The Quality Assurance programme of the Radiotherapy Group of the European Organization for Research and Treatment of Cancer (EORTC): a critical appraisal of 20 years of continuous efforts.

In 1982, the European Organization for Research and Treatment of Cancer (EORTC) Radiotherapy Group established the Quality Assurance (QA) programme. During the past 20 years, QA procedures have become a major part of the activities of the group. The methodology and steps of the QA programme over the past 20 years are briefly described. Problems and conclusions arising from the results of the long-lasting QA programme in the EORTC radiotherapy group are discussed and emphasised. The EORTC radiotherapy group continues to lead QA in the European radiotherapy community. Future challenges and perspectives are proposed.

Functional analysis of cyclin-dependent kinase inhibitors of Arabidopsis.

Cyclin-dependent kinase inhibitors, such as the mammalian p27(Kip1) protein, regulate correct cell cycle progression and the integration of developmental signals with the core cell cycle machinery. These inhibitors have been described in plants, but their function remains unresolved. We have isolated seven genes from Arabidopsis that encode proteins with distant sequence homology with p27(Kip1), designated Kip-related proteins (KRPs). The KRPs were characterized by their domain organization and transcript profiles. With the exception of KRP5, all presented the same cyclin-dependent kinase binding specificity. When overproduced, KRP2 dramatically inhibited cell cycle progression in leaf primordia cells without affecting the temporal pattern of cell division and differentiation. Mature transgenic leaves were serrated and consisted of enlarged cells. Although the ploidy levels in young leaves were unaffected, endoreduplication was suppressed in older leaves. We conclude that KRP2 exerts a plant growth inhibitory activity by reducing cell proliferation in leaves, but, in contrast to its mammalian counterparts, it may not control the timing of cell cycle exit and differentiation.

Interobserver variations in gross tumor volume delineation of brain tumors on computed tomography and impact of magnetic resonance imaging.

PURPOSE: (1) To assess the interobserver variability of brain tumor delineation on computed tomography (CT). (2) To assess the impact of the addition of magnetic resonance imaging (MRI) information. METHODS: Nine physicians were asked to delineate the gross tumor volume (GTV) of five patients with supratentorial inoperable brain tumors on CT scans and 2 weeks (or more) later on MRIs. The delineations were performed on a computer screen. During delineation on MRI, the registered CT images (without delineation) were displayed on the screen (MRI+CT). RESULTS: A high interobserver variability in GTV delineation on CT is found: the ratio of the largest to the smallest defined volumes varies for the five patients by factors of resp. 2.8, 1.8, 1.8, 1.9 and 1.7. The interobserver variability is as large on MRI+CT as on CT alone (ratio largest/smallest volume: 2.4, 1.7, 1.9, 2.7 and 1.5). Volumes delineated on MRI+CT (mean: 69.6 cm(3)) are larger than on CT alone (mean: 59.5 cm(3)). Residual volumes (volume delineated on one image modality but not on the other) are >0 for CT alone and for MRI+CT. CONCLUSIONS: A large interobserver variability in GTV delineation of brain tumors is demonstrated. The addition of MRI to CT does not reduce interobserver variability. GTVs delineated on MRI+CT are larger than on CT alone, but some volumes are delineated on CT and not on MRI. Therefore, a combination of the two image modalities is recommended for brain tumor delineation for treatment planning.

Arabidopsis thaliana genes expressed in the early compatible interaction with root-knot nematodes.

In the compatible interaction between Arabidopsis thaliana and the endoparasitic nematode Meloidogyne incognita, galls are formed on the roots of the host plant. Differential display was used to identify alterations of gene expression in young A. thaliana root galls caused by M. incognita. Six genes were confirmed as plant genes by DNA gel blot hybridizations. Significant homology was found with a trypsin inhibitor, peroxidase, mitochondrial uncoupling protein, endomembrane protein, 20S proteasome alpha-subunit, and diaminopimelate decarboxylase. The cellular and temporal expression of each of the six genes was analyzed by mRNA in situ hybridizations.

