Dose-finding study of oxaliplatin associated to capecitabine-based preoperative chemoradiotherapy in locally advanced rectal cancer

Introduction Proper administration timing, dose-intensity, efficacy/toxicity ratio of oxaliplatin added to fluoropyrimidin should be improved to safely perform two-drugs intensive preoperative chemoradiotherapy in locally advanced rectal cancer (LARC). This dose-finding study investigated recommended oxaliplatin dose, safety of oxaliplatin/capecitabine regimen and preliminary activity. Methods Schedule: oxaliplatin dose-levels, 35-40 mg/m2/week; capecitabine 825 mg/m2/ twice daily, radiotherapy on rectum/nodes, 50/45 Gy, 45 and 9 boost/45 Gy, in first 5 and subsequent patients, 5 days/week, respectively; for 5 weeks. Pathologic complete response (pCR) 10% was projected in order to positively affect clinical outcome. Results Seventeen fit <75 years patients enrolled: median age 60; young-elderly 4 (23%); T3/T4, 15/2, N0/N1/N2, 7/9/1. At first dose-level, no dose-limiting toxicity (DLT). At second, 2 DLT, G3 mucositis, G3 thrombocytopenia, in 2/6 patients (33%). Oxaliplatin recommended dose, 40 mg/m2/week. Cumulative G3-4 toxicities: mucositis 6%, thrombocytopenia 6%. Limiting toxicity syndromes 18%, 25% in young-elderly, all single site. Objective response rate intent-to-treat 94%. Sphinter preservation 87%, pCR 6%. After 17 months follow-up, progression-free survival and overall survival were not reached. Conclusions Oxaliplatin can be safely added to preoperative capecitabine-based chemoradiotherapy at the recommended dose 40 mg/m2/week, in LARC, with promising pCR and high activity.


INTRODUCTION
Clinical management of locally advanced rectal cancer (LARC) faces with different options of treatment strategies according to patients' fitness (age, performance status (PS), comorbidities), extension of primary tumor, and lymph nodes involvement. Over the last 15 years, multimodality treatments, consisting of surgery, radiotherapy and chemoradiotherapy, were evaluated, and different active drugs were used in mono and, recently, doublet chemotherapy combinations. The improving activity and efficacy of chemoradiotherapy supported preoperative sequential integration of combined modality treatment with surgical resection of LARC.
Platinum derivatives represent a class of chemotherapeutics widely used in oncology. Over the years researchers have studied the formulation of new platinum-based chemotherapeutic agents with the aim of reduce the incidence of drug related adverse events, based on the technological and biological improvement. These new compounds would be able to target specific cellular structures, carrying the pharmacological action only at the site of interest and reducing the involvement of healthy structures. Among the main examples of this strategy we find platinum A able to specifically bind the oxygenase-2 cycle (COX-2) while platinum B is able to interact with mitochondrial DNA by interfering with tumor resistance mechanisms [1].
Short-term regimen of high-dose preoperative radiotherapy (25 Gy in five fractions of 5 Gy), compared to surgery alone, significantly reduced LRR, and increased 5-year OS (58%) [11]. Early radiation toxicity was higher with chemoradiotherapy compared to shortterm radiotherapy (18.2%), with no different LRR and clinical outcome [12,13]. Long-course preoperative chemoradiation resulted in significantly greater tumour downsizing and downstaging compared with short-term radiation, with no difference in R0 resection rates [14].
The major challenge of the addition of more drugs in a chemotherapy combination is the proper design of schedule and dose, providing the balance between dose intensity (DI) of each drug and safety. Oxaliplatin and 5-fluorouracil-or capecitabine-based chemoradiotherapy was performed at different doses and schedules with significantly increased toxicity in randomized studies, limiting not only the favourable impact of the association, but, also, the expected effectiveness of radiotherapy [17][18][19][20]. Oxaliplatin addition achieved pCR 16-19.2%, 3-years LRR 4.4%, and 3-years OS 88.3%. Significantly increased pCR was demonstrated only in the CAO/ARO/AIO-04 trial [19]. More active doublet chemotherapy seems to require continuous 5-fluorouracil infusion 250 mg/m 2 / die days 1-14 and 22-35, and oxaliplatin at projected DI (pDI) 40 mg/m 2 /w, respectively. Other schedules failed to significantly demonstrate improved activity and clinical efficacy.
The present dose-finding study, proposing preoperative chemoradiotherapy combining oxaliplatin and capecitabine for LARC patients, assess oxaliplatin dose to be recommended for prospective clinical trials, safety and preliminary activity.

