J. Randolph Hecht

The molecular evolution of acquired resistance to targeted EGFR blockade in colorectal cancers

Colorectal tumours that are wild type for KRAS are often sensitive to EGFR blockade, but almost always develop resistance within several months of initiating therapy. The mechanisms underlying this acquired resistance to anti-EGFR antibodies are largely unknown. This situation is in marked contrast to that of small-molecule targeted agents, such as inhibitors of ABL, EGFR, BRAF and MEK, in which mutations in the genes encoding the protein targets render the tumours resistant to the effects of the drugs. The simplest hypothesis to account for the development of resistance to EGFR blockade is that rare cells with KRAS mutations pre-exist at low levels in tumours with ostensibly wild-type KRAS genes. Although this hypothesis would seem readily testable, there is no evidence in pre-clinical models to support it, nor is there data from patients. To test this hypothesis, we determined whether mutant KRAS DNA could be detected in the circulation of 28 patients receiving monotherapy with panitumumab, a therapeutic anti-EGFR antibody. We found that 9 out of 24 (38%) patients whose tumours were initially KRAS wild type developed detectable mutations in KRAS in their sera, three of which developed multiple different KRAS mutations. The appearance of these mutations was very consistent, generally occurring between 5 and 6 months following treatment. Mathematical modelling indicated that the mutations were present in expanded subclones before the initiation of panitumumab treatment. These results suggest that the emergence of KRAS mutations is a mediator of acquired resistance to EGFR blockade and that these mutations can be detected in a non-invasive manner. They explain why solid tumours develop resistance to targeted therapies in a highly reproducible fashion.

Addition of Bevacizumab to Bolus Fluorouracil and Leucovorin in First-Line Metastatic Colorectal Cancer: Results of a Randomized Phase II Trial

PURPOSE Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, increases survival when combined with irinotecan-based chemotherapy in first-line treatment of metastatic colorectal cancer (CRC). This randomized, phase II trial compared bevacizumab plus fluorouracil and leucovorin (FU/LV) versus placebo plus FU/LV as first-line therapy in patients considered nonoptimal candidates for first-line irinotecan. PATIENTS AND METHODS Patients had metastatic CRC and one of the following characteristics: age > or = 65 years, Eastern Cooperative Oncology Group performance status 1 or 2, serum albumin < or = 3.5 g/dL, or prior abdominal/pelvic radiotherapy. Patients were randomly assigned to FU/LV/placebo (n = 105) or FU/LV/bevacizumab (n = 104). The primary end point was overall survival. Secondary end points were progression-free survival, response rate, response duration, and quality of life. Safety was also assessed. RESULTS Median survival was 16.6 months for the FU/LV/bevacizumab group and 12.9 months for the FU/LV/placebo group (hazard ratio, 0.79; P = .16). Median progression-free survival was 9.2 months (FU/LV/bevacizumab) and 5.5 months (FU/LV/placebo); hazard ratio was 0.50; P = .0002. Response rates were 26.0% (FU/LV/bevacizumab) and 15.2% (FU/LV/placebo) (P = .055); duration of response was 9.2 months (FU/LV/bevacizumab) and 6.8 months (FU/LV/placebo); hazard ratio was 0.42; P = .088. Grade 3 hypertension was more common with bevacizumab treatment (16% v 3%) but was controlled with oral medication and did not cause study drug discontinuation. CONCLUSION Addition of bevacizumab to FU/LV as first-line therapy in CRC patients who were not considered optimal candidates for first-line irinotecan treatment provided clinically significant patient benefit, including statistically significant improvement in progression-free survival.

