Randomized Trial of Postoperative Radiation Therapy After Wide Excision of Neurotropic Melanoma of the Head and Neck (RTN2 Trial 01.09).

BACKGROUND: Cutaneous neurotropic melanoma (NM) of the head and neck (H&N) is prone to local relapse, possibly due to difficulties widely excising the tumor. This trial assessed radiation therapy (RT) to the primary site after local excision. METHODS: Participants from 15 international centers were randomized to observation or RT. The participants were required to have microscopically negative excision margins 5 mm wide or wider and no evidence of disease elsewhere. The primary outcome was time to local relapse. The secondary outcomes included time to any recurrence, overall survival (OS), and toxicity. RESULTS: The trial ceased prematurely due to slow recruitment and the COVID-19 pandemic. During 2009-2020, 50 participants were randomized: 23 to observation and 27 to RT. The most common NM subsites were scalp (32%), midface (22%), and lip (20%). The median depth of invasion was 5 mm, and desmoplasia observed in 69%. The median duration from randomization to last contact was 4.8 years. Four participants (8%) experienced local relapse as a first recurrence during the study period: 3 in the observation arm and 1 in the RT arm (hazard ratio [HR] 0.29; 95% confidence interval [CI] 0.03-2.76; p = 0.279). No statistically significant difference in time to any relapse or OS was observed. More than 6 months after randomization, grade 3 or greater toxicity was experienced by 10% of the participants in the observation arm and 12.5% of the participants in the RT arm of the study. CONCLUSION: Due to low accrual, the role of adjuvant RT for cutaneous NM of the H&N excised with microscopically negative margins 5 mm wide or wider remains undefined. Its routine use cannot be recommended. Local relapse might be less common than previously anticipated based on retrospective reports.

Inguinal and Ilio-inguinal Lymphadenectomy in Management of Palpable Melanoma Lymph Node Metastasis: A Long-Term Prospective Evaluation of Morbidity and Quality of Life.

PURPOSE: Prospective data are lacking on long-term morbidity of inguinal lymphadenectomy including the influence of extent of surgery, use of radiotherapy, and patient factors. The aim of this study is to evaluate the effects of these factors on patient outcome, quality of life (QOL), regional symptoms, and limb volumes after inguinal or ilio-inguinal lymphadenectomy for melanoma. METHODS: Analysis of the subgroup of patients with inguinal lymph node field relapse of melanoma, treated by inguinal or ilio-inguinal lymphadenectomy in the ANZMTG/TROG randomized trial of adjuvant radiotherapy versus observation. RESULTS: Sixty-nine patients, 46 having undergone inguinal and 23 ilio-inguinal lymphadenectomy, with median follow-up of 73 months were analyzed. Mean limb volume increased rapidly after surgery (7% by 3 months) and continued to increase for at least another 18 months. Patients with body mass index (BMI) ≥ 25 kg/m2 had greater limb volume increase than normal-weight patients (13.3% versus 6.9%, P = 0.030). QOL improved over the first 18 months, but despite initial improvement, regional symptoms persisted long term. Type of surgery (inguinal or ilio-inguinal lymphadenectomy) had no demonstrably significant effect on limb volume (9.9% versus 13.4%, P = 0.35), QOL (P = 0.68), or regional symptoms (P = 0.65). There was no difference in overall survival between inguinal and ilio-inguinal lymphadenectomy [hazard ratio (HR) 0.75, 95% confidence interval (CI) 0.40-1.40, P = 0.43]. CONCLUSIONS: Inguinal lymphadenectomy for melanoma is a potentially morbid procedure with significant increases in limb volume. Patients report reasonable QOL but may have ongoing regional symptoms. Overweight/obesity is associated with poorer QOL, increased limb volume, and regional symptoms.

Patterns of Failure Following Dose-escalated Chemoradiotherapy for Fluorodeoxyglucose Positron Emission Tomography Staged Squamous Cell Carcinoma of the Oesophagus.