Long-term results of a randomized trial comparing breast-conserving therapy with mastectomy: European Organization for Research and Treatment of Cancer 10801 trial.

BACKGROUND: Breast-conserving therapy (BCT) has been shown to be as effective as mastectomy in the treatment of tumors 2 cm or smaller. However, evidence of its efficacy, over the long term, in patients with tumors larger than 2 cm is limited. From May 1980 to May 1986, the European Organization for Research and Treatment of Cancer carried out a randomized, multicenter trial comparing BCT with modified radical mastectomy for patients with tumors up to 5 cm. In this analysis, we investigated whether the treatments resulted in different overall survival, time to distant metastasis, or time to locoregional recurrence. METHODS: Of 868 eligible breast cancer patients randomly assigned to the BCT arm or to the modified radical mastectomy arm, 80% had a tumor of 2.1-5 cm. BCT comprised lumpectomy with an attempted margin of 1 cm of healthy tissue and complete axillary clearance, followed by radiotherapy to the breast and a supplementary dose to the tumor bed. The median follow-up was 13.4 years. All P values are two-sided. RESULTS: At 10 years, there was no difference between the two groups in overall survival (66% for the mastectomy patients and 65% for the BCT patients; P =.11) or in their distant metastasis-free rates (66% for the mastectomy patients and 61% for the BCT patients; P =.24). The rate of locoregional recurrence (occurring before or at the same time as distant metastasis) at 10 years did show a statistically significant difference (12% of the mastectomy and 20% of the BCT patients; P =. 01). CONCLUSIONS: BCT and mastectomy demonstrate similar survival rates in a trial in which the great majority of the patients had stage II breast cancer.

Improved management of radiotherapy departments through accurate cost data.

BACKGROUND AND PURPOSE: Escalating health care expenses urge governments towards cost containment. More accurate data on the precise costs of health care interventions are needed. We performed an aggregate cost calculation of radiation therapy departments and treatments and discussed the different cost components. MATERIALS AND METHODS: The costs of a radiotherapy department were estimated, based on accreditation norms for radiotherapy departments set forth in the Belgian legislation. RESULTS: The major cost components of radiotherapy are the cost of buildings and facilities, equipment, medical and non-medical staff, materials and overhead. They respectively represent around 3, 30, 50, 4 and 13% of the total costs, irrespective of the department size. The average cost per patient lowers with increasing department size and optimal utilization of resources. Radiotherapy treatment costs vary in a stepwise fashion: minor variations of patient load do not affect the cost picture significantly due to a small impact of variable costs. With larger increases in patient load however, additional equipment and/or staff will become necessary, resulting in additional semi-fixed costs and an important increase in costs. A sensitivity analysis of these two major cost inputs shows that a decrease in total costs of 12-13% can be obtained by assuming a 20% less than full time availability of personnel; that due to evolving seniority levels, the annual increase in wage costs is estimated to be more than 1%; that by changing the clinical life-time of buildings and equipment with unchanged interest rate, a 5% reduction of total costs and cost per patient can be calculated. More sophisticated equipment will not have a very large impact on the cost (+/-4000 BEF/patient), provided that the additional equipment is adapted to the size of the department. That the recommendations we used, based on the Belgian legislation, are not outrageous is shown by replacing them by the USA Blue book recommendations. Depending on the department size, costs in our model would then increase with 14-36%. CONCLUSION: We showed that cost information can be used to analyze the precise financial consequences of changes in routine clinical practice in radiotherapy. Comparing the cost data with the prevailing reimbursement may reveal inconsistencies and stimulate to develop improved financing systems.

Clinical radiation doses for spinal cord: the 1998 international questionnaire.

