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Background: Primary lymphoepithelioma-like carcinoma (LELC) of the lung is a rare histological type of lung cancer with a relatively better prognosis. It is common in Chinese population, is associated with Epstein Barr Virus (EBV), and has morphological similarities to nasopharyngeal carcinoma. Methods: We retrospectively analysed medical records of patients with LELC at Tan Tock Seng Hospital, Singapore from November 2010 to January 2016 and evaluated baseline characteristics, staging, therapeutic interventions and survival. Results: Ten patients were diagnosed with pulmonary LELC, all were Chinese. The median age (range) at diagnosis was 62 (42-88) years, with a female preponderance ratio of 4:1. All had Epstein-Barr virus encoded small non-polyadenylated ribonucleic acid positive status. Six (60%) patients had stage IV, 3 (30%) stage IIIA, and 1 (10%) stage IIA disease. The median overall survival was 24.2 (4.7-59.4) months; in stage II, IIIA, and IV it was 27.6, 20.7 (19.8-48.9), and 26.6 (4.7-59.4) months respectively. The 1-year, 2-year, 3-year, and 5-year survival rate was 90%, 50%, 30%, and 10% in the whole group, but 100%, 43%, 28.6%, and 14.3% in 7 patients who received chemotherapy. Gemcitabine/carboplatin was the most commonly used 1st line chemotherapy. Conclusion: LELC is associated with Chinese ethnicity, younger age of onset, EBV, lack of smoking, advanced stage, and better prognosis than other subtypes of lung cancers. For improving outcomes, future efforts should focus on increased awareness, early diagnosis, development of an ASEAN registry and international collaboration. Options such as EBV-directed adopted immunotherapy or the role of EBV vaccine also merit evaluation.

The FDA-approved starting dosage of capecitabine is 1,250 mg/m2, and market research indicates that U.S. physicians routinely prescribe 1,000 mg/m2. Retrospective analyses however report reduced toxicity and efficacy in a subset of patients with the 3R/3R genotype of the thymidylate synthase gene enhancer region (TSER). This study sought to develop TSER genotype-specific guidelines for capecitabine dosing. Capecitabine was dose-escalated in advanced and/or metastatic cancer patients with TSER 3R/3R (Group A; N = 18) or 2R/2R + 2R/3R (Group B; N = 5) from 1,250 to 1,625 mg/m2 b.i.d., every 2 weeks on/1 week off for up to 8 cycles. Parent and metabolites pharmacokinetics, adverse events, and tumour response were assessed. The maximum tolerated and recommended doses in 3R/3R patients are 1,625 mg/m2 and 1,500 mg/m2. At 1,500 mg/m2, one in nine 3R/3R patients experienced a dose-limiting toxicity. Dosing guidelines for 2R/2R + 2R/3R remain undetermined due to poor accrual. The results indicate that 3R/3R patients may be amenable to 1,500 mg/m2 b.i.d. on an intermittent schedule, and is the first to prospectively validate the utility of TSER pharmacogenetic-testing before capecitabine treatment.

Biomedical research involving human participants is highly regulated and subject to stringent ethical requirements. Clinical research ethics, regulation and policy have tended to focus almost exclusively on the protection of participants' interests against harms that might result from taking part in research. Less consideration, however, has been given to the interests that patients may themselves have in research participation, even in trials that may be beyond the bounds of current clinical research practice. In this paper, we consider the case of a suggested extension to clinical trial protocols to explore the ethics of participation in ‘risky’ research. We argue that patients may have a strong interest in taking part in research, and that even when greater-than-usual risks may be present, such research can be both ethically and scientifically justified. Finally, we suggest that there might be scope in some cases to assert a right to participate in research, and that the possibility of such a right merits further consideration.

