The second Klaas Breur memorial lecture. La Ronde--radiation sciences and medical radiology

Effects of the Perfluorochemical Emulsion FMIQ on the Radiation Response of EMT6 Tumours

The effects of FMIQ, a perfluorochemical emulsion based on perfluoro-N-methyldecahydroisoquinoline, were examined using BALB/c mice and EMT6 mammary carcinomas. The radiobiological effects of FMIQ were similar to those found previously for Fluosol in the same tumour/host system. Although the perfluorochemical content (20% w/v) and oxygen-carrying capacity of FMIQ are similar to those of Fluosol, the formulation of FMIQ offers some advantages over that of Fluosol. For example, FMIQ has greater stability during storage. FMIQ also is formulated without pluronic F-68 and is based on a perfluorochemical (FMIQ) having a shorter tissue dwell time than the perfluorotripropylamine in Fluosol; it therefore may produce fewer side-effects than Fluosol. The lifetime of the circulating perfluorochemical droplets in BALB/c mice was longer than FMIQ than for Fluosol; this could offer an advantage in fractionated radiotherapy. These findings give reason to expect that FMIQ may prove to be a better emulsion than Fluosol for clinical use as an adjunct to cancer therapy.

Final report of a randomized trial on altered-fractionated radiotherapy in nasopharyngeal carcinoma prematurely terminated by significant increase in neurologic complications

PURPOSE

The aim of the present study was to compare the survival, local control and complications of conventional/accelerated-hyperfractionated radiotherapy and conventional radiotherapy in nonmetastatic nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS

From February 1993 to October 1995, 159 patients with newly diagnosed nonmetastatic (M0) NPC with N0 or 4 cm or less N1 disease (Ho's N-stage classification, 1978) were randomized to receive either conventional radiotherapy (Arm I, n = 82) or conventional/accelerated-hyperfractionated radiotherapy (Arm II, n = 77). Stratification was according to the T stage. The biologic effective dose (10 Grays) to the primary and the upper cervical lymphatics were 75.0 and 73.1 for Arm I and 84.4 and 77.2 for Arm II, respectively.

RESULTS

With comparable distribution among the T stages between the two arms, the free from local failure rate at 5 years after radiotherapy was not significantly different between the two arms (85.3%; 95% confidence interval, 77.2-93.4% for Arm I; and 88.9%; 95% confidence interval, 81.7-96.2% for Arm II). The two arms were also comparable in overall survival, relapse-free survival, and rates of distant metastasis and regional relapse. Conventional/accelerated-hyperfractionated radiotherapy was associated with significantly increased radiation-induced damage to the central nervous system (including temporal lobe, cranial nerves, optic nerve/chiasma, and brainstem/spinal cord) in Arm II. Although insignificant, radiation-induced cranial nerve(s) palsy (typically involving VIII-XII), trismus, neck soft tissue fibrosis, and hypopituiturism and hypothyroidism occurred more often in Arm II. In addition, the complications occurred at significantly shorter intervals after radiotherapy in Arm II.

CONCLUSION

Accelerated hyperfractionation when used in conjunction with a two-dimensional radiotherapy planning technique, in this case the Ho's technique, resulted in increased radiation damage to the central nervous system without significant improvement in efficacy.

RSR13, a synthetic allosteric modifier of hemoglobin, as an adjunct to radiotherapy: preliminary studies with EMT6 cells and tumors and normal tissues in mice

