Endocrine treatments of breast cancer patients antagonize estrogen and may lead 
to consequences of estrogen deprivation including menopausal symptoms. We 
analyzed the changes in frequency and severity of menopausal symptoms in 
patients receiving tamoxifen or aromatase inhibitors and identified factors 
influencing these symptoms. One hundred and eighty-one consecutive 
postmenopausal breast cancer patients scheduled to start endocrine treatment 
were included in this prospective study. A menopause symptom questionnaire 
covering vasomotor, atrophic, psychological, cognitive and somatic symptoms was 
filled in at baseline, and after 1 and 3 months of therapy. Both first-line 
tamoxifen and aromatase inhibitors induced an increase in the occurrence and 
severity of hot flashes (p<0.0001 and p=0.014, respectively). Musculoskeletal 
pain and dyspareunia significantly increased under first-line non-steroidal 
aromatase inhibitors (p=0.0039 and p=0.001, respectively), while patients under 
tamoxifen had significant decrease in sexual interest (p< or =0.0001). Younger 
age was associated with more hot flashes and vaginal dryness at baseline, and 
after 1 and 3 months of therapy (all p<0.02). We conclude that there are 
significant differences between the early effects of tamoxifen and aromatase 
inhibitors on menopausal symptoms of breast cancer patients. Our results 
underscore the need for safe and effective non-hormonal interventions to 
alleviate vasomotor and musculoskeletal symptoms which were the most prevalent 
and severe symptoms.