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Background: Immune check-point blockade (ICB) has shown clinical benefit in mismatch repair-deficient/microsatellite instability high metastatic colorectal cancer (mCRC) but not in mismatch repair-proficient/microsatellite stable patients. Cancer vaccines with autologous dendritic cells (ADC) could be a complementary therapeutic approach to ICB as this combination has the potential to achieve synergistic effects., Methods: This was a Phase I/II multicentric study with translational sub-studies, to evaluate the safety, pharmacodynamics and anti-tumor effects of Avelumab plus ADC vaccine in heavily pre-treated MSS mCRC patients. Primary objective was to determine the maximum tolerated dose and the efficacy of the combination. The primary end-point was 40% progression-free survival at 6 months with a 2 Simon Stage., Results: A total of 28 patients were screened and 19 pts were included. Combined therapy was safe and well tolerated. An interim analysis (Simon design first-stage) recommended early termination because only 2/19 (11%) patients were disease free at 6 months. Median PFS was 3.1 months [2.1-5.3 months] and overall survival was 12.2 months [3.2-23.2 months]. Stimulation of immune system was observed in vitro but not clinically. The evaluation of basal RNA-seq noted significant changes between pre and post-therapy liver biopsies related to lipid metabolism and transport, inflammation and oxidative stress pathways., Conclusions: The combination of Avelumab plus ADC vaccine is safe and well tolerated but exhibited modest clinical activity. Our study describes, for the first-time, a de novo post-therapy metabolic rewiring, that could represent novel immunotherapy-induced tumor vulnerabilities., (© 2022. The Author(s).)

Background: RAS testing is used to select patients with anti-epidermal growth factor receptor (EGFR) therapies sensitivity in metastatic colorectal cancer (mCRC). However, other biomarkers such as BRAF, PIK3CA/PTEN, and p-IGF-1R+/MMP7+ (double positive [DP] phenotype) have not been prospectively assessed to predict anti-EGFR resistance., Materials and Methods: We designed a multicenter prospective trial (NCT01276379) to evaluate whether the biomarkers BRAF mutation, PIK3CA mutation/PTEN loss, and DP phenotype can improve the prediction for 12-months progression-free survival (PFS) over the use of clinical variables exclusively in patients with RAS wild-type (WT) mCRC treated with standard chemotherapy plus biweekly cetuximab as first-line therapy. The planned sample size was 170 RAS WT patients to detect a 20% difference in 12-month PFS based on the analysis of clinical and selected biomarkers (α = .05, β = .2). The discriminatory capacity of the biomarkers was evaluated using receiver operating characteristic curves., Results: We included 181 RAS WT patients. The biomarker distribution was as follows: BRAF mutant, 20 patients (11%); PIK3CA mutated/PTEN loss, 98 patients (58%); DP, 23 patients (12.7%). The clinical variables in the clinical score were progression status >0, left-sided tumor, and resectable liver metastasis as the only metastatic site. The area under the curve (AUC) of the score containing the clinical variables was 0.67 (95% confidence interval [CI], 0.60-0.75). The AUC of the score with clinical variables and BRAF mutational status was 0.68 (0.61-0.75, p = .37). The AUC of the score with clinical variables and PI3KCA mutation/PTEN status was 0.69 (0.61-0.76, p = .32). The AUC of the score with clinical variables and DP phenotype was 0.66 (0.58-0.73, p = .09)., Conclusion: The addition of BRAF, PIK3CA/PTEN, and DP to a clinical score does not improve the discrimination of 12-month PFS., Implications for Practice: This prospective biomarker design study has important clinical implications because many prospective clinical trials are designed with the hypothesis that BRAF mutation per se and MEK and PIK3CA downstream pathways are critical for colorectal tumor survival. The results lead to the question of whether these pathways should be considered as passengers instead of drivers., Competing Interests: Disclosures of potential conflicts of interest may be found at the end of this article., (© 2019 The Authors. The Oncologist published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)

