Status quo report on wastewater treatment plant, receiving water's biocoenosis and quality as basis for evaluation of large-scale ozonation process

The project DemO₃AC (demonstration of large-scale wastewater ozonation at the Aachen-Soers wastewater treatment plant, Germany) of the Eifel-Rur Waterboard contains the construction of a large-scale ozonation plant for advanced treatment of the entire 25 million m³/yr of wastewater passing through its largest wastewater treatment plant (WWTP). In dry periods, up to 70% of the receiving water consists of treated wastewater. Thus, it is expected that effects of ozonation on downstream water biocoenosis will become observable. Extensive monitoring of receiving water and the WWTP shows a severe pollution with micropollutants (already prior to WWTP inlet). (Eco-)Toxicological investigations showed increased toxicity at the inlet of the WWTP for all assays. However, endocrine-disrupting potential was also present at other sampling points at the WWTP and in the river and could not be eliminated sufficiently by the WWTP. Total cell counts at the WWTP are slightly below average. Investigations of antibiotic resistances show no increase after the WWTP outlet in the river. However, cells carrying antibiotic-resistant genes seem to be more stress resistant in general. Comparing investigations after implementation of ozonation should lead to an approximation of the correlation between micropollutants and water quality/biocoenosis and the effects that ozonation has on this matter.

Evaluation of different biomarkers to predict individual radiosensitivity in an inter-laboratory comparison--lessons for future studies

Radiotherapy is a powerful cure for several types of solid tumours, but its application is often limited because of severe side effects in individual patients. With the aim to find biomarkers capable of predicting normal tissue side reactions we analysed the radiation responses of cells from individual head and neck tumour and breast cancer patients of different clinical radiosensitivity in a multicentric study. Multiple parameters of cellular radiosensitivity were analysed in coded samples of peripheral blood lymphocytes (PBLs) and derived lymphoblastoid cell lines (LCLs) from 15 clinical radio-hypersensitive tumour patients and compared to age- and sex-matched non-radiosensitive patient controls and 15 lymphoblastoid cell lines from age- and sex- matched healthy controls of the KORA study. Experimental parameters included ionizing radiation (IR)-induced cell death (AnnexinV), induction and repair of DNA strand breaks (Comet assay), induction of yH2AX foci (as a result of DNA double strand breaks), and whole genome expression analyses. Considerable inter-individual differences in IR-induced DNA strand breaks and their repair and/or cell death could be detected in primary and immortalised cells with the applied assays. The group of clinically radiosensitive patients was not unequivocally distinguishable from normal responding patients nor were individual overreacting patients in the test system unambiguously identified by two different laboratories. Thus, the in vitro test systems investigated here seem not to be appropriate for a general prediction of clinical reactions during or after radiotherapy due to the experimental variability compared to the small effect of radiation sensitivity. Genome-wide expression analysis however revealed a set of 67 marker genes which were differentially induced 6 h after in vitro-irradiation in lymphocytes from radio-hypersensitive and non-radiosensitive patients. These results warrant future validation in larger cohorts in order to determine parameters potentially predictive for clinical radiosensitivity.

Heterogeneity of radiation- and TNF-alpha-induced programmed cell death in carcinoma, sarcoma and lymphoma cell lines

AIM

To characterize the interaction of tumour necrosis factor alpha (TNF-alpha) and ionising radiation in six sarcoma, lymphoma and carcinoma cell lines.

MATERIALS AND METHODS

Cells were characterized regarding annexin V/propiduim iodine affinity and caspase-3 status after application of TNF-alpha, radiation, or combined treatment.

RESULTS

Three cell lines showed similar results with additive effects of TNF-alpha and radiation in both assays. The other three cell lines significantly differed regarding the detection of apoptotic cells between treatment conditions (radiation and/or TNF application) and between the two apoptosis assays.

CONCLUSION

The interaction between TNF-alpha and radiation differs between tumour entities and cannot be described by using only one parameter.

Kidney-autotransplantation before radiotherapy: a case report

BACKGROUND

A 28-year-old man suffering from a Ewing tumour arising from the 9th-11th ribs with infiltration of neuroforamina without distant metastases was planned to receive radiotherapy following primary intralesional surgery and induction chemotherapy. Due to pleural infiltration and effusion, a hemithorax irradiation with a sequential boost to the primary tumour site had to be administered. Different treatment planning variants failed to provide sufficient radiotherapy planning in view of target volume coverage and avoidance of organs at risk, especially due to high calculated radiation doses potentially compromising the left kidney.

MATERIALS AND METHODS

To prevent left kidney organ exposure, an autotransplantation of the left kidney into the right fossa iliaca was performed. An infiltration of the kidney was initially excluded.

RESULTS

Postoperatively, a renal scintigraphy showed a normal function of both kidneys allowing sufficient radiotherapy treatment planning. Target volume coverage was easily obtained using a combination of hemithorax irradiation and a sequential boost by an intensity-modulated-radiotherapy technique.

CONCLUSION

In difficult individual treatment situations, surgical transpositions as well as organ autotransplantation might be useful in reducing radiotherapy organ dose levels.

Perioperative high-dose rate brachytherapy using a bendy applicator (flab): treatment results of 74 patients

BACKGROUND

Radiotherapy plays a pivotal role in tumor treatment. Brachytherapy as an additional radiation technique allows local dose increments in areas at high risk of local failure.

PATIENTS AND METHODS

Our past 15-year experience with tissue-equivalent bendy applicator brachytherapy at the University Hospital Münster, Germany was reviewed. A series of 74 consecutive patients who had mainly been treated for sarcomas with perioperative brachytherapy was analyzed with a focus on local relapse-free survival and side-effects.

RESULTS

The 5-year local control rate was 73% in primary treatment situations with a significant influence of additional external irradiation, surgical margin depth and tumor entity. Late sequelae of combined modality treatment were observed in 40 patients (54%) and mainly concerned wound healing (n = 18, 24%).

CONCLUSION

A high-risk collective, in view of local failure, showed adequate local control rates as well as acceptable late sequelae. Flab brachytherapy is a good treatment option to achieve local radiation dose increments in patients at high risk of local failure.

Radiotherapy of benign diseases-scleredema adultorum Buschke

BACKGROUND

Scleredema adultorum Buschke is a rare disorder characterized by thickening of the dermis of the neck, head and upper trunk. Its etiology is unknown, but there may be a preceding history of infection and there is a known association with diabetes mellitus. Women are more frequently affected. Usually, the disease is self-limiting but some patients show progressive disease. In these cases therapeutic options are poor, with only case reports and small series supporting their use.

