The effects of leucovorin and dipyridamole on fluoropyrimidine-induced radiosensitization

Synthesis, aerobic cytotoxicity, and radiosensitizing activity of novel 2,4-dinitrophenylamine tethered 5-fluorouracil and hydroxyurea

Two novel dual functional agents, 3[3-(2,4-dinitro-phenylamino)-propyl]-5-fluoro-1H-pyrimidine-2,4-dione 7 and N-[3-(2,4-dinitro-phenylamino)-propoxy]urea 8, resulting from linkage of 2,4-dinitrophenylamine through three carbon atoms with 5-fluorouracil 5 and hydroxyurea 6, respectively, were prepared and their in vitro aerobic cytotoxicities in HT-29 cell line with and without radiation were determined. Compounds 7 and 8 unlike their components were not cytotoxic but showed radiosensitizing activity.

Phase I study of 5-fluorouracil and leucovorin by continuous infusion chronotherapy and pelvic radiotherapy in patients with locally advanced or recurrent rectal cancer

PURPOSE

To determine the maximal tolerated dose of chronomodulated 5-fluorouracil (5-FU) and leucovorin (LV) given concurrently with radiotherapy in patients with rectal cancer.

METHODS AND MATERIALS

Forty-five patients with T3, T4 or recurrent rectal cancer received concurrent radiotherapy to a minimal dose of 4500 cGy. Chemotherapy was administered by a programmable pump in chronomodulated fashion, with 62.5% of the total dose given within 7 hours around 9:30 pm. The starting doses were LV at 5 mg/m2/d and 5-FU at 150 mg/m2/d. LV was escalated in 5-mg/m2 increments to 20 mg/m2/d; 5-FU was then escalated in 25 mg/m2 increments to the maximal tolerated dose.

RESULTS

Diarrhea and stomatitis were dose limiting, with Grade 3 or worse toxicity occurring in 16% and 5% of patients, respectively. Thirty-seven patients (84%) received their scheduled dose of radiotherapy (range, 4500-6000 cGy). Thirty-two patients had clinical T3 disease; all were treated with definitive surgery; 23 (71%) underwent sphincter-sparing surgery with complete resection in 28 (87%). Ten patients (31%) had no evidence of tumor in the pathologic specimen.

CONCLUSION

Preoperative chemoradiotherapy in rectal cancer using chronomodulated 5-FU and LV is feasible. The recommended Phase II dose is 5-FU 200 mg/m2 and LV 20 mg/m2 daily for 5 weeks.

Recent advances in the use of radiosensitizing nucleosides

Chemotherapeutic drugs that perturb nucleotide metabolism have the potential to produce substantial sensitization of tumor cells to radiation treatment. The clinical effectiveness of fluoropyrimidines as radiosensitizers has been proven in multiple randomized trials. The development of oral fluoropyrimidine formulations may allow protracted exposure without the need for indwelling intravenous lines and infusion pumps. These agents may also provide more selective radiosensitization and are likely to be widely incorporated into chemoradiotherapy regimens for patients with gastrointestinal malignancies. Gemcitabine has been well studied in the laboratory, with respect to mechanisms of radiosensitization and strategies that may increase the therapeutic index. Clinical trials based on these studies are now defining the role of this radiosensitizing nucleoside. Issues regarding the use oral fluoropyrimidines and gemcitabine need to be viewed in the context of both local and distant disease control, given the potential systemic activity of these agents.

Postoperative concurrent chronomodulated 5-fluorouracil/leucovorin infusion and pelvic radiotherapy for squamous cell carcinoma of the ovary arising from mature cystic teratoma

Primary squamous cell carcinoma (SCC) of the ovary arising from mature cystic teratoma (MCT) is rare. Survival is very poor. Although different postoperative treatments have been tried, none appears to have influenced outcomes. A 44-year-old patient with FIGO stage IIB SCC of the ovary arising in MCT had exploratory laparotomy and left salpingo-oophorectomy, leaving macroscopic residual pelvic disease. Postoperative treatment consisted of a continuous concurrent chronomodulated infusion of 5-fluorouracil 150 mg/m2/day and leucovorin 10 mg/m2/day with 5 weeks of pelvic radiotherapy. Three years after initial surgery, she remains disease and complication free. Given this patient's unusually long disease-free survival and the efficacy of concurrent chemotherapy and radiotherapy in other SCCs, the concurrent circadian treatment approach used for this patient should be explored in other cases of SCC of the ovary.