BACKGROUND AND PURPOSE: Emmanuel van der Schueren gave a keynote lecture at the 1988 ASTRO annual conference pointing out that the spinal cord 'tolerance doses' then prescribed were probably unnecessarily cautious, resulting in probable underdosing of some tumours. This lecture was supported both by an international questionnaire which he and two of the present authors had conducted, and by animal experimental data. In 1997 he initiated a 10-year follow-up questionnaire, the results of which are summarised here. MATERIALS AND METHODS: The present report analyses the change in prescriptions from 1988 to 1998 and the variation in prescriptions among various regions of the World. RESULTS AND CONCLUSIONS: The main conclusion is that prescribed dose levels have increased significantly in this period. Large geographical variations still exist. Among responders who use a formula to correct for changed dose per fraction, 90% are now using the linear-quadratic model vs. 33% in 1988. The current status of clinically acceptable doses to spinal cord in 2-Gy fractions is discussed briefly. Further details from the responses to the 1998 questionnaire will be presented in another publication.

Federation of European Cancer Societies. Full report. Economic evaluation in cancer care: questions and answers on how to alleviate conflicts between rising needs and expectations and tightening budgets.

All Western countries have experienced a fast growth in their healthcare expenses over recent decades. It is expected that pressure for such growth will continue in the future. But spending an ever larger share of our nation's resources on healthcare cannot be afforded. As a consequence, making choices will become more and more inevitable, even in cancer care. Economic evaluation is a very supportive tool for such decisions. This position statement concludes with recommendations for providers and healthcare policy-makers, to safeguard and further improve good clinical decision making and healthcare policy in cancer care under tightening budgets.

Radiation dose homogeneity in an EORTC multicenter trial on breast irradiation.

The influence of the radiation dose on local control and cosmetic outcome in breast-conserving treatment for breast cancer is investigated in EORTC trial 2288110882. In this study 50 Gy is administered to the whole breast, and the effect of an additional dose to the tumor-bearing area (boost dose) is evaluated. The purpose of this analysis is to document the dose homogeneity of the radiation dose as reported in the first 1915 treatment forms, received at the EORTC Data Center. The dose to the prescription Point (A) was within 95 and 110% of 50 Gy in all but 13 (99.3%) patients (median dose 50 Gy) and the minimum and maximum doses in the central plane of the breast were within 95% and 110% of the dose to point A in 82% of patients. The dose to the tumor excision area (point B) was within the homogeneity criteria in 97% of patients, and the boost doses were consistent with randomization in 93% of cases. These data, based on one-third of the randomized patients in trial 22881/10882, demonstrate a high level of homogeneity in radiation doses, despite a number of ambiguities in the protocol, which were efficiently clarified a few months after the beginning of the trial. This high level of consistency is a remarkable achievement given the number of centers, the number of patients, and the number of countries involved in this trial.

Validation of the methods of cosmetic assessment after breast-conserving therapy in the EORTC "boost versus no boost" trial. EORTC Radiotherapy and Breast Cancer Cooperative Groups. European Organization for Research and Treatment of Cancer.

