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Biomedical subjects

A Gregor

Publications and source records attributed to A Gregor.

At least 109 records · Page 6Linked to original sources
PubMed1987

The effect on human neuroblastoma spheroids of fractionated radiation regimes calculated to be equivalent for damage to late responding normal tissues.

Multicellular tumour spheroids (MTS) are a useful in vitro model of human cancer. An experiment was designed to assess the likely therapeutic advantage of hyperfractionation--a proposed strategy in radiotherapy. A cell line (NB1-G) derived from human neuroblastoma was grown as MTS. This MTS line is radiosensitive with low capacity for repair of sublethal radiation damage. These properties make NB1-G a suitable line to test the theoretical advantage of hyperfractionation. MTS were irradiated using alternative fractionated regimens, with fraction sizes varying from 0.5 to 4 Gy. In each experiment, the total dose was chosen to make the regimens theoretically isoeffective for damage to late-responding normal tissues (calculated using the linear-quadratic mathematical model with alpha/beta = 3 Gy). The radiation responses of MTS were evaluated using the end-points of regrowth delay and "proportion cured". Regimens using smaller doses per fraction were found to be markedly more effective in causing damage to neuroblastoma MTS, as assessed by either end-point. These experimental findings support the proposal that hyperfractionation should be a therapeutically advantageous strategy in the treatment of tumours whose radiobiological properties are similar to those of the MTS neuroblastoma line NB1-G.

Cell Line↗
PubMed1987

The implications of in-vitro radiation-survival curves for the optimal scheduling of total-body irradiation with bone marrow rescue in the treatment of leukaemia.

A mathematical model for optimal scheduling of total-body irradiation (TBI) in the treatment of leukaemia is described. A survey of the radiosensitivities of human leukaemic cells indicate that they are highly radiosensitive with little fraction size dependence (median D0 = 0.74 Gy; median Dq = 0.14 Gy). These properties, when considered alongside the high repair capacity of lung, suggest that TBI schedules of the "accelerated hyperfractionation" type are optimal. The antileukaemic effects of alternative schedules, chosen to be isoeffective for lung damage to a reference schedule of 6 X 2 Gy in 3 days, were compared. A modestly hyperfractionated schedule of 10 fractions of 1.3-1.5 Gy in 5 days has theoretical advantages while retaining practicality of clinical administration.

Bone Marrow Transplantation↗
PubMed1986

Radiation studies on multicellular tumour spheroids derived from human neuroblastoma: absence of sparing effect of dose fractionation.

In vitro experiments were carried out to compare the effects of single-dose and split-dose irradiation on a cell line (NB1-G) derived from human neuroblastoma and grown as multicellular tumour spheroids (MTS). The radiation response was evaluated in terms of regrowth delay; estimates of in situ cell survival were made by back-extrapolation of regrowth curves. These studies showed no significant difference in the effectiveness of single as compared to split dose irradiation i.e. no sparing effect of fractionation. If MTS constitute a realistic model for micrometastases in vivo, these results provide a radiobiological rationale for hyperfractionated treatment regimes in the adjuvant radiotherapy of neuroblastoma.

Cell Line↗
PubMed1986

Radiobiological considerations in the treatment of neuroblastoma by total body irradiation.

Neuroblastoma is a radiosensitive neoplasm for which total body irradiation (TBI) is presently under clinical consideration. Collated data on the radiobiology of human neuroblastoma cells in vitro (11 cell lines derived from seven patients) indicates moderate cellular radiosensitivity and low capacity for accumulation of sublethal damage (median survival curve parameters: Do = 104 cGy, Dq = 32 cGy, n = 1.36). Mathematical studies incorporating these parameters suggest that low dose fractionated TBI is unlikely to achieve significant levels of tumour cell kill. When high dose TBI is used in conjunction with bone marrow rescue a tumour "log cell kill" of 4-5 should be achievable. This effect would be additional to that achieved by chemotherapy. The optimum schedule for exploitation of radiobiological differences between neuroblastoma cells and the dose-limiting normal tissues has a hyperfractionated structure. Twice-daily treatments with fraction sizes in the region 120-150 cGy seems appropriate. Single dose treatments at high dose rate are contraindicated. Fractionated TBI with bone marrow rescue may be curative for some patients in clinical remission who are presently destined to relapse.

Cell Survival↗
PubMed1986

Short duration combination chemotherapy in the treatment of small cell lung cancer.

