Not only the cemotherapy but all the other intervention factors; surgery, radiotherapy, high stress and oestrogen blockers. see:

Jenkins V, Shilling V, Fallowfield L, et al. Does hormone therapy for the treatment of breast cancer have a detrimental effect on memory and cognition? A pilot study. Psycho-Oncology. Volume 13, Issue 1, pages 61–66, January 2004

Gibbs RB, Gabor R. Estrogen and cognition: Applying preclinical findings to clinical perspectivesJournal of Neuroscience Research. Volume 74, Issue 5, pages 637–643, 1 December 2003

Sano M. Understanding the role of estrogen on cognition and dementia. J Neural Transm Suppl. 2000;59:223-9.

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