INCREASED CHROMOSOME-TYPE CHROMOSOME ABERRATION FREQUENCIES AS BIOMARKERS OF CANCER RISK IN A BLACKFOOT ENDEMIC AREA

To examine whether biomarkers such as sister chromatid
exchanges (SCEs) and chromosome aberrations (CAs) can
predict cancer development, a nested case-control study was
performed in a blackfoot endemic area with a known high
cancer risk, A cohort of 686 residents was recruited from
three villages in the blackfoot endemic area. Personal
characteristics were collected, and venous blood was drawn
for lymphocyte culture and stored in a refrigerator. The
vital status and cancer development were followed using the
National Death Registry, Cancer Registry, and Blackfoot
Disease Registry. The follow-up period was from August 1991
to July 1995, During this 4-year period, 31 residents
developed various types of cancer. Blood culture samples
from nine of these subjects were unsuitable for experiments
due to improper storage. Finally, a total of 22 cancer cases
had cytogenetic samples that could be analyzed. Twenty-two
control subjects were selected from those who did not
develop cancer in the study period, and these subjects were
matched to cases by set, age, smoking habits, and
residential area. The results showed that there was no
significant difference in the frequencies of SCE and
chromatid-type CAs between the case and control groups. How-
ever, the frequencies of chromosome-type CAs, e.g.,
chromosome-type gaps, chromosome-type breaks, chromosome-
type breaks plus exchanges, total chromosome-type
aberrations, and total frequencies of CAs in the case group,
were significantly higher than those in the control group (
P < 0.05), The odds ratio of cancer risk in subjects with
more than zero chromosome-type breaks was 5.0 (95%
confidence interval = 1.09-22.82) compared to those with
zero chromosomal breaks. The odds ratios for more than zero
chromosome-type breaks plus exchanges and a frequency of
total chromosome-type aberrations of >1.007% were 11.0 and
12.0, respectively (P < 0.05, Subjects with a total Ch
frequency of >4.023% had a 9-fold increase for cancer risk.
These results indicate that chromosome-type CAs are good
biomarkers for the prediction of cancer development, whereas
SCEs and chromatid-type CAs cannot predict cancer risk.