Interactions of radiation and cancer chemotherapeutic drugs in a C3H mouse mammary carcinoma

Postoperative concomitant irradiation and chemotherapy with mitomycin C and bleomycin for advanced head-and-neck carcinoma

PURPOSE

In a prospective randomized clinical study, simultaneous postoperative application of irradiation (RT), mitomycin C, and bleomycin was tested in a group of patients with operable advanced head-and-neck carcinoma. It was expected that the planned combined postoperative therapy would reduce the number of locoregional recurrences and prolong survival.

METHODS AND MATERIALS

A total of 114 eligible patients with Stage III or IV squamous cell head-and-neck carcinoma were randomized to receive postoperative RT alone (Group 1) or RT combined with simultaneous mitomycin C and bleomycin (Group 2). Patients were stratified according to the stage and site of the primary tumor and the presence or absence of high-risk prognostic factors. Primary surgical treatment was performed with curative intent in all patients. Patients in both groups were postoperatively irradiated to the total dose of 56-70 Gy. Chemotherapy included mitomycin C 15 mg/m(2) after 10 Gy and 5 mg of bleomycin twice a week during RT to the planned total dose of 70 mg.

RESULTS

At 2 years, patients in the radiochemotherapy group had better locoregional control (86%) than those in the RT alone group (69%; p = 0.037). Disease-free survival and overall survival was also better in the radiochemotherapy group compared with the RT-alone group (76% vs. 60%, p = 0.099; and 74% vs. 64%, p = 0.036, respectively). Patients who benefited from chemotherapy were those with high-risk factors.

CONCLUSION

The results of the present study indicate that concomitant postoperative radiochemotherapy with mitomycin C and bleomycin improves locoregional control and survival in patients with advanced head-and-neck carcinoma. The patients who benefited from chemotherapy were those with high-risk factors.

Enhancement of tumor radioresponse by combined chemotherapy in murine hepatocarcinoma

BACKGROUND AND AIMS

Recent studies have shown that local radiotherapy can be an effective component of the treatment for hepatocellular carcinoma. To further improve therapeutic efficacy, use of drugs that can beneficially interact with radiation has been suggested. The purpose of this study was to identify drugs that can enhance radioresponse of murine hepatocarcinoma.

METHODS

C3H/HeJ mice bearing 8 mm tumors of murine hepatocarcinoma, HCa-I, were treated with 25 Gy radiation and one of the following drugs: 5-Fu, 150 mg/kg; adriamycin, 8 mg/kg; cisplatin, 6 mg/kg; paclitaxel, 40 mg/kg; and gemcitabine, 50 mg/kg. Tumor response to the treatment was determined by the use of a tumor growth delay assay and by an enhancement factor. The apoptotic level was assessed in tissue sections. The expression of regulating molecules was analyzed by using western blotting for p53, Bcl-2, Bax, Bcl-XL, Bcl-XS, and p21(WAF1/CIP1).

RESULTS

Among the drugs tested, only gemcitabine enhanced the antitumor effect of radiation, with an enhancement factor of 1.6. The induction of apoptosis by a combination of gemcitabine and radiation was shown as only an additive level. In the analysis of radiation-induced expression of regulating molecules, the most significant change by combining gemcitabine with radiation was the activation of p21(WAF1/CIP1).

CONCLUSION

Gemcitabine is the first to show an enhancement of radioresponse of murine hepatocarcinoma when combined with radiation. The key element of enhancement is thought to be p21(WAF1/CIP1).

Concomitant radiotherapy with mitomycin C and bleomycin compared with radiotherapy alone in inoperable head and neck cancer: final report

PURPOSE

To compare the efficacy of concomitant irradiation with mitomycin C and bleomycin in patients with inoperable head and neck carcinoma with radiotherapy alone.

METHODS AND MATERIALS

Between March 1991 and December 1993, 64 patients with inoperable head and neck carcinoma (41 with oropharyngeal site) were randomized to radiotherapy alone (group A) or radiotherapy combined with simultaneous application of mitomycin C and bleomycin (group B). In both groups patients were irradiated five times weekly with 2 Gy to a total dose of 66-70 Gy. The planned concomitant treatment in group B was: bleomycin 5 units twice a week i.m., total dose 70 units, mitomycin C 15 mg/m2 i.v. after delivery of 10 Gy, and 10 mg/m2 i.v. on the last day of radiotherapy. To enhance the effect of these two drugs, patients received also nicotinamide, chlorpromazine, and dicoumarol. Because significantly better results were achieved in arm B for patients with inoperable oropharyngeal carcinoma, the study was closed and such patients were after December 1993 routinely treated with the combined therapy (as in arm B). Until October 1996, we treated and followed up 48 such consecutive patients.