CASE REPORT

A 58-year-old patient with a scleredema of the neck and upper trunk is described, who was treated twice within 6 months by electron-beam radiation therapy. After the second course his symptoms improved significantly. A review of the literature of radiation treatment of this disease is given.

CONCLUSION

. Regardless of the possible mechanisms in pathogenesis and treatment of scleredema adultorum Buschke, the application of ionizing radiation is an important, effective and well-tolerated therapy option in the treatment of severe cases and may candidate as the first-line treatment of this disease.

[Register for the evaluation of side effects after radiation in childhood and adolescence--first results]

BACKGROUND

Late effects after radiotherapy in childhood and adolescence have mainly been characterized retrospectively with small patient numbers. Therefore the German Group of Pediatric Radiation Oncology (APRO) established the "RegIster for the evaluation of late Side effects after radiation in childhood and adolescence" (RiSK). After a pilot phase starting in 2001 documentation has been performed all over Germany since 2004. This analysis shows the first results of "RiSK".

PATIENTS AND METHODS

Radiation parameters including detailed organ doses as well as toxicity evaluations were collected prospectively from centers all over Germany in the study center. Standardized documentation forms were used. Documentation is planned for all children who receive radiotherapy in one of the German pediatric therapy trials.

RESULTS

Until December 31st 2006, 696 documentations of radiotherapy and 526 acute as well as 836 late follow-up documentation forms have been collected. Altogether, 41 patients with late grade 3 and 16 patients with late grade 4-side effects were identified. Side effects mainly concerned joints with functional impairment (after combined radiotherapy and surgery), the bowel, skin and subcutis as well as blood parameters under continued chemotherapy. Patients with late side effects of a higher grade were mainly treated for Ewing's or soft tissue sarcomas (n=235 patients), representing 33.8% of all patients in this study.

CONCLUSION

Fortunately, up to now only a few late grade 3 or 4 side effects of radiotherapy are shown for almost 700 documented patients. For further results, especially for the characterization of dose-effect-relationships, this study has to be continued with a higher patient number and a longer follow-up.

Isoprenoid depletion by statins antagonizes cytokine-induced down-regulation of endothelial nitric oxide expression and increases NO synthase activity in human umbilical vein endothelial cells

Endothelial dysfunction and atherosclerosis are associated with an inflammation-induced decrease in endothelial nitric oxide synthase (eNOS) expression. Based on the differences between hydrophobic and hydrophilic statins in their reduction of cardiac events, we analyzed the effects of rosuvastatin and cerivastatin on eNOS and inducible NO synthase (iNOS) expression and NOS activity in TNF-alpha-stimulated human umbilical vein endothelial cells (HUVEC). Both statins reversed down-regulation of eNOS mRNA and protein expression by inhibiting HMG-CoA reductase and isoprenoid synthesis. Cerivastatin tended to a more pronounced effect on eNOS expression compared to rosuvastatin. NOS activity - measured by conversion of [(3)H]-L-arginine to [(3)H]-L-citrulline - was enhanced under treatment with both drugs due to inhibition of HMG-CoA reductase. Statin-treatment reduced iNOS mRNA expression under normal conditions, but had no relevant effects on iNOS mRNA expression in cytokine-treated cells. Rosuvastatin and cerivastatin reverse the detrimental effects of TNF-alpha-induced down-regulation in eNOS protein expression and increase NO synthase activity by inhibiting HMG-CoA reductase and subsequent blocking of isoprenoid synthesis. These results provide evidence that statins have beneficial effects by increasing eNOS expression and activity during the atherosclerotic process.

Ovarian Function Following Pelvic Irradiation in Prepubertal and Pubertal Girls and Young Adult Women

PURPOSE

To analyze the effect of pelvic radiotherapy on ovarian function in prepubertal and pubertal girls and young adult women.

PATIENTS AND METHODS

In a retrospective monoinstitutional analysis, patients < 30 years of age at diagnosis were included who had been irradiated between 1979 and 1998. The main tumor types were Hodgkin's disease (38%), Ewing's sarcoma (20%) and nephroblastoma (11%). Patients were classified into three groups according to the position of the ovary in relation to the radiation portals. Group 1 was defined by direct irradiation of both ovaries. Group 2 patients were included with both ovaries potentially located in the radiation portals. In group 3, at least one ovary was not directly irradiated. The median follow-up was 128 months.

RESULTS

16 of 55 analyzed patients were categorized in group 1. In ten of these patients, hormone status was evaluable. The ovarian doses were >/= 15 Gy. Except for one patient treated with 15 Gy all developed hormone failure. Eight of 14 patients of group 2 were evaluable. Seven of these patients developed ovarian failure. 19 of 24 patients in group 3 were evaluable. Nine of these patients developed ovarian failure. The observed difference in the rate of ovarian failure between the groups is statistically significant (p = 0.045).

CONCLUSION

All patients receiving > 15 Gy to the ovaries developed hormone failure. In one case of a patient receiving an ovarian dose of 15 Gy, hormone failure was not found. In case of pelvic irradiation excluding at least one ovary, approximately half of the patients developed ovarian dysfunction, probably also due to the effects of polychemotherapy.

Early effects of irradiation on [(123)I]-IMT and [(18)F]-FDG uptake in rat C6 glioma cells

BACKGROUND

Single-photon emission computed tomography (SPECT) using 3-[(123)I]-iodo-L-alpha-methyltyrosine ([(123)I]-IMT) and positron emission tomography (PET) using 2-[(18)F]-fluoro-2-deoxy-D-glucose ([(18)F]-FDG) are valuable tools for the distinction between viable tumor and radionecrosis in patients receiving radiotherapy for high-grade gliomas. However, to date, little is known about the early effects of radiation on [(123)I]-IMT and [(18)F]-FDG uptake in gliomas.

MATERIAL AND METHODS

To determine the early effects of irradiation on [(123)I]-IMT and [(18)F]-FDG uptake in gliomas, in vitro studies were performed using rat C6 glioma cells. The glioma cells were irradiated with 20 Gy which is a common dose applied to patients receiving intraoperative radiotherapy. Subsequently, the early kinetics of [(123)I]-IMT and [(18)F]-FDG uptake in glioma cells were monitored for 3 days.