Intensified adjuvant combined modality therapy for resected periampullary adenocarcinoma: acceptable toxicity and suggestion of improved 1-year disease-free survival

PURPOSE

(1) To determine the toxicity of an intensified postoperative adjuvant regimen for periampullary adenocarcinoma (pancreatic and nonpancreatic) utilizing concurrent 5-fluorouracil (5-FU), leucovorin (LV), dipyridamole (DPM), and mitomycin-C (MMC) combined with split-course locoregional external beam radiotherapy (EBRT) to 50 Gy. This was followed by 4 cycles of the same chemotherapy as adjuvant therapy. (2) To determine preliminary estimates of the overall and disease-free survival associated with the use of this regimen. (3) To compare the toxicities and early survival results of patients treated with the current regimen to those of patients who completed our prior trial of concurrent chemoradiation infusion with 5-FU/LV chemotherapy and regional nodal and prophylactic hepatic irradiation.

METHODS

Postpancreaticoduodenectomy, patients received every 4 weeks bolus administration of 5-FU, (400 mg/m(2)), and LV, (20 mg/m(2), Days l-3), DPM (75 mg p.o., 4 times per day, Days 0-3, and every 8 weeks), MMC, (10 mg/m(2); maximum of 20 mg, Day l during EBRT). This was followed by 4 months of the same chemotherapy, beginning 1 month following the completion of EBRT. EBRT consisted of split-course 5000 cGy/20 fractions with a 2-week planned rest after the first 10 fractions (2500 cGy).

RESULTS

From 4/96 to 6/99, 45 patients were enrolled and treated. Their experience constitutes the basis of this analysis. There were 29 patients with pancreatic cancer and 16 with nonpancreatic periampullary cancer. Seventeen patients had tumors of 3 cm or more, and 39 patients had at least 1 histologically involved lymph node. Thirteen patients had a histologically positive margin of resection. The mean time to start of treatment was 63 days following surgery. During chemoradiation therapy there were no Grade 3 or worse nonhematologic toxicities and 47% Grade 3 or Grade 4 hematologic toxicities of short duration. Following chemoradiation, during chemotherapy treatment only, there was one Grade 3 hepatic and one Grade 3 pulmonary toxicity which was nondebilitating (2% each case) and 42% Grade 3 or 4 hematologic toxicity. There were 2 episodes of neutropenic fever requiring admission and no treatment-related mortalities. One patient developed a mild case of HUS, which responded to standard management. One patient developed persistent shortness of breath (nondebilitating), and another patient had occasional dyspnea on exertion, both occurring after all therapy. The majority of patients complained of increased fatigue (Grade 1-2), greatest during the combined therapy and improving post all treatment. As of 6/23/99, 20 of 45 patients have relapsed, 13 in the liver. Twelve patients have died. Median follow-up for surviving patients is 14.3 months. Disease-free survival at 12 months following surgery is 66% (as compared to 25% in our prior study), and the median disease-free survival is 17 months (as compared to 8. 3 months in our prior study). Median survival has not yet been reached, but will be greater than 17 months.

CONCLUSION

With a 14.3-month median follow-up, acute toxicity has been acceptable and manageable. Observed relapses were seen 9-13 months following surgical resection. Early survival analysis suggests a trend toward increased median disease-free survival (8.3 vs. 17 months), especially for patients with nonpancreatic periampullary adenocarcinoma.