RESULTS

Median follow-up of our study patients is 42 months. Complete remission (CR) rate in group A was 31% and in group B 59% (p = 0.04); disease-free survival (DFS) in group A was 8% and in group B 37% (P = 0.01); and overall survival (OS) was 7% in group A and 26% in group B (p = 0.08). CR rate for patients with oropharyngeal carcinoma was 29% in group A (N = 21) and 75% in group B (N = 20) (p = 0.007); DFS in group A was 10% and in group B 48% (p = 0.001); and the OS was 10% in group A and 38% in group B (p = 0.019). In patients with inoperable oropharyngeal carcinoma treated after December 1993, complete remission was achieved in 32/48 (67%, 95% CI: 52%-80%). DFS at the median follow-up of 14 months was 60% (95% CI 43-77%) and OS 58% (95% CI 42-74%).

CONCLUSION

From the results of our study it seems that the concomitant treatment significantly improves CR rate, DFS, and OS in patients with inoperable oropharyngeal carcinoma in comparison with radiotherapy alone.

Repopulation in the SCCVII squamous cell carcinoma assessed by an in vivo-in vitro excision assay

An in vivo-in vitro excision assay was used to study repopulation after a single dose of clamped irradiation (40 Gy) in the SCCVII tumour implanted in the foot of C3H/Km mice. The growth pattern of clonogenic cells was analysed by two different mathematical models: the logistic model and the Gompertz model. The logistic model described the data better than the Gompertz model. Accelerated repopulation was found when the regrowth rate after irradiation was compared to the growth rate at the time of treatment, and when it was compared to the growth rate in untreated tumours with a number of cells equivalent to the number that was found after irradiation. The clonogenic doubling time (cDT) was estimated at 15.1 h (95% c.i.: 14.2; 16.0) after irradiation, and 27.8 h (95% c.i.: 16.7; 43.5) in untreated controls of matching size. However, the estimate relies on the mathematical model chosen and on extrapolation below actually measured data. A small cDT points to shortening of the cell cycle time and recruitment of non-cycling clonogenic tumour cells to be the main mechanism behind the accelerated repopulation.

Radiotherapy, combined with simultaneous chemotherapy with mitomycin C and bleomycin for inoperable head and neck cancer--preliminary report

PURPOSE

Prospectively designed randomized clinical study was undertaken to assess the efficacy of simultaneous application of irradiation, Mitomycin C, and Bleomycin in treatment of patients with inoperable head and neck carcinoma.

METHODS AND MATERIALS

Between March 1991 and October 1993, 49 patients with inoperable head and neck carcinoma were randomly assigned to receive either radiation therapy alone (group A) or radiotherapy combined with simultaneous application of Mitomycin C and Bleomycin (group B). Patients in both groups were irradiated five times weekly with 2 Gy to the total dose of 66-70 Gy. Chemotherapy regimen included intramuscular application of Bleomycin 5 units twice a week, with the planned dose being 70 units and Mitomycin C 15 mg/m2 applied intravenously after delivery of 9-10 Gy of irradiation. The application of Mitomycin C was planned to be repeated on last day of radiotherapy in the dose of 10 mg/m2. In attempt to enhance the effect of chemotherapeutic drugs, patients in group B received also Nicotinamide, Chlorpromazine, and Dicoumarol.

RESULTS

The difference in complete response rate between both treatment groups (24% in group A and 63% in group B) was statistically significant (p = 0.015). The difference in response rate was much more pronounced in patients with oropharyngeal carcinoma only (18% in group A compared to 81% in group B; p = 0.0003), while for all other subgroups added together, there was observed no benefit of multidrug therapy. Median follow-up was 18 months. Disease-free survival of patients in group A (9%) was significantly lower then in group B (48%) (p = 0.001). The difference between both treatment groups was even greater in patients with oropharyngeal carcinoma only: disease-free survival of these patients in group B was 66%, while in group A, all recurred (p = 0.00001).