Dose finding
At the first dose-level, 3 patients were enrolled and 15 weeks of treatment were administered; no DLT was observed out of 3 patients. At the second dose level, 14 patients were treated (2 cohorts of 3 patients, and other 8 patients). A DLT, G3 mucositis, was observed in 1 out of 3 patients (33%) of the first cohort; in the second cohort of 3 patients, a DLT, G3 thrombocytopenia, was observed. Thus, 2 DLTs were observed out of 6 patients (33%) and out of 30 weeks of treatment (10%). Thus, oxaliplatin maximum tolerated dose was reached at the second dose level (Table 2), and oxaliplatin 40 mg/m 2 /week was the recommended dose. Eight more patients were treated at the recommended dose, with 1 limiting toxicity (G2 mucositis > than 2 weeks). Thus, at the recommended dose DLT were 3 out of 14 patients (21%).
Among 12 patients treated with 45 Gy in 25 daily fractions of 1.8 Gy on rectal tumour and locoregional lymph nodes and boost of 9 Gy in 25 daily fractions of 0.36 Gy on rectal tumor, 1 hematological toxicity was reported, with 1 local toxicity (G2 mucositis > than 2 weeks). Thus, radiotherapy 54 Gy on rectal tumor, and oxaliplatin 40 mg/m 2 /week, can be concomitantly administered as preoperative chemoradiotherapy in LARC.
Sphincter preserving surgery was performed in 13 of 15 patients who underwent surgery (87%); 1 pCR was achieved (7%), in a patient progression-free at 20 months. All R0 resections were performed. No post-operative toxicity or mortality were reported.
One of the major reason that can justify the failure of the association of oxaliplatin to 5-fluorouracil or capecitabine to significantly increase activity and efficacy of LARC patients can be ascribed to toxicity limiting the realization of the chemoradiotherapy strategy. Our preliminary data concerning activity and efficacy show that the present schedule of safely administration of capecitabine/oxaliplatin associated to radiotherapy may achieve 87% radical resection of LARC with sphinter preservation, 7% ypCR, median PFS not reached. 5-fluorouracil-based preoperative chemoradiotherapy achieved pCR 11.4%, 5-years LRR 5-8.7%, 5-years OS 67.9-76%, 10-years LRR 7.1%, and 10-years OS 59.6% [2][3][4][5][6][7]. In 'fit' patients, chemoradiotherapy integrated with secondary resection of rectal tumor, significantly reduced LRR, and increased survival over surgery alone. Addition of oxaliplatin to 5-fluorouracil-or capecitabinebased preoperative chemoradiotherapy represents a step forward to intensify medical preoperative treatment of LARC patients. Doublets [17][18][19][20] achieved pCR [16][17][18][19].2%, significantly increased in the CAO/ARO/AIO-  [19], with 3-years LRR 4.4%, and 3-years OS 88.3%, although a higher sphincter preservation rate, local control and efficacy were not achieved. In the subgroup of patients achieving ypT0, oxaliplatin addition significantly increased 3-year DFS, compared to the control arm [18]. Definition of the proper schedule to safely integrate oxaliplatin and capecitabine doublet chemotherapy with radiotherapy represents a mainstay to further investigate in randomized clinical studies whether more intensive medical treatments could increase pCR rate, local recurrence control, and clinical outcome in LARC patients.
The present dose-finding study proposed a feasible and safe schedule of doublet capecitabine and oxaliplatin association, at oxaliplatin recommended dose 40 mg/m 2 / week, that should be evaluated in prospective trials in LARC patients.

Patient eligibility
Patients were eligible if they had histologically confirmed diagnosis of measurable LARC, clinically staged as cT3/T4 any cN or any cT cN1/N2; age 18-75 years; World Health Organization (WHO) PS ≤ 2; adequate hematological, renal and hepatic functions; life expectancy more than 3 months.
CIRS was used to evaluate the comorbidity status, and only patients with primary and intermediate CIRS stage were enrolled [21]. Primary CIRS stage consisted of: independent Instrumental Activity of Daily Living (IADL), and absent or mild grade comorbidities; intermediate CIRS stage consisted of dependent or independent IADL, and < 3 mild or moderate grade comorbidities. Patients with secondary CIRS stage, consisting of ≥ 3 comorbidities or a severe comorbidity, with or without dependent IADL, were not enrolled. Criteria to define patients unfit for the proposed treatment strategy were: uncontrolled severe diseases; cardiovascular disease (uncontrolled hypertension, uncontrolled arrhythmia, ischemic cardiac diseases in the last year); thromboembolic disease, coagulopathy, preexisting bleeding diatheses.
Sequential chemoradiotherapy with capecitabine and oxaliplatin, and rectal surgery was proposed to consecutive eligible LARC patients as a treatment strategy in clinical practice, chosen among those in indication and approved by Agenzia Italiana del Farmaco (AIFA) for administration in label in Italian public hospitals, and published in Gazzetta Ufficiale Repubblica Italiana ("Elenco dei Medicinali erogabili a totale carico del Servizio Sanitario Nazionale", Gazzetta Ufficiale Repubblica Italiana N.1, 2 Gennaio 2009). Treatments and schedules have been used in common clinical practice, no approval by ethics committee and institutional review board was required. All patients provided written, informed consent to the proposed in label treatment strategy. Treatment was conducted in accordance with the Declaration of Helsinki.

