Study to Compare CAPTEM vs FOLFIRI as Second Line Treatment in Advanced, Colorectal Cancer Patients

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and the second in females, with over 1.2 million new cancer cases and 608,700 deaths estimated to have occurred in 2008. Approximately 35% of CRC patients present a Stage IV metastatic disease at the time of diagnosis, and 20%-50% of Stage II or III disease will progress to Stage IV at some point during the course of disease. Stage IV CRC carries a dismal prognosis: the 5-year survival rate is \<10%, and median survival time of patients given optimal supportive care without chemotherapy is approximately 5 months. Hypothesis/rationale In advanced CRC, the occurrence of chemo- refractory disease poses a major therapeutic challenge for presence of an adequate performance status to potentially receive further treatments, but absence of effective drugs which may be offered to patients with an evidence-based algorithm. Patients who progress after all approved treatments may be generally considered suitable for new investigational drugs or strategies. Thus, in the era of personalized medicine, tumor molecular profiling may lead to the identification of therapeutic targets or predictive biomarkers for pharmacological intervention. The DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT) is responsible of the elimination of alkyl groups from the O6-position of guanine. If inactive, it may be involved in early steps of colorectal tumorigenesis through an increase of the mutational rate particularly, G-to-A point mutations of KRAS gene. Epigenetic silencing of MGMT during colorectal tumorigenesis is associated with hypermethylation of the CpG island in its promoter. This transcriptional gene silencing is responsible for diminished DNA-repair of O6-alkylguanine adducts, with the consequence of enhancing chemosensitivity to alkylating agents in particular dacarbazine and its oral prodrug temozolomide. In a previous phase II study, the investigators showed that temozolomide induced an objective response rate by RECIST criteria in 12% of heavily pretreated patients with advanced CRC and MGMT promoter 6 methylation. Treatment was well tolerated, and the only grade 4 toxicity was one thrombocytopenia episode (3%). The trial met its primary end point of acceptable response rate, with a disease control rate of 31%, a median PFS (progression free survival) and OS (overall survival) of 1.8 and 8.4 months, respectively. Other studies in carcinoids cell lines demonstrated synergistic cell kill if 5-FU (5-fluorouracil) and TMZ (temozolomide) were delivered in a schedule-dependent manner. From these translational studies, it has been formulated the CAPTEM regimen using TMZ for 5 days at 150-200 mg/m2/day total daily dose on days 10-14 (given in BID oral dosing), with capecitabine 750 mg/m2 PO (per OS) BID on days 1-14 of a 28-day cycle. The use of TMZ in BID (BIS in DIE) dosing instead of daily dosing was done because the first dose binds 6-MGMT levels, thus allowing the second dose to methylate guanines with decreased repair from MGMT. Given the potential synergy of CAPTEM combination in CRC, the investigators planned a randomized study of second-line CAPTEM vs. FOLFIRI after failure of prior first-line oxaliplatin - based treatment. Study design Open-label, randomized, multicenter, Phase II trial designed to estimate the efficacy of CAPTEM versus FOLFIRI as second line treatment in MGMT methylated, RAS mutated advanced CRC patients who have progressed on or after first-line oxaliplatin containing chemotherapy for metastatic disease. MGMT will be assessed centrally at Pathology Department of Fondazione IRCCS Istituto Nazionale dei Tumori prior to enrollment. A minimum of ten 3-micron unstained sections on charged slides of tumor will be required and methylation status will be provided within a maximum of seven days to the Study Centers. Presence of RAS mutation will be assessed at each local participating center. Eligible patients will be randomized in a 1:1 ratio to one of two treatment arms:

• Arm A (experimental arm): CAPTEM

• Arm B (control arm): FOLFIRI Study treatment will be given in cycles repeated every 28 days for Arm A and every 14 days for Arm B. Patients in Arm A will receive capecitabine at the oral dose of 1500 mg/mq/die bid from day 1 to day 14 every 28 days plus temozolomide 150 mg/mq/die bid starting on day 10 to 14 every 28 days. Patients in Arm B will receive FOLFIRI chemotherapy starting Day

  1 q2w (every cycle) starting on Day 1 of Cycle 1. FOLFIRI consists of irinotecan (starting dose of 180 mg/m2) on day one only; 5-FU 7 (starting bolus and 22-hour infusional doses of 400 mg/m2 and 600 mg/m2, respectively), and leucovorin (racemic, starting dose of 200 mg/m2 or L-form, starting dose of 100 mg/m2) for two consecutive days. Treatment will continue for up to 6 cycles in Arm A and up to 12 cycles in Arm B or up to disease progression, unacceptable toxicity or informed consent withdrawal. Randomization will be stratified across the treatment arms by the following predefined stratification variables: disease progression within 9 months from the start of first-line oxaliplatin-containing chemotherapy (\< vs. ≥9 months); prior bevacizumab in combination with oxaliplatin-based chemotherapy (yes vs. no). Efficacy assessments will be performed every 2 cycles in Arm A and every 4 cycles in Arm B until progression. The study is expected to enrol approximately 82 patients who meet the eligibility criteria. Number of study centres 10 centers in Italy Primary objective and corresponding end point

• To evaluate the efficacy, as measured by progression-free survival, of FOLFIRI (administered every 2 weeks) versus CAPTEM (administered four-weekly) Secondary objectives and corresponding end points
• To evaluate the activity of the two regimens, as measured by response rate; secondary efficacy endpoints also include duration of response and overall survival of FOLFIRI (administered every 2 weeks) versus CAPTEM (administered four-weekly)
• To evaluate the safety of FOLFIRI versus CAPTEM
• To assess the quality of life as measured by Quality of life questionnaires (EORTC QLQ - CR29; QLQ-C30) Statistical methodology According to the published results of the GERCOR study, the median progression-free survival during second-line treatment with crossover from FOLFOX to FOLFIRI was 2.3 months (calculated from the start of second-line treatment with FOLFIRI). A one-sided log rank test with an overall sample size of 82 subjects (41 in the control group and 41 in the study group) achieves 90% power at a 5% significance level to detect an increase in median progression free survival from 2 months of the control group to 4 months. The study lasts for 30 months of which subject accrual (entry) occurs in 24 months