Chemotherapy cycle duration. Possible.

My aunt is suffering from breast cancer. Doctor has advised to go for 4 cycles of chemotherapy which will be given after every 15days then operating and taking out the gland and then again same 4 cycles of chemotherapy. I want to know 15days interval cycle is better or 21days interval cycle is better. Please respond to my query. Result of her Naf 18 bone scan: Indication- Case of suspected carcinoma left breast, for staging Findings- Physiological tracer distribution in visualized skeletal system IMPRESSION Scan findings reveal- No evidence of skeletal metastases noted in the present study I am attaching her Mammography and biopsy reports as well. Please respond as soon as possible. Thanks in advance!