Background:Platinum-resistant and refractory cancers of the ovary, fallopian tube, and peritoneum have a poor prognosis, yet in some cases, they can respond to multiple lines of chemotherapy. Uncertainty remains over optimal drug choice and when therapeutic focus should be switched from active therapy to supportive care.Methods:A retrospective case note review was performed on 274 women treated for platinum-resistant/refractory ovarian, fallopian tube, or peritoneal carcinoma at the Christie Hospital between 2004 and 2008. Baseline data at onset of platinum resistance and outcomes from subsequent lines of therapy were recorded.Results:A total of 689 lines of therapy were administered with a median overall survival from initiation of first-line therapy for platinum-resistant disease of 61 weeks. Twenty-eight percent of women commenced cytotoxic therapy in the last 3 months of life. Treatment efficacy declined rapidly with successive lines of therapy particularly if disease progression occurred during first-line therapy. Factors independently associated with worse overall survival at recognition of platinum resistance were performance status, presence of stage IV disease, elevated cancer antigen 125, and platinum-refractory disease.Conclusions:A significant proportion of women who were treated received therapy within the last few months of life with little clinical benefit. Disease progression on 2 consecutive lines of therapy should be used as a guide to discontinue cytotoxic treatment. A subset of patients with poor prognosis at the onset of platinum resistance, who may have little gain from anticancer treatment, can be identified.

Merkel cell carcinoma of the eyelid is a rare tumor with less than 100 reported cases worldwide. We describe an unusual presentation of Merkel cell carcinoma of the eyelid in a 60 year old Asian male. He presented with multiple left lower lid conjunctival nodules, intense conjunctival erythema, as well as ipsilateral cervical lymphadenopathy. An incisional biopsy diagnosed him with Merkel cell carcinoma with a PET scan showing distant metastatic disease. He was then treated with chemotherapy. The combination of a presentation of conjunctival nodules and erythema, location in the lower eyelid and the conjunctiva, the presence of metastatic disease on diagnosis as well as an unusual immunohistochemical profile make this an unusual case.

BACKGROUND:: The vascular endothelial growth factor pathway is strongly implicated in cancer-related angiogenesis. Antiangiogenic agents such as bevacizumab commonly cause hypertension (HTN) and proteinuria (PTN), which may be biomarkers of response and clinical outcome. STUDY:: We conducted a retrospective analysis of patients with histologically proven metastatic colorectal cancer (mCRC) treated with either bevacizumab or a tyrosine kinase inhibitor in combination with chemotherapy at The Christie Hospital from January 2006 to September 2009. RESULTS:: Of 90 patients evaluated, 50 were eligible. Seventeen (34%), 4 (8%), and 3 (6%) patients developed Common Toxicity Criteria (v 3.0) grades 1, 2, and 3 HTN, respectively. Response rates were 42% for patients with grades 0 to 1 HTN compared with 86% for patients with ?grade 2 HTN (P=0.043). Median overall survival was 21.6 months for patients with grades 0 to 1 HTN and 25.2 months for patients with ?grade 2 HTN (P=0.270). Twelve patients (24%) developed grade 1 PTN and 4 patients (8%) developed ?grade 2 PTN. Median overall survival was 23.9 months for patients with grades 0 to 1 PTN and 4.2 months for those with ?grade 2 PTN (P=0.028). CONCLUSIONS:: To our knowledge, this is the first study to demonstrate the utility of PTN as a surrogate marker of outcome in antiangiogenic therapy for metastatic colorectal cancer. Although HTN is predictive of a significantly higher response rate, the development of PTN during treatment with bevacizumab or tyrosine kinase inhibitor portends poorer survival and should be evaluated prospectively.