Introduction: The coexpression of pIGF-1R and MMP-7 (double-positive phenotype, DP) correlates with poor overall survival (OS) in KRAS wild-type (WT) (exon 2) metastatic colorectal cancer (mCRC) patients treated with irinotecan-cetuximab in second/third line., Methods: We analyzed two prospective biomarker design trials of newly diagnosed RAS-WT mCRC patients treated with panitumumab-FOLFOX6 (PULSE trial; NCT01288339) or cetuximab plus either FOLFOX6/FOLFIRI (POSIBA trial; NCT01276379). The main exposure was DP phenotype (DP/non-DP), as assessed by two independent pathologists. DP cases were defined by immunohistochemistry as >70% expression of moderate or strong intensity for both MMP-7 and pIGF-1R. Primary endpoint: progression-free survival (PFS); secondary endpoints: OS and response rate. PFS and OS were adjusted by baseline characteristics using multivariate Cox models., Results: We analyzed 67 patients (30 non-DP, 37 DP) in the PULSE trial and 181 patients in the POSIBA trial (158 non-DP, 23 DP). Response rates and PFS were similar between groups in both studies. DP was associated with prolonged OS in PULSE (adjusted HR: 0.23; 95%CI: 0.11-0.52; P=.0004) and with shorter OS in POSIBA (adjusted HR: 1.67; 95%CI: 0.96-2.90; P=.07)., Conclusion: A differential effect of anti-EGFRs on survival by DP phenotype was observed. Panitumumab might be more beneficial for RAS-WT mCRC patients with DP phenotype, whereas cetuximab might improve OS in non-DP., (Copyright © 2018. Published by Elsevier Inc.)

Background: Although chemotherapy is the cornerstone treatment for patients with metastatic colorectal cancer (mCRC), acquired chemoresistance is common and constitutes the main reason for treatment failure. Monoclonal antibodies against insulin-like growth factor-1 receptor (IGF-1R) have been tested in pre-treated mCRC patients, but results have been largely deceiving., Methods: We analysed time to progression, overall survival, and the mutational status of RAS, BRAF and nuclear p-IGF-1R expression by immunohistochemistry, in 470 metastatic CRC patients. The effect of IGF-1R activation and distribution was also assessed using cellular models of CRC and RNAi for functional validation., Results: Nuclear IGF-1R increased in metastatic tumours compared to paired untreated primary tumours, and significantly correlated with poor overall survival in mCRC patients. In vitro, chemo-resistant cell lines presented significantly higher levels of IGF-1R expression within the nuclear compartment, and PIAS3, a protein implicated also in the sumoylation process of intranuclear proteins, contributed to IGF-1R nuclear sequestration, highlighting the essential role of PIAS3 in this process. Intriguingly, we observed that ganitumab, an IGF-1R blocking-antibody used in several clinical trials, and dasatinib, an SRC inhibitor, increased the nuclear localisation of IGF-1R., Conclusions: Our study demonstrates that IGF-1R nuclear location might lead to chemotherapy and targeted agent resistance.

Colorectal cancer (CRC) is one of the world's most common cancers, and has one of the highest mortality rates. The last few decades have seen great progress in preventing, diagnosing and treating this disease, providing undeniable impact on patients' prognosis and quality of life. At all these stages of CRC management, imaging techniques play an essential role. This article reviews some important issues concerning the use of various radiological techniques in the screening, diagnosis, staging, assessment of treatment response, and follow-up of patients with CRC. It also includes a number of practical recommendations on indications for use, technical requirements, minimum information required in the radiology report, evaluation criteria for the response to various drugs, and the recommended frequency at which different examinations should be performed. This consensus statement is the result of cooperation between the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Radiology (SERAM).