RSR13, 2[4-[[(3,5dimethylanilino)carbonyl]methyl]phenoxy]-2-methylpropion ic acid, a synthetic allosteric modifier of hemoglobin, reduces the affinity of hemoglobin for oxygen. The experiments reported here examined the effect of treatment with RSR13, combined with oxygen breathing, on the radiation response of EMT6 mammary tumors in BALB/c mice and of two normal tissues. RSR13 plus oxygen breathing increased the response of EMT6 tumors to irradiation. RSR13 had no discernible effects on tumors rendered maximally hypoxic by nitrogen asphyxiation, no discernible cytotoxic effects in EMT6 tumors, and no effect on the viability or radiation response of EMT6 cells in vitro under either aerobic or hypoxic conditions. The effects of RSR13 therefore reflect changes in tumor oxygenation, rather than a direct cytotoxic or radiosensitizing effect of the drug. RSR13 plus oxygen reduced the hypoxic fraction to 9% from the value of 24% found in both air-breathing and oxygen-breathing mice. Treatment with RSR13 plus oxygen did not alter the radiation response of the bone marrow progenitor cells (CFU-S) or acute radiation reactions in the skin. The improvement in tumor radiation response produced by treatment with RSR13 plus oxygen, combined with the absence of enhanced radiation reactions in the normal tissues, support further testing of RSR13 as an adjunct to radiotherapy.

The integral biologically effective dose to predict brain stem toxicity of hypofractionated stereotactic radiotherapy

OBJECTIVE

The aim of this work was to develop a parameter for use during fractionated stereotactic radiotherapy treatment planning to aid in the determination of the appropriate treatment volume and fractionation regimen that will minimize risk of late damage to normal tissue.

MATERIALS & METHODS

We have used the linear quadratic model to assess the biologically effective dose at the periphery of stereotactic radiotherapy treatment volumes that impinge on the brain stem. This paper reports a retrospective study of 77 patients with malignant and benign intracranial lesions, treated between 1987 and 1995, with the dynamic rotation technique in 6 fractions over a period of 2 weeks, to a total dose of 42 Gy prescribed at the 90% isodose surface. From differential dose-volume histograms, we evaluated biologically effective dose-volume histograms and obtained an integral biologically-effective dose (IBED) in each case.

RESULTS

Of the 77 patients in the study, 36 had target volumes positioned so that the brain stem received more than 1% of the prescribed dose, and 4 of these, all treated for meningioma, developed serious late damage involving the brain stem. Other than type of lesion, the only significant variable was the volume of brain stem exposed. An analysis of the IBEDs received by these 36 patients shows evidence of a threshold value for late damage to the brain stem consistent with similar thresholds that have been determined for external beam radiotherapy.

CONCLUSION

We have introduced a new parameter, the IBED, that may be used to represent the fractional effective dose to structures such as the brain stem that are partially irradiated with stereotactic dose distributions. The IBED is easily calculated prior to treatment and may be used to determine appropriate treatment volumes and fractionation regimens minimizing possible toxicity to normal tissue.

How radiation oncology emerged as a discipline in Finland

The news about the discovery of Röntgen's new rays spread over Finland quite early, and the first Finnish writing about the rays appeared in February 1896. The first x-ray machine was installed in 1897. Proper training of radiologists began, however, at a comparatively late date. For a long time the position of radiologists remained a subordinate one. Radiology had the nature of a spare time hobby, because in most hospitals surgeons treated x-ray machines as a sideline. Because of this, scientific research work was delayed. The specialty of x-ray diagnosis and therapy was, however, established in 1921, and the Finnish Society of Radiology was founded in 1924. The first radiotherapy department with its own beds was opened in 1936 in Helsinki. In 1950, the first professor of medical radiology was appointed at the University of Helsinki. The Finnish Cancer Society played an important role in developing the radiotherapy net in the country by supplying cobalt devises and auxiliary hospital activities in the 1960s. In the early 1960s roentgen diagnosis and radiotherapy were separated into two distinct disciplines. There are now five medical faculties with chairs in radiation oncology. The country is divided into five regions for cancer care. The managing groups in each region are headed by the professor of radiotherapy and oncology. The radiation oncologists in Finland are involved in diagnosis and staging of cancer and are responsible for radiation therapy, chemotherapy and hormones. They are responsible for follow-up of treated patients, their own wards, and the general care of their patients.

