Thus a table of “incapacitation
weighting” can be constructed to give an estimate of the potential for sudden and insidious incapacitation
by a recurrence at each metastatic site. This is shown in Table 4.
Site Incapacitation “weighting”
in per cent
Local and lymph nodes 5
Liver 5
Lungs 5
Bone 5
Bone marrow 20
Brain 100
Table 4.– Incapacitation weighting
Defining the total risk of incapacitation
Three parameters may be known about tumour X, and these can be used to estimate a “total” risk of
　
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