There is a proven link between the ovariotoxic effect of chemotherapeutic agents and age. From an age of 35 years onwards, the pool of primordial follicles and the quality of the oocytes is reduced to such an extent that even small ovariotoxic effects can result in a premature end of the reproductive period.
Even if the patient does not suffer from amenorrhoea immediately after the cytotoxic therapy, the pool of primordial follicles may still be so reduced that premature ovarian failure will result a few years after the end of therapy. Especially in a young woman, this risk is very acute since many years will normally go by before she wants to get pregnant. However, it is very hard to estimate the individual risk. There are estimates that the risk of premature ovarian failure, which amounts to around 2% of all women below the age of 40, increases by a factor of 9 if the young women are treated with alkylating agents and by a factor of 27 if the alkylating agents are combined with radiation (Larsen et al., J Clin Endocrinol Metab, 2003, 88:5307-14). However, these figures are rough estimates and cannot be used as a basis for an individual risk estimate.