A Randomized Phase IIIB Trial of Chemotherapy, Bevacizumab, and Panitumumab Compared With Chemotherapy and Bevacizumab Alone for Metastatic Colorectal Cancer

PURPOSE Panitumumab, a fully human antibody targeting the epidermal growth factor receptor, is active in patients with metastatic colorectal cancer (mCRC). This trial evaluated panitumumab added to bevacizumab and chemotherapy (oxaliplatin- and irinotecan-based) as first-line treatment for mCRC. PATIENTS AND METHODS Patients were randomly assigned within each chemotherapy cohort to bevacizumab and chemotherapy with or without panitumumab 6 mg/kg every 2 weeks. The primary end point was progression-free survival (PFS) within the oxaliplatin cohort. Tumor assessments were performed every 12 weeks and reviewed centrally. RESULTS A total of 823 and 230 patients were randomly assigned to the oxaliplatin and irinotecan cohorts, respectively. Panitumumab was discontinued after a planned interim analysis of 812 oxaliplatin patients showed worse efficacy in the panitumumab arm. In the final analysis, median PFS was 10.0 and 11.4 months for the panitumumab and control arms, respectively (HR, 1.27; 95% CI, 1.06 to 1.52); median survival was 19.4 months and 24.5 months for the panitumumab and control arms, respectively. Grade 3/4 adverse events in the oxaliplatin cohort (panitumumab v control) included skin toxicity (36% v 1%), diarrhea (24% v 13%), infections (19% v 10%), and pulmonary embolism (6% v 4%). Increased toxicity without evidence of improved efficacy was observed in the panitumumab arm of the irinotecan cohort. KRAS analyses showed adverse outcomes for the panitumumab arm in both wild-type and mutant groups. CONCLUSION The addition of panitumumab to bevacizumab and oxaliplatin- or irinotecan-based chemotherapy results in increased toxicity and decreased PFS. These combinations are not recommended for the treatment of mCRC in clinical practice.

Multicenter Phase II Study of the Oral MEK Inhibitor, CI-1040, in Patients With Advanced Non-Small-Cell Lung, Breast, Colon, and Pancreatic Cancer

PURPOSE This multicenter, open-label, phase II study was undertaken to assess the antitumor activity and safety of the oral mitogen-activated extracellular signal regulated kinase kinase (MEK) inhibitor, CI-1040, in breast cancer, colon cancer, non-small-cell lung cancer (NSCLC), and pancreatic cancer. PATIENTS AND METHODS Patients with advanced colorectal, NSCLC, breast, or pancreatic cancer received oral CI-1040 continuously at 800 mg bid. All patients had measurable disease at baseline, a performance status of 2 or less, and adequate bone marrow, liver, and renal function. Expression of pERK, pAkt, and Ki-67 was assessed in archived tumor specimens by quantitative immunohistochemistry. RESULTS Sixty-seven patients with breast (n = 14), colon (n = 20), NSCLC (n = 18), and pancreatic (n = 15) cancer received a total of 194 courses of treatment (median, 2.0 courses; range, one to 14 courses). No complete or partial responses were observed. Stable disease (SD) lasting a median of 4.4 months (range, 4 to 18 months) was confirmed in eight patients (one breast, two colon, two pancreas, and three NSCLC patients). Treatment was well tolerated, with 81% of patients experiencing toxicities of grade 2 or less severity. Most common toxicities included diarrhea, nausea, asthenia, and rash. A mild association (P < .055) between baseline pERK expression in archived tumor specimens and SD was observed. CONCLUSION CI-1040 was generally well tolerated but demonstrated insufficient antitumor activity to warrant further development in the four tumors tested. PD 0325901, a second generation MEK inhibitor, has recently entered clinical development and, with significantly improved pharmacologic and pharmaceutical properties compared with CI-1040, it may better test the therapeutic potential of MEK inhibition in cancer.