Belinostat is a hydroxamate class HDAC inhibitor that has demonstrated activity in peripheral T-cell lymphoma and is undergoing clinical trials for non-hematologic malignancies. We studied the pharmacokinetics of belinostat in hepatocellular carcinoma patients to determine the main pathway of metabolism of belinostat. The pharmacokinetics of belinostat in liver cancer patients were characterized by rapid plasma clearance of belinostat with extensive metabolism with more than 4-fold greater relative systemic exposure of major metabolite, belinostat glucuronide than that of belinostat. There was significant interindividual variability of belinostat glucuronidation. The major pathway of metabolism involves UGT1A1-mediated glucuronidation and a good correlation has been identified between belinostat glucuronide formation and glucuronidation of known UGT1A1 substrates. In addition, liver microsomes harboring UGT1A1*28 alleles have lower glucuronidation activity for belinostat compared to those with wildtype UGT1A1. The main metabolic pathway of belinostat is through glucuronidation mediated primarily by UGT1A1, a highly polymorphic enzyme. The clinical significance of this finding remains to be determined. Trial Registration ClinicalTrials.gov NCT00321594

Drug interactions may be exploited to overcome pharmacokinetic issues in order to improve the therapeutic index of a drug, with clinical goals of reducing the dose of the active drug while preserving efficacy or reducing toxicity. This strategy has been used in infectious disease and transplant medicine, and, more recently, in oncology. Pharmacologic modulation strategies range from coadministration of either a drug that inhibits a metabolizing enzyme that would inactivate the drug of interest, a drug that induces an enzyme that activates the drug of interest or a drug that inhibits transporters that affect the uptake or elimination of the drug of interest. This review will discuss pharmacologic modulation strategies that have been tested clinically in order to increase systemic drug exposure. Important examples include ketoconazole inhibition of hepatic CYP3A4 in order to increase systemic exposure to docetaxel, irinotecan and etoposide, and cyclosporine inhibition of intestinal ATP-binding cassette transporters in order to decrease the toxicity of irinotecan and increase the bioavailability of oral docetaxel, paclitaxel and topotecan.

Angiogenesis is a key process in the growth and metastasis of cancer, and genitourinary tumors are no exception. The evolution of angiogenesis as an important target for novel anticancer therapeutics has brought with it new challenges for in vivo imaging. Most imaging techniques quantify physiological parameters, such as blood volume and capillary endothelial permeability. Although CT, PET and ultrasonography have shown promise, MRI is the most common method used to evaluate angiogenesis in clinical trials of genitourinary tumors. Pilot studies of MRI, CT and ultrasonography in patients with renal cancer have produced promising results; reductions in vascular permeability and blood flow have been correlated with progression-free survival. The vascular characteristics of prostate cancer have been evaluated by MRI, and this has been suggested as a means of assessing tumor response to hormone deprivation therapy. Current evidence highlights the potential of angiogenesis imaging in the diagnosis, staging and possibly response monitoring of bladder cancer. In the future, assessment of the angiogenic process at the structural, functional and molecular levels, before, during and after antiangiogenic therapy will undoubtedly be integrated into wider clinical practice. © 2010 Macmillan Publishers Limited. All rights reserved.