PURPOSE: To evaluate both qualitative and quantitative scoring methods for the cosmetic result after breast-conserving therapy (BCT), and to compare the usefulness and reliability of these methods. METHODS AND MATERIALS: In EORTC trial 22881/10882, stage I and II breast cancer patients were treated with tumorectomy and axillary dissection. A total of 5318 patients were randomized between no boost and a boost of 16 Gy following whole-breast irradiation of 50 Gy. The cosmetic result was assessed for 731 patients in two ways. A panel scored the qualitative appearance of the breast using photographs taken after surgery and 3 years later. Digitizer measurements of the displacement of the nipple were also made using these photographs in order to calculate the breast retraction assessment (BRA). The cosmetic results after 3-year follow-up were used to analyze the correlation between the panel evaluation and digitizer measurements. RESULTS: For the panel evaluation the intraobserver agreement for the global cosmetic score as measured by the simple Kappa statistic was 0.42, considered moderate agreement. The multiple Kappa statistic for interobserver agreement for the global cosmetic score was 0.28, considered fair agreement. The specific cosmetic items scored by the panel were all significantly related to the global cosmetic score; breast size and shape influenced the global score most. For the digitizer measurements, the standard deviation from the average value of 30.0 mm was 2.3 mm (7.7%) for the intraobserver variability and 2.6 mm (8.7%) for the interobserver variability. The two methods were significantly, though moderately, correlated; some items scored by the panel were only correlated to the digitizer measurements if the tumor was not located in the inferior quadrant of the breast. CONCLUSIONS: The intra- and interobserver variability of the digitizer evaluation of cosmesis was smaller than that of the panel evaluation. However, there are some treatment sequelae, such as disturbing scars and skin changes, that can not be evaluated by BRA measurements. Therefore, the methods of cosmetic evaluation used in a study must be chosen in a way that balances reliability and comprehensiveness.

The influence of the boost in breast-conserving therapy on cosmetic outcome in the EORTC "boost versus no boost" trial. EORTC Radiotherapy and Breast Cancer Cooperative Groups. European Organization for Research and Treatment of Cancer.

PURPOSE: To evaluate the influence of a radiotherapy boost on the cosmetic outcome after 3 years of follow-up in patients treated with breast-conserving therapy (BCT). METHODS AND MATERIALS: In EORTC trial 22881/10882, 5569 Stage I and II breast cancer patients were treated with tumorectomy and axillary dissection, followed by tangential irradiation of the breast to a dose of 50 Gy in 5 weeks, at 2 Gy per fraction. Patients having a microscopically complete tumor excision were randomized between no boost and a boost of 16 Gy. The cosmetic outcome was evaluated by a panel, scoring photographs of 731 patients taken soon after surgery and 3 years later, and by digitizer measurements, measuring the displacement of the nipple of 3000 patients postoperatively and of 1141 patients 3 years later. RESULTS: There was no difference in the cosmetic outcome between the two treatment arms after surgery, before the start of radiotherapy. At 3-year follow-up, both the panel evaluation and the digitizer measurements showed that the boost had a significant adverse effect on the cosmetic result. The panel evaluation at 3 years showed that 86% of patients in the no-boost group had an excellent or good global result, compared to 71% of patients in the boost group (p = 0.0001). The digitizer measurements at 3 years showed a relative breast retraction assessment (pBRA) of 7.6 pBRA in the no-boost group, compared to 8.3 pBRA in the boost group, indicating a worse cosmetic result in the boost group at follow-up (p = 0.04). CONCLUSIONS: These results showed that a boost dose of 16 Gy had a negative, but limited, impact on the cosmetic outcome after 3 years.

Prognosis after treatment for loco-regional recurrence after mastectomy or breast conserving therapy in two randomised trials (EORTC 10801 and DBCG-82TM). EORTC Breast Cancer Cooperative Group and the Danish Breast Cancer Cooperative Group.

The aim of this study was to investigate and compare the prognosis after treatment for loco-regional recurrences (LR) after (modified) radical mastectomy (MRM) or breast conserving therapy (BCT), in terms of overall survival and time to subsequent LR, in patients originally treated in two European randomised trials. In EORTC trial 10801 and DBCG trial 82-TM, 1,807 patients with stage I and II breast cancer were randomised to receive MRM or BCT from 1980 to 1989. All patients with a LR in these trials were analysed for survival and time to subsequent LR after salvage treatment. Of these, 133 patients had their LR as a first event, the majority within 5 years after initial treatment. The prognostic significance for survival and time to subsequent LR after salvage treatment was analysed in uni-, and multivariate analyses for a number of original tumour- and recurrence-related variables. After salvage treatment of LR after MRM or BCT, actuarial survival curves and the actuarial locoregional control curves were similar. The 5-year survival rates were 58% and 59% and the 5-year subsequent loco-regional control rates 62% and 63%, respectively. In a multivariate analysis, pN category (P = 0.03), pT category (P = 0.01) and vascular invasion (P = 0.02) of the primary tumour were the only independent prognostic factors for survival, whereas extensive LR (P < 0.001), interval < or = 2 years (P < 0.002) and pN+ at primary treatment (P = 0.004) were significant predictive factors for time to subsequent LR. The type of original treatment (MRM or BCT) did not have any prognostic impact. It is concluded that the survival and time to subsequent LR after treatment for an early loco-regional recurrence after MRM or BCT was similar in these two European randomised trials. This suggests that both after MRM and BCT an early LR is an indicator of a biologically aggressive tumour; early loco-regional relapse carries a poor prognosis and salvage treatment only cures a limited number of patients, whether treated by MRM or BCT originally.