Introduction: Endoscopic resection is the common treatment in pT1 colorectal adenocarcinoma whenever possible. The presence of adverse histological factors requires subsequent lymph node evaluation., Materials and Methods: We selected 29 colorectal pT1 adenocarcinoma including endoscopic polypectomies and the corresponding surgical specimens. All histologic parameters associated with N+ were evaluated by 2 pathologists, including: tumor differentiation grade, depth of invasion in the submucosa, angiolymphatic invasion (ALI), perineural invasion, chronic inflammation, tumor budding, poorly differentiated cluster, pre-existing adenoma, tumor border, and endoscopic resection margin. Univariate and multivariate logistic regression analysis were performed to assess the individual capacity of each variable to predict N+., Results: In the univariate analysis, rectal tumor localization, ALI and poorly differentiated cluster was significantly associated with N+. Among the significant parameters, ALI had the highest area under the ROC curve (0.875). Multivariate analysis showed no independent variables associated with N+., Conclusions: We confirm that ALI and the presence of poorly differentiated cluster are frequently associated with N+ in early colorectal cancer. Consequently, these parameters should be routinely evaluated by pathologists., (Copyright © 2015 Elsevier España, S.L.U. and AEEH y AEG. All rights reserved.)

Lipid metabolism plays an essential role in carcinogenesis due to the requirements of tumoral cells to sustain increased structural, energetic and biosynthetic precursor demands for cell proliferation. We investigated the association between expression of lipid metabolism-related genes and clinical outcome in intermediate-stage colon cancer patients with the aim of identifying a metabolic profile associated with greater malignancy and increased risk of relapse. Expression profile of 70 lipid metabolism-related genes was determined in 77 patients with stage II colon cancer. Cox regression analyses using c-index methodology was applied to identify a metabolic-related signature associated to prognosis. The metabolic signature was further confirmed in two independent validation sets of 120 patients and additionally, in a group of 264 patients from a public database. The combined analysis of these 4 genes, ABCA1, ACSL1, AGPAT1 and SCD, constitutes a metabolic-signature (ColoLipidGene) able to accurately stratify stage II colon cancer patients with 5-fold higher risk of relapse with strong statistical power in the four independent groups of patients. The identification of a group of 4 genes that predict survival in intermediate-stage colon cancer patients allows delineation of a high-risk group that may benefit from adjuvant therapy, and avoids the toxic and unnecessary chemotherapy in patients classified as low-risk group.

The FAS/FASL system, comprising membrane-bound (mFAS and mFASL) and soluble forms (sFAS and sFASL), has been related to apoptosis driven by chemotherapy administration. In vitro experiments show chemotherapy upregulating membrane-bound forms, leading to an increase of receptor availability (at 24-72 h) and favoring apoptosis. The regulatory effect of chemotherapy on sFAS in patients has never been explored prospectively in advanced colorectal cancer (ACRC). We performed a pharmacodynamic study to address sFAS/sFASL variation. A prospective phase II translational multicenter study was designed to evaluate progression-free rate (PFR) in patients with ACRC treated with irinotecan and cetuximab in third-line therapy. The effect of sFAS was studied in vitro in colorectal cancer cell lines. Our results showed that statistically significant changes were observed in sFAS at 24-72 h compared to baseline levels in the pharmacodynamic study. Of the 93 patients enrolled in the prospective study in third-line therapy with cetuximab-irinotecan, 85 were evaluated for sFAS/sFASL changes at 48 h. There was no difference in PFR at 4 months between patients with sFAS and sFASL changes. In vitro analysis showed that although LoVo cell lines were sensitive to oxaliplatin and fluorouracil due to modulation of sFAS and FAS, HT29 lines were not. In summary, chemotherapy regulates FAS soluble fractions in vitro and in vivo, but does not predict PFR in ACRC patients undergoing third-line therapy with the combination of cetuximab and irinotecan.

