Beside picture is important to understand which part of the phase does the chemotherapy drug work on. Also multiple drugs are given because they act on different phases .This leads to less toxicity and more efficacy.
Tumor growth follows the Gompertz curve of right side above. It is slow in early and late phases.
Incomplete treatment of tumor shifts the growth in middle of curve or high growth phase. This is important in stage 3 and 4 tumors where total excision is not usually done.
This becomes a problem in standard treatment regimens but becomes an advantage in Laser Therapy as chemotherapy now acts very well after 2 weeks. In fact complete dissapearences have been reported in many cases.
Metastases appear to grow more rapidly than the primaries in the same individual
A study from University of Texas documenting that cells in high growth phase are more succeptible to chemotherapy