A quality assurance network in Central European countries--radiotherapy infrastructure.

A survey of the infrastructure in radiotherapy centres in three Central European countries has been performed as a first step in the development of a quality assurance network. Data concerning radiotherapy equipment, staff and number of patients treated in most of the radiotherapy centres from Czech Republic, Poland and Hungary were collected at the beginning of 1994. Equipment data have shown that 35% of 182 treatment units are conventional x-ray units, 35% 60Co units, 19% linear accelerators, 7% 137Cs units and 4% betatrons. About 47% of high energy units are older than 12 years and about 20% older than 21 years. An important number of centres still have no simulator which would constitute an important handicap to carry out adequate radiotherapy. The number of treatment planning systems has also been registered; 44% being PC-based systems with locally developed software. Large variations are observed in the number of patients treated per year, per high energy unit, but 12/47 centres treat more than 700 patients per year and unit. On the average, staffing seems adequate in numbers though there are wide variations. The main limitation of radiotherapy infrastructure in the Central European countries is the low number of linear accelerators and simulators and the advanced age of therapy units.

Identical cis-acting elements and related trans-acting factors control activity of nonviral promoter in Schizosaccharomyces pombe and mammalian cells.

We have analyzed the transcriptional activity of the human plasminogen activator inhibitor-1 promoter in the fission yeast Schizosaccharomyces pombe. This promoter is active in S. pombe, and the initiation site of transcription corresponds to the site identified previously in mammalian cells. Mutations in the AP-1-binding site (PAI-1 A box) or the HLTF-binding site (the B box), which reduced the basal and phorbol ester-induced levels of PAI-1 expression in human cells, also decreased the transcriptional activity in S. pombe. Gel retardation assays showed that an S. pombe protein binds specifically to this B box element and displays the same B box sequence requirement as HLTF. Furthermore, this yeast protein binds specifically to other HLTF-binding sites in the human immunodeficiency virus-1 long terminal repeat (LTR) and the simian virus 40 (SV40) enhancer. The B box (but not a mutated B box) strongly stimulated transcription when combined with adh downstream promoter elements, indicating that the S. pombe B box-binding protein, like HLTF, is a transcriptional activator. We conclude that the transcriptional activity of the nonviral PAI-1 promoter is controlled by the same promoter elements in S. pombe as in mammalian cells. In addition, mammalian trans-acting factors that bind to these promoter elements were shown to have counterparts with conserved DNA-binding activity in S. pombe. These results further illustrate the conservation of the mechanism of transcription between mammalian cells and fission yeast.

Chronic lymphocytic alveolitis with migrating pulmonary infiltrates after localized chest wall irradiation.

In a number of patients, radiotherapy following surgery for breast carcinoma may induce radiation injury to the lungs. This has classically been divided into an early radiation pneumonitis and a late fibrosis, both confined to the irradiated lung volume. However we observed a female patient who similarly to other recent reports in the literature developed a recurring pneumonitis migrating from one lung to the other after radiotherapy for breast carcinoma. This migratory BOOP (bronchiolitis obliterans organizing pneumonia) was characterized by a lymphocytic alveolitis and responded well to corticosteroids. Clinicians should be aware of the possibility of a lymphocytic pneumonitis in both lungs after unilateral thoracic irradiation and recognize the distinctive features of fever, cough, dyspnoea and malaise in order to start an effective treatment with corticosteroids. They should also be aware of the high tendency for recurrence when tapering off.

