FIGURE 4. Only primary tumor resection that significantly reduces overall tumor burden improves survival.

(A) Study design: Thirty two mice six days after implantation with 1×10⁵ 4T1-luc2 cells were randomized into 4 groups (N = 8 per group): observation (Obs), primary tumor resection on day 6 (Day 6), tumor resection on day 10 (Day 10), and tumor resection on day 28 (Day 28), again controlling for overall tumor burden. (B) Representative bioluminescence imaging of a mouse from the Obs group, and immediately after resection of primary tumor of Day 6, Day 10, and Day 28 groups. (C) The percentage of remaining overall tumor burden after primary tumor resection for Day 6, Day 10 and Day 28 groups was quantified by bioluminescence. The percentage of overall tumor burden was calculated by dividing the quantification of remaining metastatic lesions by the overall tumor burden before resection (N = 8). (D) Time course of overall tumor burden quantified by bioluminescence for each group. There was no significant difference in overall tumor burden at randomization and only the Day 28 group (bold dotted line) did not reduce overall tumor burden significantly at the time of resection. (E) Kaplan-Meier analysis showed that only Day 28 (bold dotted line) failed to significantly improve survival compared to observation (Obs (bold line) vs. Day 6 (thin dotted line) P < .01, Obs vs. Day 10 (thin line) P < .01).