Radical surgery for Mesothelioma
The
epidemic is still to peak and we need more research to manage
it
One in every hundred men born in the 1940s will die of die of
malignant pleural mesothelioma, which is almost exclusively
a consequence of exposure to asbestos, with a lag time that
is rarely less than 25 years and often more than 50 years from
first exposure. Half of all cases are now aged over 70, with
80% in men. For a man first exposed as a teenager, who remained
in a high risk occupation, such as insulation, throughout his
working life, the lifetime risk of mesothelioma can be as high
as one in five.w1 There are now over 1800 deaths per year
in Britain (about one in 200 of all deaths in men and one in
1500 in women), and the number is still increasing.1
w2 As exposure in the United Kingdom continued until
1980 the peak of the epidemic is still to come, and we need a
strategy to manage these patients.
Asbestos was a valuable and versatile material and imports rose
after the second world war when it was widely used as an insulator,
in the manufacture of filters, cements, friction products, and
as a fire retardant. It found a place in shipbuilding and industry
and was used extensively in building in the form of light workable
boards.2 It was a convenient
partitioning material that combined insulation and fire
proofing. The Health and Safety Executive statistics indicate
that 25% of deaths will be in men who worked in the building
industry and that carpenters and joiners are most commonly
afflicted.w3 These men have often been self employed
in small enterprises or engaged in do it yourself home improvements.
About 90% of deaths due to mesothelioma are due to exposure
to asbestos in unmonitored settings. Wives and daughters who
washed the overalls of asbestos workers are among those who
have died.
Imports were at their highest from about 1955 to 1980 in the
UK.3 The Asbestos Licensing Regulations
came into force in the United Kingdom in 1983 and Control of
Asbestos at Work Regulations in 1987 (both amended in 1988).
The peak of the epidemic is expected in 2015 to 2020 when the
death rate is likely to be 2000 per year in the United Kingdom.
The situation in Europe is similar.4
Australia had the highest pro rata asbestos usage,w4 and
asbestos imports continue in the developing world.w5 The
epidemic in the United States has probably peaked because of
earlier awareness and action on asbestos imports.5
Many countries are seeing the rising tide of an epidemic, and
all doctors need to know how to recognise and diagnose this
disease and what treatments are available.6
Mesothelioma is a relatively slow growing tumour that most commonly
originates in the parietal pleura but can also arise in the
abdomen and the tunica vaginalis. It presents with pain in the
chest wall or breathlessness due to increased pleural fluid,
but symptoms may be absent or develop insidiously. Not infrequently,
at the time of first awareness, a thick rim (1 cm or more) of
hard dense tumour encasing and restricting the lung may already
be present. The diagnosis can be difficult to prove. When pleural
disease is found it has to be distinguished from pleural plaques
and malignant effusion from adenocarcinoma.6
Cytological examination of pleural fluid and small needle
biopsies are often inconclusive because adequate tissue is
required and it may take several attempts, culminating in
surgical biopsy—each time with a risk of infection and needle
or drain track seeding to which mesothelioma is particularly
prone. Biopsy and drain tract radiotherapy is recommended.6
Once made there is tendency for the diagnosis to be met with
a sense of hopelessness—not without good reason for it is a
horrible disease, often with months of unremitting pain,
progressively diminishing pulmonary performance, cachexia, and
the inevitability of death. Median survival from diagnosis is
usually under a year, but individual series vary markedly7
8 as is not surprising in a cancer with such a
long lead time and in which the known phase of the disease is a
small proportion of its natural history.
How can we think about it positively? The best we can offer
at present is stage specific treatments, which should whenever
possible be within clinical trials.
As with most solid tumours the first consideration is surgery—can
we cut it out and get rid of it? The operation, extrapleural
pneumonectomy, entails removal of all the parietal pleura, the
pericardium, and the diaphragm in addition to the whole lung
on that side.9 It is usually
considered as part of trimodality treatment with various
combinations of preoperative and postoperative chemotherapy and
radiotherapy to the empty hemithorax after surgery.10
This is associated with survival figures of up to 48% at five
years in highly selected subsets of patients with the more
favourable epithelioid (as opposed to sarcomatoid) histology
and no lymph node metastases.w6-w9 Radical surgery
has been performed infrequently in the United Kingdom, with an
average of only 20 patients per year in the past five years.
Some patients and their doctors desperately seek radical surgery
as their only hope, but others have doubts about the evidence.11
A trial is needed, and a pilot feasibility study (the mesothelioma
and radical surgery "MARS" trial, funded by Cancer Research
UK) is now under way. To answer the question 670 patients will
be required over three years with five years' follow up. If
achieved this would give an answer by about 2012 in time for
the peak of the epidemic.
Irrespective of whether radical surgery will be considered much
needs to be done in the care of these patients. The diagnosis
should be made early and efficiently. Without it we cannot have
meaningful discussions with the patient or plan treatment, and
the patient's legal position in terms of compensation remains
unclear. At the same time we try to control any pleural effusion
to maintain breathing as long as possible.6
This is best done by thoracoscopic talc pleurodesis, which can
usefully be combined with surgical biopsy. Then with the
diagnosis made the disease can be staged. If the pathological
stage is early extrapleural pneumonectomy should be considered,
and we would recommend that this is done in the context of
multimodality treatment and within a study.11
If the tumour is inoperable management can be with
chemotherapy, and again it would be preferable that this is
within a study.12
This disease is increasing in frequency. There is nothing we
can do now to prevent it in workers exposed to asbestos throughout
the 1950s, 1960s, and 1970s. What we can do is recognise it
early, treat it actively, and learn about best treatment with
carefully thought out studies because we will be seeing many
more mesotheliomas in the next 25 years. In the developed world
alone 100 000 people alive now will die from it.