Vindesine-ifosfamide-platinum (VIP) induction chemotherapy in surgically staged IIIA-N2 non-small-cell lung cancer: a prospective study. Leuven Lung Cancer Group.

PURPOSE: In the pioneer data from the Memorial-Sloan-Kettering group, preoperative mitomycin-C-vindesine-platinum (MVP) induction chemotherapy in N2-NSCLC was accompanied with substantial pulmonary toxicity. In this study, the efficacy and toxicity of three-drug VIP induction chemotherapy, the pathologic response in resection specimens, the early survival and relapse patterns are examined. PATIENTS AND METHODS: Between June 1995 and March 1997, 39 consecutive patients with pathology proven N2-NSCLC were treated with three cycles of VIP induction, followed by definitive locoregional treatment (resection and mediastinal dissection or radical radiotherapy). Several patients had unfavorable prognostic characteristics with respect to clinical and biological findings, tumor location and bulk of disease. RESULTS: The response rate to chemotherapy was 59% (95% Confidence Interval 34-75). Twenty-three responding patients had radical locoregional treatment: radical radiotherapy in four, resection in 19. Downstaging was present in nine of the 19 resection specimens, with two pathologic complete responses. The median survival time (MST) of all patients is 19 months, with a projected two-year survival of 49%. In patients responsive to chemotherapy who received definitive local treatment, the MST is not yet reached, and the projected two-year survival is 57%. Relapses were mainly distant, with isolated brain relapse as a disturbing finding. The main toxicity's were leukopenia and vomiting, but they were manageable. In contrast with MVP, no severe pulmonary toxicity occurred. CONCLUSIONS: VIP is a suitable induction regimen for N2-NSCLC, demonstrating a good activity and very acceptable toxicity.

Relationship between potential doubling time (Tpot), labeling index and duration of DNA synthesis in 60 esophageal and 35 breast tumors: Is it worthwhile to measure Tpot?

BACKGROUND: In recent years Tpot (potential doubling time) has been measured before treatment in human tumors in an attempt to estimate the proliferation taking place during a course of irradiation. Tpot is defined as Ts/LI, where Ts is the duration of DNA synthesis and LI is the labeling index (proportion of cells synthesizing DNA). Ts is more difficult to measure than LI, so the question arises whether variation introduced during the determination of Ts is compensated by the theoretically better relevance of the quotient Tpot than of LI alone. It is not clear from comparisons with clinical outcome whether Tpot is a useful indicator of proliferation or whether LI is more prognostic, as suggested by a currently ongoing multicenter analysis elsewhere. Therefore, we investigated intercomparisons between Tpot and its components LI and Ts in two in their proliferation rates contrasting types of tumor where multiple biopsies were taken from each tumor. MATERIALS AND METHODS: Sixty patients with esophageal carcinoma and 57 patients with breast cancer were included in this study. All patients were injected with IUdR 6-8 h before surgery. From each tumor three to five biopsies were taken at surgery. Using flow cytometry, LI and Ts were measured on all biopsies in order to calculate Tpot. Logarithmic transformations of the distributions were used to examine correlations. Kappa-tests were used to assess how reliable an LI value could be in predicting the corresponding Tpot. RESULTS: Ts and LI were not completely independent, based on the within-tumor coefficients of variation (CVw). The ratio of between-tumor coefficient of variation (CVb) to the CVw suggested that the discriminative power of Tpot was higher than LI for esophagus, but the reverse in breast tumors, which had a larger range. Pearson correlation coefficients were high for log Tpot versus log LI in both types of tumor, but the predictive power was low, as shown by kappa-values of only 0.3-0.41 starting with LI and trying to predict the corresponding value of Tpot. Increasing widths of a central 'gray zone' were investigated for improved discrimination between fast and slow proliferation. Multiples of the within-tumor standard deviation, equally on each side of the median, were used to vary the width of the gray zone. Without a gray zone no more than 70% successful matching was obtained in esophagus tumors, compared with 80% in breast tumors. However, by excluding about half of the esophageal tumors an 80% success rate was achieved. In breast tumors over 90% matching was obtained more easily, keeping 80% of the tumors classifiable. For both tumor types correlations between Ts and Tpot were weak, with a trend towards short Ts associated with short Tpot and also with low LI. The latter correlation was significant for esophageal tumors and resulted in Tpot values having a smaller range than the LIs. CONCLUSION: Although there were good correlation coefficients between Tpot and LI, the predictive power of either from the other was not reliable, except by excluding a significant number of tumors close to the medians. The predictive value of LI for Tpot was higher for breast tumors because the spread in cell kinetic measurements was wide. Until more clinical data become available on outcome in comparison with LI or Tpot, it is still worthwhile to measure Tpot and to assess the prognostic value of both LI and Tpot in relation to outcome.