RESULTS

Micromorphometric examinations of the irradiated glioma cells revealed that about 25% of the viable cells transformed into giant cells. [(123)I]-IMT uptake per 10(5) viable glioma cells was unchanged on the 1st day post irradiation, but showed a significant increase on the 2nd and 3rd day following radiotherapy (p < 0.01). In addition, there was a moderate increase in [(18)F]- FDG accumulation per 10(5) viable glioma cells during the first 3 days after irradiation (p < 0.05). The maximum increase in early [(123)I]-IMT uptake 1 h after application surpassed that of [(18)F]-FDG (p < 0.01).

CONCLUSION

Rat C6 glioma cells show an early increase in [(123)I]-IMT and [(18)F]-FDG uptake following irradiation which may be partly due to giant cell formation. These data suggest that [(123)I]-IMT SPECT and [(18)F]-FDG PET may be promising procedures for the early prediction of the therapeutic response of gliomas to radiotherapy.

Heterogeneity of radiation induced apoptosis in Ewing Tumor cell lines characterized on a single cell level

The objective of this study was to investigate heterogeneity of radiation induced apoptosis on a single cell level. Two Ewing tumor cell lines were characterized in vitro before and 24 and 72 h after radiation with 5 Gy by multiparametric flow cytometry. Annexin V, 7-AAD and fluorescence conjugated antibodies that were directed against HLA-ABC, CD11a and CD62L were used. Based on these markers radiation induced apoptosis was quantified, multiple apoptotic subpopulations were identified and a characteristic individual apoptotic profile was characterized. The characterization of HLA-ABC, CD11a and CD62L was informative to detect subpopulations of apoptotic cells. The observed heterogeneity and the identification of multiple apoptotic subpopulations reflect the complexity and diversity of biology of radiation induced cell death. This might be an indication for co-existing apoptotic pathways or it might represent sequential steps of the apoptotic cascade.

PET-CT in der Strahlentherapie

Combining positron emission tomography (PET) and X-ray computed tomography (CT) with simultaneous acquisition may improve diagnostic accuracy in oncology. Moreover this combination holds considerable promise in radiotherapy. Metabolic information may be used in decision making in radiotherapy and in planning target volumes. Furthermore early evaluation of treatment efficacy becomes possible. New tracers for the assessment of tumour hypoxia or apoptosis in clinical routine are currently being developed. These tracers may yield high relevance in radiotherapy. Hybrid scanners facilitate patient handling and shorten the duration of acquisition. Furthermore fusion accuracy is optimal. Prospective studies have to be conducted to show that the new technology improves patient care in terms of efficiency and quality.

[Legal questions in radio-oncology. Demands on patient information and documentation of the therapy with examples of current legal cases concerning specialization in radiotherapy/radio-oncology]

BACKGROUND

In recent years, also due to the media, the medical information a physician gives to his patients, the methods of medical treatment and their consequences have increasingly come to the attention of the general public. As a result, to avoid claims for compensation because of faulty treatment or even to evade prosecution, the demands on medical information given before or during treatment are getting greater and greater. Generally, claims for compensation are not based on the accusation of wrong treatment, because this accusation is difficult to prove. As a rule-as a way out of difficulties-these claims for compensation are based on the accusation of mistaken or incomplete information, because if one cannot prove any wrong treatment, faulty information can (nearly) always be proven.

METHODS

Methodically, showing the principles that must be followed when giving information on radiotherapy and when documenting it, also taking examples of current legal cases into account. Short survey of the question of liability and the future importance of principles for medical treatment.

CONCLUSION

Every attending physician should feel obliged to pay attention to legal questions concerning medical subjects, though judgments on the contents and the extent of the information that must be given to patients are complex and difficult to understand for anybody not experienced in law. Only so the ever-increasing tendency of people to try to make financial profit on information that they consider mistaken or incomplete can be opposed and a lawsuit can be won, if it cannot be avoided.

Changed adhesion molecule profile of Ewing tumor cell lines and xenografts under the influence of ionizing radiation

BACKGROUND

Adhesion molecules are involved in cell-cell and cell-matrix interactions and may be informative to characterize intercellular mechanisms of invasion and metastasis. This study was performed to characterize radiation-induced changes in the adhesion molecule profile of Ewing tumor subpopulations on a single cell level.

MATERIALS AND METHODS

In the present study, two Ewing tumors were characterized in vitro 4, 24 and 72 hours after radiation with 5 Gy and in vivo in a xenograft model 4, 6 and 15 days after radiation with 30 Gy, together with non-irradiated controls, by five parameter flow cytometry. Directly fluorescence-conjugated antibodies that were directed against adhesion molecules (LFA-1 (CD11a), HCAM (CD44), VLA-2 (CD49b), ICAM-1 (CD54), NCAM (CD56), LECAM-1 (CD62L) and CD86) were used. Annexin V and 7-AAD were used to characterize radiation-induced apoptosis.

RESULTS

Tumor cell subpopulations were identified by the expression of adhesion molecules, apoptotic markers and DNA content. Heterogeneous changes of the adhesion molecule profile were identified on tumor cell subpopulations after radiation. The expression of CD11a and CD62L correlated with the expression of apoptosis-associated markers.

CONCLUSION

The changes of flow cytometric profile under radiation may potentially correlate with a changed metastatic potential of tumor cell subpopulations.

Time- and dose-dependent changes of intracellular cytokine and cytokine receptor profile of Ewing tumour subpopulations under the influence of ionizing radiation

PURPOSE

Cytokines and their corresponding cell surface receptors are involved in intercellular signalling pathways and in the radioresistance of normal and malignant cells. The aim was the characterization of the expression of intracellular cytokines, their receptors and apoptosis-associated markers under the influence of radiation.

MATERIAL AND METHODS

Two Ewing tumours were characterized in vitro before and 4, 24 and 72 h after radiation with 5 and 10 Gy, and in vivo 4, 6 and 15 days after radiation with 5 and 30 Gy by five parameter flow cytometry. Direct fluorescence-conjugated antibodies directed against intracellular cytokines (interferon-gamma, tumour necrosis factor [TNF]-alpha, interleukin 1) and their receptors (CD119, CD120a, CD121a) were used. Annexin V and 7-amino-actinomycin D were used to identify radiation-induced apoptosis.

RESULTS

Inter- and intra-individual heterogeneities were identified by the expression of cytokine receptors and the intracellular cytokine profile before radiation. Time- and dose-dependent up-regulation of the cytokines TNF-alpha and interleukin 1 were found in vitro. In vivo, an up-regulation of CD120a and CD121a was detectable on tumour cell subpopulations. For interferon-gamma and CD119, no changes were seen.

