Citations

Abstract Background Disease-free survival (DFS) with a 3-year median follow-up (3-year DFS) was validated as a surrogate for overall survival (OS) with a 5-year median follow-up (5-year OS) in adjuvant chemotherapy colon cancer (CC) trials. Recent data show further improvements in OS and survival after recurrence in patients who received adjuvant FOLFOX. Hence, reevaluation of the association between DFS and OS and determination of the optimal follow-up duration of OS to aid its utility in future adjuvant trials are needed. Methods Individual patient data from 9 randomized studies conducted between 1998 and 2009 were included; 3 trials tested biologics. Trial-level surrogacy examining the correlation of treatment effect estimates of 3-year DFS with 5 to 6.5-year OS was evaluated using both linear regression (RWLS2) and Copula bivariate (RCopula2) models and reported with 95% confidence intervals (CIs). For R2, a value closer to 1 indicates a stronger correlation. Results Data from a total of 18 396 patients were analyzed (median age = 59 years; 54.0% male), with 54.1% having low-risk tumors (T1-3 and N1), 31.6% KRAS mutated, 12.3% BRAF mutated, and 12.4% microsatellite instability high or deficient mismatch repair tumors. Trial-level correlation between 3-year DFS and 5-year OS remained strong (RWLS2 = 0.82, 95% CI = 0.67 to 0.98; RCopula2 = 0.92, 95% CI = 0.83 to 1.00) and increased as the median follow-up of OS extended. Analyses limited to trials that tested biologics showed consistent results. Conclusions Three-year DFS remains a validated surrogate endpoint for 5-year OS in adjuvant CC trials. The correlation was likely strengthened with 6 years of follow-up for OS.

PURPOSE: As oxaliplatin results in cumulative neurotoxicity, reducing treatment duration without loss of efficacy would benefit patients and healthcare providers. PATIENTS AND METHODS: Four of the six studies in the International Duration Evaluation of Adjuvant Chemotherapy (IDEA) collaboration included patients with high-risk stage II colon and rectal cancers. Patients were treated (clinician and/or patient choice) with either fluorouracil, leucovorin, and oxaliplatin (FOLFOX) or capecitabine and oxaliplatin (CAPOX) and randomly assigned to receive 3- or 6-month treatment. The primary end point is disease-free survival (DFS), and noninferiority of 3-month treatment was defined as a hazard ratio (HR) of < 1.2- v 6-month arm. To detect this with 80% power at a one-sided type one error rate of 0.10, a total of 542 DFS events were required. RESULTS: 3,273 eligible patients were randomly assigned to either 3- or 6-month treatment with 62% receiving CAPOX and 38% FOLFOX. There were 553 DFS events. Five-year DFS was 80.7% and 83.9% for 3-month and 6-month treatment, respectively (HR, 1.17; 80% CI, 1.05 to 1.31; P [for noninferiority] .39). This crossed the noninferiority limit of 1.2. As in the IDEA stage III analysis, the duration effect appeared dependent on the chemotherapy regimen although a test of interaction was negative. HR for CAPOX was 1.02 (80% CI, 0.88 to 1.17), and HR for FOLFOX was 1.41 (80% CI, 1.18 to 1.68). CONCLUSION: Although noninferiority has not been demonstrated in the overall population, the convenience, reduced toxicity, and cost of 3-month adjuvant CAPOX suggest it as a potential option for high-risk stage II colon cancer if oxaliplatin-based chemotherapy is suitable. The relative contribution of the factors used to define high-risk stage II disease needs better understanding.