Assessment of dose inhomogeneities in clinical practice by film dosimetry.

AIM: To use portal images acquired in routine circumstances for assessment of midplane dose variations in the patient. MATERIAL AND METHODS: Optical density readings are performed on routinely acquired Verification films of breast and ear-nose-throat (ENT) cancer patients and these readings are converted into relative doses with the sensitometric curve. ( 1 ) The impact of redistribution is evaluated on films taken close to the patient exit surface and at routine focus film distance. (2) Midplane doses are estimated from film readings to assess dose variations in the patient. The influence of wedges is evaluated. Film measurements doses are compared with calculated exit doses. RESULTS: (1) In regions with large variations in the distance between the patient exit surface and the film but without inhomogeneities in tissue density, the relative doses distributions read on films acquired at large focus-film-distance (FFD) are proportional to exit doses. In regions with flat exit surfaces but with inhomogeneities in tissue density, the redistribution has only a small impact. (2) Large variations in relative midplane doses were found in both breast (85-115%) and ENT (-3.6 to +15%) patients. The application of a wedge was shown to increase dose homogeneity in the midplane. A good agreement (differences < 3%) was found between exit doses obtained from film readings and exit doses calculated with the treatment planning system (TPS). CONCLUSION: Films acquired in routine circumstances at large FFD can be used to obtain information on exit doses and to assess midplane doses in breast and ENT, without the use of a TPS. Film dosimetry can also provide a quality assurance tool to check actually delivered doses in patients by comparing exit doses estimated on film to expected exit doses calculated by the TPS.

Colonisation of Clostridium in the body is restricted to hypoxic and necrotic areas of tumours.

The use of gene therapy is one of the most recent molecular strategies for the treatment of cancer. It is essential, however, to have an efficient transfer system by which the desired gene can be delivered to the correct environment. The experiments described in this report investigate apathogenic Clostridium as a possible vector to transfer a specific gene product into the extracellular microenvironment of the tumour which is hypoxic/necrotic in parts, using WAG/Rij rats with transplantable rhabdomyosarcomas as a model. Our data show that Clostridium, after systemic administration of at least 10(7) spores, specifically colonises the hypoxic/necrotic areas of our tumour model, the most efficient species being C. acetobutylicum (NI-4082) and C. oncolyticum. Although spores were also detected in normal tissues for up to 4 weeks, they did not germinate in these tissues. We conclude that it seems likely that these bacteria can be used as a selective transfer system into the extracellular environment of tumours which have hypoxic regions. This strategy would be more tumour-specific than various other strategies that are currently being investigated in anti-cancer gene therapy.