Early tumour response and treatment toxicity after hyperfractionated radiotherapy in nasopharyngeal carcinoma

The aim of the present study was to undertake a planned interim analysis of a prospective randomized trial comparing the tumour response and the acute and subacute complications of hyperfractionated radiotherapy and conventional radiotherapy in non-metastatic nasopharyngeal carcinoma (NPC). 100 patients with newly diagnosed non-metastatic NPC were randomized to receive either conventional radiotherapy (Arm I) or hyperfractionated radiotherapy (Arm II). Stratification was done according to the T-Stage (modified Ho's T-Stage classification). The biological effective dose (10 Gy) to the primary and the upper cervical lymphatics were 75.0 and 73.1 for Arm I and 84.4 and 77.2 for Arm II, respectively. Hyperfractionated radiotherapy was associated with significant mucositis which is of higher grade than conventional radiotherapy (p = 0.0001), but the duration of mucositis was similar between the two Arms and all study patients completed radiotherapy on schedule without interruption of radiotherapy. Early survival and tumour recurrence rates were comparable between the Arms. The preliminary results indicate that the hyperfractionated radiotherapy has excellent patient compliance in Chinese patients, with acceptable acute and subacute toxicities and the local and regional complete tumour response rates being comparable with conventional radiotherapy. The significance of the time required after start of radiotherapy to achieve a complete tumour response is discussed.

Accelerated radiotherapy in glioblastoma multiforme: a dose searching prospective study

The EORTC Radiotherapy Cooperative Group performed a prospective phase II study in glioblastoma multiforme using accelerated radiotherapy in escalating doses. The aims of the study were to investigate acute and late toxicity as well as tumor response and survival. Only the CT-enhanced tumor zone plus a margin of 2-3 cm were treated (mean volume, 1034 +/- 477 cm3). Radiotherapy was administered with 5-18 MV photons. The radiation schedule consisted of 3 fractions of 2 Gy/day, separated with at least 4 h. The first group of patients was scheduled to receive a total dose of 42 Gy, 21 fractions in 9 days. The total dose was then escalated up to 48 Gy (24 fractions in 10 days), 54 Gy (27 fractions in 11 days) and 60 Gy (30 fractions in 12 days). The numbers of patients entered in each dose-level group were 15, 17, 18 and 16, respectively. Acute toxicity was mild, nausea/vomiting was absent in 91% of the patients. In 80% of the patients the neurological condition improved or remained stable compared with the start of radiotherapy but in 58% of the patients steroids were necessary, either increased in dose or initiated. Acute toxicity did not increase with increasing radiation doses although patients treated with 60 Gy more often required steroids than the other groups. Late toxicity was strongly suspected in 2 patients receiving 52 Gy and 56 Gy, respectively. Within the whole group of 66 patients only one recurrence outside the primary site was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperfractionated radiotherapy of bladder cancer. A ten-year follow-up of a randomized clinical trial

One hundred and sixty-eight patients with invasive bladder cancer, T2-T4, were randomized to one of two treatments; hyperfractionation with 1 Gy 3 times a day to a total of 84 Gy or conventional treatment 2 Gy once a day to a total of 64 Gy. Both treatments were given over 8 weeks with a rest interval of 2 weeks in the middle of the treatment period. The present report included all patients after a follow-up period of at least 10 years. The survival benefit from hyperfractionation previously reported after 5 years is still evident after 10 years. The effect was detectable in all three subsets (T2, T3 and T4) and in the pooled data. However, it only reached statistical significance in the T3 subset and in the total pooled data set. Local control was also assessed by cystoscopy and cytology on bladder washouts. An improvement in local control was seen at all follow-up intervals and at all times out to 10 years but the differences were not statistically significant due to the falling number of patients available for assessment. Complications in the bowel requiring surgical treatment were more common in the hyperfractionated group but the difference was not significant since this group consisted of a greater number of patients alive and therefore at risk. This trial showed that the benefit of the hyperfractionated schedule persisted over a 10-year follow-up period, both for local control and survival.

The Janeway Lecture 1992. Nine decades of radiobiology: is radiation therapy any the better for it?

