The uptake of 3H-vincristine by a mouse carcinoma during a course of fractionated radiotherapy

Monitoring of tumor microcirculation during fractionated radiation therapy in patients with rectal carcinoma: preliminary results and implications for therapy

PURPOSE

To measure microcirculatory changes during chemoirradiation and to correlate perfusion index (PI) values with therapy outcome.

MATERIALS AND METHODS

Perfusion data in 11 patients with cT3 (clinical staging, tumor invaded the perirectal tissue) rectal carcinoma who underwent preoperative chemoirradiation were analyzed. Perfusion data were acquired by using a T1 mapping sequence with a whole-body magnetic resonance (MR) imager. After contrast medium was intravenously infused at a constant rate, concentration-and-time curves were evaluated for arterial blood and tumor. All patients underwent MR imaging before and at constant intervals during chemoirradiation. Clinical stages before therapy were compared with surgical stages after therapy.

RESULTS

Spatial and temporal resolution on dynamic T1 maps were sufficient to reveal changes in contrast medium accumulation in the tumor. Comparison of PI values and radiation dose showed a significant increase in the 1st (P: =.003) and 2nd weeks (P: =.01) of treatment; values subsequently returned to pretreatment levels or showed a renewed increase. High initial PI values correlated with greater lymph node downstaging (P: =.042).

CONCLUSION

Dynamic T1 mapping provides a suitable tool for monitoring tumor microcirculation during chemoirradiation and offers the potential for individual optimization of therapeutic procedures. Furthermore, these results indicate that the PI map may serve as a prognostic factor.

Variations in Tumor Levels of Cis-Platinum through a Course of Fractionated Radiotherapy in Patients with Non-Small Cell Lung Cancer

Aims and background

Radiation has been shown to affect the uptake of micromolecules by the tissues within the radiation fields. We measured tumor drug uptake throughout a course of radiotherapy for stage III non-operable non-small-cell lung cancer (NSCLC).

Patients and Methods

Thirty patients were treated with radiotherapy consisting of 15 fractions of 300 cGy given over 3 weeks. They were divided into groups of 2. At 1.5 hr before a given fraction of radiotherapy, one group was given iv a bolus of 6 mg/m2 CDDP (cis-diamminedichloroplatinum). Between 1.5 and 2 hr after radiotherapy, the patients underwent bronchoscopy, during which a biopsy was taken from the tumor mass. A similar procedure was carried out on a different group of 2 patients at each of the 15 radiotherapy fractions. The amount of platinum in the biopsy sample was measured by atomic absorption spectroscopy and expressed as ng platinum/mg tissue. In another 13 patients, a biopsy was taken before beginning the radiotherapy, and they served as controls.

Results

The quantity of platinum/g of tissue in the patients was 11 ± 4.4 ng/mg tissue. During the course of fractionated radiotherapy, the quantity of platinum/g of tumor varied considerably between radiotherapy fractions. Maximum uptake was at fractions 8 and 9 (92 ng platinum/mg tissue) with the minima during the first few fractions and at fractions 10, 11 and 12 (an average 20 ng platinum/mg tissue).

Conclusions

The cyclical variations in the uptake of CDDP by the tumor tissue during the protracted course of fractionated radiotherapy are probably due to the well-known effects of radiation on vascular function and capillary permeability. The results may have implications for future clinical protocols involving chemo- and radiotherapy for the treatment of the disease.

Paclitaxel as a radiosensitiser: a proposed schedule of administration based on in vitro data and pharmacokinetic calculations

Paclitaxel is efficacious against many human cancers. Because it blocks cells at the radiosensitive G2-M interface, paclitaxel has been investigated as a radiosensitiser. The results have been equivocal and somewhat contradictory. It is impossible to obtain proper pharmacokinetic calculations, aimed at obtaining maximum cytotoxicity and/or radiosensitisation, without knowing (i) how long the drug must be in contact with the cells, (ii) how long the effect lasts after the drug is removed from the cellular environment, (iii) whether the drug acts as a radiosensitiser even when, like cis-platinum, it is added after the radiation and (iv) what the minimum quantity of drug in the cellular environment is required for both chemotoxicity and radiosensitisation. The present work addresses the above questions. Two radioresistant cell lines of human origin were used, A375 melanoma and S549 lung carcinoma, in a clonogenic assay where only colonies with 50 or more cells were counted. For the irradiation, 6 MV X-rays were used. Any G2-M block was quantified by cell cycle kinetics analysis. From the results, a simulation of pharmacokinetics was conducted to calculate the schedule of administration of paclitaxel most likely to achieve and maintain significant chemotoxocity and radiosensitisation. The minimum concentration of paclitaxel for measurable cytotoxicity was 3 nM for both cell lines, but the drug was more toxic to the A549 cells. The minimum concentration for measurable radiosensitisation was 3 nM for A375 and approximately 0.1 nM for A549, but whereas above 3 nM the radiosensitivity increased in A375, it decreased above 1 nM for A549. A minimum of 18 h incubation with the drug was necessary for measurable effects and the radiosensitising effects were lost soon after its removal. There was no radiosensitisation if paclitaxel was added after the radiation, and, at the minimum effective concentrations, it caused only a minor and transient G2-M block. The pharmacokinetic calculations predict that 15 mg/m2 paclitaxel given as a 1 h infusion 5 days/week for 3 weeks during the radiotherapy should achieve both cytotoxicity and radiosensitisation. The mechanism of radiosensitisation by paclitaxel at the concentrations suggested by our results does not appear to be via a G2-M block and is probably concentration dependent. The results imply that low-dose, daily infusions of paclitaxel for as long as possible during a course of radiotherapy are more likely to result in radiosensitisation and prolonged cytotoxicity than high-dose infusions given once a week.