e14507 Background: Regorafenib, an oral multikinase inhibitor of VEGFR2/3, PDGFRb, KIT, FGFR, RET, RAF and TIE2, is efficacious in refractory mCRC but its mechanism of action is unclear and predictive biomarkers are lacking. Methods: We assessed tumor and circulatory biomarkers in a phase 2 study of regorafenib in refractory mCRC patients. Regorafenib was administered orally at 160mg/d for 3 out of 4 weeks. Post cycle 2 response was assessed by RECIST 1.1. Subjects were scheduled for FDG PET-CT scans (pre + D15) and paired core needle tumor biopsies for IHC analysis (pre + D21) in cycle 1. Archival tumor mutations were evaluated using Sequenom MassARRAY OncoCarta Panel V1.0 assay. Results: 35 patients were treated; 49% received > 4 prior therapies and 43% had prior bevacizumab. Median PFS was 3.45 mths (95% CI: 3.40-3.49), ORR was 3% and disease control rate [DCR] (PR + SD at 8 wks) was 57%. Early PET responses (EORTC criteria) were seen in 49%, but did not predict for DCR (p=1.0). Fatigue, hand foot skin reaction (HFSR), voice change and diarrhea occurred in > 30% of subjects. Grade 3-5 toxicities occurred in 46%, the commonest being HFSR and rash (17% each). Median relative dose intensity was 92%; 43% required > 1 dose reduction, 60% required > 1 dose interruption. KRAS (29%), BRAF (9%), EGFR (9%), NRAS (6%) KIT (3%), PIK3CA (3%), PDGFRA (3%) and CDK (3%) mutations were detected in archival tumors. None predicted for ORR or DCR; PFS was identical in KRAS mutant vs wt patients (3.45 mths, p=0.39) and similar in BRAF mutant vs wt patients (3.48 vs 3.45 mths, p=0.10). The patient with the longest PFS (12.6 mths) had a BRAF mutation. Amongst the 10 paired tumor samples available, IHC markers upregulated in >50% cases were pMEK, pERK, pJun and pJNK, whilst those downregulated/ unchanged in >50% were pKIT, pVEGFR2, CD31 [vascular endothelial cells (ECs)] and podoplanin (lymphatic ECs). The greatest change was observed in podoplanin expression, corresponding to a 60% reduction in lymphatic vessel density. Conclusions: FDG-PET responses in cycle 1 did not predict for regorafenib clinical benefit in mCRC patients. Targeting lymphatic/vascular ECs in the tumor microenvironment may be a more significant antitumor mechanism of regorafenib than MAP kinase pathway inhibition. Clinical trial information: NCT01189903.

2551 Background: Thymidylate synthase (TYMS) is the target of fluoropyrimidines (FP). TYMS 3R3R is the predominant genotype in East Asian (EA) patients and is associated with increased TYMS expression, reduced FP related toxicity and relative FP resistance. Dose finding studies for FP were developed in Caucasians, a population that typically harbors TYMS 2R2R and 2R3R genotypes. We hypothesize the recommended phase II dose (RP2D) of capecitabine is higher in 3R3R and similar for 2R allele carriers compared to the FDA approved dose. Objectives 1) To determine the maximal tolerated dose (MTD) and RP2D of capecitabine in EA patients with advanced stage malignancy 2) To determine the safety and toxicity of this regimen and 3) To perform plasma pharmacokinetics (PK) of capecitabine and its metabolites. Methods: EA patients with advanced stage cancer were prospectively allocated into two cohorts: Group A (3R3R) and Group B (2R3R, 2R2R). In each cohort, dose escalation followed a standard phase I 3+3 design. Additional patients were treated at the R2P2 dose level (DL). Initial dose was 1250/m2 bd for 14 days q3w (DL 1) with 125 mg/m2 bd increments subsequently. Pharmacokinetics (PK) of capecitabine and its metabolites were performed using a LC-MS/MS method. Results: 23 patients (Group A=18; group B=5) received 94 cycles (median 2.5, range 1-8). Median age was 58 (range 34-74) years. Median turnaround time for TYMS genotyping was 1 day. In group A, grade 3-4 DLTs were seen in 3 patients: diarhoea, neutropenic fever, hand-foot syndrome, and mucositis. MTD was at DL 4 (1625mg/m2 bd) and the RP2D was 1500mg/m2 bd (DL 3). DL 3 was expanded to n=9. At DL 3, day 1 mean (± SD) capecitabine and 5FU Cmax was 12.3 ± 9.9 and 0.91 ± 0.73 µg/mL, respectively and AUC0 – t was 9.84 ± 5.53 and 1.21 ± 0.54 h*µg/mL, respectively. Compared with DL1, Cmax for capecitabine and 5FU was 2 and 2.02 fold higher and AUC 0-t was 1.49 and 1.59 fold higher at DL3. Accrual in group B was ceased at DL2 due to lack of patient enrolment; no DLT was seen. By ROC analysis, day 1 5FU AUC0 – t of 1.74 h*µg/mL predicted for DLT (p=0.022, sensitivity 100%, specificity 90%). Conclusions: In EA patients with TSER 3R3R, the RP2D was 1500 mg/m2 bd. The D1 5FU AUC0 – t at RP2D was 59% more than the FDA approved dose (DL1).

