Citations

767 Background: The CORRECT trial (NCT01103323) showed that REG improves overall survival (OS) vs placebo (PBO) in patients with mCRC who failed approved therapies (OS HR 0.77; 1-sided p=0.0052; Grothey 2013). A total of 760 patients were randomized to REG (n=505) or PBO (n=255) in more than 100 centers across North America, Europe, Asia, and Australia. We conducted a post-hoc exploratory subgroup analysis of the 83 (11%) patients from 18 US centers. Methods: Eligible patients had an ECOG PS ≤1 and had received approved therapies, including a fluoropyrimidine, oxaliplatin, irinotecan, and bevacizumab, and if KRAS wild-type cetuximab and/or panitumumab. Data from the overall cohort, including US patients, are provided for perspective. Descriptive statistics are shown. Results: Of the 83 US patients, 36 (43%) were randomized to PBO and 47 (57%) to REG. Baseline characteristics of the US group were consistent with the overall cohort: median age in the US was 58 yr (range, 34 – 85) vs 61 (22 – 85) overall, 49% of US patients were ECOG PS1 (vs 46%), and 46% received ≤ 3 treatments for mCRC (vs 52%). KRAS status mutant/wild-type was 57%/34% in the US vs 57%/39% overall. All patients in the trial had prior bevacizumab and 57% of US patients also had prior cetuximab and/or panitumumab (vs 51% overall). However, higher proportion of patients in the US were Black (11% vs 2%), KRAS status unknown (10% vs 4%), and had colon as the primary disease site (82% vs 65%). Mean percentages of planned REG dose were similar (76% US vs 79% overall) and mean REG treatment duration was 3.1 mos in US vs 2.8 mos overall. Rates of dose modifications REG/PBO were 87%/47% in the US vs 76%/38% overall and grade ≥3 adverse events REG/PBO were 74%/64% vs 78%/49%, respectively. Based on 44 total death events, the HR for OS in the US subgroup was 0.46 (95%CI 0.25 – 0.84) favoring REG; median OS was 4.7 mos for PBO, but could not be estimated for REG due to censored data. However, this analysis was based on a relatively small sample size and event count. Conclusions: Patients treated in the CORRECT study in the US appear similar to the overall cohort and results are generally consistent with the overall findings of the trial. Clinical trial information: NCT01103323.

710 Background: In the CORRECT phase III trial (NCT01103323), the multikinase inhibitor REG significantly improved overall survival (OS) and PFS vs placebo in patients with mCRC who had disease progression after other standard therapies (HR for OS: 0.77; 1-sided p =0.0052; Grothey 2013). A post-hoc exploratory subgroup analysis was conducted to evaluate patients in the REG treatment group who had a PFS longer than 4 months (long-PFS) defined as patients who progressed, died, or discontinued treatment for other reasons after 4 months. Methods: Of the505 patients randomized to REG in CORRECT, 98 (19.4%) were classified as having a long-PFS benefit. Baseline characteristics, safety, and dosing parameters were analyzed descriptively. Results: The long-PFS subpopulation was representative of the overall study population (Table). Long-PFS patients received a median of 6 cycles of REG (1-12), 92% received ≥5 cycles, and 20% had > 8 cycles. Overall 34% of patients had dose reductions and 87% had dose interruptions. The actual mean daily dose was 139 mg and the mean percent of the planned dose was 81%. Adverse events (AE) of any grade were experienced by all long-PFS patients, and the most common grade ≥3 AEs were hand-foot skin reaction (20%), hypertension (17%), diarrhea (17%), and fatigue (16%). Conclusions: A subset of 98 (19.4%) patients treated with REG in the CORRECT study had a PFS > 4 months, confirming the clinical benefit and tolerability of REG as a treatment option for patients with mCRC. Prospective validation of these findings in conjunction with biomarker analysis from real-life clinical experience is needed. Clinical trial information: NCT01103323. [Table: see text]