Combined modality treatment of the rhabdomyosarcoma R1H of the rat: tumor and normal tissue response after cisplatin and conventional or accelerated irradiation treatment

PURPOSE

To test the importance of the sequence of cisplatin and irradiation, either conventional or accelerated fractionated.

METHODS AND MATERIALS

30 fractions of 2 Gy were given in 6 or 3 weeks preceded or followed by (time interval between cisplatin and radiotherapy: 3 days) a single IP dose of 5 mg/kg cisplatin in the rhabdomyosarcoma R1H of the rat. Survival curves were generated, and comparisons were made by the log-rank test.

RESULTS

After 60 Gy in 6 weeks, no local tumor controls were observed. If cisplatin was injected 3 days before start of 60 Gy/6 weeks, 11 +/- 10% (mean +/- SE) of the tumors were controlled. Cisplatin after radiotherapy resulted in 50 +/- 14% local controls. The difference was significant (p = 0.01) for cisplatin after radiotherapy in comparison to radiotherapy alone where no local controls were observed. After accelerated fractionation, 57 +/- 19% of the animals were cured with or without cisplatin before radiotherapy. If the drug was injected after end of 60 Gy/3 weeks, 86 +/- 13% survived recurrence free. The difference to accelerated radiotherapy alone was not significant. Accelerated radiotherapy produced significantly higher control rates than conventional radiotherapy (p < 0.001).

CONCLUSIONS

Accelerated radiotherapy resulted in higher local tumor control rates as compared to conventional fractionated irradiation. Cisplatin combined with radiotherapy showed significantly better results if given after but not before irradiation, either conventional or accelerated fractionated.

Combined modality treatment of the rhabdomyosarcoma R1H of the rat: influence of sequence of cisplatin and fractionated irradiation

The effect of irradiation with 30 fractions of 2 Gy in 6 weeks combined with a single dose of 5mg/kg cisplatin was studied in the rhabdomyosarcoma R1H of the rat and tumor response and normal tissue toxicity were assessed for various combinations of radiotherapy and chemotherapy. Cisplatin was given 3 days before, during (after the 5th and after the 10th fraction), or 3 and 17 days after radiotherapy. Five of the 12 tumors treated with cisplatin injected 3 days after radiotherapy were locally controlled (42%; 95% confidence intervals: 14-70%) as compared to 0/10 for radiotherapy alone (0%; 0-21%; p < 0.02). A similar trend was found for cisplatin injected 17 days after irradiation (2/6 local controls; 33%; 0-71%). With cisplatin given 3 days before radiotherapy 1/13 local controls were observed (8%; 0-22%; p < 0.05 when tested vs. cisplatin 3 days after radiotherapy). Tumor cure was dependent upon tumor size at time of cisplatin administration with 7/9 small tumors (< 2 mm3) cured versus only 2/35 cures of larger tumors (> 2 mm3). By contrast, net growth delay and skin damage were the same for combined modality treatment and for irradiation alone. General toxicity as assessed by body weight change was significantly higher for animals treated with cisplatin before or after radiotherapy, whereas cisplatin during radiotherapy showed equal effects as compared to radiotherapy alone. Although for the rhabdomyosarcoma R1H of the rat the combined modality treatment was shown to be more effective than radiotherapy alone when cisplatin was applied after radiotherapy, general toxicity was also higher for this mode of treatment.

The effect of timing of vincristine administration during a course of fractionated radiotherapy in a mouse carcinoma

It has been previously shown that the uptake of 3H-vincristine by the NT carcinoma tumour in CBA mice can vary by a factor of 3 during a course of fractionated radiotherapy (2 Gy day-1, 5 day week-1, for 5 weeks). Here the effect of therapeutic doses of vincristine given at times of either maximum or minimum uptake has been investigated. The results show that whereas vincristine alone has a dose-related effect on this tumour, when given in combination with fractionated radiation it is only effective if administered during the first few fractions. It does not seem to matter whether it is given at times of maximum or minimum uptake. It is concluded that vincristine either exacerbates the radiation-induced vascular damage so that drug extravasation is reduced or that it causes a shift in the time of appearance of the peaks and troughs of uptake. The possibility that radiation-induced resistance to vincristine may have played a part in the results is also discussed.

Radiotherapy versus radiotherapy enhanced by cisplatin in stage III non-small cell lung cancer

Between January 1987 and June 1991, 173 patients with inoperable non-small cell lung cancer, Stage III, were entered into a randomized trial comparing radiotherapy only (RT) (45 Gy/15 fractions/3 weeks) (arm A) versus RT and a daily low dose of cDDP (6 mg/m2) (arm B). An overall response rate of 58.9% was observed in arm A and 50.6% in arm B, respectively. No differences in the pattern of relapse were noted between the two treatment groups. Median time to progression was 10.6 months for arm A and 14.2 months for arm B. Median survivals were 10.3 months and 9.97 months, respectively. Toxicity was acceptable and no treatment-related death occurred in either treatment schedule. In this study no significant advantage of the combined treatment over radiation therapy only was found. The encouraging results achieved in some trials together with the intractability of the disease suggest that further efforts should be made to optimize clinical trial protocols, perhaps by reviewing the radiobiological and pharmacological basis of the combined treatment.