Three-month life expectancy as inclusion criterion for clinical trials in advanced pancreatic cancer: is it really a valid tool for patient selection?

PURPOSE: To analyze the 3-month life expectancy rate in pancreatic cancer (PC) patients treated within prospective trials from the German AIO study group. PATIENTS AND METHODS: A pooled analysis was conducted for patients with advanced PC that were treated within five phase II/III studies conducted between 1997 and 2017 (Gem/Cis, Ro96, RC57, ACCEPT, RASH). The primary goal for the current report was to identify the actual 3-month survival rate, a standard inclusion criterion in oncology trials. RESULTS: Overall, 912 patients were included, 83% had metastatic and 17% locally advanced PC; the estimated median overall survival (OS) was 7.1 months. Twenty-one percent of the participants survived < 3 months, with a range from 26% in RC57 to 15% in RASH. Significant predictors for not reaching 3-month OS were > 1 previous treatment line (p < 0.001) and performance status (p < 0.001). CONCLUSIONS: Despite the definition of a life expectancy of > 3 months as a standard inclusion criterion in clinical trials for advanced PC, a significant proportion of study patients does not survive > 3 months. TRIAL REGISTRATION NUMBERS: NCT00440167 (AIO-PK0104), NCT01729481 (RASH), NCT01728818 (ACCEPT).

Efficacy of FOLFIRI plus cetuximab vs FOLFIRI plus bevacizumab in 1st-line treatment of older patients with RAS wild-type metastatic colorectal cancer: an analysis of the randomised trial FIRE-3.

BACKGROUND: The evidence on the efficacy of anticancer therapy is limited in older patients with metastatic colorectal cancer (mCRC). This retrospective analysis of phase III FIRE-3 trial assesses the efficacy of FOLFIRI plus either cetuximab or bevacizumab according to the patients' age and sidedness of primary tumour. METHODS: The study endpoints overall response rate (ORR), progression-free survival (PFS) and overall survival (OS) were compared between younger (<65 years) and older (≥65 years) patients, followed by stratification according to primary tumour sidedness. ORR was compared using Fisher´s exact test, OS and PFS were estimated by the Kaplan-Meier method and compared using the log-rank test. Univariate Cox regression analyses assessed hazard ratios and 95% confidence intervals for OS and PFS. RESULTS: Overall, older patients with RAS WT tumours had a significantly shorter OS when compared to younger patients (25.9 months vs 29.3 months, HR 1.29; P = 0.02). Also the proportion of right-sided tumours was significantly greater in older patients (27.1% vs 17.9%; P = 0.029). Secondary resection rates were numerically higher in younger patients (25.4% vs. 17.6%, P = 0.068) than in older patients. This was primarily seen in the Cetuximab arm, where older patients underwent less likely resection (13.1% vs. 26%; P = 0.02). Older patients with left-sided tumours showed only a trend towards greater efficacy of cetuximab (HR 0.86; P = 0.38). In patients with right-sided primary tumours, older patients did not appear to benefit from cetuximab in contrast to younger patients (≥65 years: 16.6 months vs 23.6 months, HR 1.1; P = 0.87; <65 years: 21.9 months vs 16.4 months HR 1.5; P = 0.31). CONCLUSIONS: In FIRE-3, OS was generally shorter in older patients in comparison to younger patients. This could be explained by the overrepresentation of right-sided tumours and a lower secondary resection rate in older patients. The efficacy of targeted therapy was dependent on tumour sidedness in older patients with RAS WT mCRC. CLINICAL TRIAL: FIRE-3 (NCT00433927).

FOLFIRI plus cetuximab or bevacizumab for advanced colorectal cancer: final survival and per-protocol analysis of FIRE-3, a randomised clinical trial.

