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A
definition of what a rare tumor is
P.G. Casali1, L. Ciccolallo2,
R. Capocaccia3, P. Bruzzi4, L. Licitra5,
F. Grosso6, F. Berrino7, G. Gatta8
1Istituto Nazionale Tumori, Adult
Sarcoma Medical Oncology (Melanoma Sarcoma U, Milano, Italy; 2Istituto
Nazionale Tumori, Epidemiology, Milano, Italy; 3Istituto Superiore
Sanita, Epidemiology and Biostatistics, Roma, Italy; 4Istituto
Ricerca Cancro, Clinical Epidemiology, Genova, Italy; 5Istituto
Nazionale Tumori, Head & Neck Medical Oncology, Milano, Italy; 6Istituto
Nazionale Tumori, Melanoma Sarcoma, Milano, Italy; 7Istituto
Nazionale Tumori, Epidemiology, Milano, Italy; 8Istituto Nazionale
Tumori, Epidemiology, Milano, Italy
Background. Medical
decisions, clinical research, and healthcare organization pose unique
difficulties in rare tumors.
In fact, clinical decisions are to be based on weaker evidence; clinical trials
are less easy to perform and the development of new drugs (orphan drugs) should
receive incentives; patient referral could follow different criteria from
frequent tumors.
However, a specific definition of rare tumors is lacking.
On the other hand, definitions of rare diseases do exist, and they are based on
prevalence.
In Europe, rare diseases are defined as those with a prevalence <50/100,000.
Material
and methods. The EUROCARE database was used in order to provide estimates of
the incidence of rare tumors in Europe.
The ITAPREVAL database was used in order to provide estimates of the prevalence
of rare tumors in a European country such as Italy.
Results were compared and evaluated by a group of clinicians and
epidemiologists.
Results.
If the European definition of rare diseases were used also for tumors, by using
the sole ICDO codes for tumor topography, a proportion in excess of 10% of tumor
sites would be placed among rare diseases.
They would include also esophageal cancer, brain tumors, pancreatic tumors, and
leukemias, which have an incidence >3/100,000/year.
On the other hand, tumors such as testicular cancer and thyroid gland tumors,
with an incidence <3/100,000/year, would not be considered rare, their
prevalence being not so lower than that of one of the most frequent tumors, lung
cancer.
Conclusions.
Prevalence is a good criterion to define mainly chronic, slowly or non-evolving,
rare diseases.
In cancer, however, clinical, research, and organizational problems are often
stage-specific and related to some windows in the natural history of the
disease.
Patients with some cancers may be often cured soon after diagnosis, while those
with other cancers may not be, and require continuous care.
Therefore, the diverse prognosis of different tumors gives rise to
inconsistencies if prevalence is used to split them into rare and
frequent.
In conclusion, a list of rare tumors is under development, based on ICDO codes
for topography, morphology, and a combination of both, by using incidence, not
prevalence, as a criterion.
An incidence threshold around 3/100,000/year might well define a group of tumors
likely to be felt as rare by clinicians.
A consensus development process about that should then be promoted within the
oncology community.
©
2003 Elsevier Ltd. All rights reserved.
Source: http://ex2.excerptamedica.com/ciw-03ecco/abstracts/index.cfm?fuseaction=abs.prn&abstractID=1046
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