702 Background: Median overall survival (OS) in mCRC has significantly improved over the past 20 yrs, but the observed range of OS in pts remains wide; a large percentage of pts have OS <1 yr or >4 yrs. ARIES was a prospective OCS conducted from 2006–2012 that evaluated outcomes in pts receiving BV + chemotherapy (CT) for mCRC in general clinical practice. The objective of this analysis is to examine clinical characteristics of pts with long vs short OS. Methods: This analysis included 1,417/1,550 first-line (1L) BV-treated mCRC pts who died or had complete follow-up on study. Long OS was defined as OS within the upper quartile of the analysis population (range 42–67 mos); short OS was defined as OS within the lower quartile (range 0.3–12 mos). Progression-free survival (PFS) was estimated using Kaplan-Meier methods. Pt and disease characteristics and treatment patterns were described using summary statistics. Results: Pt and disease characteristics are shown in the Table. Median PFS was 22.3 mos (95% CI, 19.9–23.3) vs. 4.9 mos (95% CI, 4.6–5.4), in the long-OS vs. short-OS groups. More pts with long OS received any second-line (2L) therapy (71% vs. 46%), and were exposed to 5-fluorouracil, oxaliplatin, and irinotecan throughout the course of their disease (53% vs. 32%) compared with pts with short OS. KRAS/BRAF mutation status was not collected. Conclusions: Pts with long OS had better baseline performance status, primary tumors more likely to have been resected, and were more likely to have received 2L CT. Additional analyses of detailed treatment patterns and safety are ongoing. Clinical trial information: NCT00388206. [Table: see text]

686 Background: Preclinical evidence suggests that statins have anti-neoplastic properties by inhibiting cell proliferation, and inducing apoptosis. Statins may be associated with reduced risk of colorectal cancer (CRC), but their effect on CRC related mortality is unclear. We performed a meta-analysis of published observational studies evaluating statin use in patients with CRC and its association with overall and CRC-specific mortality. Methods: Through a systematic search upto August 2014, we identified 7 observational studies (64,773 patients with CRC;19.5% statin users) reporting the association between statin use and mortality in patients with CRC. Summary hazard ratio (HR) with 95% confidence intervals (CI) was estimated using the random effects model, and heterogeneity was measured using the inconsistency index (I2). Results: On meta-analysis, statin use was associated with a 26% reduction in all-cause mortality in CRC patients as compared to non-use (6 studies; adjusted HR, 0.74; 95% CI, 0.67-0.83) with minimal heterogeneity (I2=18%), after adjusting for age, sex and CRC stage. Only one study adjusted for concomitant metformin use. Five studies evaluated CRC-specific mortality; on meta-analysis, use of statins (vs non-use) was also associated with decreased CRC-specific mortality (adjusted HR, 0.74; 95% CI, 0.70-0.83; minimal heterogeneity, I2=17%). On limiting analysis to statin use after diagnosis of CRC, use of statins remained significantly associated with reduced CRC-specific mortality (3 studies; adjusted HR, 0.70; 95% CI, 0.60-0.81), but not overall mortality (4 studies; adjusted HR, 0.82; 95% CI, 0.64-1.05). On restricting analysis to studies, which adjusted for concomitant use of aspirin/NSAID, the inverse association between statin use and overall- (5 studies; adjusted HR, 0.74; 95% CI, 0.66-0.84) and CRC-specific mortality (4 studies; adjusted HR, 0.76; 95% CI, 0.69-0.84) remained significant. Conclusions: Based on this meta-analysis, statin use in patients with CRC may be associated with reduced all-cause and CRC-specific mortality. This observation merits prospective investigation of statins’ effect on outcome in CRC patients.

678 Background: Improvements in outcome of medical therapy for mCRC are closely linked to availability of active agents. Based on phase III clinical data, regorafenib, a multikinase inhibitor, received FDA approval September 2012 for patients with mCRC previously treated with all approved therapies. Post regorafenib therapy (PRTx) has not been established. Based on clinical observations, we established a multi-institution collaboration to assess chemotherapy response in mCRC after regorafenib therapy. Methods: After IRB approval, patient records at Mayo Clinic (MC), MD Anderson (MDA) and the University of Southern California (USC) from April 2010 to February 2014 were reviewed for regorafenib use and outcomes for mCRC. Therapies, patient and tumor characteristics were reviewed. Response and progression were determined by investigator review. Kaplan-Meier method was used to calculate survival. Results: Regorafenib was given to 173 patients with mCRC (MC:59 MDA:95 and USC:19). Of these, 11 (6%) continued on regorafenib at time of analysis and 98 (57%) received no additional therapy. PRTx was given to 64 (37%) patients, 31 of which went on a clinic trial. 33 patients were treated with standard approved therapy of which 11 (33%) progressed, 20 (61%) showed response or SD, and 2 (6%) were not evaluable. Out of the 33 treated with standard agents, 8 (24%) had stable disease or response to a treatment previously discontinued without definitive PD, whereas 4 (12%) responded to rechallenge with chemotherapy previously discontinued due to PD. Response was noted in 8 (24%) patients that received an agent not given prior to regorafenib. After discontinuation of regorafenib, mOS was 6.5 mo (CI 4.9 – 9.4), and the probability of survival at 6 and 12 months was 52% and 27% respectively. Conclusions: With the caveat of a small sample size and a potential selection bias, our multi-institution study shows that re-utilizing standard treatment options after regorafenib may be beneficial in select patients with mCRC including in patients with progression on identical therapy before regorafenib. Further retrospective and prospective studies could be warranted to define the role of regorafenib as a chemotherapy re-sensitizing agent.