BACKGROUND: Cetuximab plus FOLFIRI improved overall survival compared with bevacizumab plus FOLFIRI in KRAS wild-type metastatic colorectal cancer (mCRC) in FIRE-3, but no corresponding benefit was found for progression-free survival. This analysis aimed to determine whether cetuximab improves response and survival versus bevacizumab among response-evaluable patients receiving first-line FOLFIRI for RAS wild-type mCRC and the effect of primary tumour side on outcomes. METHODS: The intent-to-treat population included 593 patients with KRAS exon 2 wild-type mCRC. Further testing identified 400 patients with extended RAS wild-type disease; of these, 352 (88%) who received ≥3 cycles of therapy and had ≥1 post-baseline scan were evaluable for response and constituted the per-protocol population (169 cetuximab and 183 bevacizumab). Patients received 5-fluorouracil, folinic acid and irinotecan (FOLFIRI) with either weekly cetuximab or biweekly bevacizumab given on day 1 of each 14-day cycle until response, progression or toxicity occurred. The primary endpoint was the objective response rate (ORR) in the per-protocol population. Secondary endpoints included overall survival (OS) and progression-free survival (PFS). The effect of primary tumour location was evaluated. RESULTS: Median OS in the RAS wild-type population was 31 vs 26 months in the cetuximab and bevacizumab groups, respectively (HR 0.76, P = 0.012). In the per-protocol population, outcomes favoured cetuximab for ORR (77% vs 65%, P = 0.014) and median OS (33 vs 26 months, HR 0.75, P = 0.011), while PFS was comparable between groups. The advantage of cetuximab over bevacizumab occurred only in patients with left-sided primary tumours. CONCLUSIONS: FOLFIRI plus cetuximab resulted in a significantly higher ORR and longer OS compared to FOLFIRI plus bevacizumab among patients with left-sided tumours. The superior response associated with cetuximab may particularly benefit patients with symptomatic tumours or borderline-resectable metastases. CLINICALTRIALS. GOV IDENTIFIER: NCT00433927.

Exploring the effect of primary tumor sidedness on therapeutic efficacy across treatment lines in patients with metastatic colorectal cancer: analysis of FIRE-3 (AIOKRK0306).

PURPOSE: To assess the impact of primary tumor sidedness on outcome of patients with metastatic colorectal cancer (mCRC) across treatment lines. PATIENTS AND METHODS: Patients of the FIRE-3 trial (initial FOLFIRI plus either cetuximab or bevacizumab) were separately evaluated according to primary tumor site differentiating left-sided (LPT) from right-sided primary tumors (RPT). Efficacy (i.e. progression-free survival (PFS2nd) and overall survival (OS2nd) of second-line therapy) was evaluated by Kaplan-Meier method and compared by log rank test as well as Cox regression analyses. All analyses were also reported according to drug sequences. RESULTS: 411 of 592 patients (69%) with KRAS exon 2 wild-type tumors received 2nd-line therapy has and had available information on primary tumor location, of those 309 patients (75%) presented with LPT. In patients with LPT, PFS2nd was markedly longer than in patients with RPT (6.0 months [95% CI 5.5-6.5] versus 3.8 months [95% CI 2.5-5.2], hazard ratio: 0.61 [95% CI 0.47-0.78], P<0.001). Differences in PFS2nd between study-arms were evident in patients with LPT, but not in patients with RPT (Cox model interaction test, P=0.12). Consistent observations were also made for OS2nd. CONCLUSION: This retrospective analysis of FIRE-3 indicates that efficacy of second-line therapy was significantly greater in patients with left-sided tumors as compared to right-sided tumors. This difference was driven by superior activity of second-line regimens of the initial cetuximab-arm as compared to the initial bevacizumab-arm in left-sided tumors. Our observations confirm the strong prognostic value of primary tumor location in second-line therapy of mCRC.

Relation of early tumor shrinkage (ETS) observed in first-line treatment to efficacy parameters of subsequent treatment in FIRE-3 (AIOKRK0306).

We explored the association of early tumor shrinkage (ETS) and non-ETS with efficacy of first-line and consecutive second-line treatment in patients with KRAS wild-type metastatic colorectal cancer treated in FIRE-3. Assessment of tumor shrinkage was based on the sum of longest diameters of target lesions, evaluated after 6 weeks of treatment. Shrinkage was classified as ETS (shrinkage by ≥ 20%), mETS (shrinkage by 0 to <20%), mPD (minor progression >0 to <20%) and PD (progression ≥20%). Overall survival (OS) was 33.2 (95% CI 28.0-38.4) months in ETS patients, while non-ETS was associated with less favorable outcome (mETS 24.0 (95% CI 21.2-26.9) months, mPD 19.0 (95% CI 13.0-25.0) months, PD 12.8 (95% CI 11.1-14.5) months). Differences in PFS of first-line therapy were less pronounced. ETS subgroups defined in first-line therapy also correlated with efficacy of second-line therapy. Progression-free survival in second-line (PFS2nd) was 6.5 months (5.8-7.2) for ETS, and was 5.6 (95% CI 4.7-6.5) months for mETS, 4.9 (95% CI 3.7-6.1) months for mPD and 3.3 (95% CI 2.3-4.3) months for PD. PFS of first-line and PFS2nd showed a linear correlation (Bravais-Pearson coefficient: 0.16, p = 0.006). While ETS is associated with the most favorable outcome, non-ETS represents a heterogeneous subgroup with distinct characteristics of less favorable initial tumor response to treatment. This is the first analysis to demonstrate that early tumor response observed during first-line FOLFIRI-based therapy may also relate to efficacy of second-line treatment. Early response parameters may serve as stratification factors in trials recruiting pretreated patients.

FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab for metastatic colorectal cancer (FIRE-3): a post-hoc analysis of tumour dynamics in the final RAS wild-type subgroup of this randomised open-label phase 3 trial.

BACKGROUND: FIRE-3 compared first-line 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) plus cetuximab with FOLFIRI plus bevacizumab in patients with KRAS exon 2 wild-type metastatic colorectal cancer. The same study also reported an exploratory analysis of a subgroup of patients with tumours that were wild-type at other RAS genes (KRAS and NRAS exons 2-4). We report here efficacy results for the FIRE-3 final RAS (KRAS/NRAS, exons 2-4) wild-type subgroup. Moreover, new metrics of tumour dynamics were explored during a centralised radiological review to investigate how FOLFIRI plus cetuximab conferred overall survival benefit in the absence of differences in investigator-assessed objective responses and progression-free survival. METHODS: FIRE-3 was a randomised phase 3 trial comparing FOLFIRI plus cetuximab with FOLFIRI plus bevacizumab in the first-line treatment of patients with KRAS exon 2 wild-type metastatic colorectal cancer. The primary endpoint of the FIRE-3 study was the proportion of patients achieving an objective response according to Response Evaluation Criteria In Solid Tumors (RECIST) 1.0 in the intention-to-treat population. A centralised radiological review of CT scans was done in a post-hoc analysis to assess objective response according to RECIST 1.1, early tumour shrinkage, depth of response, duration of response, and time to response in the final RAS wild-type subgroup. Comparisons between treatment groups with respect to objective response rate and early tumour shrinkage were made using Fisher's exact test (two-sided), while differences in depth of response were investigated with a two-sided Wilcoxon test. This trial is registered at ClinicalTrials.gov, number NCT00433927. FINDINGS: In the final RAS wild-type population (n=400), median overall survival was better in the FOLFIRI plus cetuximab group than the FOLFIRI plus bevacizumab group (33·1 months [95% CI 24·5-39·4] vs 25·0 months [23·0-28·1]; hazard ratio 0·70 [0·54-0·90]; p=0·0059), although investigator-assessed objective response and progression-free survival were comparable between treatment groups. Centralised radiological review of CT-assessable patients (n=330) showed that the proportion of patients achieving an objective response (113 of 157, 72·0% [95% CI 64·3-78·8] vs 97 of 173, 56·1% [48·3-63·6]; p=0·0029), frequency of early tumour shrinkage (107 of 157, 68·2% [60·3-75·4] vs 85 of 173, 49·1% [41·5-56·8]; p=0·0005), and median depth of response (-48·9% [-54·3 to -42·0] vs -32·3% [-38·2 to -29·2]; p<0·0001) were significantly better in extended RAS wild-type patients receiving FOLFIRI plus cetuximab versus those receiving FOLFIRI plus bevacizumab. No differences in duration of response and time to response were observed between treatment groups. INTERPRETATION: This analysis provides a new framework that connects alternative metrics of response to overall survival. Superior response-related outcome parameters, such as early tumour shrinkage and depth of response, obtained by centralised radiological review correlated with the overall survival benefit conferred by FOLFIRI plus cetuximab compared with FOLFIRI plus bevacizumab in the extended RAS wild-type subgroup. FUNDING: Merck KGaA and Pfizer.

Impact of Subsequent Therapies on Outcome of the FIRE-3/AIO KRK0306 Trial: First-Line Therapy With FOLFIRI Plus Cetuximab or Bevacizumab in Patients With KRAS Wild-Type Tumors in Metastatic Colorectal Cancer.

