While the addition of vorinostat to 5-FU resulted in 1 partial response and in some disease stabilizations, the limited activity does not warrant the unselected use of this combination in chemotherapy-refractory colorectal cancer.
Objectives: We conducted a phase II clinical trial of high-dose cetuximab plus irinotecan in KRAS wild-type patients who progressed on standard-dose cetuximab plus irinotecan. Methods: Patients who progressed within 4 weeks from receiving a minimum of 6 weeks of standard-dose cetuximab plus irinotecan were included in this study. Cetuximab was administered at 500 mg/m2/week and irinotecan was administered at the same dose/schedule on which each individual patient had previously progressed. The study was closed early after having met its primary end point. Results: Twenty patients were treated. The regimen was found to be efficacious, with 9 patients achieving disease control lasting more than 12 weeks. The median progression-free survival and overall survival were 2.8 and 6.6 months, respectively. The toxicity profile was favorable, with the exception of grade 3–4 hypomagnesemia which was noted in 25% of patients. Conclusions: High-dose cetuximab plus irinotecan rechallenge can re-elicit clinical benefits in patients who have previously failed cetuximab plus irinotecan treatment. The clinical benefits are modest and may be related to cetuximab rechallenge rather than cetuximab dose escalation.
3582 Background: Prior clinical data suggest a dose-related response to cetuximab (cmab) when combined with irinotecan in patients (pts) with KRAS WT tumors who do not develop grade ≥ 2 rash with standard cmab dosing. However, the investigation of higher doses of cmab in the setting of acquired or innate resistance to standard dose cmab has not been previously investigated. We conducted a phase II clinical trial of high-dose cmab plus irinotecan in KRAS WT pts who progressed on standard-dose cmab plus irinotecan. Methods: Pts who progressed within 4 weeks from receiving a minimum of 6 weeks of standard dose cmab plus irinotecan were included in this study. Cmab was administered at 500 mg/m2/week and irinotecan was administered at the same dose/schedule on which each individual patient previously progressed. All pts received doxycyline 100 mg PO bid starting day 1 of treatment. 12-week PFS rate was the primary endpoint. The regimen was considered interesting if 7/36 patients had stable disease or response at 12 weeks. The study was closed early after meeting its primary endpoint. Results: 20 pts were treated on study: median age 65.5 yrs (44-84), 14 pts were males. 8 pts had grade ≥ 2 hypomagnesaemia (3 grade 3 and 2 grade 4), 6 pts had grade ≥ 2 skin rash (1 grade 3, 0 grade 4), and 4 pts had grade ≥ 2 diarrhea (1 grade 3, 0 grade 4). 1 pt had a confirmed PR and 12 pts had a SD (at 6 weeks). In 9 pts, SD was confirmed at 12 weeks (3 pts> 24 weeks). Median PFS and OS were 2.8 and 6.6 months, respectively. The 1-year survival was 25%. Conclusions: High-dose cmab plus irinotecan is well tolerated with an acceptable rate of diarrhea and skin toxicities but with an increased rate of grade 3-4 hypomagnesemia. The prolonged disease stabilization and single response suggest that resistance to standard dose cmab plus irinotecan can be overcome by cmab dose escalation. The identification of predictive markers of response from dose escalation will be necessary to implement this strategy selectively in KRAS WT colorectal cancer patients.
598 Background: Prior clinical data suggest a dose-related response to cmab when combined with irinotecan in pts with KRAS WT tumors who do not develop grade 2 and above rash with standard cmab dosing. However, the investigation of higher doses of cmab in the setting of acquired or innate resistance to standard dose cmab has not been previously investigated. We conducted a phase II clinical trial of high-dose cmab plus irinotecan in KRAS WT pts with standard-dose cmab plus irinotecan – refractory disease to address this question. Methods: Pts with KRAS WT MCRC progressing on standard dose of cmab with irinotecan were eligible for study. Pts should have received a minimum of 6 weeks of prior standard dose cmab plus irinotecan and progressed within 4 weeks from the last dose. Cmab was administered at 500 mg/m2/week and irinotecan was administered at the same dose/schedule on which the patient previously progressed. 12-week PFS rate was the primary endpoint. Results: 8 pts were treated on study: median age 68 yrs (45-85), 5 pts were males, ECOG performance status was 1 in all 8 pts. Grade ≥ 3 toxicities consisted of hypomagnesaemia (4 pts), anemia (1 pt), leucopenia (1 pt), fatigue (1 pt), and diarrhea (1 pt). 6 pts achieved stable disease (with regression in target lesions noted in 3 pts). 12 week PFS rate is 5/8 and 18 week PFS is 4/8. 3 pts remain on study at 4.5, 5, and 8 months from enrollment. Conclusions: High-dose cmab/irinotecan is well tolerated except for hypomagnesemia. Encouraging prolonged disease stabilizations warrant further investigation of this approach in pts in KRAS WT population. Accrual is ongoing. [Table: see text]
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