PURPOSE: In patients with stage III colon cancer (CC) whose tumors demonstrate microsatellite instability (MSI), the efficacy of adjuvant fluoropyrimidine (FP) with or without oxaliplatin has not been clearly demonstrated and the prognostic value of MSI remains uncertain. MATERIALS AND METHODS: Individual patient data from the ACCENT database were used to evaluate the effect of FP with or without oxaliplatin on disease-free survival (DFS) and overall survival (OS) among patients with MSI stage III CC and the prognostic value of MSI in patients treated with FP plus oxaliplatin, by stratified Cox models adjusted for demographic and clinicopathological factors. RESULTS: MSI status was available for 5,457 patients (609 MSI, 11.2%; 4848 microsatellite stable [MSS], 88.8%) from 12 randomized clinical trials (RCTs). Oxaliplatin significantly improved OS of MSI patients from the two RCTs testing FP with or without oxaliplatin (n = 185; adjusted hazard ratio [aHR] = 0.52, 95% CI, 0.28 to 0.93). Among the 4,250 patients treated with FP plus oxaliplatin (461 MSI and 3789 MSS), MSI was associated with better OS in the N1 group compared with MSS (aHR = 0.66; 95% CI, 0.46 to 0.95) but similar survival in the N2 population (aHR = 1.13; 95% CI, 0.86 to 1.48; P interaction = .029). The main independent prognosticators of MSI patients treated with FP plus oxaliplatin were T stage (aHR = 2.09; 95% CI, 1.29 to 3.38) and N stage (aHR = 3.57; 95% CI, 2.32 to 5.48). Similar results were observed for DFS in all analyses. CONCLUSION: Adding oxaliplatin to FP improves OS and DFS in patients with MSI stage III CC. Compared with MSS, MSI patients experienced better outcomes in the N1 group but similar survival in the N2 group.

3525 Background: Microsatellite instable/deficient mismatch repair (MSI) metastatic colorectal cancers have been reported to be of poor prognosis. The interaction between MSI and BRAFV600E mutation complicates the picture. Methods: Patients with resected stage III CC from 7 studies with disease recurrence and data available for MSI and BRAFV600E status were analyzed. The primary endpoint was survival after recurrence (SAR) to assess the prognostic roles of MSI and BRAFV600E, respectively. Associations of markers with SAR were analyzed using Cox proportional hazards models adjusted for clinicopathologic features (data collected 12/1998 to 11/2009). Results: Among 2630 patients with cancer recurrence (1491 men [56.7%], mean age, 58.5 [19-85] years), multivariable analysis revealed that patients with MSI tumors (n = 220) had significantly better SAR (adjusted hazard ratio [aHR], 0.82; 95% CI, 0.69-0.98; P = .029) than patients with microsatellite stable /proficient MMR (MSS) tumors (n = 1766). This was also observed when looking at patients treated by the standard FOLFOX adjuvant regimen only (aHR, 0.76; 0.58-1.00; P = .048). Same trends were observed when looking at MSI/dMMR patients outcome in BRAFV600E wild-type (aHR, 0.84; P = .10) and mutant (aHR, 0.88; P = .43) subgroups separately, without reaching statistical significance. As previously described poor SAR was observed in BRAFV600E mutants vs wild type patients (n = 244; aHR, 2.06; 95% CI, 1.73-2.46; P < .0001) and this was also true in BRAFV600E mutants MSI/dMMR patients (n = 77, aHR, 2.65 ; 95% CI, 1.67-4.21; p < .0001). Other factors associated with a poor SAR were : olderage, male gender, T4/N2, proximal primary tumor location, poorly differentiated adenocarcinoma, and early recurrence (by 1y increase). Conclusions: In stage III colon cancer patients recurring after adjuvant chemotherapy and before the era of immuno-oncologic agents, MSI/dMMR was associated with a better survival compared to MSS. BRAFV600E mutation seems to be a poor prognostic factor for both MSI/dMMR and MSS/pMMR patients.

3502 Background: DFS with 3 years median follow-up (3yDFS) was validated as a surrogate for OS with 5 years median follow-up (5yOS) in adjuvant chemotherapy CC trials prior. Recent data showed improved survival after recurrence and OS, over time, in pts who received adjuvant FOLFOX. Hence, re-evaluation of the association between DFS and OS, as well as the optimal follow-up of OS to aid its utility in future adjuvant trials is needed. Methods: Individual patient data from 8 randomized adjuvant studies conducted from 1998-2009 were included; 3 trials tested anti-VEGF or anti-EGFR agents. Trial-level surrogacy examining the correlation of treatment effect estimates (i.e. hazard ratios) of 3yDFS and 5y to 8yOS was evaluated using both linear regression (R2WLS) and Copula bivariate (R2Copula) models. For the R2, a value closer to 1 indicates a stronger correlation. Prespecified criteria for surrogacy required either R2WLS or R2Copula ≥ 0.80 and neither < 0.7, with lower-bound 95% Confidence Interval (CI) > 0.60. The rank correlation coefficient (ρ) quantified the individual-level surrogacy. Results: Total of 18,886 pts were analyzed, with median age 60, 54% male, 83% stage III, 59% > 12 nodes examined. Median follow-up for survival ranged from 5 to 10 years across trials. Trial level correlation between 3yDFS and OS remained strong (R2WLS ≥0.74; R2Copula ≥ 0.89) and increased as the median follow-up of OS extended longer (see table). Analyses limited to stage III pts and/or trials tested biologics showed consistent results. Conclusions: 3yDFS remains a validated surrogate endpoint for 5yOS in adjuvant trials in CC pts per prespecified criteria. The correlation was strengthened with more than 6 years of follow-up for OS. [Table: see text]

