Journal of Surgical Oncology Supplement 2:124-128 (1991)

Doxifluridine in Advanced Colorectal Cancer FEDERICO CALABRESI, MD, AND MARINA REPETTO, MU From the Department o f Clinical Oncology, lstituto Regina Elena (F.C.), Rome, and the Department of Clinical Research, Prodotti Roche (M.R.), Milan, ltaly

KEYWORDS:doxifluridine, advanced colorectal cancer, fluoropyrimidines

INTRODUCTION

(biochemical modulators, biological response modifiers) or investigating new ways and routes of administration Colorectal cancer is responsible for about 16,000 (continuous infusion, regional chemotherapy); 2) to dedeaths per year in Italy. The treatment of colorectal velop 5-FU analogs with a better therapeutic index. cancer, by tradition, lies in the surgery field. However, Following this latter point, the latest and more promdespite the high resectability rate and a genera1 improveising fluoropyrimidine analog developed is 5 ‘deoxyment in therapy, nearly half of the patients with colorectal 5-fluorouridine (5’-dFUR) that was introduced about 10 cancer still die of metastatic tumor. The outcome is to a years ago by Cook et a1 [6]. great extent related to the stage of the disease at the time of surgery according to Dukes classification. Individuals METABOLISM AND MECHANISM OF ACTION with stage A or B have a 5-year survival with surgery The molecular structure of 5’-dFUR consists of a 5-FU alone ranging from 60-90%, while for patients with lymph nodes involvement (Dukes C) their 5-year survival molecule attached to a pseudopentose (Fig. 1). Its expectance drops to less than 40% [I]. Patients with this antineoplastic activity has been shown to be superior to latter stage of disease are therefore at high risk of 5-FU when tested against several experimental rodent recurrence following complete surgical resection and are tumors. In these in vivo tumor models, the therapeutic excellent candidates for adjuvant therapy. In this field, a index of doxifluridine was 10-1 5 times higher than that metanalysis conducted on 27 randomized controlled trials of 5-FU and of other fluoropyrimidines [7]. As for the performed from 1960 through 1986, showed that regi- mechanism of action, due to the missing hydroxyl groups mens containing fluorouracil (5-FU) resulted in a small in position 5 ‘ , this compound cannot be directly metabbenefit in terms of survival, with a mortality odds ratio of olized in DNA or RNA synthesis. The active component 0.83 in favor of therapy [2]. More important are the of 5‘-dFUR is 5-FU which is released by the action of results of two recent trials on adjuvant therapy that have pyrimidine phosphorylases that in the animal model have shown a risk of recurrence reduced by 41 % and an overall been shown to be present at a higher concentration in death rate reduced by 33% for 5-FU combined with malignant tissues, leading, eventually, to a preferential levamisole, in comparison with control and levamisole release of 5-FU within tumors compared with most normal tissues [8- 101. Preliminary observations in a alone, in patients with node-positive colon cancer [3]. clinical study seem to confirm these experimental findWhile for patients with resectable disease significant ings [ l l ] . improvements have been reached, for patients with Cytotoxicity of 5’-dFUR and other fluoropyrimidines advanced disease only palliative treatments are at present was compared in human bone marrow stem cells and available. Chemotherapy is the only feasible approach to several cultured human tumor cell lines. Results indicontrol advanced disease, but patients with unresectable cated that 5’-dFUR can exhibit a cytotoxic selectivity for tumors or metastatic disease have a median survival of human tumor cells compared with human bone marrow only 6- 10 months. Fluoropyrimidines remain at present stem cells leading to a superior therapeutic ratio on 5-FU the only options for chemotherapy of colorectal cancers. or 5-fluoro-2’deoxyuridine (FUDR) [ 121. The parent compound of this class, 5-FU, was introduced 5’-dFUR is rapidly metabolized to 5-FU both in man in 1957 and many different fluorouracil regimens have been investigated but, overall, poor response rate ranging from 10-20% and no significant impact upon overall survival were obtained [4,5]. Later on efforts were made Accepted for publication May 30, 1991 Address reprint requests to Dr. Federico Calabresi, Department of essentially towards two directions: 1) to improve the Clinical Oncology, Istituto Regina Elena, Wale Regina Elena 291, activity profile of 5-FU either testing new associations 00100 Rome, Italy. 0 1991 Wiley-Liss, Inc.