CONCLUSIONS

The observed radiation-induced changes of cytokine and receptor profile are an indication for complex intercellular interactions in view of radioresistance-associated mechanisms between cell populations within one individual tumour. The observed heterogeneous response on radiation might have therapeutic implications for an individualized therapy based on combined radiation and cytokine modulation, defined by flow cytometric characterization of markers potentially informative for radioresistance.

Effect of radiation on Ewing tumour subpopulations characterized on a single-cell level: intracellular cytokine, immunophenotypic, DNA and apoptotic profile

PURPOSE

Adhesion molecules, cytokines and their corresponding cell-surface receptors are involved in intercellular signalling pathways, radioresistance and metastasis-mediating mechanisms of malignant cells. The aim was the characterization of changes in the marker profile of Ewing tumour cell subpopulations under the influence of radiation.

MATERIALS AND METHODS

Three Ewing tumours were characterized in vitro and in vivo in a xenograft model before and after radiation by five-parameter flow cytometry. Antibodies directed against cell surface and intracellular antigens, apoptosis-associated markers and the DNA dye 7-aminoactinomycin D were used.

RESULTS

Tumour cell subpopulations were identified by expression of adhesion molecules and cytokine receptors, intracellular cytokines, apoptotic markers and DNA content. Heterogeneous changes of flow cytometric profile were identified on tumour cell subpopulations after radiation.

CONCLUSIONS

The changed profile of tumour cells under radiation might be associated with biological changes of tumour subpopulations in view of radioresistance and metastatic potential and might be useful to identify intercellular regulation mechanisms and to define parameters being predictive for a response to therapy.

Local therapy in localized Ewing tumors: results of 1058 patients treated in the CESS 81, CESS 86, and EICESS 92 trials

PURPOSE

The impact of different local therapy approaches on local control, event-free survival, and secondary malignancies in the CESS 81, CESS 86, and EICESS 92 trials was investigated.

METHODS AND MATERIALS

The data of 1058 patients with localized Ewing tumors were analyzed. Wherever feasible, a surgical local therapy approach was used. In patients with a poor histologic response or with intralesional and marginal resections, this was to be followed by radiotherapy (RT). In EICESS 92, preoperative RT was introduced for patients with expected close resection margins. Definitive RT was used in cases in which surgical resection seemed impossible. In CESS 81, vincristine, adriamycin, cyclophosphamide, and actinomycin D was used. In CESS 86, vincristine, adriamycin, ifosfamide, and actinomycin D was introduced for patients with central tumors or primaries >100 cm(3). In CESS 92, etoposide, vincristine, adriamycin, ifosfamide, and actinomycin D was randomized against vincristine, adriamycin, ifosfamide, and actinomycin D in patients with primaries >100 cm(3).

RESULTS

The rate of local failure was 7.5% after surgery with or without postoperative RT, and was 5.3% after preoperative and 26.3% after definitive RT (p = 0.001). Event-free survival was reduced after definitive RT (p = 0.0001). Irradiated patients represented a negatively selected population with unfavorable tumor sites. Definitive RT showed comparable local control to that of postoperative RT after intralesional resections. Patients with postoperative RT had improved local control after intralesional resections and in tumors with wide resection and poor histologic response compared with patients receiving surgery alone. Patients with marginal resections with or without postoperative radiotherapy showed comparable local control, yet the number of patients with good histologic response was higher in the latter treatment group (72.2% vs. 38.5%).

CONCLUSION

Patients with resectable tumors after initial chemotherapy had a low local failure rate. With preoperative RT, local control was comparable. RT is indicated to avoid intralesional resections. After intralesional or marginal resections and after a poor histologic response and wide resection, postoperative RT may improve local control.

[Time factor and repopulation during fractionated radiotherapy. Comparison between two xenografted human squamous cell carcinoma]

BACKGROUND

A series of experiments were performed to determine the local tumour control of two human squamous cell carcinoma lines in nude mice. An accelerated-fractionated radiation therapy regime is compared to a conventional-fractionated therapy regime.

MATERIAL AND METHODS

KB is a well established human nasopharyngeal squamous cell carcinoma line (ATCC CCL 17). In nude mice KB grows as an low differentiated carcinoma. PEC MB is an undifferentiated squamous cell carcinoma of the maxillary sinus, which was successfully established in nude mice by our group 1993. Both tumors were serially passaged in nude mice. Local irradiation was given without anaesthesia under ambient conditions to air breathing animals using 18 MeV electrons of an linear accelerator (Mevatron 77, Siemens, Munich). Each dose level group consists of six to eight animals. The radiation treatments were given in ten equals fractions using graded dose levels of 2, 3, 4.5, 6 and 8 Gy. The interfraction time interval was 6 hours in the accelerated-fractionated group and 24 hours in the conventional-fractionated group (Figure 1). In the conventional-fractionated group a therapy break was given after 5 fractions for 72 h. The endpoint of the experiments was the dose, which was necessary to control 50% of the tumors (TCD(50)). The TCD(50) values were calculated after 60 days (Tables 1a and 1b).

RESULTS

The experiments show, that with increasing overall treatment time of 8 3/4 days using the same number of fractions under ambient conditions the tumor control dose of the tumor KB increases from 36.3 Gy (95% CI 30.9...42.7) to 44.3 Gy (38.3...51.2) (Figure 2a). For the tumor PEC MB the tumor control dose increases from 39.5 Gy (33.4...46.7) to 45.5 Gy (37.0...56.0 (Figure 2b).

CONCLUSION

This observed increase of the dose necessary to control the squamous cell carcinoma KB and PEC MB can be caused by repopulation of clonogenic tumors cells, however, other mechanism such as an increasing fraction of hypoxic tumor cells can not be ruled out.

Radiation-induced changes of telomerase activity in a human Ewing xenograft tumor

AIM

The effect of ionizing irradiation on telomerase activity and further associated biological factors was evaluated in a human Ewing tumor xenograft model on nude mice.

MATERIAL AND METHODS

The human Ewing tumor cell line STA-ET-1 was established in a nude mouse model. Initially, the dose-response relationship for the tumor model was established. For the radiation experiments two dose levels were chosen: 5 Gy and 30 Gy. After 5 Gy, there was no significant growth delay whereas after 30 Gy there was a marked growth delay without the induction of a complete remission. Tumors were examined 6, 12, 24, 48, 72, and 96 hours post irradiation. After irradiation with 30 Gy further time points were 6, 9, 12 and 15 days. For each dose and time group, three tumors were evaluated.