4100^ Background: Preclinical studies have shown that pharmacological inhibition of the MEK/ERK pathway by AZD6244 enhanced the anti-tumor effect of sorafenib in both orthotopic and ectopic models of HCC. We conducted this study to determine tolerability, pharmacokinetics, and pharmacodynamics of AZD6244 when combined with sorafenib in advanced HCC. Methods: Patients with biopsy-proven unresectable BCLC B/C hepatocellular carcinoma were recruited. Only those with Childs-Pugh A or B (7) liver cirrhosis and without prior systemic therapy were included. Sorafenib at 400mg bd was given 1 week before initiation of AZD6244 which was escalated in subsequent cohorts from 75mg om based on 3+3 design. PK and PD studies and QOL assessments were performed. DCE-MRI imaging was performed to assess tumor vascularity in response to treatment. Results: Fourteen patients were recruited (including 2 replaced). 11 had evaluable disease. Characteristics: all male, all Chinese, 12 were BCLC C stage. Two DLTs were seen out of 6 patients at dose level 1 (AZD6244 at 50mg bd) which were grade 3 fatigue and grade 3 abdominal pain with elevated transaminases. When an additional dose level 1A was added (ADZ6244 at 100mg om), 2 out of 3 patients had DLTs of grade 3 raised aspartate transaminase and grade 3 diarrhea. Thus, the MTD was determined to be AZD6244 at 75mg om when combined with sorafenib 400mg bd. Common toxicities were diarrhea (83%), rash (58%), fatigue (50%), hypertension (42%), anorexia/vomiting/thrombocytopenia (25%). Two patients had reversible LVEF dysfunction and there were no eye toxicities. PK of AZD6244 showed oral clearance of 11.2 + 6.8 L/h and terminal half-life of 6.0 +2.0 h.Objective responses were 3 PR, 6 SD and 2 PD.DCE-MRI measurements demonstrated significant reductions in permeability surface area product (PS, ml/100ml/min) and fractional intravascular blood volume (v1, ml/100ml) seven days after starting sorafenib. No additional antivascular activity was observed when AZD6244 was added to sorafenib. Conclusions: The recommended phase II dose for AZD6244 is 75mg om when combined with sorafenib 400mg bd for advanced HCC patients. This combination is feasible, shows activity and warrants further investigation.

3002 Background: STAT3 is constitutively activated by growth signaling pathways in many malignancies; in many cell lines inhibition of STAT3 leads to cell death. OPB51602 is a small molecule inhibitor of STAT3 phosphorylation (Tyr705) and activation. Methods: A phase I study of OPB51602 administered for 2 weeks every 3 weeks was initiated to determine the maximum tolerable dose (MTD), evaluate pharmacokinetics (PK), and assess pharmacodynamics effects on STAT3 in peripheral blood mononuclear cells (PBMCs). The starting dose was 2mg/day, and dose escalations to 5mg/d, 10mg/d, 20mg/d, were planned. Single dose PK was done on the first day of administration for 4 days. Dose escalation was based on the “3+3” design, MTD was defined as the dose with at least 2/6 dose limiting toxicities (DLTs) in the first cycle and toxicities were graded by NCICTCv4.0. Results: 32 patients (pt) were treated at doses of 2mg/d (n=7), 4mg/d (n=18), 5mg/d (n=7). The main toxicities observed included nausea/vomiting, diarrhea, peripheral neuropathy and fatigue. 5 mg/d was the MTD, where cycle 1 DLTs of grade 3 diarrhea/dehydration and hyponatremia occurred in 1 patient respectively. One pt developed grade 3 peripheral neuropathy at 4mg/d cohort. PK showed maximal drug levels 2-3 hours after administration, bi-exponential decay, with mean oral clearance of 316.5 +/- 638.9 L/h and long terminal mean half-life of 61.8 +/- 15.9 h on day 17. STAT3 phosphorylation in PBMCs assessed in 6 pts receiving 4mg/d was reduced from 67.4 +/- 17.4% at baseline to 53.0 +/- 18.1% (p=0.001) after administration on day 1. Interestingly, reduction in tumor metabolism by PET CT on day 15 was observed in 4/8 pts receiving 4mg/d. A pt with heavily pretreated adenocarcinoma of lung at 5mg/d dose had partial response; another pt with metastatic endometrial cancer at 4mg/d dose experienced stable disease for 6 cycles. Conclusions: OPB51602 has an MTD of 5mg/d on this schedule, demonstrates inhibition of STAT3 phosphorylation, and evidence of clinical activity. Further proof of concept studies of OPB51602 are warranted.