Cell line specific radiosensitizing effect of zalcitabine (2',3'-dideoxycytidine)

The potential of zalcitabine (ddC) to act as an ionizing radiation response modifier was tested on exponentially growing human cancer cells in vitro. Two human cell lines, WiDr (colon) and MCF-7 (breast) were exposed to ddC at 10 microM concentration for various lengths of time (18, 24, 48 and 72 h). On the WiDr cell line the dual effect of concentration and duration of exposure prior to irradiation was investigated. Experimental endpoints were clonogenicity and viability, as measured by colony formation assay (CFA) and MTT assay respectively. The impact on cell-cycle distribution prior to irradiation was assessed by flow cytometry using a double labeling technique (propidium iodide and bromodeoxyuridine pulse label). A significant reduction in surviving fraction and viability was observed for WiDr-cells irradiated after pre-exposure to 10 microM for 18, 48 and 72 h as compared to corresponding irradiated controls. At lower concentrations (1 and 5 microM), the radiosensitizing effect was only significant after a 72-h exposure (assessed by CFA). For MCF-7, ddC induced a significant modification of the dose response only with 24 and 48 h preincubation. However, the overall effect was less pronounced as compared to WiDr. Cell-cycle analysis showed accumulation in S-phase, 48 and 72 h after treatment with 10 microM ddC in the WiDr cells, with a progressive shift to late S-phase as shown by the biparametric analysis. The degree of radiosensitization is cell-line dependent with the most important sensitization observed on the most "radioresistant cell line", i.e., the cell line with the lowest alpha value and highest SF 2 (WiDr). For WiDr, radiosensitization by ddC depends on the duration of exposure and the concentration of the drug.

Preclinical studies of chemotherapy and radiation therapy for pancreatic carcinoma

The use of radiation therapy combined with 5-fluorouracil (5-FU) in the treatment of pancreatic cancer has been well established. It has been hypothesized that any benefit from combined 5-FU and radiation has been due to radiosensitization. Improved therapy could result from a better understanding of the mechanism of radiosensitization and the development of compounds capable of providing better radiosensitization. This article reviews preclinical findings on the mechanism of cytotoxicity and radiosensitization for 5-FU, fluorodeoxyuridine, thymidine analogs, and gemcitabine (2',2'-difluorodeoxycytidine) and discusses the clinical implications of these findings.

Role of Radiation Therapy and Fluoropyrimidines in the Treatment of Gastrointestinal Malignancies

BACKGROUND: The use of combined chemotherapy and radiation for gastrointestinal malignancies has several theoretical advantages, and clinical trials to determine the type and extent of clinical benefits have been performed. METHODS: The basic science and clinical trial data evaluating such combinations are reviewed, with an emphasis on the interactions between fluoropyrimidines and radiation. RESULTS: Improved outcomes from chemoradiotherapy have been demonstrated in patients with selected stages of anal, esophageal, rectal, and pancreatic cancer. CONCLUSIONS: Despite these positive results, further work is needed to demonstrate even more effective and less toxic treatment regimens.

Early evaluation of abdominal/hepatic irradiation and 5-fluorouracil/leucovorin infusion after pancreaticoduodenectomy

PURPOSE

To describe the toxicities of a combined modality adjuvant regimen for patients with resectable periampullary adenocarcinoma.

METHODS AND MATERIALS

Fourteen patients with surgically resected periampullary adenocarcinoma were treated with adjuvant therapy consisting of prophylactic hepatic irradiation and pancreatic bed irradiation and concurrent infusional 5-fluorouracil and leucovorin (5-FU/LV). Starting within 60 days of surgery, patients received radiation treatments of 1.8 Gy per fraction to the liver and pancreatic bed (13 fractions), followed by 1.8 Gy per fraction to the pancreatic region (15 fractions). All radiation treatments were given with infusional 5-FU (200 mg/m2/day) and leucovorin (5 mg/m2/day) for 5 out of every 7 days during the 38-day treatment sequence. After a 1-month break, patients were scheduled to receive four cycles of infusional 5-FU/LV (2 weeks on/2 weeks off).