PURPOSE: We investigated choice and efficacy of subsequent treatment, with special focus on second-line therapy, in the FIRE-3 trial (FOLFIRI plus cetuximab [arm A] or bevacizumab [arm B]) for patients with KRAS wild-type metastatic colorectal cancer. PATIENTS AND METHODS: Start of subsequent-line (second or third) therapy was defined as use of an antitumor drug that was not part of the previous regimen. We evaluated choice, duration, and efficacy of subsequent therapy and determined the impact of subsequent-line treatment on outcome of patients in FIRE-3. RESULTS: Of 592 patients in the intent-to-treat population, 414 (69.9%) received second-line and 256 (43.2%) received third-line therapy. In subsequent treatment lines, 47.1% of patients originally assigned to arm A received bevacizumab, and 52.2% originally assigned to arm B received either cetuximab or panitumumab. Oxaliplatin was subsequently used in 55.9% (arm A) and 53.2% (arm B) of patients. Second-line therapy was administered for a median duration of 5.0 versus 3.2 months (P < .001) in study arm A versus B. Progression-free (6.5 v 4.7 months; hazard ratio, 0.68; 95% CI, 0.54 to 0.85; P < .001) and overall survival (16.3 v 13.2 months; hazard ratio, 0.70; 95% CI, 0.55 to 0.88; P = .0021) from start of second-line therapy were longer in patients in arm A compared with arm B. CONCLUSION: Our data suggest that the sequence of drug application might be more important than exposure to single agents. In patients with RAS wild-type tumors, first-line application of anti-epidermal growth factor receptor-directed therapy may represent a favorable condition for promoting effective subsequent therapy including antiangiogenic agents.

FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab as first-line treatment for patients with metastatic colorectal cancer (FIRE-3): a randomised, open-label, phase 3 trial.

BACKGROUND: Cetuximab and bevacizumab have both been shown to improve outcomes in patients with metastatic colorectal cancer when added to chemotherapy regimens; however, their comparative effectiveness when partnered with first-line fluorouracil, folinic acid, and irinotecan (FOLFIRI) is unknown. We aimed to compare these agents in patients with KRAS (exon 2) codon 12/13 wild-type metastatic colorectal cancer. METHODS: In this open-label, randomised, phase 3 trial, we recruited patients aged 18-75 years with stage IV, histologically confirmed colorectal cancer, an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2, an estimated life expectancy of greater than 3 months, and adequate organ function, from centres in Germany and Austria. Patients were centrally randomised by fax (1:1) to FOLFIRI plus cetuximab or FOLFIRI plus bevacizumab (using permuted blocks of randomly varying size), stratified according to ECOG performance status, number of metastatic sites, white blood cell count, and alkaline phosphatase concentration. The primary endpoint was objective response analysed by intention to treat. The study has completed recruitment, but follow-up of participants is ongoing. The trial is registered with ClinicalTrials.gov, number NCT00433927. FINDINGS: Between Jan 23, 2007, and Sept 19, 2012, 592 patients with KRAS exon 2 wild-type tumours were randomly assigned and received treatment (297 in the FOLFIRI plus cetuximab group and 295 in the FOLFIRI plus bevacizumab group). 184 (62·0%, 95% CI 56·2-67·5) patients in the cetuximab group achieved an objective response compared with 171 (58·0%, 52·1-63·7) in the bevacizumab group (odds ratio 1·18, 95% CI 0·85-1·64; p=0·18). Median progression-free survival was 10·0 months (95% CI 8·8-10·8) in the cetuximab group and 10·3 months (9·8-11·3) in the bevacizumab group (hazard ratio [HR] 1·06, 95% CI 0·88-1·26; p=0·55); however, median overall survival was 28·7 months (95% CI 24·0-36·6) in the cetuximab group compared with 25·0 months (22·7-27·6) in the bevacizumab group (HR 0·77, 95% CI 0·62-0·96; p=0·017). Safety profiles were consistent with the known side-effects of the study drugs. The most common grade 3 or worse adverse events in both treatment groups were haematotoxicity (73 [25%] of 297 patients in the cetuximab group vs 62 [21%] of 295 patients in the bevacizumab group), skin reactions (77 [26%] vs six [2%]), and diarrhoea (34 [11%] vs 40 [14%]). INTERPRETATION: Although the proportion of patients who achieved an objective response did not significantly differ between the FOLFIRI plus cetuximab and FOLFIRI plus bevacizumab groups, the association with longer overall survival suggests that FOLFIRI plus cetuximab could be the preferred first-line regimen for patients with KRAS exon 2 wild-type metastatic colorectal cancer. FUNDING: Merck KGaA.

Phase III trial in metastatic gastroesophageal adenocarcinoma with fluorouracil, leucovorin plus either oxaliplatin or cisplatin: a study of the Arbeitsgemeinschaft Internistische Onkologie.