CONCLUSION

From results of our prospective randomized study it seems that the group of patients that received multidrug treatment with Mytomycin C, Bleomycin, Nicotinamide, Chlorpromazine, and Dicoumarol as enhancers of radiotherapy fared better than patients treated by radiotherapy alone.

A procedure for estimating the dose modifying effect of chemotherapy on radiation response

A procedure based on a logistic regression model was used to estimate the dose-modifying effect of chemotherapy on the response of normal tissues to radiation. The magnitude of this modifying effect is usually expressed as a dose-effect factor (DEF). Values > 1.0 indicate an enhancing effect of chemotherapy while values < 1.0 suggest a 'protective' effect. The DEF in the proposed procedure is expressed as a function of logistic regression coefficients, response levels and values of covariates in the model. The proposed procedure is advantageous as it allows consideration of both the response levels and the values of covariates in calculating the DEF. A plot of the DEF against the response or a covariate describes how the DEF varies with the response levels or a covariate describes how the DEF varies with the response levels or the covariate values. Confidence intervals of the DEF were obtained based on the normal approximation of the distribution of the estimated DEF and on a non-parametric Bootstrap method. An example is given to illustrate the proposed procedure.

Cisplatin and hyperthermia treatment of a C3H mammary carcinoma in vivo. Importance of sequence, interval, drug dose, and temperature

The effect of combining cisplatin and hyperthermia was investigated in a C3H mammary carcinoma in vivo, using a regrowth delay assay. Cisplatin (6 mg/kg) was given i.p. at intervals ranging from 24 h before to 24 h after a 43.5 degrees C/60 min treatment. A supra-additive effect was obtained by giving cisplatin 15 min before heat, whereas an additive effect was obtained at all other intervals. The importance of cisplatin dose and heating temperature were investigated by giving variable cisplatin doses (2-8 mg/kg) 4 h or 15 min before a 60 min heating at temperatures in the range 40.5-43.5 degrees C. Linear relationships between length of regrowth delay and cisplatin dose were obtained both for cisplatin alone and for the combined treatment. The effect of the combined treatment could therefore be quantitated by a ratio (ER) between the slopes of dose-response curves. The ER values for cisplatin give 4 h before a 60 min heating at 42.5 or 43.5 degrees C were not significantly different from 1 (p greater than 0.5). In contrast, significant ER values were obtained above 40.5 degrees C (p less than 0.05) for cisplatin given 15 min before heat. The data demonstrates the possibility of achieving chemosensitization at clinically relevant temperatures.

The effect of radiation and cytotoxic platinum compounds on the growth of normal and tumour bladder explant cultures

Using an explant tissue culture model developed by this group for use with human surgical and biopsy specimens, data are presented showing the response of normal and tumor bladder urothelium to radiation in combination with cis- and carboplatin. Cellular response is measured after two weeks in culture as a reduction in the extent of outgrowth from the explant. The outgrowth has been shown to be growing and to be epithelial. Results showed that when either drug or radiation is used singly, the tumour is resistant to treatment while the normal cells are severely affected. However, appropriate combinations of either drug with radiation reverse the unfavourable therapeutic ratio and result in higher tumour cell kill. The model may be useful for investigating mechanisms of radiation/chemotherapy action at the cellular level and, if integrated into appropriate clinical trials, may serve as an easy-to-use in vitro test for optimising single agent or combination therapy regimens.

Histological grading of therapy induced regression in squamous cell carcinomas of the oral cavity. A morphological and immunohistochemical study

Squamous cell carcinomas in the oral cavity and the oropharynx were diagnosed in 84 patients. After verification by biopsy, 79 of these patients were treated preoperatively with mitomycin C and 5-fluro-uracil, radiated and operated 3-5 weeks later. The effectiveness of adjuvant preoperative radio-chemotherapy was evaluated histologically. Serial sections of the entire tumor specimen were investigated and the percentage of vital cancerous tissue in the total tumor area was assessed. Regression was classified into four grades. Grades I and II were regarded as good response to adjuvant preoperative radio-chemotherapy, while grades III and IV stood for bad or no response. Morphologically questionable residual tumor infiltrates could be clarified by immunohistochemical methods with antibodies against vimentin, desmin and Lu-5. The histological assessment of the regression grade of operated tumor specimens allows a clinically relevant, morphologically exact and reproducible evaluation of the effect of preoperative radiochemotherapy.

