Maughan, Tim

108 Background: Primary tumor sidedness has emerged as a prognostic and predictive biomarker for patients (pts) with metastatic colorectal cancer (mCRC). Tumor bulk has also been postulated to predict response to anti-EGFR therapy. We sought to evaluate the role of tumor bulk as a predictive biomarker to anti-EGFR therapy in pts with left- (LS) and right-sided (RS) mCRC. Methods: Data from 476 pts with mCRC enrolled across 2 first-line trials of anti-EGFR plus chemotherapy versus chemotherapy were pooled. Pts were included if there was available information on tumor sidedness and tumor bulk. All were KRAS wild-type and BRAF wild-type or unknown BRAF status. The right colon was defined as the cecum through the transverse colon, and the left colon as the splenic flexure through the rectum. Tumor bulk was the mean tumor size of target lesions at baseline, bulky defined as > 3.5 cm. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox models adjusting for performance status (PS), platelet count, primary tumor (PT) resection, number of metastatic sites, and stratified by study. Results: Pts with bulky tumors (211, 44%) had higher PS, white blood cell and platelet counts, higher CEA, fewer sites of metastatic disease, more liver than lung metastases, and fewer had PT resection. OS and PFS medians in months (mos) are presented in the table with 95% confidence intervals (95%CIs). Bulky tumors had inferior median OS compared with non-bulky (mOS, 17.9 vs. 21.3 mos, HRadj 1.33, 95% CI 1.05-1.69, P = 0.016) although median PFS was similar (mPFS, 8.6 vs. 8.7 mos, HRadj 1.15, 95% CI 0.92-1.42, P = 0.21). Conclusions: Tumor bulk is an independent prognostic factor for OS in KRAS wild-type and BRAF wild-type or unknown BRAF status pts. Pts with non-bulky RS tumors have survival outcomes similar to pts with bulky LS tumors. Although the mPFS for pts with RS tumors treated with anti-EGFR therapy was the lowest across subgroups, this finding was not statistically significant. Further research is warranted into whether pts with bulky RS tumors benefit from anti-EGFR therapy. Clinical trial information: NCT00182715, NCT00640081. [Table: see text]

4090 Background: EGFR mAbs have become incorporated into clinical practice for the management of mCRC over the last decade. KRAS and NRAS mutations are used as predictive biomarkers and BRAF V600E mutations are associated with an adverse prognosis. The observed TE within biomarker subpopulations has varied between studies. Methods: IPD from randomized trials with head-to-head comparison between EGFR mAb versus no EGFR mAb (chemotherapy alone or BSC) in mCRC, across all lines of therapy (first, second and later), were pooled. Biomarker subpopulations are defined in the table. Overall survival (OS) and progression-free survival (PFS) were compared between groups by Cox model, stratified by studies and adjusted by age, gender, and performance status. TEs were estimated by adjusted hazard ratio (HRadj) and 95% confidence interval (CI). Within each biomarker subgroup, EGFR mAb efficacy was explored according to multiple exploratory factors, including line of therapy, type of backbone chemo, gender, sidedness and site of metastasis. Interaction tests were performed. P-values < 0.01 were considered statistically significant to account for multiple comparisons. Results: 5729 pts from 8 studies with data available for ≥ 1 biomarker were analysed. PFS benefits (median 9.2 mos in EGFR mAbs, 8.0 mos in no EGFR mAbs) were confirmed in triple-WT pts, but not for OS (refer to table). No OS/PFS benefits were observed for pts with any of the MT tumors. Exploratory analyses showed a potential detrimental TE of EGFR mAbs in KRAS MT mCRC with liver metastasis (OS: HRadj 1.22, p = .003, pinteraction .0056; PFS: HRadj 1.24, p = .0009, pinteraction .0008). These results were confirmed within the subgroup of pts with all 3 biomarkers available. Conclusions: This is the largest IPD analysis to explore the predictive value of RAS/BRAF biomarkers in mCRC. Our findings demonstrate that there is no evidence of efficacy of EGFR mAbs in KRAS, BRAF and/or NRAS MT mCRC. EGFR mAbs might have a detrimental effect in KRAS MT mCRC with liver metastases. [Table: see text]