RESULTS

There was a reduction of telomerase activity after 5 Gy to 50% (not statistically significant) after 3 days; however, after 30 Gy there was a reduction of telomerase activity to 23% of the initial value after 6 days (p = 0.001). Telomerase activity correlated with the expression of human telomerase reverse transcriptase (hTERT), but not with the expression of telomerase-associated protein (TP1) and human telomerase RNA (hTR). The maximal amounts of necrosis or apoptosis after 30 Gy were 19% and 6.9%, respectively.

CONCLUSIONS

Ionizing radiation reduces telomerase activity and the expression of hTERT which cannot be explained by the induction of necrosis or apoptosis alone. The reduction of telomerase activity may contribute to delayed cell death after radiotherapy. The combined use of radiation and specific telomerase inhibitors may be a potentially synergistic treatment strategy.

Hemithorax irradiation for Ewing tumors of the chest wall

PURPOSE

In the Cooperative Ewing's Sarcoma Study 86 and the European Intergroup Cooperative Ewing's Sarcoma Study 92, hemithorax irradiation (RT) was performed in patients with Ewing tumors of the chest wall involving the pleura or contaminating the pleural cavity. In a retrospective analysis, the outcomes of these patients were evaluated and compared with those of patients with chest wall tumors who did not receive hemithorax RT.

METHODS AND MATERIALS

Between 1985 and 1996, 138 patients presented with nonmetastatic Ewing tumors of the chest wall. They were treated in a multimodal treatment regimen that included polychemotherapy and local therapy depending on the tumor characteristics. Hemithorax RT was performed at a dose of 15 Gy for patients <14 years old and 20 Gy for patients >or=14 years old. Forty-two patients received hemithorax RT (Group 1) and 86 patients did not (Group 2). The data were insufficient for the other 10 patients.

RESULTS

Comparing both groups, the initial pleural effusion, pleural infiltration, and intraoperative contamination of the pleural space were significantly more frequent in Group 1. The event-free survival rate after 7 years was 63% for patients in Group 1 and 46% for patients in Group 2 (not statistically significant). The 7-year local relapse rate (including combined local-systemic relapses) was 12% in Group 1 and 10% in Group 2; the corresponding systemic relapse rates were 22% and 39%.

CONCLUSION

Patients with chest wall tumors who received hemithorax RT were negatively selected; yet the rate of event-free survival was better for patients who received hemithorax RT than for those who did not (although the difference was not statistically significant). This result was due to a reduction of metastases, mainly lung metastases. Local control was equivalent between the two groups. These favorable results have caused us to continue using hemithorax RT to treat high-risk patients with Ewing tumors of the chest wall.

Combined radiochemotherapy with paclitaxel in the treatment of malignant glioma

BACKGROUND

Paclitaxel is a radiosensitizing agent that shows a synergistic effect with radiation in malignant glioma cells. A phase I/II trial was performed in order to evaluate both feasibility and outcome of combined radiochemotherapy in malignant glioma.

PATIENTS AND METHODS

56 patients were included in the trial. Paclitaxel was administered on days 1-4, 15-18 and 29-32 18 to 24 hours prior to irradiation. Radiotherapy with 60 Gy in conventional fractionation was initiated on day 2.31 patients were included in a dose-escalation trial starting with 20 mg/m2/d and increasing up to 60 mg/m2/d in 10-mg steps. Additional 25 patients were treated with 50 mg/m2/d.

RESULTS

The regimen was very well tolerated with minimal subjective impairment such as sickness or weakness. Maximal tolerable dose was 50 mg/m2/d, with neutropenia being the dose-limiting toxicity. There were four allergic reactions and five thromboembolisms; furthermore, one patient with a normal blood count died due to pneumonia. The median survival was 12 months, and significantly favorable factors were a young age, a lower tumor grade (grade 3) and a complete resection. Varying the paclitaxel dose had no influence on outcome.

CONCLUSIONS

Combined radiochemotherapy with paclitaxel in the treatment of malignant glioma was well tolerated. Maximal tolerable dose was 50 mg/m2/d. There was no increase in survival compared with results reported in the literature.

Radiotherapy in the treatment of locoregional relapses of breast cancer

Locoregional recurrences of breast cancer are associated with considerable morbidity and frequently present with concurrent metastatic disease. Yet patients without systemic spread can be treated with curative intent. In a retrospective analysis, the results of treatment of these patients have been evaluated at our institution. Between 1987 and 1996, 113 patients with locoregional breast cancer relapse, without systemic manifestation, received irradiation after local tumour excision. 13 patients (11.5%) had already received radiotherapy as part of their primary treatment. In these cases, only the area involved was treated. In all other patients, the chest wall and the ipsilateral lymph nodes were irradiated. Median dose was 50 Gy (range 20-65 Gy). Median follow-up was 4.4 years. 76 patients (67.3%) presented with chest wall recurrence only, 25 patients (22.1%) with nodal relapse only and 12 patients (10.6%) with combined relapses. 93% of patients had local control of disease after treatment. Local control rate after 5 years was 59%. 63 patients (55.8%) died within the follow-up interval, 45 patients (39.8%) owing to metastases, 4 patients (3.5%) owing to local failure and 8 patients (7%) owing to causes unrelated to tumour. Overall survival after 5 years was 43%. In multivariate analysis, positive hormone receptor status, small tumours on relapse and chest wall relapses alone were associated with improved survival. Radical local therapy is necessary in order to achieve and maintain local control and to prevent secondary dissemination in patients with only local recurrence of breast cancer.

Microscopic residual disease is a risk factor in the primary treatment of breast cancer

OBJECTIVES

In the primary treatment of breast cancer, postoperative radiotherapy is performed in high-risk patients after mastectomy and in patients who received breast conserving surgery. In a retrospective analysis, our mono-institutional results of postoperative irradiation have been evaluated.

PATIENTS AND METHODS

Between 1992 and 1996, 500 patients have been irradiated after surgery for primary breast cancer. Of these, 489 patients had no initial metastases. 89 patients with loco-regional disease had a mastectomy, 400 patients were irradiated after breast conserving surgery. Radiotherapy at the chest wall was performed with 50 Gy and 2 Gy fractions. After microscopically incomplete resection, an electron boost of 10 Gy was given. The ipsilateral lymph nodes were irradiated with 50 Gy when there was extensive lymph node involvement or invasion of tumor in the axillary fat tissue.