3501 Background: 6m of oxaliplatin-based treatment is an option as adj chemotherapy for patients with high risk stage II CC (T4, inadequate nodal harvest, poorly differentiated, obstruction, perforation or vascular/perineural invasion). The IDEA collaboration showed shorter treatment duration to be appropriate for most pts with stage III colon cancer. The results of the 4 IDEA studies with stage II pts are presented here. Methods: A prospective, pre-planned pooled analysis of high-risk stage II patients from 4 concurrently conducted randomized phase III trials (SCOT, TOSCA, ACHIEVE-2, HORG) was performed to evaluate non-inferiority (NI) of 3m compared with 6m (ref) of adj FOLFOX/CAPOX (regimen preselected, not randomized). The primary endpoint was disease-free survival (DFS), NI was to be declared if the 2-sided 80% confidence interval (CI) for DFS hazard ratio (HR 3m v 6m) estimated by a stratified Cox model was below 1.2. 542 DFS events were required to provide 80% power to declare NI. NI was also examined within regimen, T4 (Yes v No) and inadequate nodal harvest (Yes v No) as pre-planned subgroups. Results: The primary analysis included 3273 randomised pts of which 1254 had FOLFOX and 2019 had CAPOX. There were 552 events and the median follow-up was 60.2 m. There was significantly less grade 3-5 toxicity with 3m treatment (p < .0001). The 5-year DFS rate was 80.7% and 84.0% for 3m and 6m treatment with an estimated DFS HR of 1.18 (80% CI:1.05-1.31, p for NI = 0.404). For CAPOX the estimated HR was 1.02 (80% CI: 0.88-1.17, p for NI = 0.087) and for FOLFOX the estimated HR was 1.42 (80% CI: 1.19-1.70, p for NI = 0.894). The test for interaction between duration and regimen was not statistically significant (p = .174 adjusted for multiple testing) but was stronger than that for the other subgroups examined. Conclusions: In the overall population non-inferiority for 3m adj treatment in pts with high-risk stage II CC was not shown. As with the stage III population the choice of adj regimen appears important (although this did not reach statistical significance) with a small difference in DFS between 3 and 6 m treatment if CAPOX is used. Clinical trial information: ISRCTN59757862.

728 Background: Adjuvant FOLFOX therapy for stage II patients remains controversial, and selection criteria are imprecise. We examined the trend of disease-free survival (DFS: time to recurrence or death, whichever occurs first); time to recurrence (TTR: time to recurrence, censored at death without recurrence); survival after recurrence (SAR); and overall survival (OS) of pts treated with FOLFOX over a ten-year period. Methods: Outcomes of pts with stage II colon cancer enrolled in 6 adjuvant trials receiving FOLFOX alone were analyzed. Pt enrollment period was dichotomized as old (1998 – 2003) vs. new era (2004 – 2009) based on the FDA approval date of bevacizumab. 3/5yr event-free rates were estimated using adjusted Kaplan-Meier methods. Outcomes were compared between the two eras by multivariate Cox model. To control for potential confounding effects, all analyses were adjusted for age, gender, performance score, T stage, number of lymph nodes (LNs) examined, tumor side, and histologic grade. Results: In total, 1,122 pts with stage II were identified; 71% and 29% were treated in the old and new era, respectively. Pts enrolled in the new era were significantly younger and more likely to have higher tumor-grade and right-sided tumors compared to old era. More pts in the new era (71%) had ≥12 LNs examined compared to the old era (53%). After adjusting for potential confounding effects, no difference in DFS, TTR, SAR or OS between old and new eras was found (Table). Although median SAR increased from 13.6 to 26 months over time, this was not statistically significant, likely due to lack of power. An increased TTR over time (HRadj. 0.41, padj.= 0.002) was observed in pts with ≥12 LNs examined (3-yr TTR: 92% in old era vs. 96% in new era), but not pts with <12 LNs examined (pinteraction = 0.04). Conclusions: In stage II colon cancer pts who received adjuvant FOLFOX, no significant increase of DFS or OS was observed over time. However TTR was longer only in pts with ≥12 LNs examined. [Table: see text]