188 Background: Unplanned subgroup analyses from several studies have suggested primary tumor sidedness (PTS) as a potential prognostic and predictive parameter in metastatic colorectal cancer (mCRC). We aimed to investigate the prognostic and predictive impact of PTS on outcomes. Methods: PTS data of 7,828 mCRC patients (pts) from 10 first-line randomized trials in the ARCAD database were pooled. PTS was defined as right-sided (RS) or left-sided (LS) if tumor arose from the cecum to the hepatic flexure or from the splenic flexure to the rectum, respectively; transverse colon cancers were not included. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox models adjusting for age, sex, performance status (PS), prior radiation/chemo, and stratified by treatment arm. Predictive value was tested by interaction term between PTS and treatment (anti-EGFR plus chemotherapy vs. chemotherapy alone). Results: Compared to RS pts (2407, 31%), LS pts (5421, 69%) had better OS (median: 21.6 v 16.8 mos; HRadj: 0.73, 95% CI 0.69-0.78, P < .001) and PFS (median 8.4 v 7.2 mos; HRadj: 0.81, 95% CI 0.76-0.86, P < .001). Results were consistent among subgroups defined by age, sex, PS, metastatic sites and chemo backbone (irinotecan- and oxaliplatin-based). Interaction between PTS and KRAS mutation was significant (Pinteraction< .001): LS is associated with better prognosis only among KRAS wild-type (wt) (HRadj: OS 0.62, 95% CI, 0.55-0.70; PFS 0.71, 95% CI 0.63-0.80), but not among KRAS mutated pts. Among KRAS wt pts, survival benefit from anti-EGFR was observed for LS, but not for RS (table). Conclusions: The prognostic value of PTS is restricted to the KRAS wt population. PTS is predictive of anti-EGFR efficacy, with a significant improvement of survival for LS mCRC pts. These results suggest treatment stratification in mCRC studies by both PTS and KRAS status. [Table: see text]

3539 Background: Previous studies suggest a possible gender-specific response to Bev in mCRC, showing a benefit in males, while the effect in females is less significant. Therefore, we evaluated response to Bev according to gender. Methods: Data from 3369 mCRC patients enrolled on 4 first-line randomized trials testing Bev (2000-2007) were pooled. Association between gender and progression-free survival (PFS)/overall survival (OS) was evaluated by stratified Cox regression model, adjusted for potential confounders. Predictive value was evaluated by interaction (inter.) effect between gender and treatment. In a pre-planned secondary analysis, analyses were stratified using an age cut-point of 60 years (commonly used in breast cancer trials) to evaluate the possible role of menopausal-related effects. Results: OS was not statistically different between males and females (median OS [mOS], 18.8 vs. 17.6 months [mo], adjusted hazard ratio [HRadj], 0.93, 95% confidence interval [CI], 0.84-1.03, p, 0.15) in the overall population. Bev was associated with an improved mOS in males and females, with a 2.3 and 0.6 mo benefit, respectively, as well as an improved PFS. There was no statistically significant interaction effect between gender and treatment (see table). Further stratified by age (< vs. ≥ 60 years), Bev resulted in improved PFS and OS in both genders, at all ages, except for the effect in young females which did not reach statistical significance (see table). Conclusions: Our results confirmed the mOS benefit from addition of Bev to first-line chemotherapy in mCRC in both genders, although the benefit in females was < 1 month. For females under the age of 60, there are uncertainties for mOS benefit from addition of Bev and further evaluation is needed. [Table: see text]

617 Background: There is limited, often conflicting evidence about AE timing, severity or associations with outcomes with the use of cytotoxic agents in cancer treatment. We investigated the impact on overall survival (OS) and progression-free survival (PFS) of selected common AEs (neutropenia, diarrhea, nausea, vomiting, neuropathy) occurring in patients receiving first line oxaliplatin (Oxa)- and/or irinotecan(Iri)-based regimens for mCRC. Methods: The CTCAE grading scores of at least one AE of interest were available on 9812 pts treated with chemotherapy alone (median age 63; 62.4% male, 50.1% ECOG PS 0) from 17 1st-line randomized trials. Patients who also received biologics were excluded in the primary analyses. AEs occurring during the first 6 weeks of treatment and entire treatment were analyzed by stratified multivariable Cox models in relationship to OS/PFS. 55.7% pts received Oxa- regimens, 35.7% Iri-regimens, and 8.6% combined Oxa- and Iri-regimens. Results: Within the first 6 weeks of treatment, G3+ neutropenia (HRadj= 1.3, 95% CI, 1.06-1.59, padj 0.01), diarrhea (HRadj= 1.48, 95% CI, 1.23-1.79, padj < .0001), nausea (HRadj= 1.53, 95% CI, 1.17-1.99, padj 0.002) and vomiting (HRadj= 1.56, 95% CI, 1.18-2.07, padj 0.002) were associated with significantly worse OS for Iri-regimens, but only G3+ nausea predicted for worse OS for Oxa- regimens (HRadj= 1.61, 95% CI, 1.18-2.21, padj 0.003). For AEs experienced at any time, G3+ neutropenia and neuropathy were significantly associated with longer PFS and OS for Oxa-regimens, while G3+ vomiting and nausea were associated with worse OS for both Oxa- and Iri-based regimens. Sensitivity analysis showed largely concordant results by including pts who also received biologics. Conclusions: The association between more severe selected AEs and outcome varies between AEs and is influenced by timing of the occurrence. More severe selected AEs occurring early in treatment are associated with worse outcomes. In contrast, for AEs occurring at any time, G3+ neutropenia and neuropathy predicted for longer PFS and/or OS in Oxa-treated pts.