AIMS: To analyse outcomes and patterns of failure following dose-escalated definitive chemoradiotherapy (CRT) for oesophageal squamous cell carcinoma using fluorodeoxyglucose positron emission tomography for staging and treatment planning. MATERIALS AND METHODS: A retrospective review of patients with oesophageal squamous cell carcinoma receiving definitive CRT to a dose of ≥56 Gy was conducted. Patient and tumour characteristics, treatment received and first sites of relapse were analysed. RESULTS: Between 2003 and 2014, 72 patients were treated with CRT to a median dose of 60 Gy (range 56-66 Gy). The median age was 63 years; most (61%) were stage III/IVa. The median follow-up was 57 months. Three year in-field control, relapse-free survival and overall survival was 64% (95% confidence interval 50-75%), 38% (95% confidence interval 27-50%) and 42% (95% confidence interval 30-53%), respectively. Of the 41 failures prior to death or at last follow-up date, isolated locoregional relapse occurred in 16 patients (22%) with isolated in-field recurrence in 11 patients (15%). Distant failure as first site of relapse was present in 25 patients (35%). No in-field failures occurred in the 11 patients with cT1-2, N0-1 tumours. The median survival for cT4 tumours was 8 months, with five of eight patients developing local progression within the first 6 months. CONCLUSIONS: Dose-escalated radiotherapy was associated with promising rates of in-field local control, with the exception of cT4 tumours. Distant failure remains a significant competing risk. Our data supports the need for current trials re-examining the role of dose escalation in the modern era.

Predictors of overall and recurrence-free survival after neoadjuvant chemotherapy for gastroesophageal adenocarcinoma: Pooled analysis of individual patient data (IPD) from randomized controlled trials (RCTs).

BACKGROUND: Neoadjuvant chemotherapy improves prognosis of patients with locally advanced gastroesophageal adenocarcinoma. The aim of this study was to identify predictors for postoperative survival following neoadjuvant therapy. These could be useful in deciding about postoperative continuation of chemotherapy. METHODS: This meta-analysis used IPD from RCTs comparing neoadjuvant chemotherapy with surgery alone for gastroesophageal adenocarcinoma. Trials providing IPD on age, sex, performance status, pT/N stage, resection status, overall and recurrence-free survival were included. Survival was calculated in the entire study population and subgroups stratified by supposed predictors and compared using the log-rank test. Multivariable Cox models were used to identify independent survival predictors. RESULTS: Four RCTs providing IPD from 553 patients fulfilled the inclusion criteria. (y)pT and (y)pN stage and resection status strongly predicted postoperative survival both after neoadjuvant therapy and surgery alone. Patients with R1 resection after neoadjuvant therapy survived longer than those with R1 resection after surgery alone. Patients with stage pN0 after surgery alone had better prognosis than those with ypN0 after neoadjuvant therapy. Patients with stage ypT3/4 after neoadjuvant therapy survived longer than those with stage pT3/4 after surgery alone. Multivariable regression identified resection status and (y)pN stage as predictors of survival in both groups. (y)pT stage predicted survival only after surgery alone. CONCLUSION: After neoadjuvant therapy for gastroesophageal adenocarcinoma, survival is determined by the same factors as after surgery alone. However, ypT stage is not an independent predictor. These results can facilitate the decision about postoperative continuation of chemotherapy in pretreated patients.

Survival benefit and additional value of preoperative chemoradiotherapy in resectable gastric and gastro-oesophageal junction cancer: a direct and adjusted indirect comparison meta-analysis.

Several phase I/II studies of chemoradiotherapy for gastric cancer have reported promising results, but the significance of preoperative radiotherapy in addition to chemotherapy has not been proven. In this study, a systematic literature search was performed to capture survival and postoperative morbidity and mortality data in randomised clinical studies comparing preoperative (chemo)radiotherapy or chemotherapy versus surgery alone, or preoperative chemoradiotherapy versus chemotherapy for gastric and/or gastro-oesophageal junction (GOJ) cancer. Hazard ratios (HRs) for overall mortality were extracted from the original studies, individual patient data provided from the principal investigators of eligible studies or the earlier published meta-analysis. The incidences of postoperative morbidities and mortalities were also analysed. In total 18 studies were eligible and data were available from 14 of these. The meta-analysis on overall survival yielded HRs of 0.75 (95% CI 0.65-0.86, P < 0.001) for preoperative (chemo)radiotherapy and 0.83 (95% CI 0.67-1.01, P = 0.065) for preoperative chemotherapy when compared to surgery alone. Direct comparison between preoperative chemoradiotherapy and chemotherapy resulted in an HR of 0.71 (95% CI 0.45-1.12, P = 0.146). Combination of direct and adjusted indirect comparisons yielded an HR of 0.86 (95% CI 0.69-1.07, P = 0.171). No statistically significant differences were seen in the risk for postoperative morbidity or mortality between preoperative treatments and surgery alone, or preoperative (chemo)radiotherapy and chemotherapy. Preoperative (chemo)radiotherapy for gastric and GOJ cancer showed significant survival benefit over surgery alone. In comparisons between preoperative chemotherapy and (chemo)radiotherapy, there is a trend towards improved survival when adding radiotherapy, without increased postoperative morbidity or mortality.