Doxifluridine in Advanced Colorectal Cancer

Fig. 1 .

Chemical structure of 5’-dFUR.

and in animals and after different routes of administration [ 131 (Fig. 2). The relationship between activity and 5-FU plasma concentration was studied in the rat by infusing different doses of 5-FU and 5’-dFUR and comparing 5-FU levels. 5-FU at 35 mglkg and 5’-dFUR at 500 mg/ kg produced a 70-90% cure rate. At these dosages, the steady-state 5-FU plasma concentrations derived from 5’-dFUR were significantly lower than those from 5-FU administration itself. Infusion of 5-FU at a lower dose, 25 mg/kg, gave a 5-FU concentration similar to that produced by 5’-dFUR at 500 mglkg, but with only 30% cures. These data, together with the observation that 5’-dFUR produces 5-FU in tumor cells, indicate that its activity is in part due to a selective action within tumor cells [ 141. Systemic levels of 5-FU then should contribute to its efficacy. Following the metabolic pathway of 5-FU, it could be hypothesized that 5’-dFUR activity is dependent, from one side, on intratumoral activation into 5-fluoro-2‘deoxyuridine 5 ’monophosphate (FdUMP) and 5-fluorouridine-5’-triphosphate(FUTP) with consequent inhibition of DNA synthesis through the covalent bond with thymidylate synthase (TS) and inclusion on RNA molecule respectively, and on the other side, on extratumoral conversion to 5-FU with subsequent exposure of tumor cells to 5-FU [ 151. This hypothesis is confirmed by an animal experiment where the intracellular kinetic of 5’dFUR was studied measuring intracellular FdUMP and TS level in a transplantable colon carcinoma in the rat. The inhibition of TS was complete (>99%) 5 hours after the intraperitoneal injection of 5’-dFUR [ 161. Very recent studies performed on mice bearing a human colon transplantable tumor, suggest an anticachectic action of the compound [ 171.

CLINICAL EXPERIENCE ON ADVANCED COLORECTALCANCER Based on this promising preclinical work, 5’-dFUR has been extensively tested on advanced colorectal cancer

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using different doses and different schedules in order to verify in human beings the advantages suggested by experimental models in such a relatively unresponsive tumor. Table I summarizes the number of patients treated and results obtained in the different studies. In a phase I1 study the drug was given in a 5consecutive day schedule by a bolus intravenous injection at a dose of 4 g/smq per day and repeated every 3-4 weeks [ 181. Of 42 eligible patients 40 had no previous chemotherapy. Response was defined in 27 patients having received two or more courses of 5’-dFUR. Seven patients responded to treatment (26%). Leukopenia (53%), nausea and vomiting (38%), stomatitis (38%), and neurotoxicity (33%) were the most frequent toxic effects observed. Following this study, a randomized phase 111 comparison trial vs. 5-FU was initiated. 5’dFUR, administered at the same dose and schedule of the previous study, was compared with 5-FU 450 mglsmq for 5 days in a bolus injection [19]. The study was prematurely discontinued due to a severe cardiac toxicity that occurred in one patient of the 5’-dFUR group. Anyhow, 52 eligible patients were entered and partial responses were seen in 5/25 (20%) and 2/27 (7%) in the 5’-dFUR and 5-FU groups, respectively. The most frequent adverse effects were neurotoxicity (48%) and mucositis (43%) for 5’-dFUR, leukopenia (48%), and nausedvomiting (37%) for 5-FU. In a disease-oriented phase I1 trial, 88 patients with colorectal cancer were entered to receive 5’-dFUR 12.5 gismq (reduced to 10 g/smq in case of toxicity) by continuous intravenous infusion over 6 hours once a week for 3 weeks followed by a l-week rest [20]. Fifty-eight patients were evaluable for response and 13 partial responses (22%) were observed (15% the response rate if all patients included are considered). With this schedule the major toxicity was severe neurological effects observed in about 40% of the patients treated both with 12.5 glsmq and 10 g/smq. The suggestion from these studies was that despite an interesting antitumor effect of 5‘-dFUR on colorectal cancer, the schedules tested could not be recommended due to major non-hematological toxicities (i.e., neurotoxicity and cardiotoxicity). In order to improve the therapeutic index of the compound it was decided essentially to prolong the infusion time and to maintain the total monthly dose not over 36-38 g. A 5’-dFUR schedule of 4 gismqiday for 5 days q 28 in a l-hour infusion time was tested in a comparative randomized trial vs. 5-FU (450 mg/smq/day for 5 days q 28 l-hour infusion) [21]. Response rates €or 31 and 30 evaluable patients in the 5’-dFUR and 5-FU groups were 23% and 7%, respectively. There was no difference in the toxicity of both drugs: mainly gastrointestinal and hematological effects were observed. Neither neuro nor cardiotoxicity was seen. In a phase 1-11 study, a continuous 24-hour infusion