Background: The Maintenance in Colorectal Cancer trial was a phase III study to assess maintenance therapy with single-agent bevacizumab versus bevacizumab plus chemotherapy in patients with metastatic colorectal cancer. An ancillary study was conducted to evaluate the circulating tumor cell (CTC) count as a prognostic and/or predictive marker for efficacy endpoints., Patients and Methods: One hundred eighty patients were included. Blood samples were obtained at baseline and after three cycles. CTC enumeration was carried out using the CellSearch® System (Veridex LLC, Raritan, NJ). Computed tomography scans were performed at cycle 3 and 6 and every 12 weeks thereafter for tumor response assessment., Results: The median progression-free survival (PFS) interval for patients with a CTC count ≥3 at baseline was 7.8 months, versus the 12.0 months achieved by patients with a CTC count <3 (p = .0002). The median overall survival (OS) time was 17.7 months for patients with a CTC count ≥3, compared with 25.1 months for patients with a lower count (p = .0059). After three cycles, the median PFS interval for patients with a low CTC count was 10.8 months, significantly longer than the 7.5 months for patients with a high CTC count (p = .005). The median OS time for patients with a CTC count <3 was significantly longer than for patients with a CTC count ≥3, 25.1 months versus 16.2 months, respectively (p = .0095)., Conclusions: The CTC count is a strong prognostic factor for PFS and OS outcomes in metastatic colorectal cancer patients.

Purpose: The aim of this phase III trial was to compare the efficacy and safety of bevacizumab alone with those of bevacizumab and capecitabine plus oxaliplatin (XELOX) as maintenance treatment following induction chemotherapy with XELOX plus bevacizumab in the first-line treatment of patients with metastatic colorectal cancer (mCRC)., Patients and Methods: Patients were randomly assigned to receive six cycles of bevacizumab, capecitabine, and oxaliplatin every 3 weeks followed by XELOX plus bevacizumab or bevacizumab alone until progression. The primary endpoint was the progression-free survival (PFS) interval; secondary endpoints were the overall survival (OS) time, objective response rate (RR), time to response, duration of response, and safety., Results: The intent-to-treat population comprised 480 patients (XELOX plus bevacizumab, n = 239; bevacizumab, n = 241); there were no significant differences in baseline characteristics. The median follow-up was 29.0 months (range, 0-53.2 months). There were no statistically significant differences in the median PFS or OS times or in the RR between the two arms. The most common grade 3 or 4 toxicities in the XELOX plus bevacizumab versus bevacizumab arms were diarrhea, hand-foot syndrome, and neuropathy., Conclusion: Although the noninferiority of bevacizumab versus XELOX plus bevacizumab cannot be confirmed, we can reliably exclude a median PFS detriment >3 weeks. This study suggests that maintenance therapy with single-agent bevacizumab may be an appropriate option following induction XELOX plus bevacizumab in mCRC patients.

Background: In the MACRO study, patients with metastatic colorectal cancer (mCRC) were randomised to first-line treatment with 6 cycles of capecitabine and oxaliplatin (XELOX) plus bevacizumab followed by either single-agent bevacizumab or XELOX plus bevacizumab until disease progression. An additional retrospective analysis was performed to define the prognostic value of tumour KRAS status on progression-free survival (PFS), overall survival (OS) and response rates., Methodology/principal Findings: KRAS data (tumour KRAS status and type of mutation) were collected by questionnaire from participating centres that performed KRAS analyses. These data were then cross-referenced with efficacy data for relevant patients in the MACRO study database. KRAS status was analysed in 394 of the 480 patients (82.1%) in the MACRO study. Wild-type (WT) KRAS tumours were found in 219 patients (56%) and mutant (MT) KRAS in 175 patients (44%). Median PFS was 10.9 months for patients with WT KRAS and 9.4 months for patients with MT KRAS tumours (p=0.0038; HR: 1.40; 95% CI:1.12-1.77). The difference in OS was also significant: 26.7 months versus 18.0 months for WT versus MT KRAS, respectively (p=0.0002; HR: 1.55; 95% CI: 1.23-1.96). Univariate and multivariate analyses showed that KRAS was an independent variable for both PFS and OS. Responses were observed in 126 patients (57.5%) with WT KRAS tumours and 76 patients (43.4%) with MT KRAS tumours (p=0.0054; OR: 1.77; 95% CI: 1.18-2.64)., Conclusions/significance: This analysis of the MACRO study suggests a prognostic role for tumour KRAS status in patients with mCRC treated with XELOX plus bevacizumab. For both PFS and OS, KRAS status was an independent factor in univariate and multivariate analyses.