Response to preoperative concomitant radiochemotherapy with mitomycin C and 5-fluorouracil in advanced head and neck cancer

Advanced head and neck tumours have a poor prognosis due to the high frequency of local recurrence. Multimodality treatment has been shown to be effective in decreasing local recurrence. In this study, 51 patients with advanced oral and oropharyngeal carcinoma were entered in a trial of preoperative radio-chemotherapy. After exclusion of -10 protocol violations (no surgery or no chemotherapy), 41 patients remained evaluable. Chemotherapy consisted of 15 mg mitomycin C/m2 given intravenously (bolus) on day 1. 5-Fluorouracil (750 mg/m2/24 h) was infused during days 1-5 (continuous infusion for 120 h). Radiotherapy was performed simultaneously with chemotherapy beginning on day 1. A total dose of 50 Gy to the primary tumour and neck region was delivered over 5 weeks. Treatment was well tolerated. Side-effects were mainly of local character (mucositis). No severe systemic toxicity was seen. Some delayed wound healing was noted at the operation (4 weeks after irradiation). The CR rate of the primary tumours was 56% (23/41). In 39% (16/41) only histological residual tumour was found. Two patients had minor response (categorized as NR) of their tumour (macroscopic residual tumour). None had tumour progression. The response rates considering lymph node metastases were 59% (22/37) CR, 35% (13/37) PR and 5% (2/37) NR. After a follow up of 18-30 months, analysis of local recurrent disease and survival was performed. The loco-regional recurrence rate was 32% (13/41) and the survival rate 63% (26/41). All deceased patients, except two, died of tumour progression. Patients with T4 tumours showed inferior prognosis whereas no significant difference in survival of T2 and T3 patients was found. Patients with CR of tumour and lymph nodes (including NO) have all survived and are without evidence of disease.

Interaction between the microtubule inhibitor tubulozole and gamma-irradiation in murine tumors in vivo

The combined effect of the microtubule inhibitor tubulozole and gamma-irradiation has been investigated in vivo in subcutaneous MO4 fibrosarcomas and Lewis Lung carcinomas. A marked interactive effect on tumor growth was observed when 160 mg/kg tubulozole was orally administered before the tumors were treated with 10 Gy radiation. Dose dependency and optimal effect were obtained on tumor growth of MO4 tumor bearing animals when the drug treatment was given 6 hr prior to the irradiation. The optimal pretreatment time coincided with the time at which a peak mitotic index in the tumor tissue was observed. An enhancing effect is also noticed at other doses of radiation in MO4 tumors pretreated 6 hr before with 160 mg/kg tubulozole. The interactive effect is maintained in a clinically relevant dose fractionation schedule whereby 8 fractions of 2 Gy each were pretreated 6 hr before with 80 mg/kg tubulozole. Tubulozole-T, the stereo-isomer of tubulozole, neither exhibits any antimicrotubular action nor exerts an antitumoral effect on its own or in combination with gamma-irradiation. The possible mechanisms of interaction between tubulozole and gamma-irradiation in tumor tissue are discussed.

Effect of cancer chemotherapy on the hypoxic fraction of a solid tumor measured using a local tumor control assay

The effect of mitomycin C (MMC), adriamycin (ADM), cyclophosphamide (CTX), cisplatinum (cis-DDP) and bleomycin (BLM) on the aerobic and hypoxic cells of a C3H mammary carcinoma in CDF1 mice was investigated using the tumor control assay. Hypoxic fractions (HF) were calculated by an indirect technique using the horizontal displacement of the TCD50 value from the dose-response curves of tumors irradiated under normal or clamped conditions. The HF and absolute number of tumor cells following a combined treatment was compared to that obtained with radiation alone. MMC, ADM and CTX had a significant enhancing effect on the unclamped TCD50. All three drugs caused a marked reduction in the proportion of hypoxic cells, decreasing the HF from 5.4% to about 1% of the total cell number. The surviving proportion of hypoxic cells were 11.1, 8.9 and 6.5% respectively. Killing of aerobic cells was also observed but the effect was less than that seen on the hypoxic cells, with the survival only being reduced to between 38 and 68% of the total number of aerobic cells. In contrast, cis-DDP and BLM were shown to produce major cell killing in the aerobic compartment but actually showed no cytotoxicity towards hypoxic cells. This would explain the lack of radiation enhancement observed for these two drugs. We conclude that the ability of adjuvant drugs to improve radiation response is dependent on the hypoxic cell killing by the drugs.