T-category remains an important prognostic factor for oropharyngeal carcinoma in the era of human papillomavirus.

AIMS: To determine prognostic factors for locoregional relapse (LRR), distant relapse and all-cause death in a contemporary cohort of locoregionally advanced oropharyngeal squamous cell carcinoma (OSCC) treated with definitive chemoradiotherapy or radiotherapy alone. MATERIALS AND METHODS: OSCC patients treated with definitive radiotherapy between 2005 and 2010 were identified from a prospective head and neck database. Patient age, gender, smoking history, human papillomavirus (HPV) status, T- and N-category, lowest involved nodal level and gross tumour volume of the primary (GTV-p) and nodal (GTV-n) disease were analysed in relation to LRR, distant relapse and death by way of univariate and multivariate analysis. RESULTS: In total, 130 patients were identified, 88 HPV positive, with a median follow-up of 42 months. On multivariate analysis HPV status was a significant predictor of LRR (hazard ratio 0.15; 95% confidence interval 0.05-0.51) and death (hazard ratio 0.29; 95% confidence interval 0.14-0.59) but not distant relapse (hazard ratio 0.53, 95% confidence interval 0.22-1.27). Increasing T-category was associated with a higher risk of LRR (hazard ratio 1.80 for T3/4 versus T1/2; 95% confidence interval 1.08-2.99), death (hazard ratio 1.37, 95% confidence interval 1.06-1.77) and distant relapse (hazard ratio 1.35; 95% confidence interval 1.00-1.83). Increasing GTV-p was associated with increased risk of distant relapse and death. N3 disease and low neck nodes were significant for LRR, distant relapse and death on univariate analysis only. CONCLUSION: Tumour HPV status was the strongest predictor of LRR and death. T-category is more predictive of distant relapse and may provide additional prognostic value for LRR and death when accounting for HPV status.

Distinct patterns of stomatitis with concurrent cetuximab and radiotherapy for head and neck squamous cell carcinoma.

To describe the distinct patterns of severe anterior stomatitis seen with concurrent cetuximab and radiotherapy (RT) compared to chemoRT or altered fractionation RT (AFRT) and explore potential associations with clinical and dosimetric parameters. We reviewed acute toxicity data from 42 patients receiving cetuximab-RT and a matched cohort of 36 patients receiving chemoRT or AFRT. The occurrence of grade ≥3 oral toxicities was analysed with respect to clinical (age, gender, smoking/alcohol history, tumour subsite, grade of acneiform rash) and dosimetric parameters. Cetuximab-RT patients experienced higher rates of grade ≥3 cheilitis (26% vs 6%, p=0.01) and anterior stomatitis (38% vs 6%, p=0.002), despite these structures receiving low RT doses (median maximum dose to lips 9.3 Gy, anterior oral cavity 20 Gy). Multivariable analyses identified increasing severity of acneiform rash as the strongest predictor of grade ≥3 cheilitis whilst increasing RT dose was weakly correlated. A trend was observed for increasing pack years of smoking on univariate analysis only. The combination of cetuximab and low doses of RT to the anterior oral cavity has resulted in a distinctive pattern of cheilitis and anterior stomatitis in our patients. Further exploration of this phenomenon may yield additional insights into the interaction of cetuximab with RT in non-target tissues.

Hypofractionated whole-breast radiotherapy: impact on departmental waiting times and cost.