666 Background: Early tumor shrinkage (ETS; ≥20% decrease from baseline) and early objective tumor response (EOTR; CR/PR by RECIST) are associated with improved PFS/OS to a similar extent than best overall response (BOR), confirmed response (ConfR) and non-progression rate (NPR; CR/PR/SD by RECIST) at the individual level in first-line mCRC (ASCO 2014, abstr 3538/3578). We assessed these RBEs at the trial level. Methods: Data were available on 12,185 pts enrolled in a total of 17 randomized trials of chemotherapy (CT) alone or with targeted agents (TAs). ETS, EOTR and NPR were assessed at 6/8/9 and 12 weeks (wks), whereas BOR and ConfR were ascertained within 26 wks from randomization. Association between treatment effects on RBEs and on PFS/OS was assessed by coefficients of determination (R2, adjusted for estimation errors) using a copula model). Results: None of the RBEs had consistently strong correlations with PFS or OS (Table). The number of trials was insufficient to obtain reliable estimates for antiangiogenics and anti-EGFR separately. Conclusions: Despite their individual-level associations with PFS and OS, RBEs do not appear to be surrogate endpoints in first-line mCRC, given their poor predictive ability. [Table: see text]

603 Background: Anal squamous cell carcinoma (Anal SCC) is a rare, HPV-associated malignancy accounting for 2.4% of digestive system cancers. In most cases, these malignancies are detected in the early stages and successfully managed with chemoradiation therapy. Uncommonly, these cancers recur or present with metastases. In this setting, cisplatin and 5-fluorouracil represent the only endorsed regimen. Once beyond standard therapy, few therapeutic options exist for those patients with aggressive disease. The purpose of this study is to identify other novel, potential targets and therapeutic options for this disease, utilizing a multiplatform approach. Methods: 206 anal SCC specimenswere tested via a multiplatform profiling service (Caris Life Sciences, Phoenix, AZ) consisting of gene sequencing (Sanger or next generation sequencing [NGS]), protein expression (immunohistochemistry [IHC]) and gene amplification (CISH or FISH). 6 cases were documented as positive for HPV or HIV; status was not provided on the remaining 200. Results: Key results are shown in the table below, shown as percent change/total cases. Conclusions: Multiplatform tumor profiling identified a low incidence of gene mutations. Protein expression aberrations identified potential treatment options not routinely considered, such as topoisomerase inhibitors and taxanes. Mutations in PIK3CA, Akt1, and FBXW7 as well as PTEN loss indicate potential for targeting the PI3 kinase pathway. Additionally, immunomodulatory agents may be a therapeutic option, based on PD-1 expression levels. Targeting the ErbB-family receptors, namely with anti-EGFR agents or newer generation pan-HER - inhibitors, may represent another option, given EGFR and HER2 amplification as well as EGFR overexpression. It should be mentioned that differences in anal carcinomas whose etiology is of viral origin may present different treatment options based on the driver mutations. [Table: see text]

600 Background: Experimental and clinical evidence suggests that constitutively decreased Transforming Growth Factor Beta type I receptor (TGFBR1) signaling predisposes to colorectal cancer (CRC) development. However, associations between TGFBR1 variants and CRC risk in case-control studies have been inconsistent. Methods: We utilized 1,043 CRC cases and their 1,627 unaffected sibling controls obtained from the Colon Cancer Family Registry (C-CFR). Individuals were genotyped for twelve TGFBR1 haplotype tagging SNPs. SNPs associated with CRC risk were validated in 261 CRC cases and 531 controls of African American ancestry and 990 CRC cases and 3,427 controls of Han Chinese ancestry. Validated SNPs were functionally characterized with respect to TGFBR1 expression and TGF-β signaling. Results: The TGFBR1 rs7034462-TT genotype was associated with CRC risk in C-CFR participants (OR 3.80[1.46-9.85]) and African Americans (OR 8.16[2.07-32.08]) (see Table). The TT genotype was associated with stage III and stage IV at diagnosis in C-CFR participants (OR 2.99[1.15-7.81] and OR 9.38[1.54-57.28]) and African Americans (OR 5.89[1.15-30.02] and OR 12.75[1.88-86.33]), respectively. The rs7034462-CT genotype was associated with decreased risk for CRC in African Americans (OR 0.55[0.31-0.99]) and Han Chinese (OR 0.67[0.48-0.95]) (see table). Cells carrying the rs7034462-TT genotype exhibited decreased constitutive TGFBR1 expression, increased SMAD7 expression, and decreased TGF-β signaling. Conclusions: The TGFBR1 rs7034462-T allele has dual, opposite roles with respect to CRC risk. The rare rs7034462-TT genotype is a moderate penetrance genotype associated with risk for CRC and advanced stage disease at diagnosis. In contrast, the common rs7034462-CT genotype is associated with decreased CRC risk. [Table: see text]