Thermochemotherapy in vivo of a C3H mouse mammary carcinoma: single fraction heat and drug treatment

The interaction between water bath hyperthermia (43.5 degrees C) and six cancer chemotherapeutic agents in vivo was studied in a transplantable C3H mouse mammary carcinoma grown s.c. in the feet of C3D2F1/Bom mice. Due to differences in tumour regrowth rate between treatment groups, both tumour growth time (TGT) and specific growth delay (SGD) were used as effect parameters. The largest tumour response was observed when the drug was given 15 min prior to heat--this timing was used for dose-effect experiments. Enhancement ratios were the ratios of slopes of dose-effect curves subjected to linear regression analysis. The drug enhancement ratio (DER) was not significantly larger than 1.0 for LD 1% of adriamycin, 5-fluorouracil, methotrexate and vincristine. For cyclophosphamide (CTX) and mitomycin C (MMC) both DER and TER (thermal enhancement ratio) were significantly larger than 1.0. The TGT ratios (SGD ratios in parentheses) were: DER (LD 1%): CTX 1.4 +/- 0.1 (2.1 +/- 0.1), MMC 1.3 +/- 0.1 (1.4 +/- 0.1); TER (43.5 degrees C 30 min): CTX 1.6 +/- 0.1 (2.7 +/- 0.2), MMC 2.8 +/- 0.5 (3.3 +/- 0.7). The data support the choice of CTX and MMC in preference to the other drugs investigated for clinical thermochemotherapy studies.

Rationale for use of local hyperthermia with radiation therapy and selected anticancer drugs in locally advanced human malignancies

The addition of local hyperthermia to radiation therapy has significantly improved the ability of oncologists to control superficial malignancies. Large tumours, tumours which cannot be heated adequately, and those situated in areas where surrounding normal tissues have decreased radiation tolerance, however, are difficult to eradicate even with this combination treatment. We believe that properly selected and scheduled anticancer drugs will add substantially to the efficacy of local hyperthermia and radiation. A review of the literature concerning the cytotoxic interactions of various anticancer agents with hyperthermia, with radiation and with relevant physiological parameters is presented. From this review, anticancer drugs which are good candidates for trimodality therapy are identified and a general approach to trimodality scheduling is suggested.

Effect of step-down heating on hyperthermic radiosensitization in an experimental tumor and a normal tissue in vivo

The effect of step-down heating (SDH) on the radiosensitization induced by simultaneous hyperthermia and radiation was investigated in a C3H mammary carcinoma inoculated into the feet of CDF1 mice and the skin of normal CDF1 feet. SDH consisted of a sensitizing treatment (ST) of 44.5 degrees C/10 min followed by a test treatment (TT) of 41.5 degrees C for 30, 60 or 120 min. Simultaneous administration of radiation and hyperthermia was achieved by delivering radiation in the middle of the TT. The endpoint selected was the radiation dose needed to achieve either tumor control or moist desquamation in 50% of the animals. The results were evaluated by the thermal enhancement ratio (TER), defined as dose of radiation needed to achieve endpoint in relation to dose of combined radiation and hyperthermia needed to achieve the endpoint. SDH of tumors increased the TER significantly compared with step-up heating (SUH). The ratios between TCD50 values for corresponding SDH and SUH increased with TT heating time and at 120 min a 2.5-fold increase in the radiosensitizing effect was achieved. It has previously been shown that SDH alone causes thermosensitization in tumors by decreasing the activation energy. However, the effect was too small to explain the increased radiosensitization observed with SDH. In the normal tissue studies SDH combined with radiation treatment gave a lower TER compared to the SDH tumor results, suggesting a possible therapeutic gain.

