There’s studies suggesting the opposite.
https://pubmed.ncbi.nlm.nih.gov/33460767/
https://pubmed.ncbi.nlm.nih.gov/17644189/
https://pubmed.ncbi.nlm.nih.gov/29275469/
None of those suggest “the opposite.” They all describe tryptophan being used WITHOUT CHEMO.
This study was specific to using chemo, only.