PEAK: A Randomized, Multicenter Phase II Study of Panitumumab Plus Modified Fluorouracil, Leucovorin, and Oxaliplatin (mFOLFOX6) or Bevacizumab Plus mFOLFOX6 in Patients With Previously Untreated, Unresectable, Wild-Type KRAS Exon 2 Metastatic Colorectal Cancer

PURPOSE To evaluate panitumumab plus modified fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) or bevacizumab plus mFOLFOX6 in patients with previously untreated wild-type (WT) KRAS exon 2 (codons 12 and 13) metastatic colorectal cancer (mCRC). A prespecified secondary objective was to assess treatment effects in an extended RAS analysis that included exons 2, 3, and 4 of KRAS and NRAS. PATIENTS AND METHODS Patients with WT KRAS exon 2 tumors were randomly assigned at a one-to-one ratio to panitumumab plus mFOLFOX6 or bevacizumab plus mFOLFOX6. The primary end point was progression-free survival (PFS); secondary end points included overall survival (OS) and safety. RESULTS Of 285 randomly assigned patients, 278 received treatment. In the WT KRAS exon 2 intent-to-treat group, PFS was similar between arms (hazard ratio [HR], 0.87; 95% CI, 0.65 to 1.17; P = .353). Median OS was 34.2 and 24.3 months in the panitumumab and bevacizumab arms, respectively (HR, 0.62; 95% CI, 0.44 to 0.89; P = .009). In the WT RAS subgroup (WT exons 2, 3, and 4 of KRAS and NRAS), PFS favored the panitumumab arm (HR, 0.65; 95% CI, 0.44 to 0.96; P = .029). Median OS was 41.3 and 28.9 months (HR, 0.63; 95% CI, 0.39 to 1.02; P = .058) in the panitumumab and bevacizumab arms, respectively. Treatment discontinuation rates because of adverse events were similar between arms. CONCLUSION PFS was similar and OS was improved with panitumumab relative to bevacizumab when combined with mFOLFOX6 in patients with WT KRAS exon 2 tumors. Patients with WT RAS tumors seemed to experience more clinical benefit with anti-epidermal growth factor receptor therapy.

Bevacizumab plus oxaliplatin-based chemotherapy as adjuvant treatment for colon cancer (AVANT): a phase 3 randomised controlled trial

