Comparison of radiotherapy with and without razoxane (ICRF 159) in the treatment of soft tissue sarcomas

Radiotherapy vs. radiotherapy and razoxane in the treatment of soft tissue sarcomas: final results of a randomized study

PURPOSE

The effect of the sensitizer razoxane on soft tissue sarcomas (STS) was prospectively evaluated in a randomized, controlled trial. The main purpose of the study was to determine the response rates and local control under the combined treatment compared to irradiation alone.

METHODS AND MATERIALS

Between 1978 and 1988, 144 patients entered the study; 130 were evaluable for response, toxicity, or survival. The patients were randomized to receive radiotherapy alone or radiotherapy with razoxane. They were divided into postoperative cases and patients with gross disease (unresectable primaries, recurrent disease, or metastatic disease). The median radiation dose was 60 Gy postoperatively, and 56-58 Gy in patients with gross disease. The dose difference has palliative reasons. Razoxane was given orally at a daily dose of 150 mg/m2 during the time of the radiotherapy, starting 5 days before the first irradiation. In general, the groups were comparable as to their prognostic factors. There was some imbalance, however, in favor of the postoperative group reveiving radiotherapy alone.

RESULTS

Between the patient groups treated postoperatively in an adjuvant form, there were no substantial differences in local control and survival. Among 82 patients with gross disease, the treatment with radiotherapy and razoxane led to an increased response rate compared to photon irradiation alone (74 vs. 49%). The local control rate was likewise improved (64 vs. 30%;p < 0.05). The acute toxicity was somewhat higher in the sensitizer arm, but there was no difference in the occurrence of late complications.

CONCLUSIONS

Radiotherapy combined with razoxane seems to improve the local control in inoperable, residual, or recurrent STS compared to radiotherapy alone. The combined treatment is a fairly well tolerated procedure at low costs. It can be recommended for inoperable primary STS or gross disease after incomplete resection, conditions which are still associated with limited local control and a grave prognosis.

Tumor radioresponsiveness versus fractionation sensitivity

Since the introduction of mammalian cell survival curves, the parameters D0 and N have been used as quantitative measures of inherent radiation sensitivity, as was the shoulder width Dq. These parameters are more generally applicable at high doses. We propose to introduce a measure of tumor radioresponsitivity that is more applicable to the clinical treatment schedules that employ small fractional doses (1-2 Gy), the ratio alpha/E, derived from the linear quadratic model for cell inactivation as the intercept on the reciprocal-dose plot. For tumor-control experiments this ratio is the reciprocal of the TCD50 when radiation is given in very small fractions or at low dose rates (assuming negligible clonogen proliferation). The rationales for this choice are: alpha is a measure of the steepness of the initial linear segment of the dose-survival curve. Accordingly, at doses per fraction of 1-2 Gy the observed effect increases with alpha. E is by definition a positive measure of the clonogen kill required for a specified tumor response, e.g., E = -log (surviving fraction of clonogens at the 50% control level). Therefore it is also a measure of the number of clonogens present at the time of inception of treatment, which for a given dose is a prime determinant of the probability of tumor control. This measure of radioresponsitivity is to be distinguished from the ratio alpha/beta, which is a measure of fractionation sensitivity. A survey of the literature indicates that these do not correlate, except in highly hypoxic tumors (e.g., clamped); such tumors are characterized by low radioresponsitivity as well as low fractionation sensitivity (high alpha/beta ratio). There are at present only limited data for determination of this ratio, however, since reciprocal-dose analysis requires tumor control doses for several different sizes of dose per fraction.

The design of a sequential clinical trial for the comparison of two lung cancer treatments

The steps in designing a controlled trial to evaluate a new treatment for inoperable carcinoma of the bronchus are described. The principal outcome measure is survival time from treatment allocation, and the duration of the trial is determined by application of the sequential logrank test. The detailed determination of the stopping rule and the arrangements for analyses are described.

The influence of ICRF-159 and levamisole on the incidence of metastases following local irradiation of a solid tumor

Courses of irradiation consisting of 6000 rad in ten equal fractions over 12 days delivered to KHT sarcomas in mice controlled 55% of the local tumors but 83% of the mice died from metastases. Three strategies to reduce the risk of metastatic spread were tested. The fractionation scheme was changed to deliver the same total dose using a large initial fraction followed by seven equal portions with the same overall time. ICRF-159 was used with the intention of partially synchronizing the tumor growth fraction in a radiosensitive state of the growth cycle and of promoting normalization of the tumor vasculature. Levamisole was used to stimulate the immune system. The combination of ICRF-159 with the eight-fraction radiation course proved to be effective for both increasing local control and decreasing the incidence of metastases. The addition of levamisole did not improve the results obtained with a combination of ICRF-159 and irradiation.

Combination therapy of a mouse sarcoma using razoxane and electron irradiation

The combination of a single dose of razoxane (ICRF 159) with a single dose of electron radiation has been studied with the murine sarcoma S180. A drug dose of 30 mg/kg combined with radiation produced a greater tumour response than either agent alone, but it was not possible to establish whether the effect was more than additive. Direct measurements of tumour and s.c. oxygen concentrations and studies of tumour-cell respiration were carried out after various razoxane treatments in an attempt to elucidate mechanisms of action. There were no indications at the drug dose levels used in the radiation studies of any significant changes in tissue oxygenation or cellular respiration.

Combination of radiotherapy and razoxane (ICRF 159) for chondrosarcoma

Eight patients with 12 chondrosarcomas were treated with radiation and razoxane (ICRF 159). Two tumors in 1 patient progressed unequivocally, 3 tumors in 3 patients showed no change, and 7 tumors in 5 patients had complete or partial (more than 50%) regressions. At least 2 complete regressions have responded for more than 2 1/2 years at the present time.