First chemotherapy regimen theoretically kills what % of cancer cells?

Variable: dependent on the type of cancer, chemotherapy and response to therapy

No definitive answer: There is no one answer for this question, as it depends on the type of cancer being treated, underlying co-morbid conditions, other treatments that may have been tried already, etc. Sometimes chemo is used to help supplement the previous treatment and prevent the chance even more of recurrence, etc. Ask your Treating oncologist what statistics are available for your specific type, best wishes.