BACKGROUND Bevacizumab improves the efficacy of oxaliplatin-based chemotherapy in metastatic colorectal cancer. Our aim was to assess the use of bevacizumab in combination with oxaliplatin-based chemotherapy in the adjuvant treatment of patients with resected stage III or high-risk stage II colon carcinoma. METHODS Patients from 330 centres in 34 countries were enrolled into this phase 3, open-label randomised trial. Patients with curatively resected stage III or high-risk stage II colon carcinoma were randomly assigned (1:1:1) to receive FOLFOX4 (oxaliplatin 85 mg/m(2), leucovorin 200 mg/m(2), and fluorouracil 400 mg/m(2) bolus plus 600 mg/m(2) 22-h continuous infusion on day 1; leucovorin 200 mg/m(2) plus fluorouracil 400 mg/m(2) bolus plus 600 mg/m(2) 22-h continuous infusion on day 2) every 2 weeks for 12 cycles; bevacizumab 5 mg/kg plus FOLFOX4 (every 2 weeks for 12 cycles) followed by bevacizumab monotherapy 7·5 mg/kg every 3 weeks (eight cycles over 24 weeks); or bevacizumab 7·5 mg/kg plus XELOX (oxaliplatin 130 mg/m(2) on day 1 every 2 weeks plus oral capecitabine 1000 mg/m(2) twice daily on days 1-15) every 3 weeks for eight cycles followed by bevacizumab monotherapy 7·5 mg/kg every 3 weeks (eight cycles over 24 weeks). Block randomisation was done with a central interactive computerised system, stratified by geographic region and disease stage. Surgery with curative intent occurred 4-8 weeks before randomisation. The primary endpoint was disease-free survival, analysed for all randomised patients with stage III disease. This study is registered with ClinicalTrials.gov, number NCT00112918. FINDINGS Of the total intention-to-treat population (n=3451), 2867 patients had stage III disease, of whom 955 were randomly assigned to receive FOLFOX4, 960 to receive bevacizumab-FOLFOX4, and 952 to receive bevacizumab-XELOX. After a median follow-up of 48 months (range 0-66 months), 237 patients (25%) in the FOLFOX4 group, 280 (29%) in the bevacizumab-FOLFOX4 group, and 253 (27%) in the bevacizumab-XELOX group had relapsed, developed a new colon cancer, or died. The disease-free survival hazard ratio for bevacizumab-FOLFOX4 versus FOLFOX4 was 1·17 (95% CI 0·98-1·39; p=0·07), and for bevacizumab-XELOX versus FOLFOX4 was 1·07 (0·90-1·28; p=0·44). After a minimum follow-up of 60 months, the overall survival hazard ratio for bevacizumab-FOLFOX4 versus FOLFOX4 was 1·27 (1·03-1·57; p=0·02), and for bevacizumab-XELOX versus FOLFOX4 was 1·15 (0·93-1·42; p=0·21). The 573 patients with high-risk stage II cancer were included in the safety analysis. The most common grade 3-5 adverse events were neutropenia (FOLFOX4: 477 [42%] of 1126 patients, bevacizumab-FOLFOX4: 416 [36%] of 1145 patients, and bevacizumab-XELOX: 74 [7%] of 1135 patients), diarrhoea (110 [10%], 135 [12%], and 181 [16%], respectively), and hypertension (12 [1%], 122 [11%], and 116 [10%], respectively). Serious adverse events were more common in the bevacizumab groups (bevacizumab-FOLFOX4: 297 [26%]; bevacizumab-XELOX: 284 [25%]) than in the FOLFOX4 group (226 [20%]). Treatment-related deaths were reported in one patient receiving FOLFOX4, two receiving bevacizumab-FOLFOX4, and five receiving bevacizumab-XELOX. INTERPRETATION Bevacizumab does not prolong disease-free survival when added to adjuvant chemotherapy in resected stage III colon cancer. Overall survival data suggest a potential detrimental effect with bevacizumab plus oxaliplatin-based adjuvant therapy in these patients. On the basis of these and other data, we do not recommend the use of bevacizumab in the adjuvant treatment of patients with curatively resected stage III colon cancer. FUNDING Genentech, Roche, and Chugai.

Phase III Comparison of Two Irinotecan Dosing Regimens in Second-Line Therapy of Metastatic Colorectal Cancer

PURPOSE Randomized trials in fluorouracil (FU)-refractory colorectal cancer demonstrate significant survival advantages for patients receiving irinotecan. We prospectively compared the efficacy and tolerability of two irinotecan regimens (once a week for 4 weeks followed by a 2-week rest period [weekly] v once every 3 weeks) in such patients. PATIENTS AND METHODS This multicenter, open-label, phase III study randomly assigned patients in a 1:2 ratio to irinotecan given either weekly (125 mg/m(2)) or once every 3 weeks (350 mg/m(2), or 300 mg/m(2) in patients who were >/= 70 years of age, who had Eastern Cooperative Oncology Group performance status equal to 2, or who had prior pelvic irradiation). RESULTS With median follow-up of 15.8 months, there was no significant difference in 1-year survival (46% v 41%, respectively; P =.42), median survival (9.9 v 9.9 months, respectively; P =.43), or median time to progression (4.0 v 3.0 months, respectively; P =.54) between the two regimens. Grade 3/4 diarrhea occurred in 36% of patients treated weekly and in 19% of those treated once every 3 weeks (P =.002). Grade 3/4 neutropenia occurred in 29% of patients treated weekly and 34% of those treated once every 3 weeks (P =.35). Treatment-related mortality occurred in five patients (5.3%) receiving irinotecan weekly and three patients (1.6%) given therapy once every 3 weeks (P =.12). Global quality of life was not statistically different between treatment groups. CONCLUSION Irinotecan schedules of weekly and of once every 3 weeks demonstrated similar efficacy and quality of life in patients with FU-refractory, metastatic colorectal cancer. The regimen of once every 3 weeks was associated with a significantly lower incidence of severe diarrhea.