PURPOSE: This study was designed to compare fluorouracil, leucovorin, and oxaliplatin with fluorouracil, leucovorin, and cisplatin in patients with advanced gastric cancer. PATIENTS AND METHODS: Patients with previously untreated advanced adenocarcinoma of the stomach or esophagogastric junction were randomly assigned to receive either fluorouracil 2,600 mg/m(2) via 24-hour infusion, leucovorin 200 mg/m(2), and oxaliplatin 85 mg/m(2) (FLO) every 2 weeks or fluorouracil 2,000 mg/m(2) via 24-hour infusion, leucovorin 200 mg/m(2) weekly, and cisplatin 50 mg/m(2) every 2 weeks (FLP). The primary end point was progression-free survival (PFS). RESULTS: Two hundred twenty patients (median age, 64 years; metastatic, 94%) were randomly assigned. FLO was associated with significantly less (any grade) anemia (54% v 72%), nausea (53% v 70%), vomiting (31% v 52%), alopecia (22% v 39%), fatigue (19% v 34%), renal toxicity (11% v 34%), thromboembolic events (0.9% v 7.8%), and serious adverse events related to the treatment (9% v 19%). FLP was associated with significantly less peripheral neuropathy (22% v 63%). There was a trend toward improved median PFS with FLO versus FLP (5.8 v 3.9 months, respectively; P = .077) and no significant difference in median overall survival (10.7 v 8.8 months, respectively). However, in patients older than 65 years (n = 94), treatment with FLO resulted in significantly superior response rates (41.3% v 16.7%; P = .012), time to treatment failure (5.4 v 2.3 months; P < .001), and PFS (6.0 v 3.1 month; P = .029) and an improved OS (13.9 v 7.2 months) as compared with FLP, respectively. CONCLUSION: FLO reduced toxicity as compared with FLP. In older adult patients, FLO also seemed to be associated with improved efficacy.

A pilot study of alemtuzumab (anti-CD52 monoclonal antibody) therapy for patients with relapsed or chemotherapy-refractory peripheral T-cell lymphomas.

Patients with peripheral T-cell lymphomas (PTLs) have an extremely poor prognosis when relapsed or refractory to conventional chemotherapy. We have studied alemtuzumab, a humanized anti-CD52 monoclonal antibody, as therapy for patients with heavily pretreated and refractory PTL. Fourteen patients entered the study. All had clinical stage III or IV disease. Patients received a rapidly escalating dosage of alemtuzumab during the first week and, thereafter, 30 mg intravenously 3 times per week for a maximum of 12 weeks. Trimethoprim/sulphamethoxazole and valaciclovir prophylaxis was given to all patients. The overall response rate was 36% (5 of 14). Three patients achieved a complete remission (CR) and 2 patients a partial remission. The durations of the CRs were 2, 6, and 12 months, respectively. Toxicity included cytomegalovirus reactivation in 6 patients, which was successfully treated with ganciclovir or foscarnet; pulmonary aspergillosis in 2 patients; and pancytopenia in 4 patients. Epstein-Barr virus-related hemophagocytosis was observed in 2 patients. Five patients died of causes related to the treatment, in combination with advanced disease. We conclude that alemtuzumab is active when used in patients with advanced, heavily pretreated PTL, although it is associated with significant hematologic toxicity and infectious complications. Further studies are warranted in younger patients and patients with less advanced disease.

Phase II trial of biweekly infusional fluorouracil, folinic acid, and oxaliplatin in patients with advanced gastric cancer.

PURPOSE: To evaluate the toxicity and activity of infusional fluorouracil (FU), folinic acid (FA), and oxaliplatin, administered every 2 weeks in patients with metastatic gastric cancer. PATIENTS AND METHODS: Forty-one previously untreated patients with measurable adenocarcinoma of the stomach were eligible for the study. Patients received FU 2.6 g/m(2) (24-hour continuous infusion), FA 500 mg/m(2) (2-hour intravenous infusion), and oxaliplatin 85 mg/m(2) (2-hour intravenous infusion) every 2 weeks for 6 weeks. Treatment was continued until progression of disease was observed. RESULTS: All patients were assessable for toxicity and 37 of 41 patients were assessable for response. Patient characteristics were: sex (male, 28; female,13), median age 60 years (range, 20 to 77 years), and median Eastern Cooperative Oncology Group performance status of 1. Response was evaluated every 6 weeks. Of 37 assessable patients, one complete and 15 partial remissions were observed (overall response rate, 43%). Stable disease was observed in 12 patients (32%) and progressive disease in nine patients (24%). The median overall survival was 9.6 months. WHO grade 3 or 4 hematologic toxicities included neutropenia in two patients (4.9%) and thrombocytopenia in one patient (2.4%). Other WHO grade 3 or 4 toxicities included diarrhea in three patients (7.3%) and vomiting in two patients (4.9%). There were no cases of grade 3 peripheral neuropathy and no treatment-related deaths. CONCLUSION: Biweekly fluorouracil, folinic acid, and oxaliplatin is active and well-tolerated in patients with advanced gastric cancer. Response rates, time to progression, and overall survival were comparable to those achieved with other combination chemotherapy regimens, including FOLFOX6, with significantly less toxicity.

