1. Definition of oxaliplatin sensitivity in pts with advanced colorectal cancer previously treated with oxaliplatin-based therapy A. de Gramont, B. Chibaudel, O. Bourges, N. Perez-Staub, C. Tournigand, F. Maindrault-Goebel, T. André, A. K. Larsen, P. Afchain, C. Louvet; Hôpital Saint Antoine, Paris VI, France; GERCOR, Paris, France; Hôpital La Pitié Salpétrière, Paris, France; INSERM UMRS938, Paris, France

2. Abstract: Background: Oxaliplatin combined with fluoropyrimidines is standard adjuvant therapy in stage III colon cancer and first-line therapy in stage IV colorectal cancer. Oxaliplatin can be reintroduced either at relapse, or after maintenance or after chemotherapy holidays. In this study we defined the sensitivity to oxaliplatin reintroduction based on the oxaliplatin-free interval. Methods: Stage IV pts entered in the OPTIMOX1 and 2 studies (FOLFOX4, FOLFOX7 followed by maintenance without oxaliplatin or chemotherapy holidays) and pts having relapsed after metastases surgery and neoadjuvant or adjuvant FOLFOX for resectable stage IV were eligible if they were rechallenged with FOLFOX. Endpoints were: survival from reintroduction according to interval between the last cycle of oxaliplatin first-line and reintroduction, survival and response at reintroduction according to first FOLFOX response and PFS. Results: 330 pts were included: male 60%, colon/rectum/both 62%/35%/2%, resectable/unresectable: 14%/86%, PS 0-1 / >1: 90%/10%, sites 1/>1: 57%/43%. 23 pts had adjuvant and 22 pts had neoadjuvant chemotherapy. 58 pts (18%) had FOLFOX reintroduction before progression. PFS/OS from reintroduction according to induction FOLFOX response were 8.7/19.5 mths if CR, 4.6/15.2 mths if PR, and 3.2/9.7 mths if SD (P=.0019/.01). PFS/OS from reintroduction according to induction FOLFOX PFS were 2.9/9.3 mths if PFS<6 mths, 4.6/14.7 mths if PFS 6-12 mths and 8.5/23.7 if PFS=12 mths. There was no difference between 0-3 and 3-6 mths or 6-9 and 9-12 mths intervals. Conclusion: A prolonged interval between two FOLFOX therapies or a prolonged PFS at first-line FOLFOX predict the efficacy of oxaliplatin reintroduction. The interval between two FOLFOX therapies does not identify a completely refractory population. Resistance (PD rate) is divided by two at each 6 month intervals.

3. Introduction Oxaliplatin combined with fluoropyrimidines is a standard first- line treatment for patients with metastatic coloretal cancer. Despite a high response rate in first-line, the majority of patients will ultimately experience disease progression. In ovarian cancer, it is well known that patients who responded to an initial chemotherapy with a platinum compound may respond again to the same or another platinum derivative when they relapse (Markman 91-97). In metastatic colorectal cancer, we previously reported that reintroduction of oxaliplatin in patients pre-treated with oxaliplatin and who later had a progressive disease, 73% had a disease control with a median progression-free survival of 18 weeks (Maindrault, Ann Oncol, Tournigand JCO). In an effort to better define the oxaliplatin sensitivity in patients with metastatic colorectal cancer who previously received oxaliplatin, we performed an analysis of clinical characteristics and survival outcomes of patients included in two prospective studies allowing reintroduction of oxaliplatin (OPTIMOX1, OPTIMOX2) and in patients having adjuvant or neoadjuvant oxaliplatin and surgery of metastases.