Experimental studies on interactions of radiation and cancer chemotherapeutic drugs in normal tissues and a solid tumour

The interactions of radiation and seven cancer chemotherapeutic drugs have been investigated in four normal tissues (intestinal crypts, skin, haemopoietic tissue and lung) and in a solid C3H mouse mammary carcinoma in vivo. All experiments were carried out with male C3D2F1 mice. The investigated drugs were adriamycin (ADM), bleomycin (BLM), cyclophosphamide (CTX), 5-fluorouracil (5-FU), methotrexate (MTX), mitomycin C (MM-C) and cis-diamminedichloroplatinum(II) (cis-DDP). Single drug doses were given at different intervals before, simultaneously with and after single doses of radiation. The normal tissue reactions following drug-radiation combinations were found to be highly complex. The interactions varied both quantitatively and qualitatively from drug to drug and from tissue to tissue. The drugs enhanced the radiation response in most cases. However, signs of radioprotection was observed for CTX in skin and for MTX in haemopoietic tissue. The interval and the sequence of the two treatment modalities were of utmost importance for the normal tissue reactions. In general, the most serious interactions occurred when drugs were administered simultaneously with or a few hours before radiation. The radiation-modifying effect of the drugs deviated from this pattern in the haemopoietic tissue as the radiation response was most enhanced on drug administration 1-3 days after radiation. Enhancement of the radiation response was generally less pronounced in the tumour model than in the normal tissues. The combined drug-radiation effect was apparently less time-dependent in the tumour than in the normal tissues.

Interactions of radiation, cyclophosphamide and nimorazole in a C3H mammary carcinoma in vivo

The combined effect of adjuvant Cyclophosphamide (CTX) and the hypoxic radiosensitizer, Nimorazole (NIM), on the radiation response was studied in a C3H mammary carcinoma in CDF1 mice. The effect of NIM and CTX alone or in combination without radiation was assessed by tumor growth delay measured by tumor growth time (TGT). Administration of CTX (100 mg/kg) increased the TGT from 5.2 days in untreated controls to 18.8 days. NIM (1000 mg/kg) had no effect on the TGT. The combined treatment with NIM given 4 hrs before CTX did not increase the TGT compared with CTX alone, which suggests that NIM does not potentiate CTX. The possible effect of an interaction between the therapeutic parameters was determined by administration of NIM, CTX, and radiation in different sequences to C3H mammary tumor bearing mice. The drugs were administered as single doses before or after graded single doses of irradiation. The end point was the radiation dose required to achieve local tumor control in 50% of the mice (TCD50). The enhancement ratio (ER)--defined as TCD50 for radiation alone relative to TCD50 for radiation combined with drug--was 1.2 for CTX given either 15 min before or 4 hrs after radiation. NIM given 30 min before radiation showed an ER of 1.6, but no enhancement was obtained when NIM was given after radiation. When NIM was given immediately after radiation, followed 4 hrs later by CTX, the ER was 1.2. However, applying NIM 30 min before radiation and CTX 3.5 hrs after radiation, the ER increased to 1.6. NIM given 30 min before, together with CTX given 15 min before radiation, showed an ER of 1.8. Our data suggest that: an improved tumor response may be expected when CTX is added to a radiation and hypoxic radiosensitizer treatment; this improvement is attributable to an additive effect based on the chemotherapy response alone rather than to chemopotentiation by the hypoxic radiosensitizer.

Effect of cancer chemotherapeutic drugs on radiation-induced lung damage in mice

The effect of adriamycin (ADM), bleomycin (BLM), cyclophosphamide (CTX), 5-fluorouracil (5-FU), methotrexate (MTX), mitomycin C (MM-C) and cis-diamminedichloroplatinum(II) (cis-DDP) on the radiation-induced lung damage in mice was assessed by the ventilation rate (VR) and the lethality. Single drug doses were administered 15 min before graded single doses of irradiation and at different intervals from 28 days before to 28 days after fixed radiation doses. ADM, BLM and CTX administered 15 min before irradiation enhanced the radiation response with dose effect factors (DEF) of 1.46, 1.56 and 2.35, respectively. The effect of MM-C presented a complex picture. The drug had no effect at administration 15 min before 14-20 Gy, but enhanced the radiation response if given 15 min before 6-12 Gy (DEF = 1.57). The radiation-modifying effect of ADM, BLM, CTX and MM-C was most pronounced when the drugs were given 15 min before irradiation. The effect of ADM was present when administered from 7 days before to 7 days after irradiation. BLM and CTX enhanced the radiation response at administration from 24 h before to 3 days after irradiation, and the effect of MM-C was observed when the drug was given from 24 h before to 24 h after irradiation. 5-FU, MTX and cis-DDP had no effect on the radiation response at any of the investigated intervals.