RESULTS

The 5-year local control rate after mastectomy was 97.4% and 91.2% after breast conserving surgery. The only statistically significant risk factor for local failure was microscopically incomplete resection. The corresponding 5-year local control rates for microscopically incomplete and complete resections were 76.4% and 92.7% (p = 0.01). The risk of local relapse was increased with both marginal invasive and marginal DCIS-tissue. 86.6% of local relapses were in the same quadrant.

CONCLUSIONS

High-risk patients after mastectomy and patients with breast conserving surgery achieve a high local control rate with postoperative irradiation. After microscopically incomplete resection, there is an increased risk for local relapse.

Fractionated perioperative high dose rate brachytherapy using a tissue equivalent bendy applicator

Intraoperative radiation techniques allow an additional local dose in areas at high-risk for local failure. With brachytherapy techniques, perioperative radiation can be fractionated. Fractionated treatment might offer an interesting alternative to a single dose, both to increase the therapeutic ratio and to protect late reacting tissues at risk. The dose distribution for brachytherapy applicators can be optimized using spacer materials. In this prospective study a new tissue equivalent bendy applicator (TEBA) that can remain in situ for several days is introduced, and the feasibility of fractionated perioperative high dose rate (HDR) brachytherapy is examined. 31 patients with different tumours (soft tissue sarcoma, Ewings sarcoma, rectal cancer, and locally infiltrating diseases) were treated. The TEBA was applied, depending on resection status and intraoperative findings. Planning was based on digitized radiographs and CT scans. Perioperative HDR brachytherapy was performed using an individual treatment schedule. In 29 patients perioperative radiation was given and in 26 cases fractionated brachytherapy application was possible. TEBA application time varied from 1 day to 11 days. During this time between 1 and 8 fractions were given with total doses from 10 Gy to 25 Gy. Fractionated perioperative brachytherapy with this technique is feasible and adequate. Further studies will show whether fractionated perioperative treatment using the TEBA technique fulfils its theoretical advantages over single dose intraoperative radiotherapy by decreased late toxicity and increased local tumour control.

Postoperative radiotherapy in the treatment of Ewing tumors: influence of the interval between surgery and radiotherapy

BACKGROUND

The impact of the timing of postoperative irradiation was evaluated in patients with Ewing tumors who received postoperative irradiation.

PATIENTS AND METHODS

153 patients treated in the CESS 86 and EICESS 92 trials were evaluated in a retrospective analysis. They received surgery and postoperative irradiation as local treatment modalities. In 46 patients, postoperative irradiation was started within 60 days after surgery, in 107 patients after more than 60 days. A median dose of 45 Gy was administered. The median follow-up was 70 months.

RESULTS

There was no substantial difference between the two groups concerning risk factors for local failure and survival. The local control rate after 5 years was 98% in the group with early onset of radiation and 92% in the group with later onset (n.s.). There is no difference in event free survival between the two groups (both 64% after 5 years). If the cutpoint of the onset of postoperative irradiation was chosen after 90 days, there was no difference in local control or event free survival.

CONCLUSIONS

Patients with early onset of postoperative irradiation show a trend for improved local control compared to patients with a later onset; the difference is statistically not significant. This trend has no influence on survival.

[Experimental studies of the value of SPIO for MRI of bone marrow before and after whole body irradiation]

PURPOSE

Evaluation of the value of superparamagnetic iron oxides (SPIO; Endorem) for MRI-derived quantifications of the permeability of the blood-bone marrow barrier and the phagocytic activity of reticuloendothelial system (RES) bone marrow cells before and after TBI.

METHODS

12 New Zealand white rabbits underwent MRI of the lumbar spine and os sacrum using T1-weighted spinecho (SE) and T2-weighted Turbo-SE (TSE) sequences before and after injection of SPIO (Endorem). Four animals each were examined without irradiation, after 4 Gy total body irradiation (TBI), and after 12 Gy TBI. Changes in bone marrow signal intensities (SI) after contrast agent injection were quantified as delta SI(%) = SIpost-SIpre)/SIpre) x 100% and these data were correlated with bone marrow histopathology.

RESULTS

Histopathology of the bone marrow revealed a radiation-induced decline of all hematopoetic cell lines. SPIO were phagocytosed by bone marrow RES cells and caused a significant bone marrow signal decline on postcontrast T2-weighted images (p < 0.05). delta SI(%) data for T2-weighted images were significantly higher for the irradiated bone marrow as compared to non-irradiated controls (p < 0.05). Dynamic T1-weighted images directly after contrast medium injection were not able to characterize the permeability of the blood-bone marrow barrier.

CONCLUSION

Hematopoetic bone marrow can be labelled with SPIO. Irradiation does not impair the phagocytic activity of bone marrow RES cells. However, the bone marrow enhancement with SPIO is smaller as compared to previous results obtained by our group with USPIO.

Cell heterogeneity and subpopulations in solid tumors characterized by simultaneous immunophenotyping and DNA content analysis

BACKGROUND

Heterogeneity in human malignant tumors is a well-described phenomenon and of interest with regard to subpopulations with differences in clonality, metastatic potential, and response to therapy under different treatment regimes. The aim of this study was the simultaneous characterization of surface markers and DNA content of solid tumors to identify tumor cell subpopulations and to study the association between the expression of antigens and DNA content.

METHODS

In the present study, six different malignant tumors grown as xenografts in nude mice were characterized by five-parameter flow cytometry. Immunophenotyping was performed using a variety of direct fluorescence-conjugated antibodies. In all cases, simultaneous detection of DNA content was done after staining with 7-aminoactinomycin D.

RESULTS

Tumor cells were characterized by light scatter properties, antigen expression, and DNA content. Tumor cell heterogeneity, subpopulations, and DNA content-dependent antigen expression were identified.

CONCLUSIONS

This method offers the possibility of characterizing solid tumors according to their immunophenotype and DNA content. The results obtained can be used to identify changes in immunophenotypic and DNA profiles of tumor cell populations before and after therapy and might be useful to define parameters predictive for response to therapy.