Conventionally fractionated breast radiation therapy is delivered over 5-6 weeks. Randomised evidence has shown that hypofractionated whole-breast radiotherapy (HWBRT) over 3 weeks results in similar local control without increased toxicity. HWBRT is not standard practice in Australia for all eligible women. We examined the effect of using HWBRT (for eligible patients) on waiting lists and monetary costs. We identified factors associated with prescribing HWBRT. The Princess Alexandra Hospital Radiation Oncology Database was searched for all women with breast cancer treated with adjuvant radiotherapy in 2008. Included patients had undergone breast conserving surgery and had T1-2N0 tumours with negative margins. Women with large breasts and those receiving nodal irradiation were excluded. The outcome evaluated was fractionation schedule. Patient, tumour and treatment factors associated with the use of HWBRT were examined. The impact on departmental resources and health-care costs were calculated assuming the entire cohort received HWBRT. Two hundred seventy-nine patients met the inclusion criteria. Sixty-seven (24%) of these patients were treated with HWBRT. Compared with the conventionally fractionated breast radiation therapy group, the HWBRT group were older (median 69 vs. 54 years; P < 0.001) and more likely to have smaller tumours (12 mm vs. 15 mm; P = 0.02). Had all eligible patients received HWBRT an extra 14 patients each month could be treated and health-care costs would be reduced by 24%. HWBRT was more frequently prescribed in older women with small tumours. More widespread use of HWBRT would allow significantly more patients to be treated each month with considerable cost savings.

Lung cancer patients in Queensland suffer delays in receiving radiation therapy--but not as a result of distance.

AIM: To determine whether lung cancer radiation therapy waiting times in Queensland public hospitals are associated with distance of residence from the nearest treatment facility. METHODS: Retrospective analysis of radiation therapy waiting times of 1535 Queensland residents who were diagnosed with lung cancer from 2000 to 2004 and received radiation therapy as initial treatment at a public hospital. The effect of distance of residence from treatment centre on median waiting time was analysed by quantile regression controlling for sex, age, lung cancer histology, stage and therapeutic intent. RESULTS: The median waiting time from diagnosis to start of radiation therapy was 33 days for all patients. There was no significant difference (P = 0.141) in median waiting times in relation to distance of residence from a treatment centre. However, in most patients, waiting times were significantly longer than recommended by the Royal Australian and New Zealand College of Radiologists. Curative patients waited longer than palliative patients, while patients with earlier stage cancer waited longer than those with more advanced disease. CONCLUSION: Waiting times for radiation therapy among lung cancer patients in Queensland was not associated with distance from place of residence to the nearest public treatment facility. However, delays overall are excessive and are likely to worsen unless radiation treatment capabilities are enhanced to keep pace with population growth in Queensland.

In vitro investigations of bone remodeling on a transparent hydroxyapatite ceramic.

The light microscopic examination of cells directly on bioceramic materials in the transmission mode is impossible because many of these materials are opaque. In order to enable direct viewing of living cells and to perform time-lapse studies, nearly transparent bioceramic materials were developed. A dense and fine-grained transparent hydroxyapatite (tHA) was processed by a gel-casting route followed by low-temperature sintering (1000 degrees C). By virtue of its transparency, direct visualization of cellular events on this material is possible in transmitted light. In this study, the interaction of different bone cell types with the tHA ceramic was envisaged. Investigation of rat calvaria osteoblasts (RCO) cultured on tHA by means of transmission light microscopy indicated good cytocompatibility of tHA. Microscopic analysis of osteogenic-induced human bone marrow stromal cells (hBMSC) on tHA and quantitative analysis of their lactate dehydrogenase (LDH) activity at different time points of culture revealed favorable proliferation as well. An increase of the alkaline phosphatase (ALP) activity indicated the differentiation of osteogenic-induced hBMSC towards the osteoblastic lineage. In addition, the differentiation of human monocytes to osteoclast-like cells could also be demonstrated on tHA and was confirmed by fluorescent microscopy imaging of multinucleated cells on the transparent material.

Positron emission tomography and pathological evidence of response to neoadjuvant therapy in adenocarcinoma of the esophagus.

Our aim was to determine if fluorodeoxyglucose positron emission tomography (FDG-PET) could be correlated with a pathological response in patients with esophageal adenocarcinoma receiving neoadjuvant chemotherapy and/or chemoradiation therapy. Patients with resectable, histologically proven adenocarcinoma of the esophagus were entered in the study. Preoperative chemotherapy comprised two cycles of cisplatin and 5-fluorouracil. Radiation therapy commenced with the second cycle on day 22. FDG-PET images were obtained pre-treatment and on completion of intended neo-adjuvant treatment. Quantification was achieved by the calculation of both standardized uptake values (SUV) and tumor/liver ratios (TLR). Evidence of histopathological response was identified according to the Mandard tumor regression scoring system. There were 45 patients, 22 receiving neoadjuvant chemotherapy and 23 chemoradiation therapy. Forty patients underwent surgical resection. Seven patients (16%) had a histopathological response. The mean percentage change in SUV in the histological responders group was -56.8% (SD 29) and in the non-responders -27.8% (SD 32.1) (P = 0.035). The mean percentage change in TLR was -49.1% (SD 44.8) in the responders and in the non-responders -27.3% (SD 31.3) (P = 0.128). There was no difference between the two methods of assessment, however there was less variation with SUV. There was no correlation between the FDG-PET response and the histopathological response. Presently an FDG-PET scan performed 3-6 weeks after neoadjuvant therapy for adenocarcinoma of the esophagus should not be used as a marker of the potential result of the treatment. The optimal timing of a second FDG-PET remains unclear.