4. Eligible patients entered in two randomized studies including a stop and go strategy Patients who relapsed after surgery of metastases and adjuvant/neoadjuvant therapy were also included Patients and Methods R FOLFOX7–LV5FU2–FOLFOX7 FOLFOX4 FOLFOX7–LV5FU2–FOLFOX7 FOLFOX7–STOP–FOLFOX7 R OPTIMOX 1 N=165/620 OPTIMOX 2 N=120/202 FOLFOX7–Surgery–FOLFOX Surgery–FOLFOX7 N=45

5. Specific problems Parameters which could influence oxaliplatin sensitivity at reintroduction are: R0-R1 surgery of metastases before chemo, or after chemo, or no surgery Chemotherapy-free interval (CFI) after induction or maintenance or no CFI Bevacizumab with reintroduction or no Bev: N=19 No proof of progression before reintroduction: N=58

6. N=330 Surgery first Neoadj FOLFOX or FOLFOX+/-sLV5FU FOLFOX Reintroduction Surgery after chemo Unresectable M+ FOLFOX+/-sLV5FU PFS: 14.5 m OS: >92 m PFS: 14.7 m OS: 39.3 m PFS: 9.0 m OS: 22.5 m FOLFOX Reintroduction FOLFOX Reintroduction PFS: 6.9 m OS*: 43 m RR: 11 SD: 5 PD: 3 NE: 3 * from reintroduction PFS: 6.7 m OS*: 18.6 m RR: 18 SD: 20 PD: 5 NE: 12 PFS: 4.1 m OS*: 12.6 m RR: 47 SD: 90 PD: 95 NE: 21 N=22N=55N=253 P = 0.46 P = 0.14 Regrouping of these patients Surgery

7. N=330 R0-R1 M+ Surgery FOLFOX+/-sLV5FU FOLFOX Reintroduction Unresectable M+ FOLFOX+/-sLV5FU FOLFOX Reintroduction * from reintroduction PFS: 5.0 m OS*: 13.5 m RR: 20 SD: 30 PD: 23 NE: 6 N=77N=253 P = 0.13 P = 0.10 No separation of these patients Break in Chemotherapy N=79 No Break in Chemotherapy N=174 FOLFOX Reintroduction PFS: 3.7 m OS*: 12.7 m RR: 27 SD: 63 PD: 72 NE: 12 Chemotherapy duration

8. Statistical Analyzes Patients having R0-R1 resection of metastases Patients having no surgery Patients having no surgery, proof of progressive disease before oxaliplatin reintroduction and not received bevacizumab All patients Cut-off determination PFS and Survival from reintroduction 3 classes according to interval between last cycle of induction FOLFOX and first cycle of FOLFOX reintroduction: 12 months

9. Response Rate PFS/OS from reintroduction according to induction FOLFOX response were 8.7/19.5 months if CR, 4.6/15.2 months if PR, and 3.2/9.7 months if SD (P=.0019/.01). PFS/OS from reintroduction according to induction FOLFOX PFS/OS were 2.9/9.3 mths if PFS 12 months. FOLFOX Reintroduction Response Rate (%) IntervalNCR+PRSDPDNE <6 months1161530523 6-12 months14824392413 >12 months6635361118

10. Progression-free Survival from Reintroduction

11. Survival from Reintroduction

12. Subsets of Patients RO-R1 Surgery No Surgery –No bev. – Prog.

13. Conclusions Oxaliplatin reintroduction efficacy in patients previously responders or stable with FOLFOX for advanced colorectal cancer depends on RR and PFS of induction FOLFOX and on the oxaliplatin-free interval between the last cycle of induction FOLFOX and the first cycle of FOLFOX reintroduction. An oxaliplatin-free interval of at least one year define a sensitive population with results of reintroduction in the range of oxaliplatin naive patients, an interval between 6 and 12 months define a partially sensitive patients with results better than most second-line options, an interval of less than 6 months define a partially resistant population with results in the range of second- or third-line therapies Next steps will be to study: oxaliplatin combination in first-line therapy in patients who relapsed after adjuvant FOLFOX for stage III colon cancer oxaliplatin reintroduction after second-line irinotecan-based therapy and the efficacy of oxaliplatin-based chemotherapy with targeted therapies