RESULTS

All 14 patients completed the initial combination treatment. Toxicities were tolerable; three patients had Grade 3/4 toxicities that were primarily gastrointestinal in nature. Six patients required hospitalization during therapy for treatment-related toxicities. Two patients required radiation treatment breaks of less than 1 week, and two others had radiation held for 2-4 weeks. Three patients required chemotherapy dose reductions secondary to toxicities. Toxicities in the subsequent chemotherapy-alone cycles were few and primarily manifested by Grade 2 rises in liver injury tests. Higher toxicity grades were associated with tumor progression. Twelve patients have developed recurrent disease with an equal number of recurrences occurring in the pancreatic bed as in the liver over the 12-month median follow-up. Median survival for this cohort is 417 days, not significantly different from previously reported adjuvant trials in this patient population.

CONCLUSION

These data indicate that adjuvant therapy with concomitant large-field radiation and infusional chemotherapy is feasible and associated with mangeable toxicities in patients undergoing pancreaticoduodenectomy for periampullary adenocarcinoma. Improvement in survival over other adjuvant regimens has not thus far been observed. Modification of this strategy may be required.

Combined intensive chemoradiotherapy for organ preservation in patients with resectable and non-resectable oesophageal cancer

From January 1990 to April 1993, 60 oesophageal cancer patients were enrolled in a protocol of non-surgical treatment that consisted of induction chemotherapy followed by concurrent chemoradiotherapy. Induction chemotherapy consisted of cisplatin 40 mg/m2 intravenous bolus days 1, 2, 14, 15; 24 h continuous infusion of 5-fluorouracil (5-FU) 1000 mg/m2 days 1 and 14; leucovorin 20 mg/m2 days 1 and 14 given before and with 5-FU; bleomycin 30 UI days 1 and 14; mitomycin C 10 mg/m2 day 14. Concurrent chemoradiotherapy consisted of 60 Gy (6 weeks) from day 21 and cisplatin 70 mg/m2 days 28, 42 and 56; leucovorin 20 mg/m2 followed by 5-FU 425 mg/m2 days 28, 35, 42, 49 and 56. Complete response occurred in 44 of 55 evaluable patients (80%). The median survival is 32 months; the actuarial survival at 40 months is 35% (CI 18-53). These results appear improved over those reported with surgery or radiation alone, and suggest that organ preservation as a secondary treatment goal should be vigorously investigated.

New targets for pyrimidine antimetabolites in the treatment of solid tumours. 1: Thymidylate synthase

Thymidylate synthase forms the target for anticancer therapy with fluoropyrimidines. Anticancer activity can be increased by the use of different modulators of fluoropyrimidine metabolism, which lead to an enhanced inhibition of thymidylate synthase. In vitro and in vivo studies with fluoropyrimidines and two of these modulators, folinic acid (leucovorin) and interferon, are summarized. The promise of these preclinical results is reflected by the response data of several clinical trials. The biochemical effects of these modulators are described and illustrated by the fluoropyrimidine-mediated inhibition of thymidylate synthase in tumour samples, which is clearly enhanced by folinic acid. The regulation of thymidylate synthase synthesis may also be crucial for total blockade of thymidylate synthase activity. This regulation may be influenced by interferon-gamma. Although the addition of modulators increases the activity of fluoropyrimidines at the level of thymidylate synthase, most solid tumours, especially colorectal carcinomas, are resistant to these combinations. For this reason, new, more potent inhibitors of thymidylate synthase have been developed, the antifolates. Preclinical data show that some of these compounds have good antitumour activity, but they still have to prove their value in the clinic. These two approaches, the use of modulators and new compounds, have shown activity preclinically and the extension of these findings to clinical studies stresses the importance of thymidylate synthase as a target in fluoropyrimidine therapy of solid tumours.

