M. Mccredie et al., 2ND PRIMARY CANCERS AFTER CANCERS OF THE COLON AND RECTUM IN NEW-SOUTH-WALES, AUSTRALIA, 1972-1991, Cancer epidemiology, biomarkers & prevention, 6(3), 1997, pp. 155-160
Data from the New South Wales Central Cancer Registry for the period 1
972-1991 were examined to determine the risk of second primary cancers
after an initial invasive cancer of the colon (ICD-9 153) or rectum (
ICD-9 154). The expected numbers of cancers were obtained by assuming
that subjects experienced the same cancer incidence as prevailed in th
e corresponding general population and by applying sex-, age-, and cal
endar-specific rates to the appropriate person-years at risk. The rela
tive risk (RR) of a second primary cancer was taken to be the ratio of
observed:expected numbers of second cancers, After colon cancer, ther
e was an excess of cancers of the small intestine in both sexes (RRs o
f 4.5 and 4.4); prostate (RR = 1.4) and kidney (RR = 1.8) in men; and
breast (RR = 1.3), body of uterus (RR = 1.9), ovary (RR = 2.8), and th
yroid (RR = 2.7) in women. Lung cancer occurred less frequently in men
than expected (RR = 0.7), After rectal cancer, men had increased risk
s of cancers of the colon (RR = 1.5) and prostate (RR = 1.3) and a red
uced risk of pancreatic cancer (RR = 0.3). A reciprocal relationship o
f increased risk was seen between cancers of the proximal (but not the
distal) colon and rectum. Shared luminal risk factors for proximal co
lon cancer and rectal cancer and three syndromes of hereditary predisp
osition to colon cancer seem to be the major contributors to second pr
imary cancers in patients with an initial colon cancer. Sources of bia
s have been considered.