TY - JOUR
T1 - Incidence of childhood cancer in twins
AU - Inskip, Peter D.
AU - Harvey, Elizabeth B.
AU - Boice, John D.
AU - Stone, B. J.
AU - Matanoski, Genevieve
AU - Flannery, John T.
AU - Fraumeni, Joseph F.
PY - 1991/9/1
Y1 - 1991/9/1
N2 - The incidence of childhood cancer in twins was evaluated by linking a roster of 30,925 twins born in Connecticut (United States) between 1930 and 1969 with the Connecticut Tumor Registry. Cancer, exclusive of nonmelanoma skin cancer, was identified in 19 females and 12 males under 15 years of age. The incidence rate among twins was 7.9 cancers per 100,000 person-years (PY) overall, and 9.7 and 6.1 per 100,000 PYs for females and males, respectively. Four of 13 leukemias occurred in two female twin pairs, representing concordance rates of 18 percent overall and 29 percent for like-sex pairs, which are somewhat higher than values reported previously. The number of cancers expected was computed on the assumption that twins experienced the same sex-, age-, and calendar time-specific cancer rates as recorded for all Connecticut-born children. Because active follow-up of individuals was not conducted, an adjustment to person-years of observation was made to account for childhood mortality, including the high perinatal mortality characteristie of twins. Childhood cancer was 30 percent less frequent than expected (standardized incidence ratio [SIR]=0.7; 95 percent confidence interval [CI]=0.5-0.9), a deficit that is marginally greater than those found in previous studies. Both leukemia (SIR=0.8; CI=0.4-1.4), and all other cancers combined (SIR=0.6; CI=0.3-0.9) occurred less often than expected. The deficit was greater among males (SIR=0.5; CI=0.2-0.8) than among females (SIR=0.9; CI=0.5-1.4) and was especially pronounced among males younger than five years (SIR=0.2; CI=0.0-0.7). The data support the view that twins, particularly male twins, have a lower risk of childhood cancer than single-born children. Any added risk for twins associated with their greater frequency of exposure to prenatal X-rays appears to have been insufficient to offset an 'effect' of twinning per se. Possible explanations for this finding include (i) the low birthweight distribution of twins, or (ii) selective early mortality of twin fetuses or neonates who would otherwise have developed a clinical cancer.
AB - The incidence of childhood cancer in twins was evaluated by linking a roster of 30,925 twins born in Connecticut (United States) between 1930 and 1969 with the Connecticut Tumor Registry. Cancer, exclusive of nonmelanoma skin cancer, was identified in 19 females and 12 males under 15 years of age. The incidence rate among twins was 7.9 cancers per 100,000 person-years (PY) overall, and 9.7 and 6.1 per 100,000 PYs for females and males, respectively. Four of 13 leukemias occurred in two female twin pairs, representing concordance rates of 18 percent overall and 29 percent for like-sex pairs, which are somewhat higher than values reported previously. The number of cancers expected was computed on the assumption that twins experienced the same sex-, age-, and calendar time-specific cancer rates as recorded for all Connecticut-born children. Because active follow-up of individuals was not conducted, an adjustment to person-years of observation was made to account for childhood mortality, including the high perinatal mortality characteristie of twins. Childhood cancer was 30 percent less frequent than expected (standardized incidence ratio [SIR]=0.7; 95 percent confidence interval [CI]=0.5-0.9), a deficit that is marginally greater than those found in previous studies. Both leukemia (SIR=0.8; CI=0.4-1.4), and all other cancers combined (SIR=0.6; CI=0.3-0.9) occurred less often than expected. The deficit was greater among males (SIR=0.5; CI=0.2-0.8) than among females (SIR=0.9; CI=0.5-1.4) and was especially pronounced among males younger than five years (SIR=0.2; CI=0.0-0.7). The data support the view that twins, particularly male twins, have a lower risk of childhood cancer than single-born children. Any added risk for twins associated with their greater frequency of exposure to prenatal X-rays appears to have been insufficient to offset an 'effect' of twinning per se. Possible explanations for this finding include (i) the low birthweight distribution of twins, or (ii) selective early mortality of twin fetuses or neonates who would otherwise have developed a clinical cancer.
KW - Cancer
KW - United States
KW - leukemia
KW - record-linkage
KW - registries
KW - twins
UR - http://www.scopus.com/inward/record.url?scp=0026230875&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0026230875&partnerID=8YFLogxK
U2 - 10.1007/BF00051671
DO - 10.1007/BF00051671
M3 - Article
C2 - 1932544
AN - SCOPUS:0026230875
SN - 0957-5243
VL - 2
SP - 315
EP - 324
JO - Cancer Causes and Control
JF - Cancer Causes and Control
IS - 5
ER -