The clinical rationale for S-phase radiosensitization in human tumors

Nonhypoxic cell radiosensitizers, principally the halogenated pyrimidines and hydroxyurea, have been studied in the laboratory and clinical setting for more than 30 years. Early clinical experience in the 1960s and 1970s with the thymidine analogs 5-bromodeoxyuridine (BUdR) and 5-iododeoxyuridine (IUdR) was disappointing because normal tissue toxicity eliminated any potential for therapeutic gain. Inadequate delivery systems for intravenous and intraarterial infusions also contributed to the decline of this strategy. More recently, laboratory investigations have revealed further information regarding the mechanism of IUdR/BUdR radiosensitization. This knowledge provided a rationale for the sequence and timing of drug and radiation exposure, which could be both effective and tolerable. Advancing technology also provided safer infusion devices, and a resurgence in clinical trials combining IUdR or BUdR and radiation resulted. Current laboratory studies are now providing data on tumor cell kinetics, which is being applied to ongoing clinical trials. Fluoropyrimidines, principally 5-fluorouracil (5-FU), were also used in early clinical trials and unlike IUdR/BUdR were found to have significant activity as single agents against a variety of tumor types. The clinical integration of 5-FU and radiation occurred more slowly, but recent trials have demonstrated a therapeutic gain. Improved rates of local control and survival with combined 5-FU and radiation versus radiation alone have now been demonstrated in patients with rectal, esophageal, and anal carcinomas. However, the mechanism of interaction between the fluoropyrimidines and radiation remains uncertain and continues to be investigated with the hope of improved clinical outcome. As the cellular pathways influenced by the halogenated pyrimidines have been defined, the potential for biochemical modulation of these agents has been recognized. Leucovorin, the most commonly applied modulator, has been shown to enhance the activity of 5-FU in patients with metastatic colorectal carcinoma. These studies serve as an example for current trials that use biochemical modulators of IUdR, BUdR, and 5-FU as radiosensitizers. Hydroxyurea, currently used in the treatment of chronic leukemia, has also been considered a radiosensitizer. As with IUdR/BUdR, the clinical trials have often been inconclusive and interest in this radiosensitizer has waned. A poor understanding of the mechanism of action and tumor cell/normal tissue kinetics may be responsible for the lack of overall success with this strategy. Current investigations of cell kinetics in humans and potential mechanisms of hydroxyurea action could provide information critical to future trials of hydroxyurea radiosensitization.

Phase I study of 5-fluorouracil and leucovorin by a 14-day circadian infusion in metastatic adenocarcinoma patients

Initial experimental and clinical studies have indicated that 5-fluorouracil (5-FU) toxicity can be reduced by delivering 5-FU at around 4 a.m. More recent data have suggested that the toxicity might be reduced even more with delivery at around 9-10 p.m. The current study determined the maximum tolerated dose (MTD) for 5-FU and leucovorin (LV) delivered as a continuous circadian infusion over 14 days every 28 days, with the peak of the infusion occurring at around 3-4 a.m. The peak drug delivery was shifted to 9-10 p.m. in all patients developing toxicity of > or = grade II (Eastern Cooperative Oncology Group) to determine if this timing further reduced toxicity and enabled increased dose intensity. A total of 14 patients with metastatic adenocarcinoma received an admixture of 5-FU and LV via a programmable portable infusion pump, with 62.5% of the 24-h dose being given over 7 h around the infusion peak. The starting dose level of 5-FU (200 mg/m2 daily) and LV (5 mg/m2 daily) was that established as the highest tolerable dose rate in a previously reported phase I study using a 14-day flat infusion of 5-FU and LV. The LV dose was first escalated to 20 mg/m2 daily, followed by escalations of the 5-FU dose. A total of 51 courses were evaluable for toxicity. The dose-limiting toxicity was oral mucositis and hand-foot syndrome. More dose intensity could be delivered using a circadian infusion peaking at around 3-4 a.m. than was possible with a flat infusion of these drugs. Toxicity was reduced even further with peak drug delivery at around 9-10 p.m. The recommended dose for phase II studies using this schedule is 250 mg/m2 5-FU daily and 20 mg/m2 LV daily with the peak of the infusion occurring at 9-10 p.m. This is a 300% and 25% higher dose for LV and 5-FU, respectively, than was found to be safe for a flat infusion.