Childhood and adult cancer in twins: evidence from the Utah genealogy.

OBJECTIVE: Evidence suggests that the in utero environment may contribute to subsequent development of cancers in childhood and adulthood. Raised levels of estrogen during pregnancy may be the primary in utero etiologic factor. Mothers of twins have higher estrogen levels during pregnancy than mothers of singletons, therefore, assessment of cancer risk in twins may be informative. METHOD: We conducted a retrospective cohort study of cancer among twin and singleton newborns selected from the Utah Population Database, matched on birth year and sex. Cancer diagnoses were determined by linkage with the Utah state cancer register. Relative rates of all cancers in childhood and in adulthood in twins compared with singletons, and for specific cancers including testicular, breast and melanoma, were calculated using Poisson regression. RESULTS: Twin (35,271) and singleton (74,199) births were identified, among whom there were 336 and 691 cancer diagnoses, respectively. The relative risk (RR) of childhood cancer in twins compared with singletons was 0.82 [95% confidence interval (CI) 0.55-1.24] and of adult cancer was 1.06 (0.92-1.22). We found nonsignificant increases in risk among adult twins for cancers of the breast, prostate, testis, lymphatic system, thyroid, and large bowel. The largest departures from unity were for testicular cancer (RR 1.47; 95% CI, 0.73-2.95) and melanoma (RR 0.67; 95% CI, 0.42-1.06). CONCLUSIONS: These results are consistent with the body of evidence suggesting that twins have a reduced risk of cancer in childhood. Although there is no overall differential in adult cancer risk, these data support the hypothesis that the in utero environment may play an important role in specific cancers.

Paediatric myelodysplastic syndromes and juvenile myelomonocytic leukaemia in the UK: a population-based study of incidence and survival.

We aimed to identify and classify cases of paediatric myelodysplastic syndromes (MDS) occurring in Britain to estimate the incidence of this rare group of diseases, investigate the results of therapy and identify prognostic risk factors. Patients aged below 15 years at diagnosis were collected from England, Scotland and Wales, inclusively between 1990 and 1999. One hundred and thirty-five patients were accepted as de novo MDS or juvenile myelomonocytic leukaemia (JMML). The incidence for this period was 1.35 per million (age standardized rate) which is below that reported outside the UK. The overall survival was 45%[standard error (SE) = 4%] at 5 years: 40% (SE = 6%) for JMML and 50% (SE = 6%) for other MDS. Significant adverse prognostic factors for JMML were a platelet count < 40 x 10(9)/l, raised fetal haemoglobin, FPC score and age above 2 years at diagnosis, for other MDS only monosomy 7 was significant. To conclude, the incidence of MDS/JMML in children in the UK appears to be lower than that reported outside the UK. This may be either a real difference in incidence or variation in reporting. Monosomy 7 is associated with poor outcome in MDS other than JMML. The prognosis of JMML depends on age, platelet count and fetal haemoglobin.