Nine decades have elapsed since Pierre Curie performed the first radiobiologic experiment when he used a radium tube to produce an ulcer on his arm and charted its progress and ultimate healing. A wide range of topics have been investigated in experimental radiation biology from chromosomal aberrations to fractionation effects in normal tissues to the use of neutrons and bioreductive drugs. Many of the strategies used in clinical radiation therapy, including hyperfractionation and accelerated treatment, are firmly based on laboratory experiments conducted in the past. Much current research is focused on understanding the molecular genetics of cancer to identify the genes that are activated or deleted in cells exposed to radiation. Radiobiology has played a key role in shaping radiation therapy into the vigorous, scientifically based, and highly quantitative branch of medicine that it is currently. In addition, research is preparing the field for the future when treatment protocols must be based on molecular rather than cellular biology.

Preclinical evaluation of Oxygent as an adjunct to radiotherapy

These studies examine the potential value of a concentrated emulsion of perfluorooctylbromide (perflubron; Oxygent, Alliance Pharmaceutical Corp.) as an adjunct to radiotherapy. The effects of Oxygent on solid tumors were examined using EMT6 mammary tumors in BALB/c mice and BA1112 rhabdomyosarcomas in WAG/rij rats. Treatment with Oxygent plus O2, carbogen (95% O2/5% CO2), or hyperbaric oxygen (HBO) increased the effects of radiation on the tumors. Analyses of tumor cell survival curves and measurements of intratumor pO2 showed that this potentiation reflected an increase in the proportion of well-oxygenated tumor cells. Neither treatment of the animals with carbogen, O2, or HBO alone nor treatment of air-breathing rodents with Oxygent produced changes of similar magnitude. Treatment with a vehicle emulsion containing all the components of Oxygent except the perflubron did not alter tumor radiosensitivity, showing that tumor radiosensitization required the oxygen-transporting perfluorocarbon, and did not result from any biologic or physiologic effects of other components of the emulsion. These studies also examined the effects of Oxygent on the radiation responses of mouse skin and bone marrow. Oxygent selectively increased the radiation sensitivity of tumors relative to these normal tissues, thereby increasing the therapeutic ratio and producing therapeutic gain. Oxygent appears to warrant further testing as an adjunct to cancer therapy.

Intermittent blood flow in the KHT sarcoma--flow cytometry studies using Hoechst 33342

The administration of the fluorescent DNA stain, Hoechst 33342, to mice bearing the KHT sarcoma, combined with flow cytometry, can be used to select cells according to their proximity to functional vasculature. Different protocols of administration of Hoechst 33342 were used in order to differentiate between the presence of temporary and chronically hypoxic cells. The results show a large difference in radiosensitivity between cells close to, and distant from, functional vasculature. However, this pattern of radiosensitivity is observed only when the staining period with Hoechst 33342 is short and coincides with the period of irradiation. When the radiation treatment is temporally divorced from the staining period then the radiosensitivity and staining intensity are not related. This result can be interpreted as indicating that hypoxic cells exist within this tumour as a result of fluctuations in tumour blood flow.

Applicability of animal tumor data to cancer therapy in humans

The problem of applying experimental tumor studies to clinical cancer therapy is a complex one. The radiotherapy literature contains many examples of premature efforts to apply laboratory observations to the clinic, and many examples of failures to adequately consider animal tumor observations in the design of clinical studies. This review covers three areas: tumor hypoxia, where clinical trials based on animal tumor data have been conducted with radiosensitizers, hyperbaric oxygen, and systemic oxygen carriers; dose fractionation, where current trials of hyperfractionation are based in part on animal tumor studies; and chemo-radiotherapy, where clinical trials are only beginning to exploit concepts developed in animal tumor systems. The use of animal tumor systems extends past the screening of new agents. Animal tumor models can be used in biological, physiological, and pharmacological studies to elucidate the biological factors influencing the efficacy of therapeutic agents. Tumor studies can be combined with studies of normal tissues to predict the toxicities to be anticipated in clinical trials, and to assess the potential for therapeutic gain. Animal studies can also provide data which are useful in designing optimal clinical trials of new agents and maximizing the potential for successful clinical application of new approaches. In general, it is not possible to apply specific laboratory data directly to man. To translate, rather than transpose, information from the laboratory to the clinic, the model studies must be directed at evaluating principles, rather than merely quantifying results. Only through studies of mechanisms, by designing experiments to test or refute a hypothesis, will it be possible to apply model studies to man.