The purpose of the study was to prospectively explore the role of serum MMP-7 as a predictive and prognostic marker of anti-epidermal growth factor receptor (EGFR) therapy and irinotecan efficacy in third-line advanced colorectal cancer therapy. One hundred patients were recruited prospectively from six Spanish hospitals. Patients were treated with biweekly irinotecan 180 mg/m(2) and cetuximab 400 mg/m(2) (loading dose) and weekly cetuximab 250 mg/m(2) until progressive disease or unacceptable toxicity. Baseline MMP-7 was determined using a quantitative solid-phase sandwich ELISA. KRAS and BRAF mutational status were also assessed. The clinical endpoints examined were overall survival (OS), progression-free survival (PFS), and response rate. No association between serum MMP-7 and neither KRAS nor BRAF mutational status was found. The multivariate analysis revealed that MMP-7 predicts PFS both in wild-type (WT) KRAS patients (HR 1.03, 95% CI 1.00-1.06; p = 0.046) and in mutant KRAS patients (HR 1.18, 95% CI 1.01-1.35; p = 0.036). The presence of mutant BRAF was associated with shorter PFS (HR 8.49, 95% CI 2.88-25.0; p < 0.001) and worse OS (HR 3.55, 95% CI 1.39-9.09; p = 0.008) in the subset of WT KRAS patients. Serum MMP-7 is associated with PFS in colorectal patients treated with anti-EGFR therapy as third-line treatment independently of KRAS status.

Background: Irinotecan (CPT-11) and raltitrexed are active against advanced colorectal cancer (ACC), act through different mechanisms, and have only partially overlapping toxicity profiles. Phase I studies have shown that single-agent full doses of both drugs can be safely combined. The aim of this multicenter study was to assess the efficacy and toxicity of the combination in patients with 5-fluorouracil (5-FU)-refractory ACC., Patients and Methods: Between October 1999 and December 2000, 52 patients (31 males, 21 females) with a median age of 62 years (range 39-75) were included and received CPT-11 (350 mg/m(2) as a 60-min infusion) plus raltitrexed (3 mg/m(2) as a 15-min infusion, 1 h after CPT-11), with courses repeated every 21 days. Objective response was assessed after every three courses, and treatment maintained until tumor progression or unacceptable toxicity., Results: A total of 313 cycles were administered, with a median of six cycles per patient (range 1-14). Seven patients (13.5%) achieved a partial response and one a complete response (1.9%), for an overall intention-to-treat response rate of 15.4% (95% confidence interval 6.1% to 27.2%). The incidence of grade 3/4 toxicity was 23.1% for diarrhea, 21.2% for asthenia, 17.3% for neutropenia, 13.4% for emesis and 7.7% for infection. There were no treatment-related deaths. With a median follow-up of 20 months, median survival was 11.9 months and median time to progression was 4.6 months., Conclusions: CPT-11 plus raltitrexed is active in patients with 5-FU-refractory ACC, at the expense of moderate toxicity.