89 Background: Perioperative chemotherapy has been shown to improve outcomes among patients with locally advanced gastric adenocarcinoma. As docetaxel (D), cisplatin (C), and capecitabine (X) are active agents in gastric adenocarcinoma, we conducted a phase II trial to assess the efficacy and tolerability of preoperative DCX in patients with gastric adenocarcinoma. Methods: We enrolled patients with locally advanced gastric adenocarcinoma (clinical T3/4 or N positive) to preoperative DCX repeated every 21 days for three cycles, followed by surgery. The first cohort of 10 patients received docetaxel 35 mg/m2, cisplatin 35mg/m2 on days 1 and 8, with capecitabine 750 mg/m2 twice daily from day 1 to day 14. A subsequent cohort of another 11 patients had dose modifications for docetaxel and cisplatin, both to 30mg/ m2 on days 1 and 8. Results: Twenty-one patients were recruited. Median age was 61 years. Seventy-one percent of patients completed a total of 3 cycles of planned chemotherapy. Fourteen patients have successfully undergone surgery. R0 resection rate was 88%. Pathological complete response (pCR) and near complete response (pnCR) were both 17%. Preoperative radiological assessment showed a partial response rate of 65% after 2 cycles of treatment. Good pathological response (pCR and pnCR) was associated with better event-free survival (26 months vs 12 months, p=0.031). Common grade 3/4 toxicities were diarrhea (38%), neutropenia (30%), stomatitis (14%) and hypokalemia (14%). However, the diarrhea rate was reduced to 15% with dose modifications as mentioned above after 50% of the first cohort of 10 patients developed grade 3/4 diarrhea during the first cycle of chemotherapy. Febrile neutropenia rate was 14%. There was one treatment related death before surgery but no postoperative mortality. Conclusions: Preoperative DCX is highly active with modest toxicity in locally advanced gastric adenocarcinoma. DCX represents an attractive alternative regimen without the need for protracted infusional drug in perioperative chemotherapy for patients with locally advanced gastric adenocarcinoma. Good pathological response is associated with better outcome.

