Dose-Dense Chemotherapy Based on the Norton-Simon Hypothesis

Theoretical Foundation

The Norton-Simon hypothesis predicts that tumor regrowth between chemotherapy cycles is most rapid immediately after cytoreduction, when the tumor burden is smallest and growth kinetics are fastest, supporting the administration of chemotherapy at shorter intervals 1

For localized breast cancer, dose-dense AC followed by paclitaxel given every 2 weeks with G-CSF support demonstrates superior outcomes compared to conventional 3-week scheduling, with a 26% reduction in hazard of recurrence and 31% reduction in hazard of death, as recommended by the NCCN guidelines 1, 2, 3, 4
The dose-dense approach involves doxorubicin 60 mg/m² + cyclophosphamide 600 mg/m² every 14 days for 4 cycles, followed by paclitaxel 175 mg/m² every 14 days for 4 cycles, with mandatory G-CSF support 2

For localized Ewing's sarcoma, VAC alternating with ifosfamide/etoposide (VAC/IE) given on an every-2-week schedule is more effective than every-3-week scheduling, with a median 3-year event-free survival rate of 76% for the 2-week schedule versus 65% for the 3-week schedule 1

The dose-dense approach requires mandatory G-CSF support to prevent severe neutropenia and maintain the 2-week interval, as supported by the NCCN guidelines 1, 2