The objective of this study was to evaluate the activity and toxicity of tegafur and uracil (UFT; 1:4 molar ratio) plus leucovorin (LV) in patients with advanced colorectal cancer. One hundred forty-one patients were entered into the study. The treatment schedule consisted of UFT 300 mg/m2/day (in three divided doses) plus oral LV 150 mg/day (50 mg t.i.d.) over 28 days. The treatment cycle was repeated every 5 weeks until progression or unacceptable toxicity was observed. The treatment was interrupted if grade 3/4 toxicity appeared and was resumed at the same dosage on recovery. One hundred thirty-six patients were evaluable for response and 141 were evaluable for toxicity. The response rate was 19.9% (95% confidence interval: 12%-28%). The total number of patients without progression (objective response + stable disease) was 76 (55.9%). The median time to progression was 5.6 months, and the overall survival was 11.6 months. The toxicity profile was low, with 11% of patients experiencing grade 3/4 nausea and vomiting, while 17% had grade 3/4 diarrhea. Oral administration of UFT modulated with LV is a comfortable regimen of chemotherapy for patients with advanced colorectal cancer.

Two studies were carried out to determine the activity and evaluate the toxicity of oral chemotherapy with uracil and tegafur in a 4:1 molar ratio (UFT) plus or minus calcium folinate in elderly patients with advanced colorectal cancer. In one study, 106 patients received a fixed dose of UFT 400 mg/day in two daily doses every 12 hours continuously, plus calcium folinate 45 mg/day administered in three divided doses every 8 hours continuously. In study 2, calcium folinate was omitted, and the dose of UFT was increased to 400 mg/m2/day in two daily doses administered every 12 hours continuously to 95 patients. Treatments for both studies were administered until grade 3 or grade 4 toxicity occurred or disease progressed. The response rate among the 96 available patients in study 1 was 17.7% (95% confidence interval [CI], 10% to 27%); 41 patients (43%) achieved an objective response or stable disease. Overall survival was 13.7 months with a statistically significant difference between patients with no progressive disease and patients with progressive disease (P < .01). In study 2, 62 of 95 patients have now been evaluated for response. The response rate was 21% (95% CI, 13% to 30%); 38 patients (61%) experienced an objective response or stable disease. The overall survival for study 2 has not yet been evaluated. Toxicity was generally mild, consisting of grade 3 nausea/vomiting (6% in study 1 and 2% in study 2), grade 3 or grade 4 diarrhea (11% in study 1 and 7% in study 2), plus one case of grade 3 mucositis in study 1. These findings suggest that chemotherapy with UFT (with or without modulation with calcium folinate) is feasible for elderly patients with advanced colorectal carcinoma.

Background: In a previous phase I-II trial we showed that the maximum tolerable dose (MTD) of 5-fluorouracil (5-FU) in a weekly 48-hour continuous infusion (CI) was 3.5 g/m2. In a subsequent confirmative phase II trial with 85 evaluable patients, a 38.5% response rate was obtained, and a median survival of 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with leucovorin. On this basis we attempted to modulate high-dose 5-FU (3 g/m2) with oral leucovorin (LV) but the regimen was too toxic and the dose had to be reduced. A new phase II trial with 2 g/m2/week plus oral leucovorin was planned., Patients and Methods: From July 1992 to June 1994, 110 previously untreated patients with advanced, measurable colorectal cancer were included in a multicenter study. The patients received, on an outpatient basis, 5-FU 2 g/m2 by continuous infusion for 48 hours once a week until progression or the appearance of toxic effects. Oral leucovorin (60 mg every six hours) was also given during the 5-FU infusion., Results: Patients received a median dose intensity of 5-FU of 1.6 g/m2/week (range 0.9-2). Three complete responses and 36 partial responses were observed. The overall response rate was 37.5% (95% CI, 28% to 46.8%), the median time to progression 7.4 months and median survival 14.5 months. W.H.O. grade 3 diarrhea occurred in 27 patients (24.5%); grade 3 mucositis was observed in 9 (8.1%) patients and grade 4 in one. Grade 3 nausea and vomiting was reported in 13 (11.7%) patients, while grade 3 hand-foot syndrome was detected in only 5 (4.5%). Grade 4 leukopenia occurred in one patient and grade 3-4 thrombocytopenia in two., Conclusions: Oral leucovorin modulation of weekly 48-hour continuous infusion of 5-FU at 2 g/m2 is an active regimen, with diarrhea and mucositis as the main limiting toxic effects. Its antitumor activity does not seem superior to that obtained with a weekly 48-hour continuous infusion of 5-FU alone at a dose of 3.5 g/m2.