Background: The PI3K-AKT-mTOR signaling pathway is deregulated in a wide variety of cancers. GDC-0980 is a potent, selective, dual inhibitor of class I PI3K and mTOR kinase with in vitro IC50 of 4.8 nM for p110α/p85 and apparent Ki of 17.3 nM for human mTOR. GDC-0980 potently inhibits tumor growth of xenografts and has demonstrated activity in preclinical models bearing PI3K mutant, PTEN-null, K-ras mutant, as well as PI3K pathway wild-type tumors in vitro and in vivo. Methods: Two Phase I dose escalation studies were initiated using a 3+3 design in patients (pts) with solid tumors or non-Hodgkin's lymphoma who had progressed on, or were intolerant of, standard therapy. In study PIM4604g, GDC-0980 is administered as a single oral dose followed by a 1-week PK sampling period, and then administered daily (QD) on a 3-week on/1-week off schedule. Steady-state PK is evaluated after 1 week of continuous dosing. A second trial, PIM4605g, evaluating a once weekly (QW) dosing of GDC-0980 with a 4-week cycle was also initiated with a focus on PD evaluation using mandatory tumor biopsies and imaging. Immunohistochemical assays for pS6 PD marker evaluation were developed for clinical evaluation of pre- and post-dose tumor biopsies. Surrogate PD assays include an assessment of pAKT levels in platelet-rich plasma (PRP) coinciding with PK evaluation in both studies and an evaluation of tumor biopsies for marker modulation in PIM4605g. Results: As of September 2009, a total of 15 patients have been treated in the two Phase I studies. Nine pts were treated in three successive cohorts of 2 mg, 4 mg, and 8 mg GDC-0980 QD in PIM4604g, and 6 pts were treated in the first cohort with 6 mg GDC-0980 QW in PIM4605g. GDC-0980 has been generally well tolerated. There have been no dose-limiting toxicities and no drug-related Grade ≥ 3 events reported in either study. Preliminary PK data suggests that GDC-0980 is rapidly absorbed with dose-appropriate increases in Cmax and AUC under fasting conditions. Preliminary surrogate PD data show decreases in pAKT levels in PRP reflective of drug levels in plasma. Preliminary data from comparison of tumor biopsies obtained at baseline and following administration of GDC-0980 demonstrate a > 50% decrease in pS6 staining by immunostaining consistent with downstream modulation of the PI3K pathway. Conclusions: GDC-0980 is a potent, oral, dual PI3K/mTOR inhibitor with promising preclinical activity. No significant toxicities have been observed to date in these ongoing Phase I studies at exposures producing PD modulation in surrogate tissue and tumor. Favorable preliminary PK profiles have been observed at initial dose levels. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B137.

Background Regorafenib, a multi-kinase inhibitor, is used in the treatment of patients with metastatic colorectal cancer refractory to standard therapy. However, this benefit was limited to 1.4 months improvement in overall survival, with more than half of patients experiencing grade 3 to 4 adverse events. We aim to elucidate the pharmacodynamic effects of regorafenib in metastatic colorectal cancer and discover potential biomarkers that may predict clinical benefit. Methods Patients with metastatic colorectal adenocarcinoma refractory to standard therapy with tumours amenable to biopsy were eligible for the study. Regorafenib was administered orally at 160 mg daily for 3 out of 4 weeks with tumour assessment every 2 cycles. Metabolic response was assessed by FDG PET-CT scans (pre-treatment and day 15); paired tumour biopsies (pre-treatment and day 21 post-treatment) were sampled for immunohistochemistry and proteomic profiling analyses. Plasma circulating cell free DNA was quantified serially before and after treatment. Results There were 2(6%) partial responses out of 35 patients, and 8(23%) patients had stable disease for more than 7 months. Adverse event profile was similar to reported data. Recurrent somatic mutations in K-RAS, PIK3CA and BRAF were detected in plasma circulating cell free DNA in 14 patients; some mutations were not found in archival tumour. Total plasma circulating cell free DNA inversely correlated with progression free survival (PFS), and presence of KRAS mutations associated with shorter PFS. Immunohistochemistry of pre- and post- treatment biopsies showed majority of patients had downregulation of phosphorylated-VEGFR2, podoplanin, phosphorylated-AKT, Ki-67 and upregulation of the MEK-ERK axis, phosphorylated-C-MET, phosphorylated-SRC, phosphorylated-STAT3 and phosphorylated-JUN. Proteomic analysis of fine needle tumour aspirates showed down-regulation of PI3K was associated with longer PFS. Conclusion Plasma circulating cell free DNA may yield potential predictive biomarkers of regorafenib treatment. Downregulation of the PI3K-AKT axis may be an important predictor of clinical benefit. Electronic supplementary material The online version of this article (doi:10.1186/s12967-015-0405-4) contains supplementary material, which is available to authorized users.