Validation of the fluorescent dye Hoechst 33342 as a vascular space marker in tumours

The DNA-binding fluorescent dye Hoechst 33342 (H33342) has been used in a series of investigations of the vascular parameters of two murine tumours. This dye has been shown, to have a short half-life in the circulation (T1/2 less than 2 min), but is stably bound for at least 2 h after it enters cells. It can be used in morphometric studies on frozen sections to determine the effective vascular volume, the capillary fraction and the size distribution of blood vessels in each tumour. These latter two parameters cannot be deduced from the less labour intensive techniques using radioactive isotopes. The effective vascular volume perfused in 1 min by H33342 was compared with the volume perfused in 30 min with 51Cr labelled erythrocytes. Similar volumes were estimated with the two techniques in a murine carcinoma and in a sarcoma. Both techniques showed that the vascular volume decreased in larger tumours. The H33342 analysis of vessel size showed the decrease in capillary vessels in the carcinomas was even greater, falling from 70% in small tumours to 20% in larger tumours. The deteriorating vascular network in larger tumours is associated with an increasing fraction of necrotic tissue. Experiments in which the isotopes and dye were co-injected suggest that at 40 mgkg-1 the dye may rapidly lead to a partial shutdown of the tumour vascular bed. This is less marked with 20 mg kg-1. In spite of this effect there is in general a close correlation between the volumes perfused by labelled red blood cells and the fluorescent dye.

The effect of mixed fractionation with X rays and neutrons on tumour growth delay and skin reactions in mice

We have compared the effects of mixed fractionation schedules with X rays and neutrons on growth delay of a murine tumour and skin reactions in mice. The schedules were five daily fractions of X rays, neutrons or mixtures (NNXXX, XXXNN or NXXXN). For clamped tumours or skin all three mixed schedules had the same effect. In contrast, for unclamped tumours giving the neutrons first (NNXXX) was more effective than the other two mixed schedules. This represented a true therapeutic gain and implies that if neutrons are used clinically as only part of a course of fractionated radiotherapy, they should be given at the beginning rather than at the end of treatment.

Klaas Breur memorial lecture 1986. Differences in radiosensitivity among cells in culture and in experimental tumours: significance for the effectiveness of human cancer therapy

Problems in the application of radiobiological data on various types of models, cell in vitro, experimental tumours, and clinical models, to the prediction of tumour radiocurability are discussed. On the basis of observations on cells in culture and experimental tumours it is suggested that heterogeneity in responsiveness of tumours in patients is caused in a large part by differences in intrinsic cellular radiosensitivity. Methods and developments are reviewed, which may yield better assays for the prediction of tumour responsiveness to treatments.

Tumor hypoxia: its impact on cancer therapy

The presence of radiation resistant cells in solid human tumors is believed to be a major reason why radiotherapy fails to eradicate some such neoplasms. The presence of unperfused regions containing hypoxic cells may also contribute to resistance to some chemotherapeutic agents. This paper reviews the evidence that radiation resistant hypoxic cells exist in solid tumors, the assumptions and results of the methods used to detect hypoxic cells, and the causes and nature of tumor hypoxia. Evidence that radiation resistant hypoxic cells exist in the vast majority of transplanted rodent tumors and xenografted human tumors is direct and convincing, but problems with the current methodology make quantitative statements about the magnitude of the hypoxic fractions problematic. Evidence that radiation resistant hypoxic cells exist in human tumors is considerably more indirect than the evidence for their existence in transplanted tumors, but it is convincing. However, evidence that hypoxic cells are a significant cause of local failure after optimal clinical radiotherapy or chemotherapy regimens is limited and less definitive. The nature and causes of tumor hypoxia are not definitively known. In particular, it is not certain whether hypoxia is a chronic or a transient state, whether hypoxic cells are proliferating or quiescent, or whether hypoxic cells have the same repair capacity as aerobic cells. A number of new methods for assessing hypoxia are reviewed. While there are still problems with all of the new techniques, some of them have the potential of allowing the assessment of hypoxia in individual human tumors.