724 Background: Adjuvant FOLFOX is the standard of care for pts with stage III colon cancer and a platform to test new agents. Improvements in supportive care and development of newer treatments for metastatic disease impact the overall outcome of pts treated with adjuvant therapy. We examined the trend of disease-free survival (DFS), survival after recurrence (SAR), and overall survival (OS) of pts treated with FOLFOX over a ten-year period. Methods: Outcomes of colon cancer pts enrolled in 6 adjuvant trials receiving FOLFOX alone were analyzed. Pt enrollment period was dichotomized as old (1998 – 2003) vs. new era (2004 – 2009) based on the FDA approval date of bevacizumab. 3/5yr event-free rates were estimated by adjusted Kaplan-Meier methods. Outcomes were compared between the two eras by Cox model. To control for potential confounding effects, all analyses were adjusted for age, gender, performance score, T/N stage, tumor sidedness and histologic grade. Results: In total, 7,230 pts (stage II [n = 1122]; stage III [n = 6,108]) were identified; 32% and 68% were treated in the old and new era, respectively. Stage III pts enrolled in the new era were significantly younger, more likely to have T4/N2 disease, higher tumor grade, and left-sided tumors. After adjusting for pt characteristics, no difference in DFS was seen over time. However prolonged SAR and OS were observed in pts treated in the new era (Table). 5yr OS increased from 76% to 80% over time. Median SAR improved from 14.8 to 26.4 months. Conclusions: Stage III colon cancer pts who received adjuvant FOLFOX experienced significant improvements in SAR and OS—but not DFS—over time. In view of the improvements in OS and nearly doubled SAR, the optimal duration of OS follow-up to evaluate the benefits of adjuvant therapy (currently 5 years) should be reassessed, and ACCENT investigators are planning to conduct these additional analyses using their large pooled-trial database. [Table: see text]

668 Background: Ramucirumab is a human IgG1 monoclonal antibody antagonist of VEGFR-2. Overall survival (OS) and progression-free survival (PFS) in 2nd line FOLFIRI based treatment for metastatic colorectal cancer (mCRC) were improved with RAM therapy versus PBO in the RAISE trial. Recent work suggests mCRC primary tumor location is both prognostic and predictive; with improved OS and therapy-specific sensitivity observed in left (L)- vs right (R)-sided tumors. Given these findings, the RAISE trial data was subjected to post-hoc analysis to determine if sidedness influenced RAM efficacy. Methods: Primary tumor site was obtained. L-CRC was defined as the splenic flexure, descending and sigmoid colon, and rectum, while R-CRC included transverse, ascending colon and cecum. OS/PFS in L and R subgroups were analyzed via Kaplan-Meier method and unstratified log-rank test (treatments within subgroup), unstratified Cox proportional hazards model (estimate hazard ratio [HR] and 95% CI), and Wald test (treatment-by-subgroup interaction). Results: Tumor location was available for 1012/1072 (94%) patients, 699 L- and 313 R-CRC. Baseline characteristics were balanced between arms. RAM treatment enhanced L-CRC median OS by 2.5 mo (median 14.5 vs 12.0 mo) with a HR (95% CI) = 0.807 (0.675, 0.965), P = 0.019; compared to a 1.1 mo increase in median OS in R-CRC vs PBO (12.7 vs 11.6) with a HR (95% CI) = 0.971 (0.750, 1.258), P = 0.823; and, RAM enhanced L-CRC median PFS by 1.6 mo (6.0 vs 4.4 mo) and HR (95% CI) = 0.776 (0.664, 0.906), P = 0.001 compared to a 1.1 mo increase in median PFS R-CRC vs PBO (5.6 vs 4.5) with a HR (95% CI) = 0.855 (0.674, 1.084), P = 0.197. The treatment-by-subgroup interaction for both OS and PFS was not significant ( P = 0.276, 0.578, respectively). Conclusions: Despite L-CRC patients having longer OS/PFS and a seemingly stronger RAM treatment effect than R-CRC, the non-significant interaction test cannot verify sidedness as being predictive of RAM efficacy. The current study confirms ramucirumab benefits mCRC patients regardless primary tumor location. Clinical trial information: NCT01183780.