Assessing permeability alterations of the blood-bone marrow barrier due to total body irradiation: in vivo quantification with contrast enhanced magnetic resonance imaging

Our aim was to quantify irradiation-induced permeability alterations of the blood-bone marrow barrier (BMB) with dynamic contrast enhanced magnetic resonance imaging (MRI). The standard small molecular contrast agent, gadoterate meglumine, and a new macromolecular contrast agent, carboxymethyldextran-Gd-DOTA (CMD-Gd-DOTA), were compared. Twenty New Zealand white rabbits underwent MRI of the bone marrow before and 1-2 days after total body irradiation (TBI). Dynamic, repetitive T1-weighted MRI was performed before and after injection of either 0.05 mmol/kg BW CMD-Gd-DOTA (n = 10) or 0.5 mmol/kg BW gadoterate (n = 10). Bone marrow contrast enhancement was quantified as delta signal intensity: DeltaSI = |(SIpost - SIpre) / SIpre| * 100%. All MRI data were compared with the histopathologic BMB ultrastructure. Dynamic bone marrow DeltaSI data steadily increased after CMD-Gd-DOTA injection, while blood DeltaSI data slightly decreased. This bone marrow contrast enhancement, indicative of contrast agent extravasation, was significantly higher and prolonged in the irradiated group as compared to non-irradiated controls (P < 0.05) and corresponded to irradiation-induced alterations of the BMB ultrastructure seen on electron microscopy. By contrast, DeltaSI data of non-irradiated and irradiated marrow were not significantly different following gadoterate injection (P > 0.05). We conclude that irradiation-induced alterations in BMB permeability could be reliably assessed with dynamic MRI, using the new macromolecular contrast agent CMD-Gd-DOTA. Bone Marrow Transplantation (2000) 25, 71-78.

Monitoring radiation-induced changes in bone marrow histopathology with ultra-small superparamagnetic iron oxide (USPIO)-enhanced MRI

The purpose of this study was to monitor radiation-induced alterations of the blood-bone marrow barrier (BMB) and the reticuloendothelial system (RES) with AMI-227-enhanced magnetic resonance imaging (MRI). Twenty New Zealand white rabbits (n = 10 following total body irradiation and n = 10 controls) underwent AMI-227-enhanced MRI. Pulse sequences included dynamic fast low-angle shot (FLASH; TR/TE 50/4 msec, flip angle 60 degrees) MRI and static T1- and T2-weighted spin-echo (SE) and turbo-SE sequences of the lumbar spine and sacrum. Bone marrow enhancement was quantified as delta signal intensity (SI) (%) =|[(SIpost - SIpre)/SIpre] x 100%| and compared with histopathology, including iron stains and electron microscopy. Dynamic bone marrow deltaSI (%) data steadily increased up to 10-15 minutes after AMI-227 administration, while blood deltaSI (%) data stayed nearly constant, histologically corresponding to iron oxide leakage into the bone marrow interstitium. This bone marrow contrast enhancement increased significantly following irradiation, corresponding to alterations of the endothelial lining of the bone marrow sinusoids. Late postcontrast images exhibited a significant positive T1 enhancement and negative T2 enhancement of the normal bone marrow, which further increased with irradiation due to increased RES activity. Irradiation-induced changes in bone marrow physiology could be reliably assessed with AMI-227-enhanced MRI.

Lectin-induced increase in clonogenic growth of haematopoietic progenitor cells

The galactoside-specific plant lectin, Viscum album agglutinin (VAA-I) increases cellular parameters of natural host defence. It also binds to a variety of haematopoietic cells, including progenitors. We investigated whether VAA-I has a stimulatory effect on haematopoietic progenitor cells. Peripheral blood progenitor cells from 7 healthy volunteers were cultured in a colony assay with VAA-I plus erythropoietin (EPO) and stem cell factor (SCF). At 50 pg/ml VAA-I induced a significant increase in the cytokine-dependent clonogenic growth (52% in median, p < 0.05). In another set of experiments purified CD34+ cells were isolated from the bone marrow aspirate of 4 patients with non-metastatic breast cancer using fluorescence-activated cell sorting. Binding to CD34+ cells was demonstrated by using directly fluorescence-conjugated VAA-I. Co-incubation with D-galactose significantly abrogated this effect. CD34+ cells were cultured in the presence of EPO, SCF, interleukin-3, granulocyte/monocyte colony-stimulating factor and granulocyte colony-stimulating factor. VAA-I alone had no measurable effect on the clonogenic growth of the isolated cells. However, at concentrations of 100 and 250 pg/ml VAA-I increased the cytokine-dependent proliferation and differentiation of CD34+ cells by a median of 75 and 85%, respectively. The results show that VAA-I binds to haematopoietic progenitor cells and has a co-stimulatory effect on their proliferation.

Evidence for malignant transformation in acute myeloid leukemia at the level of early hematopoietic stem cells by cytogenetic analysis of CD34+ subpopulations

Acute myeloid leukemia (AML) is a heterogenous disease according to morphology, immunophenotype, and genetics. The retained capacity of differentiation is the basis for the phenotypic classification of the bulk population of leukemic blasts and the identification of distinct subpopulations. Within the hierarchy of hematopoietic development and differentiation it is still unknown at which stage the malignant transformation occurs. It was our aim to analyze the potential involvement of cells with the immunophenotype of pluripotent stem cells in the leukemic process by the use of cytogenetic and cell sorting techniques. Cytogenetic analyses of bone marrow aspirates were performed in 13 patients with AML (11 de novo and 2 secondary) and showed karyotype abnormalities in 10 cases [2q+, +4, 6p, t(6:9), 7, +8 in 1 patient each and inv(16) in 4 patients each]. Aliquots of the samples were fractionated by fluorescence-activated cell sorting of CD34+ cells. Two subpopulations, CD34+/CD38- (early hematopoietic stem cells) and CD34+/CD38+ (more mature progenitor cells), were screened for karyotype aberations as a marker for leukemic cells. Clonal abnormalities and evaluable metaphases were found in 8 highly purified CD34+/CD38- populations and in 9 of the CD34+/CD38- specimens, respectively. In the majority of cases (CD34+/CD38-, 6 of 8 informative samples; CD34+/CD38+, 5 of 9 informative samples), the highly purified CD34+ specimens also contained cytogenetically normal cells. Secondary, progression-associated chromosomal changes (+8, 12) were identified in the CD34+/CD38- cells of 2 patients. We conclude that clonal karyotypic abnormalities are frequently found in the stem cell-like (CD34+/CD38-) and more mature (CD34+/CD38+) populations of patients with AML, irrespective of the phenotype of the bulk population of leukemic blasts and of the primary or secondary character of the leukemia. Our data suggest that, in AML, malignant transformation as well as disease progression may occur at the level of CD34+/CD38- cells with multilineage potential.