562 Background: An interim futility analysis at ASTRO 2013 led to early closure of N08C9 (Alliance), a randomized controlled trial (RCT) comparing sulfasalazine (SSZ) versus placebo (PBO) in the prevention of radiation enteritis during pelvic RT. This is the full analysis of the primary endpoint (PE) and secondary endpoints (SEs) of the trial. Methods: A multi-institutional RCT conducted by the Alliance for Clinical Trials in Oncology assessed the effect of 1000 mg SSZ b.i.d. versus PBO b.i.d. in the treatment of pelvic RT related enteritis. Study participants (SPs) received the study agents during RT and for 4 weeks afterwards. The PEwas the maximal severity of diarrhea toxicity (CTCAE version 4.0) during and up to 6 weeks after RT. SEs, including the maximum severity of diarrhea (MSD) and the duration of MSD, rectal bleeding, abdominal cramping, tenesmus, and constipation, were graded weekly during RT by a health care provider. Bowel function was assessed using a self-administered bowel function questionnaire weekly during RT, afterwards at 6 weeks, and at 12 and 24 months. A two-sided 0.05-level Wilcoxon rank-sum test was used to test the equality of the distributions of MSD grades. The planned study size was 128 SPs. Results: 87 SPs were enrolled in the study between 4/29/2011 and 5/13/2013, with evenly distributed baseline factors. Toxicity data were available in 84 SPs during RT and in 54 SPs in the 6 weeks following RT. There was no significant difference in the distribution of MSD grades between the SSZ and PBO arms (p=0.41 regardless of attribution; p=0.09 at least possibly attributed to the study agent). No significant differences were observed in SEs during RT and after RT, except the abdominal pain occurring after completion of RT was higher in SPs receiving SSZ (p=0.02). More SPs required antidiarrheal agents on the SSZ arm (49% vs. 29%, p=0.06). Conclusions: Despite prior single institution RCT’s suggesting a benefit for SSZ (Kilic 2001; Pal 2013) in this clinical context, the results of this large, multi-institutional trial demonstrate that SSZ does not reduce the risk of enteritis and may worsen acute GI toxicity during pelvic RT. Clinical trial information: NCT01198145.

541 Background: A long wait-time for colectomy for colon cancer should theoretically affect survival but, to date, the association between delay to colectomy and survival remains unresolved. Methods: We studied 4,692 patients who underwent colectomy for colon cancer between 1990 and 2012. Wait-time was defined as the number of days between diagnosis and colectomy. Cox regression models were used to estimate all-cause mortality across wait-time categories. Multivariable analyses were controlled for clinicopathologic variables and Charlson comorbidity index. Results: The number of patients in the wait-time group of 1-28 days was 3,950 (84.2%), 29-84 days was 681 (22.7%), and >84 days was 61 (1.3%). A wait-time of 29-84 days was not associated with an increased risk of death (HR=1.13; p=0.056) when compared to a wait-time of 1-28 days. Though a wait-time >84 days represented a small group, it was associated with an increased risk of death (HR=1.60; p=0.013). For patients with stage I and II disease, wait-times of 29-84 days (HR =1.44; p=0.0001) and >84 days (adjusted HR=2.24; p=0.0007) were associated with an increased risk of mortality. Conclusions: A wait-time for colon cancer surgery of up to 12 weeks is likely safe for most patients. However, those suspected to have early-stage colon cancer may benefit from less of delay. These data provide a framework to address concerns over prolonged wait-times and can direct efforts for timely surgical intervention in patients with colon cancer. [Table: see text]