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t (min) Fig. 2. Plasma concentration-time curves for 5’-dFUR and its major blood plasma metabolite 5-FU in humans (a,b) and in laboratory animals (c+). a: intravenous 5’-dFUR (D: 600 mgimq); b: oral 5‘-dFUR, drinking solution (D: 400 mgimq); c: intravenous 5’-dFUR (D: 50 mgiKg); d: oral 5’-dFUR (D: 50 mgimq); e: intraperitoneal 5’-dFUR (D: 50 mg/Kg). In all figures 0 , 5’-dFUR; B, 5-FU. (Modified from Bruijn et al., 1989, with permission of the publisher.)

schedule of 1 gismqiday, reduced to 0.75 glsmqlday in velopment has been carried out in Japan with 5‘-dFUR case of severe toxicity for at least 90 days, was investi- given orally. A continuous daily administration of a gated [22]. Twenty-one patients entered the study, 20 800 mglsmqlday dose or an intermittent schedule of completed the study period and were evaluable for 2,250 mglday 4 days a week was tested. Toxicity has response: seven patients showed a partial response been shown to be very low, with better results for the (35%). Toxicity was minimal and mainly defined as intermittent schedule, and gastrointestinal effects, most hand-foot syndrome in 50% of the patients; in three cases diarrhea, had the highest incidence. Neither neurotoxic only, treated at the higher dose, it was severe. The dose nor cardiotoxic effects were observed. Some activity has been shown on colorectal cancer [25,26]. chosen for further studies was 0.75 glsmqiday. In a phase I study a 5-day continuous infusion in a DISCUSSION 28-day cycle has also been tested and the maximum Colorectal cancer is a relatively unresponsive tumor tolerated dose determined: 20 glsmqll20 hours. This schedule seems to have some phannacokinetic advan- and for many years 5-FU has been the standard treatment tages, but in order to translate these features to a clinical with, nevertheless, a very unsatisfactory tumor response, improvement on advanced colorectal cancer, phase I1 variably reported in the 10-20% range with a modest to studies are requested [23,24]. minimal impact on survival. Many trials have been Besides intravenous formulation, a large clinical de- conducted to improve the treatment results of 5-FU by

Doxifluridine in Advanced Colorectal Cancer

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TABLE I. Summary of the Clinical Studies on Colorectal Cancer With Doxifluridine

+ RP

Patients entered

Patients evaluable

RC

Schedule

(%I

Reference

Bolus intravenous 5 days 6-hour infusion Bolus VS.5-FU

42 88 34 vs. 30

27 58 25 vs. 27

Abele et al. [ 181 Hurteloup et al. [20] Alberto et al. [I91

I-hour infusion vs. 5-FU

36 vs. 35

31 vs. 30

21 122

20 76

7 (26) 1 3 (22) 5 vs. 2 (20 vs. 7) 7 vs. 2 (23 vs. 7) 7 (35) 7 (9)