Background In a previous phase I to II trial, we have shown that the maximum tolerable dose (MTD) of 5-Fluorouracil (5-FU) in 48-hour continuous infusion (CI) weekly was 3.5 gr/m2. In a subsequent confirmative phase II trial with 85 evaluable patients, a 38.5% response rate was obtained and the median survival reached was 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with Leucovorin. On this basis we tried to modulate high-dose 5-FU (3 gr/m2) with oral leucovorin (LV) but the regimen was too toxic and the dose had to be reduced. A new phase II trial with 2 g/m2/week plus oral leucovorin was planned. Patients received a median dose intensity of 5-FU of 1.6 g/m2/week (range 0.9-2). Three complete responses and 36 partial responses were observed. Overall response rate was 37.5% (95% CI, 28% to 46.8%). Median time to progression has been 7.4 months, and median survival 14.4 months. WHO grade 3 diarrhea was seen in 27 patients (24.5%). Grade 3 mucositis was also seen in 9 (8.1%) patients, and grade 4 was observed in one. Grade 3 nausea and vomiting was reported in 13 (11.7%) patients. Grade 3 hand-foot syndrome was detected in only 5 (4.5%) patients. Grade 4 leukopenia was observed in 1 case and grade 3 to 4 thrombocytopenia was observed in two cases, respectively. Oral leucovorin modulation of weekly 48-hour continuous infusion of 5-FU at 2 g/m2 is an active regimen, with diarrhea and mucositis as main limiting toxicities. Its antitumor activity does not seem superior to that obtained with a weekly 48 hour continuous infusion of 5-FU alone at a dose of 3.5 g/m2.

Background: In a previous Phase II trial, the authors showed that a weekly continuous infusion of 5-fluorouracil (5-FU) at a dose of 3.5 g/m2 for 48 hours is an active treatment for advanced colorectal cancer. The overall response rate was 38.5%, and the median survival was 12 months. These data were comparable to those achieved by biochemical modulation of 5-FU with leucovorin. To study the modulation of this weekly, high dose, continuous infusion 5-FU with oral leucovorin, a new Phase II trial was planned., Methods: From December 1991 to July 1992, 43 previously untreated patients with measurable advanced colorectal cancer were included in a multicenter study. They received on an outpatient basis 5-FU at a weekly dose of 3 g/m2 by continuous infusion for 48 hours until progression or toxicity. Oral leucovorin (60 mg every 6 hours) also was given during the infusion of 5-FU., Results: Patients received a median dose intensity of 5-FU of 2.2 g/m2/week (range, 0.76-3 g/m2/week). One complete response and 11 partial responses were observed. The overall response rate was 29% (95% confidence interval [CI], 16-45%). Median time to progression was 7 months, and the median survival was 15 months. World Health Organization Grades 3 and 4 diarrhea were observed in 19 (45%) and 6 (14%) patients, respectively. Grade 3 mucositis also was observed in 10 (24%) patients, and Grade 4 mucositis was observed in 1. Grade 3 nausea and vomiting were reported in seven (17%) patients. Grade 3 hand-foot syndrome was detected in only two (2.5%) patients. No leukopenia or thrombocytopenia was observed., Conclusions: Oral leucovorin modulation of a weekly 48-hour infusion of 5-FU at a dose of 3 g/m2 of leucovorin is a toxic regimen, always requiring dose reduction, with diarrhea and mucositis as the main limiting toxicities. Its antitumor activity does not seem superior to that observed with a weekly 48-hour infusion of 5-FU alone at a dose of 3.5 g/m2.