Panitumumab monotherapy in patients with previously treated metastatic colorectal cancer.

The safety and efficacy of the fully human antibody panitumumab was evaluated in patients with metastatic colorectal cancer refractory to available therapies.

Association of K-ras Mutational Status and Clinical Outcomes in Patients with Metastatic Colorectal Cancer Receiving Panitumumab Alone

BACKGROUND Identifying predictive biomarkers is important to optimally treat patients. This analysis evaluated the association of K-ras, BRAF, and PIK3CA gene mutations with tumor resistance to panitumumab alone. PATIENTS AND METHODS From 3 phase II panitumumab metastatic colorectal cancer (mCRC) studies, 62 of 533 patient samples were available. Mutations were identified from genomic DNA by sequencing. RESULTS Of the 62 samples, 24 (38.7%) harbored a K-ras mutation, and 38 (61.3%) were wild type. In the wild-type K-ras group, 11% of patients had a partial response (PR), 53% had stable disease (SD), and 37% had progressive disease (PD). In the mutant K-ras group, 21% of patients had SD, and 79% of patients had PD; there were no responses. The absence of a K-ras mutation was associated with response to panitumumab (PR vs. SD vs. PD; P = .0028). The hazard ratio for wild-type versus mutant K-ras was 0.4 (95% CI, 0.2-0.7) for progression-free survival and 0.5 (95% CI, 0.3-0.9) for overall survival. Four patients had a V600E BRAF mutation, and 2 patients had a PIK3CA mutation. CONCLUSION These data suggest that patients with mCRC with activating K-ras mutations are less likely to respond to panitumumab alone. The small sample size limits us from defining a predictive role of PIK3CA and BRAF mutations for panitumumab treatment.

Lapatinib, a dual EGFR and HER2 kinase inhibitor, selectively inhibits HER2-amplified human gastric cancer cells and is synergistic with trastuzumab in vitro and in vivo.

Purpose: HER2 amplification occurs in 18% to 27% of gastric and gastroesophageal junction cancers. Lapatinib, a potent ATP-competitive inhibitor simultaneously inhibits both EGFR and HER2. To explore the role of HER family biology in upper gastrointestinal cancers, we evaluated the effect of lapatinib, erlotinib, and trastuzumab in a panel of molecularly characterized human upper gastrointestinal cancer cell lines and xenografts. Experimental Design: EGFR and HER2 protein expression were determined in a panel of 14 human upper gastrointestinal cancer cell lines and HER2 status was assessed by fluorescent in situ hybridization. Dose-response curves were generated to determine sensitivity to lapatinib, erlotinib, and trastuzumab. In HER2-amplified cells, the combination of trastuzumab and lapatinib was evaluated using the median effects principal. The efficacy of lapatinib, trastuzumab, or the combination was examined in HER2-amplified xenograft models. Results: Lapatinib had concentration-dependent antiproliferative activity across the panel with the greatest effects in HER2-amplified cells. There was no association between EGFR protein expression and sensitivity to any of the HER-targeted agents. Cell cycle analysis revealed that lapatinib induced G1 arrest in sensitive lines and phosphorylated AKT and phosphorylated ERK were decreased in response to lapatinib as well. The combination of lapatinib and trastuzumab was highly synergistic in inhibiting cell growth with a combination index of <1. The combination also induced greater decreases in AKT and ERK activation, G0-G1 cell cycle arrest, and increased rates of apoptosis. In vivo studies showed that the combination of lapatinib and trastuzumab had greater antitumor efficacy than either drug alone. Conclusion: Together, these data suggest that lapatinib has activity in HER2-amplified upper gastrointestinal cancer and supports the ongoing clinical investigation of lapatinib in patients with HER2-amplified disease. Clin Cancer Res; 16(5); 1509–19