24-hour infusion Oral

Quifier et al. [21] Schuster et al. [22] Kimura et al. [25]

combining with other cytostatics or biochemical modu- this study that started in January 1990 and involves 11 lators. The most promising combination came out being centers. Two hundred patients, out of 230 foreseen, have 5-FU plus folinic acid that showed a response rate of already been recruited and final results will be available 3 0 4 0 % and, in some experience, a survival advantage in a few months. Preliminary data confirm a good [27]. Very initial are the experiences with the combina- tolerability profile in comparison with 5-FU. The purpose tion of 5-FU and interferon a-2a (aIFN) that in phase I1 is to definitely demonstrate the activity advantage on studies resulted in objective responses in 2 6 6 3 % pa- 5-FU on a sufficient number of patients in order to reach tients tested [28,29]. 5’-dFUR has been the most prom- a statistically significant result. On the other hand, also the oral administration seems ising analog developed and in preclinical studies has shown a therapeutic index 1&15 times higher than 5-FU. promising and interesting from a practical view point, A fascinating rationale supports its high activity: a especially for elderly patients where dose intensity is less crucial than quality of life. A study testing a long term selective delivery of 5-FU in tumor cells. From clinical experiencewith 5’-dFUR on colorectal schedule of 5 ‘-dFUR given orally on elderly patients with cancer, two essential points must be underlined: 1) the advanced colorectal cancer is in progress. The aim is to speed of intravenous administration influences the fre- assess activity and define the toxicity profile of the quency and the degree of toxicity. The toxic effects are compound in this patient population, and, besides, parbelieved to be dependent on the occurrence of 5’-dFUR ticular attention will be addressed to the evaluation of metabolites and the production of these metabolites may quality of life. be decreased if the drug is administered as a slow infusion Finally, from a theoretical point of view, those agents rather than as a bolus injection or rapid infusion; 2) the that enhance the therapeutic efficacy of 5-FU should also toxicity profile is also influenced by the total dose be capable of enhancing 5’-dFUR efficacy, since 5-FU is administered over 1 month. High doses in a weekly present both inside and outside tumor cells following its schedule, even if administered as a slow infusion, administration. The most attractive biochemical modulation of 5-FU to date is the combination of 5-FU with resulted to be too toxic. A slow infusion in a 5-day every 28-day cycle and, leucovorin. Since this form of biochemical modulation is even better considering activity as endpoint, a continuous targetted at the intratumoral FdUMP-TS complex and 24-hour infusion for 90 days are the dose schedules 5’-dFUR exposure results in enhanced intratumoral 5-FU suggested for further trials due to their lack of toxic delivery, 5’-dFUR and leucovorin should be recognized effects on nervous and cardiac systems. With the latter as an interesting combination. On the other hand, recent schedule a 35% response rate was shown and this result clinical studies suggest synergistic antitumor activity is in agreement with that obtained in a randomized study when 5-FU and aIFN are used in combination. Being the of a 5-FU bolus vs. 5-FU continuous infusion [30]. This biological effect of 5’-dFUR dependent upon its transphenomenon is probably due to the peculiar pharmaco- formation to 5-FU, it was tested in combination with kinetics behavior of fluoropyrimidines. However, con- aIFN on the proliferative activity of eight human colon tinuous infusion therapy represents an alternative in cancer cell lines (311. The results showed a synergized delivery of chemotherapy of cancer but it cannot be inhibition with 5’-dFUR but not with 5-FU in four lines. considered as standard treatment because of the high In these lines an increased pyrimidine phosphorylase costs and the necessity of patient collaboration. This is activity after 5 days of exposure to aIFN was observed. the reason why in Italy a large multicenter randomized Moreover, 5’-dFUR in an in vivo experiment on nontrial vs. 5-FU was designed with the recommended tumor-bearing mice has been shown to reverse methdosage of 4 g/smq given by 1-hour infusion for 5 days per otrexate toxicity, behaving as a pharmacological antidote 28 days treatment cycle. We are actually participating in [321.

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A clinical application of these experimental suggestions is planned in order to complete the profile of the drug.

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