Schedule
It was a dose-finding study evaluating safety, activity and efficacy of doublet chemotherapy association, consisting of capecitabine and oxaliplatin, combined with radiotherapy, as preoperative treatment in LARC patients. Doublet chemotherapy association was administered according to the following schedule: capecitabine (Xeloda, Roche, Welwyn Garden City, United Kingdom), per os, at the dose of 825 mg/m 2 / twice daily 5 days/week; oxaliplatin (Eloxatin; Sanofi-Aventis, Milan, Italy), over 2-hours as a 250 ml intravenous infusion of a solution containing 5% glucose, at the dose of 35-40 mg/m 2 /week. The concentration of the capecitabine used is already enstabilished in neoadjuvant setting trials, 825 mg / m2 twice daily for 5 days as radiosensitizing agent.
Radiation therapy in 25 daily fractions, 5 days a week: 50 Gy of 2 Gy on rectal tumor and 45 Gy of 1.8 Gy on locoregional lymph nodes, in the former 5 patients; 45 Gy of 1.8 Gy on rectal tumour and locoregional lymph nodes and boost of 9 Gy in 25 daily fractions of 0.36 Gy on rectal tumor, in the latter 12 patients.

Study design
Physical examination and routine laboratory tests were performed at baseline and every week on-treatment, including complete blood cell count, electrolytes, liver and renal function, urine examination and coagulation function; tumor markers every 4 weeks; electrocardiogram every four weeks and echocardiogram at baseline, and at the end of treatment.
Primary end-point was to define the recommended oxaliplatin dose. Secondary end-points were evaluation of toxicity, pCR rate, ORR, progression-free survival (PFS), OS. Toxicity was registered every week according to National Cancer Institute Common Toxicity Criteria (version 3.0). Dose-limiting toxicity (DLT) was defined as grade 3-4 non-haematological toxicity (mainly represented by diarrhea, mucositis, neurotoxicity, hand-foot syndrome, asthenia), grade 4 hematologic toxicity (leuconeutropenia), febrile neutropenia, grade 3-4 thrombocytopenia, or any toxicity determining > 2 weeks treatment delay. To discriminate individual safety, LTS, consisting of at least a limiting toxicity (LT) associated or not to other limiting or G2 toxicities, were evaluated, as previously reported [22,23]. LTS were classified as LTS single site (LTS-ss), characterized only by the LT, and LTS multiple sites (LTSms), ≥ 2 LTs or a LT associated to other, at least G2, nonlimiting toxicities.
ORR was evaluated according to RECIST criteria [24]; pCR was defined as absence of residual cancer cells in surgically resected specimens; PFS and OS, using Kaplan-Meier method [25]. PFS was defined as length of time between the beginning of treatment and disease progression or death (resulting from any cause) or to last contact; OS as length of time between the beginning of treatment and death or to last contact.
Patients were evaluated at baseline and after treatment by a multidisciplinary team, consisting of medical oncologist, radiotherapist, surgeon, and radiologist, to dynamically evaluate multimodality treatment strategy. Resection of primary rectal tumor was defined R0, if radical surgery, R1, if microscopic residual cancer cells were present at resection margins. Surgery was recommended > 6-8 weeks after chemo radiotherapy discontinuation.
Clinical evaluation of response was planned by rectoscopy, CT-scan, and transrectal magnetic resonance; PET was added based on investigators' assessment. Follow-up was scheduled every three months up to disease progression or death.

Statistical design
This dose-finding study was developed to verify recommended oxaliplatin dose, by 2 escalating steps at 35 and 40 mg/m 2 , according to an inter-patient approach [26]. It is preliminary to a phase II study, evaluating activity and efficacy of doublet chemotherapy associated to preoperative radiotherapy, assuming as minimal interesting activity a rate of pCR 10% [27]. For the study design, we used a two stage Simon procedure.

ACKNOWLEDGMENTS
Antonio Galvano PhDst is supported, for this research, by the University of Palermo (IT), Doctoral Course of Experimental Oncology and Surgery, Cycle XXX.

CONFLICTS OF INTEREST
Authors declare that they have no conflicts of interest.