Irradiation therapy with multiple small fractions per day in urinary bladder cancer

In a clinical trial 168 patients with carcinoma of the bladder, T2-T4, were randomized to one of two treatments; 1 Gy 3 times a day to a total of 84 Gy or 2 Gy once a day to a total of 64 Gy. Local eradication of the tumour in the bladder cystoscopically and cytologically at 6 months after completion of treatment and patient survival were analyzed. The results favoured significantly the patients treated with 84 Gy. All patients were followed 5-9 years. The survival was significantly improved in patients with T3 lesions treated with 84 Gy (p less than 0.01). Complications in the bowel requiring surgical treatment were not significantly different between the two groups of patients. The results indicate a therapeutic gain by hyperfractionated radiotherapy in comparison to conventional fractionated radiotherapy.

Predicting radiocurability

Several predictors of tumor radiocurability are already integrated into clinical practice, e.g., tumor size, gross morphologic features (i.e., infiltrative or exophytic), histologic type, and grade. These are relatively imprecise, however, and none is specific. The aim of research into predictive assays is not only to refine the discrimination of existing predictors but also to suggest specific experimental approaches for overcoming tumor radioresistance in individual patients. Two broad categories of predictive assays can be defined: direct and indirect measurements of tumor cell survival and/or repair capability following irradiation and measurement of cellular and extracellular parameters affecting radiosensitivity. Examples from ongoing research at the University of Texas M. D. Anderson Hospital using one technique from each category (the micronucleus assay and flow cytometric analysis of tumor cell proliferation kinetics and ploidy) are used to illustrate potential methods of selecting patients for fast neutron radiotherapy.

Eighth annual Juan del Regato lecture. Chemical modifiers of radiosensitivity--theory and reality: a review

In this review the poor clinical gains from hyperbaric oxygen (HBO) and misonidazole (MISO) are discussed critically. The biggest factor reducing clinical gains is almost certainly reoxygenation. Other possible reasons include vasoconstrictive self-limitation of HBO and neurotoxicity of MISO, so that the radiosensitization of any hypoxic cells in human tumors was not adequate. Nevertheless, there have been some positive clinical results, so that hypoxic cells can sometimes be a problem in some tumors, especially those of the head and neck, even after multiple fraction radiotherapy. While hypoxic cell radioresistance is obviously only one form of radioresistance it is a large factor of resistance when hypoxic cells are present. Current developments are briefly reviewed: the 'new' clinical sensitizers Ro-03-8799 and SR-2508 which should be 3 to 10 times more efficient than MISO if viable hypoxic cells are present; and methods of measuring which human tumors might have significant numbers of hypoxic viable cells.

Cell-cycle distributions and radiation responses of Chinese hamster cells cultured continuously under hypoxic conditions

Cell-cycle distributions were measured by flow cytometry for Chinese hamster (CHO) cells cultured continuously under hypoxic conditions. DNA histograms showed an accumulation of cells in the early S phase followed by a traverse delay through the S phase, and a G2 block. During hypoxic culturing, cell viability decreased rapidly to less than 0.1% at 120 h. Radiation responses for cells cultured under these conditions showed an extreme radioresistance at 72 h. Results suggest that hypoxia induces a condition similar to cell synchrony which itself changes the radioresistance of hypoxic cells.

The eighteenth Douglas Lea lecture. 40 years of radiobiology: its impact on radiotherapy

The contributions of radiobiology to radiotherapy in the past 40 years are reviewed, taking the work of Gray and Read on bean roots with high LET radiation as the starting point. The main impact has been strategic and didactic because methods of measuring parameters in patients so as to affect individual treatments have not yet been developed. Many patients are now being treated with radiotherapy who would have been considered unsuitable 40 years ago and the radiobiological reasons for these changes are discussed. Improvements that have occurred in radiotherapy are reviewed and some projections about future potential improvements are made.