Salvage definitive chemo-radiotherapy for locally recurrent oesophageal carcinoma after primary surgery: retrospective review.

To determine the overall survival and gastrointestinal toxicity for patients treated with salvage definitive chemo-radiotherapy after primary surgery for locoregional relapse of oesophageal carcinoma. A retrospective review of 525 patients who had a resection for oesophageal or oesophagogastric carcinoma at Princess Alexandra Hospital identified 14 patients treated with salvage definitive radiotherapy or chemo-radiotherapy, following localized recurrence of their disease. We analysed the patient and treatment characteristics to determine the median overall survival as the primary end point. Gastrointestinal toxicity was examined to determine if increased toxicity occurred when the stomach was irradiated within the intrathoracic radiotherapy field. The median overall survival for patients treated with curative intent using salvage definitive chemo-radiotherapy was 16 months and the 2-year overall survival is 21%. One patient is in clinical remission more than 5 years after therapy. Age <60 years old and nodal recurrence were favourable prognostic factors. Treatment compliance was 93% with only one patient unable to complete the intended schedule. Fourteen per cent of patients experienced grade 3 or 4 gastrointestinal toxicity. Salvage definitive chemo-radiotherapy should be considered for good performance status patients with oesophageal carcinoma who have a locoregional relapse after primary surgery. The schedule is tolerable with low toxicity and an acceptable median survival.

Outcomes from salvage esophagectomy post definitive chemoradiotherapy compared with resection following preoperative neoadjuvant chemoradiotherapy.

Chemoradiotherapy (CRT) as a definitive treatment for esophageal cancer, is being used with increasing frequency and as a result, surgeons will be required to assess more patients who have residual or recurrent local malignancy. This article aimed to assess outcomes after esophagectomy following definitive CRT (dCRT) and compare any difference between them and patients who had preoperative neoadjuvant CRT (nCRT) using a similar regimen of chemotherapy. From a prospective database the details of patients who had a resection following nCRT and dCRT were analyzed. The main therapeutic difference between the groups was the dose of radiotherapy (35 vs 60 Gy) and the timing of the resection following completion of the CRT (median 4 vs 28 weeks). Fourteen patients had an esophagectomy following a dCRT and 53 had one following a nCRT. Preoperatively, the dCRT group had worse respiratory function and more ECG abnormalities. Preoperative tumor length, pathological TNM staging and R0 resection rates were the same in both groups. Post resection, the dCRT group had greater morbidity than the nCRT group, spending longer in the intensive care unit (median 48 vs 24 h), more days in hospital (median 31 vs 13) and having more severe respiratory complications (37%vs 6%). The operative mortality was higher in the dCRT group (7%vs 0%). The three-year survival was 24% after dCRT. Patients selected for salvage esophagectomy following dCRT are a major challenge in postoperative care. However, some patients survive for a reasonable period of time, making resection a worthwhile option.

Radiotherapy for metastatic melanoma presenting in pregnancy.

We describe the study of a patient with metastatic melanoma to axillary nodes presenting during pregnancy. The factors considered in her management are discussed, including issues related to staging, the decision not to terminate the pregnancy and the relative efficacy and fetal toxicity of the available treatment options. An overview of the known effects of radiotherapy on the fetus is presented and the technical alterations that were used to decrease the toxicity of radiotherapy are discussed.

A phase I study of moderate-dose radiation therapy and weekly gemcitabine in patients with locally advanced non-small cell lung cancer not suitable for radical chemoradiation therapy.