Trisomy 4 in 'stem cell-like' leukemic cells of a patient with AML

CD34 positive progenitor cells were analyzed in the bone marrow aspirate from a patient with newly diagnosed AML FAB M4. The patient had trisomy 4 as sole cytogenetic abnormality and a dominant population of CD34 negative leukemic blasts. Karyotyping of the FACS isolated, minor subpopulation of CD34+/CD38-, 'stem cell'-like cells (incidence 0.29%) revealed trisomy 4 in 11/13 metaphases. No metaphases were obtained in the CD34 negative subpopulation. The experiments point to the existence of leukemic stem cells in the CD34+/CD38- compartment in AML patients with trisomy 4.

Flow cytometric characterization of acute myeloid leukemia: IV. Comparison to the differentiation pathway of normal hematopoietic progenitor cells

Gradual increase of CD38 on cells expressing CD34 characterizes the early cell differentiation pathway of normal human hematopoietic progenitors. In this study the coordinated expression pattern of CD34 and CD38 was assessed on leukemic blasts from bone marrow aspirates of 95 patients with newly diagnosed acute myeloid leukemia (AML). Expression was divided into six categories analogous to the differentiation pathway of normal bone marrow. The CD38 antigen was expressed on the leukemic cells of all patients and CD34+ leukemic cells were found in 79 patients (83%). In 93 patients, the leukemic cells were found along the differentiation pathway defined by CD34 and CD38. In 33 of the 93 patients, a part of the CD34+ cells did not express the CD38 antigen (categories 1 and 2). In another 33 patients, all CD34+ cells expressed CD38 (categories 3 and 4). In the remaining 27 patients, only cells were found which dimly expressed CD34 or did not express CD34 (categories 5 and 6). Of the 93 patients, 88 were treated with intensive chemotherapy according to the protocol of the German AML Cooperative Group. Of these, 21 died early and were not evaluable for treatment response. Complete remission was achieved in 14 of 22 patients (64%) in categories 1 and 2, in 19 of 26 patients (73%) in categories 3 and 4, and in 18 of 19 patients (95%) in categories 5 and 6. The event-free survival was significantly longer in patients of categories 5 and 6 compared to patients in categories 1 and 2 (p less than 0.01) and categories 3 and 4 (p less than 0.05), respectively. We conclude that in the majority of AML patients the immunophenotype of leukemic cells follows the early cell differentiation pathways defined by coordinated expression of CD34 and CD38 similar to that of normal hematopoietic progenitors. The presence of cells in the late cell differentiation stages (CD34+/-, CD38 /+) identifies patients with a higher complete remission rate and longer complete remission duration.

Flow cytometric characterization of acute myeloid leukemia. Part II. Phenotypic heterogeneity at diagnosis

The frequency and distribution of aberrant antigen expression are analyzed on bone marrow aspirates from 80 patients with newly diagnosed acute myeloid leukemia (AML) by multidimensional flow cytometry. Parameters examined are the light scatter profile of the leukemic cells and the correlative expression of different combinations of the CD2, 4, 5, 7, 11b, 11c, 13, 14, 15, 16, 33, 34, 38, and HLA-DR antigens. Antigen expression on leukemic cells in bone marrow is described by characteristic antigen expression patterns describing: (i) the percentage of cells expressing the antigen; (ii) the antigen density; and (iii) the distribution of the antigen on the leukemic cells. Typically the non-myeloid antigens are homogeneously expressed by the leukemic cells, whereas the myeloid associated antigen CD11b, CD11c, CD14, and CD15 are heterogeneously expressed. Comparison of the antigenic profiles of 80 bone marrow aspirates revealed an extreme interclonal heterogeneity. Comparison of the antigen expression patterns found in AML patients with the antigen expression in normal bone marrow revealed four patterns of aberrant antigen expression in AML: (i) expression of nonmyeloid antigens (i.e. CD2, CD5, and CD7 were present in 57, 60, and 37% of the patients, respectively); (ii) asynchronous expression of myeloid associated antigens (i.e. co-expression of CD34 and CD15 in 25% of the patients and expression of CD16 on immature myeloid cells in 15% of the cases); (iii) over-expression of myeloid associated antigens (e.g. CD34 in 16% of the cases and CD14 on neutrophilic cells in 19% of all patients); and (iv) absence of expression of myeloid associated antigens (e.g. lack of CD33 in 21% of the cases and lack of both CD11b and CD15 in 6% of all patients. Multidimensional flow cytometric analysis of bone marrow aspirates of AML patients disclosed that the leukemic cells of each AML patient had a unique antigenic profile and could be discriminated from their normal counterparts based on aberrant antigen expression and typical light scatter profiles. The ability to distinguish leukemic cells from normal cells allows the detection of residual leukemic cells during and after chemotherapy.

Flow cytometric characterization of acute myeloid leukemia. Part 1. Significance of light scattering properties

Acute leukemias are classified using the morphological and cytochemical criteria set forward by the French, American and British (FAB) group. Immunophenotyping is helpful for the differential diagnosis but is secondary to the morphological criteria. Immunophenotyping performed by flow cytometry, however, can yield valuable information on cell morphology in addition to cell surface antigen expression. To provide a basis of a combined evaluation of both morphology, i.e. light scattering, and immunophenotype by flow cytometry we have compared the light scattering profiles of 70 patients newly diagnosed with acute leukemia with normal bone marrow and related the findings to the FAB classification. Three main light scattering profiles were observed in the bone marrow aspirates of the 70 patients (A1,2; B1,2,3; C1,2,3,4). A1,2, characterized by a predominant cell cluster with low forward and orthogonal light scattering, contained only and all patients diagnosed as acute lymphoblastic leukemia, acute undifferentiated leukemia, and acute non-lymphocytic leukemia M6 and M1. B1,2,3 is characterized by a predominant cell cluster with large forward and low to high orthogonal light scattering. Category B1 contained the majority of patients classified as M5; the M3 leukemias were categorized as B2. C1,2,3,4 is characterized by a predominant cell cluster with low forward and orthogonal light scattering that branches towards regions with larger light scattering. Categories C1 and C2 contained the majority of the patients classified as M2. Category C3 was specific for M4 and M4eo leukemias. The patients diagnosed as M4 were heterogeneous and equally distributed over the B and C categories. The clear relationship found between the FAB classification and classification by the light scattering profile of the acute leukemias enhances the importance of the flow cytometric classification of leukemias. In contrast with light microscopy, flow cytometry can now provide the hematologist with an objective technique to classify leukemias by the simultaneous assessment of cell surface antigen expression and cell morphology, i.e. light scattering.