A mouse model of neoadjuvant chemotherapy followed by interval cytoreductive surgery indicates impaired efficacy of perioperative cisplatin

Abstract

Background: Investigate the impact of interval cytoreductive surgery (ICS) on progression in an orthotopic mouse model of ovarian cancer and the impact of chemotherapy delivered at various timelines following surgery.

Methods: Luciferase-expressing ID8 murine ovarian cancer cells were implanted intra-bursally and IP to C57BL/7 mice. Once disease was established by bioluminescence, 2 cycles of neoadjuvant cisplatin were administered, and animals received either ICS (removal of the injected bursa/primary tumor) or anesthesia alone. Postsurgical chemotherapy was administered on the same day as the intervention (ICS/anesthesia), or on day 7 or day 28 following the intervention. Progression was quantified serially with in vivo bioluminescence imaging. Volume of ascitic fluid volume collected at necropsy was measured.

Results: Animals were matched for tumor burden at stratification. There was no accelerated growth of residual tumor after interval cytoreduction compared to controls. Animals who received chemotherapy on postoperative day (POD) 7 had better disease control compared to standard-of-care POD 28. Animals who underwent surgery had less ascites at necropsy compared to those who had anesthesia alone.

Conclusions: In this animal model, surgical wounding with suboptimal cytoreduction after neoadjuvant chemotherapy did not cause accelerated expansion of residual disease. Surgical wounding appears to impair cisplatin activity when given at time of surgery.

Keywords: Animal model; Cisplatin; Cytoreductive surgery; ID8 cells; Mouse; Neoadjuvant chemotherapy; Neoadjuvant chemotherapy treatment; Ovarian cancer; Ovarian neoplasms; Surgical oncology.

Fig. 1

Comparison of ID8-L4 and ID8-L11 cells for linearity of bioluminescence output and cisplatin sensitivity in vitro. A Graphical representation of concentration-dependent bioluminescence imaging. Different concentrations of ID8-L11 and ID8-L4 cells were seeded into a 96-well plate and imaged on an IVIS spectrum in vivo imaging system. Measured values are shown with solid lines. Linear fitting of the data was performed and is represented by dashed lines. B-D ID8 (B), ID8-L11 (C) and ID8-L4 (D) cells were seeded in 96 well plates and 24 h later were treated with different concentrations of cisplatin (0, 10, 25 or 50 μM). Cell viability was determined by XTT dye reduction assays at the time points indicated. Data shown indicate the mean ± SEM of 4 independent replicates. Within each time point, groups with different letters are statistically different from one another as determined by ANOVA followed by Fisher’s LSD test (p<0.05)

Fig. 2

Schematic summary of the overall treatment and imaging schedule for the in vivo study. All mice were innoculated with ID8-L4 cells (Day -35) and were imaged (I) and treated with cisplatin (C) 2 and 3 weeks (Days -21 and -14) later. The animals were imaged 4 weeks after innoculation (Day -7) and one week later (Day 0) were divided into 2 primary treatment arms; one arm (n = 40 mice) underwent interval cytoreductive surgery (ICS) and the other arm (n = 40) were anesthetized (A) but left intact. At Day 0, a subset of 10 mice from each arm was treated with cisplatin. One week later (Day 7), all mice were imaged and a second subset of 10 animals from each arm was treated with cisplatin. One week later (Day 14) all mice were reimaged. Two weeks later (Day 28), a third subset of 8 or 10 mice from the remaining animals in each arm were treated with cisplatin and the remaining animals (n = 9) were left untreated. All groups were reimaged 35 and 42 days after surgery/anesthesia. The number and percentage of mice surviving to day 42 in each group and the two primary arms (ICS and A) is indicated

Fig. 3

Impact of ICS and cisplatin on ascites accumulation. Ascites volume was measured at the time of necropsy on day 42 or at required euthanasia because of complications of disease progression. Volumes were categorized as minimal (≤1.0 ml), moderate (> 1.0 ml and <10 ml), or massive (≥10 ml). Pie charts show the relative proportion of mice with each category of ascites volume in the ICS (surgery) arm and anesthesia control (A) arm (χ²_{(2, n=56)}=6.552, p = 0.0378). The stacked bar graphs present the relative distribution of ascites categories within each individual treatment group. The numbers in parentheses at the top of each bar indicate the number of animals measured per group. C₀ = cisplatin on day 0, C₇ = cisplatin on day 7, C₂₈ = cisplatin on day 28

Fig. 4

Impact of ICS on tumor burden as determined by bioluminescence measurements across all imaging sessions. Results are presented to compare the impact of ICS vs. no surgery alone (A) or combined with cisplatin administered on day 0 (B), 7 (C), and 28 (D). Points indicate the mean ± SEM. Data collected at each imaging time point were analyzed by ANOVA follow by Fisher LSD test, *p<0.05. Abbreviations are defined in the legend to Fig. 3

Fig. 5

Impact of peri- and post-surgical cisplatin treatment on tumor burden. Bioluminescence data are shown to compare the impact of day of cisplatin administration within groups that had received ICS (A-C) or no surgery (D-F). A and D Comparison of Day 0 vs. Day 7 cisplatin administration. B and E Comparison of Day 0 vs. Day 28 cisplatin administration. C and F Comparison of Day 7 vs. Day 28 cisplatin administration. Points indicate the mean ± SEM. Data collected at each imaging time point were analyzed by ANOVA followed by Fisher LSD test, *p<0.05. Abbreviations are defined in the legend to Fig. 3

Fig. 6

Summary of Day 42 imaging results and representative images. A Representative imaging of tumor burden measured on day 42. B Bar chart showing results of imaging acquired on day 42. Bars represent the mean ± SEM. Data collected at each imaging time point were analyzed by ANOVA follow by Fisher LSD test; *p<0.02, **p<0.01. Abbreviations are defined in the legend to Fig. 3. C Image showing extensive peritoneal dissemination of tumor seeding within the abdominal cavity. Arrows show deposits along the posterior diaphragm surface