Effective treatment of simultaneous small cell lung cancer and B-cell lymphoma.

Malignant lymphomas have been reported previously to coincide with adenocarcinomas of the stomach and, rarely, the kidney, breast, colon, liver, or lung. Here, we describe the first case to our knowledge of a malignant lymphoma and an extensive disease small cell cancer of the lung. A 60-year-old male was admitted for severe back pain and was found to have multiple enlarged lymph nodes, hepatosplenomegaly, and bilateral pleural effusions. A B-cell non-Hodgkin's lymphoma (NHL) was diagnosed from biopsies of the stomach and liver. Further staging revealed a dense infiltration of the bone marrow by both a small cell lung cancer and a malignant lymphoma. Both tumors responded well to chemotherapy. This unique case report demonstrates that the simultaneous occurrence of small cell lung cancers and malignant lymphomas is extremely rare and may effectively be treated with chemotherapy.

Secondary acute myeloid leukaemia with monosomy 7 in identical adult twins.

We report the development of secondary acute myeloid leukaemia (AML) with monosomy 7 in identical twins, both at the age of 52 years. In the first twin, induction therapy resulted in complete remission (CR). At relapse 9 months later monosomy 7 was found. The patient died of sepsis 11 months after diagnosis. The other twin presented with leucopenia and thrombocytopenia and refractory anaemia (RA) was diagnosed. During follow-up, fluorescence in situ hybridization analysis demonstrated a monosomy 7 in 11% of the cells. Twenty-eight months following diagnosis the patient progressed to RA with excess blasts in transformation and induction chemotherapy was initiated without achieving CR. Three months later an allogeneic stem cell transplantation from a niece was performed, resulting in CR of the secondary AML.

Anti-CD20 antibody (IDEC-C2B8, rituximab) enhances efficacy of cytotoxic drugs on neoplastic lymphocytes in vitro: role of cytokines, complement, and caspases.

BACKGROUND AND OBJECTIVES: Monoclonal antibody IDEC-C2B8 (rituximab) has been shown to be highly effective in the treatment of non-Hodgkin's lymphomas (NHL). The present study was designed to investigate relationships between the efficacy of IDEC-C2B8 and expression of CD20, presence of complement, and effects of differently acting chemotherapeutic agents used in lymphoma treatment (doxorubicin, mitoxantrone, cladribine, bendamustine). DESIGN AND METHODS: DOHH-2, WSU-NHL and Raji lymphoma cell lines and ex vivo cells from patients with chronic lymphocytic leukemia (CLL) (n=17) and leukemic B-cell lymphomas (n=9) were studied. Additionally, the effect of interleukin (IL)-2, IL-4, IL-6, IL-13, granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF)alpha on expression of CD20 molecules per cell was determined. RESULTS: We demonstrate that 10 mg/mL rituximab saturated 80-95% of CD20 molecules per cell in all tested lymphoma samples. Although rituximab induced only a minor increase of apoptosis, combinations of rituximab with different cytotoxic drugs significantly decreased the IC(30)- and IC(50) dosages of the chemotherapeutic agents necessary for induction of apoptosis irrespective of addition of complement, demonstrating a chemosensitizing effect of rituximab in combination with cytotoxic drugs in the neoplastic lymphocytes. This effect seemed to be independent of the percentage of saturated CD20 molecules. After addition of caspase inhibitors to the cell lines incubated with rituximab and cytotoxic agents, caspase-7 and -8 were found, by Western blotting, to be the executioner caspases, possibly explaining the rituximab-sensitized apoptosis. Preincubation of lymphoma cells with cytokines did not alter the expression of CD20; IL-2 and IL-4 even decreased the rate of apoptosis. INTERPRETATION AND CONCLUSIONS: We conclude that rituximab sensitizes lymphoma cells to the effect of differently acting cytotoxic drugs used in lymphoma treatment, that this effect does not require complement, and that caspase-7 and -8 may represent the main executioner caspases in chemosensitization by rituximab.