A new study reveals that women who received childhood cancer treatment may enter menopause much earlier than women who are not childhood cancer survivors. Siblings were studied -- 2,800 women who did receive treatment and 1,000 sisters of cancer survivors who did not. Women who underwent ovary-removing surgery were excluded from the study -- and the study then found that eight percent of cancer survivors experienced early menopause and less than one percent of the sisters experienced the same phenomenon. The risk was highest -- 30 percent -- for those who once received radiation to the lower abdomen and who also received certain chemotherapy agents, such as cyclophosphamide. Researchers say that 30 percent may be an underestimate, however, because the study included mostly women who had not yet reached age 40. The number of childhood cancer survivors over age 40 entering early menopause is still unclear. What is clear are the unfortunate consequences of this finding that could affect family planning, middle age health, thinning bones, other problems associated with menopause.