A design for cancer case-control studies using only incident cases: experience with the GEM study of melanoma.
BACKGROUND
The population-based case-control study is not suited to the evaluation of rare genetic (or environmental) factors. The use of a novel case-control design in which cases have second primaries and controls are cancer survivors has been proposed for this purpose.


METHODS
We report results from an international study of melanoma that involved population-based ascertainment of incident cases of second or subsequent primary melanoma as the 'case' group and incident cases of first primary melanoma as the 'control' group. We evaluate the validity of the study design by comparing the results obtained for phenotypic factors that have been shown consistently to be associated with melanoma in previous conventional studies with the results from a conventional case-control study conducted in Connecticut and from literature reviews.


RESULTS
All but one of the known risk factors for melanoma were shown to be significantly associated with melanoma in our study, though the individual odds ratios appear to be somewhat attenuated relative to the magnitudes typically observed in the literature.


CONCLUSIONS
Patients with a second or subsequent primary cancer of a single type represent a potentially valuable and under-utilized resource for the study of cancer aetiology.
Begg
Colin B
CB
Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. beggc@mskcc.org
Hummer
Amanda J
AJ
Mujumdar
Urvi
U
Armstrong
Bruce K
BK
Kricker
Anne
A
Marrett
Loraine D
LD
Millikan
Robert C
RC
Gruber
Stephen B
SB
Culver
Hoda Anton
HA
Zanetti
Roberto
R
Gallagher
Richard P
RP
Dwyer
Terrence
T
Rebbeck
Timothy R
TR
Busam
Klaus
K
From
Lynn
L
Berwick
Marianne
M
D000328:Adult; D017677:Age Distribution; D000368:Aged; D016022:Case-Control Studies; D005127:Eye Color; D005192:Family Health; D005260:Female; D006200:Hair Color; D006801:Humans; D015994:Incidence; D008297:Male; D008545:Melanoma / Q000453:epidemiology* / Q000473:pathology; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000453:epidemiology*; D009506:Nevus / Q000453:epidemiology / Q000473:pathology; D010641:Phenotype; D015203:Reproducibility of Results; D012307:Risk Factors; D017678:Sex Distribution; D012878:Skin Neoplasms / Q000453:epidemiology* / Q000473:pathology