While elevated blood cholesterol has been associated with an increased risk of colorectal cancer (CRC) in observational studies, causality is uncertain. Here we apply a Mendelian randomisation (MR) analysis to examine the potential causal relationship between lipid traits and CRC risk. We used single nucleotide polymorphisms (SNPs) associated with blood levels of total cholesterol (TC), triglyceride (TG), low‐density lipoprotein (LDL), and high‐density lipoprotein (HDL) as instrumental variables (IV). We calculated MR estimates for each risk factor with CRC using SNP‐CRC associations from 9,254 cases and 18,386 controls. Genetically predicted higher TC was associated with an elevated risk of CRC (odds ratios (OR) per unit SD increase = 1.46, 95% confidence interval [CI]: 1.20–1.79, p = 1.68 × 10−4). The pooled ORs for LDL, HDL, and TG were 1.05 (95% CI: 0.92–1.18, p = 0.49), 0.94 (95% CI: 0.84–1.05, p = 0.27), and 0.98 (95% CI: 0.85–1.12, p = 0.75) respectively. A genetic risk score for 3‐hydoxy‐3‐methylglutaryl‐coenzyme A reductase (HMGCR) to mimic the effects of statin therapy was associated with a reduced CRC risk (OR = 0.69, 95% CI: 0.49–0.99, p = 0.046). This study supports a causal relationship between higher levels of TC with CRC risk, and a further rationale for implementing public health strategies to reduce the prevalence of hyperlipidaemia.

675 Background: Recent retrospective analysis of CALGB/SWOG 80405 showed that left-sided colon cancers (LCC) respond differently to biological therapy compared with right-sided tumors. However, differences between rectal cancers (RC) and LCC remain undefined. Herein, we report our exploration of differences between these two groups. Methods: Individual patient data from 4182 patients (pts) with metastatic colorectal cancers, enrolled onto 8 first-line randomized trials, were pooled. Only pts with tumor locations that were clearly defined as LCC (splenic flexure to sigmoid) or RC were included in this analysis. Differences in pt characteristics and disease factors according to LCC vs. RC were identified. The prognostic effect of primary tumor location on OS and PFS was quantified via multivariable Cox proportional hazards modeling stratified by treatment arm within each study and adjusting for age, sex, performance status, and prior surgery. Results: In total, 2,479 (59%) pts with LCC and 1,703 (41%) pts with RC were identified. Pts with RC, compared with LCC, were more likely to be male (68% vs. 62%, p < 0.001), have lung metastases (mets) (56% vs. 37%, p < 0.001), and have 2 or more metastatic sites (64% vs. 60%, p < 0.02), whereas pts with LCC were more likely to have liver mets (84% vs. 76%, p < 0.001). RC had a greater frequency of KRAS mutations (41% vs. 37%, p = 0.04) than LCC but there were no differences in the frequency of BRAF mutations (5% vs. 4%, p = 0.2). In multivariable analysis, no differences in OS or PFS were observed between pts with LCC vs. RC. While risk of death did not differ by primary tumor location, across all pts with LCC or RC, those with liver mets had a 17% increased risk of death compared to those with lung mets (HR = 1.17, p = 0.03) after adjusting for effects of other variables. Forthcoming prognostic analysis of LCC vs. RC within grouped backbone treatments (e.g., FOLFOX and FOLFIRI) is underway. Conclusions: Tumors arising in the rectum may carry clinical and molecular features that are distinct from LCC. Further investigations are warranted to determine whether RC should be treated with the same chemo backbone and biological therapy as LCC.