Breastfeeding and childhood cancer.
Total duration of breastfeeding and of exclusive breastfeeding was studied and compared in 99 childhood cancer cases and 90 controls. The difference between the average duration of breastfeeding in cases and controls was significant (p < 0.05), but when average duration of exclusive breastfeeding was compared in cases and controls the difference was highly significant (p < 0.001). In lymphoma cases and controls the difference between the average duration of breastfeeding was moderately significant (p < 0.01). However, when average duration of exclusive breastfeeding was compared in lymphoma cases and controls the difference was highly significant (p < 0.001). When other cancer groups and controls were compared with respect to their total duration of breastfeeding and duration of exclusive breastfeeding the differences when insignificant (p > 0.05). Cases and controls were not different with respect to their age, sex, birth year, birth order, age and educational status of mothers, smoking of fathers and socioeconomic status. However, a positive family history of cancer was obtained in 4 (4%) of cases whereas in controls it was obtained in only 1 (1.1%).