AIMS: To describe the toxicity and response seen in patients receiving moderate-dose radiation therapy with concurrent weekly low-dose gemcitabine in the management of locally advanced non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Eighteen patients with confirmed NSCLC were enrolled over a 17-month period from August 2000 until January 2002. All had localised disease but were considered unsuitable for curative therapy. Radiation therapy was given to a dose of 30 Gy in 15 fractions over 3 weeks. Gemcitabine was given weekly before and within 3 h of fractions 1, 6 and 11. The study was designed as a dose-escalation study, commencing at 100 mg/m2 and increasing at levels of 50 mg/m2, until the maximum tolerated dose (MTD) was reached. RESULTS: The MTD was regarded as being 150 mg/m2. The major acute toxicity observed was oesophagitis. Skin reactions were also reported. The overall response rate in all patients was 88%, with 44% achieving a complete response. CONCLUSION: The combination of gemcitabine and moderate-dose radiation therapy is feasible, and offers low toxicity and excellent response rates in patients with localised NSCLC not suitable for high-dose therapy.

Chemoradiation therapy is effective for the palliative treatment of malignant dysphagia.

Between 1993 and 2001, 106 patients with esophageal cancer were reviewed at a multidisciplinary clinic and treated with palliative intent by chemoradiation therapy. This study assesses the palliative benefit on dysphagia and documents the toxicity of this treatment. The study population comprised 72 men and 34 women with a median age of 69 years. Patients were treated with a median radiation dose of 35 Gy in 15 fractions with a concurrent single course of 5 FU-based chemotherapy. Dysphagia was measured at the beginning and completion of treatment and at monthly intervals until death, using a modified DeMeester (4-point) score. Treatment was well tolerated, with only 5% of patients failing to complete therapy. The treatment-related mortality was 6%. The median survival for the study population was 7 months. The median baseline score at presentation was 2 (difficulty with soft food). Following treatment, 49% of patients were assessed as having a dysphagia score of 0 (no dysphagia). Seventy-eight per cent had an improvement of at least one grade in their dysphagia score after treatment. Only 14% of patients showed no improvement with treatment. Fifty-one per cent maintained improved swallowing until the time of last follow-up or death. This single-institution study shows that chemoradiation therapy administered for the palliation of malignant dysphagia is well tolerated and produces a sustainable normalization in swallowing for almost half of all patients.

Effects of asbestos on initiation of DNA damage, induction of DNA-strand breaks, P53-expression and apoptosis in primary, SV40-transformed and malignant human mesothelial cells.

Human mesothelial cells (HMC), the progenitor cells of asbestos-induced mesothelioma, are particularly sensitive to the genotoxic effects of asbestos, although the molecular mechanisms by which asbestos induces injury in HMC are not well known. The high susceptibility of HMC to simian virus 40 (SV40)-mediated transformation is assumed to play a causative role in the pathogenesis of mesothelioma. The aim of this study was to investigate the asbestos-induced DNA damage in cultured HMC and SV40-transformed HMC (MeT-5A) compared with their malignant counterparts, i.e. human mesothelioma cells (MSTO). The time-dependent initiation of DNA-strand breaks as well as the induction of oxidative DNA base modifications were key factors for investigation. HMC, MeT-5A and MSTO cells were exposed to chrysotile and crocidolite asbestos (3 microg/cm2) during different time periods (1-72 h). DNA damage was investigated by use of the Comet assay and alkaline unwinding, the latter in combination with the Fpg protein. The P53 level was analyzed by immunofluorescence, and measurement of apoptosis was conducted by flow cytometry. We found a significant induction of DNA damage in asbestos-treated HMC already after an exposure time of 1.5 h. This effect could not be observed in treated MeT-5A and MSTO cells. Also, a time-dependent significant increase in DNA-strand breaks was observed by alkaline unwinding in asbestos-treated HMC, but not in treated MeT-5A and MSTO cells. In none of the three cell lines we could detect oxidative DNA damage recognized by the Fpg protein (e.g. 8-oxo-guanine), up to 24 h after exposure to asbestos. In contrast to what was found in HMC, P53 was over-expressed in untreated MeT-5A and MSTO. The induction of apoptosis by asbestos fibers was suppressed in MeT-5A and MSTO cells. Crocidolite fibers induced the higher genotoxic effects and chrysotile the more pronounced apoptotic effects. We conclude that asbestos induces DNA damage in HMC already after a very short exposure time in the absence of 8-oxo-guanine formation. The presence of SV40-Tag in MeT-5A and MSTO cells results in an increased expression of P53, but not in additive genotoxic effects after exposure to asbestos. The deregulation of the apoptotic pathway may lead to proliferation of genomically damaged cells and finally to the development of mesothelioma.