Ninety five patients (57 with limited disease and 38 with extensive disease) with previously untreated small cell lung cancer were entered into a study of short duration combination chemotherapy with intravenous cyclophosphamide (750 mg/m2) on day 1, adriamycin (40 mg/m2) on day 1, and etoposide VP-16 (100 mg/m2) on days 1, 2, and 3, with the addition on day 10 of methotrexate 50 mg/m2 with folinic acid rescue and vincristine 2 mg. The treatment was repeated on day 22 and only three courses were given. No maintenance chemotherapy was given, though patients with a complete response received radiotherapy (30-40 Gy (3000-4000 rads] to the primary site in most cases. Forty nine patients (86%) with limited disease achieved a response, with 26 (46%) complete remissions. Twenty five patients (66%) with extensive disease had a response, but only eight (21%) had a complete response. Actuarial survival analysis for the whole patient population showed a median survival of 13 months for patients with limited disease and seven months for those with extensive disease. The median survival was 14 months for those patients with limited disease who achieved a complete response, but only 10 months for non-responders. Myelosuppression was the major expression of toxicity. There were three deaths related to treatment and seven patients had febrile episodes during neutropenia that required antibiotics. Mucositis, which was usually mild, occurred in 49% of patients. The primary site was the main site of initial relapse in 56% of the patients who relapsed. Among patients with limited disease who achieved a complete response, relapses at the primary site were less common in those who received radiotherapy (five out of 12) than in those who did not (all eight). The results indicate that this short duration chemotherapy in small cell lung cancer gives response rates and the potential for long term survival similar to those obtained in other series while allowing patients the maximum time free from treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

The impact of chemotherapy on small cell carcinoma of the bronchus.

Between 1971 and 1978, 140 cases of small cell anaplastic carcinoma of the bronchus were registered by a group of chest physicians in north Edinburgh. Sixty-five of these patients received specific treatment either with radiotherapy or cyclophosphamide and 75 patients were given treatment for symptoms only. Between 1979 and 1981 83 patients referred to the same physicians and pathologists were treated with combination chemotherapy (methotrexate, cyclophosphamide and CCNU) for 12 weeks. Overall median survival in the 1971 to 1978 group was two months with the actively-treated patients surviving for five months vs. less than one month for treatment of symptoms only. For the 83 patients treated with combination chemotherapy, median survival was nine months with 33 per cent alive at one year and 13 per cent at two years. Positive factors associated with prolonged survival included performance status at presentation and response to chemotherapy. This study demonstrates that the prognosis for the majority of patients with small cell carcinoma of the bronchus has improved significantly with the introduction of combination chemotherapy.

Adult↗
PubMed1986

Increased activity of porphobilinogen deaminase in erythrocytes during attacks of acute intermittent porphyria.

The activity of porphobilinogen deaminase was determined in 25 patients with acute intermittent porphyria during and after fully developed attacks of porphyria. It was found that in most cases (in 20 of 25) it was higher than 24.3 nmoles/ml erythrocytes/hour, a value considered as characteristic for acute intermittent porphyria, and that it decreased during convalescence and remission. In a proportion of these cases the decrease in the activity of the enzyme was parallelled by decreasing urinary excretion of porphobilinogen. A normal activity of porphobilinogen deaminase during an attack of porphyria can be a source of error in the differential diagnosis of porphyria.

Acute Disease↗
PubMed1985

cis-Platinum and vindesine in combination in the treatment of non-small cell lung cancer.

Sixty-three patients with advanced non-small cell carcinoma of the bronchus were treated with a combination of cis-platinum and vindesine. All patients had measurable disease and were of good performance status; none had received prior chemotherapy or radiotherapy. Thirty-three per cent of patients responded, with five patients achieving complete remission. Median duration of response was 4 months, with a median survival of 14 months in the responsers, compared with 6.5 months in the whole group and 4.8 months in the nonresponders. Severe toxicity was encountered, with alopecia, gastrointestinal toxicity and neurotoxicity common. Myelosuppression and renal toxicity were not dose-limiting. Thus the activity of this drug combination is confirmed, but severe toxicity precludes its widespread use in clinical practice.

Adenocarcinoma↗
PubMed1985

The radiosensitivity of human neuroblastoma cells estimated from regrowth curves of multicellular tumour spheroids.

Multicellular tumour spheroids may provide a suitable in-vitro model for micrometastases in vivo. In this paper, the results are reported of experimental studies on the radiation response of two lines of spheroids derived from human neuroblastoma. Spheroids of approximately 200-250 microM mean diameter were exposed to graded doses of X rays (50-350 cGy) and, following a static or regression phase, regrew at rates which approximated those of unirradiated spheroids. Clonogenic surviving fraction was estimated, at each dose level, by extrapolation of the regrowth curve to zero dose. It is proposed that this procedure is more suitable for regrowth curves of spheroids than in-vivo tumours, because of the absence in vitro of complicating factors which occur only in vivo. By this means, survival curves were deduced and were found (for both cell lines) to be almost exponential in form, with little indication of capacity for accumulation of sublethal damage (multitarget parameters: DQ values: 17 and 25 cGy; Do values: 104 and 81 cGy respectively). These results contribute to the evidence for high radiosensitivity of neuroblastoma cells in vitro and provide a rationale for the use of hyperfractionation in the clinical treatment of neuroblastoma by radiotherapy.

Cell Division↗
PubMed1984

Phase II trial of vindesine and VP16-213 in the palliation of poor-prognosis patients and elderly patients with small cell lung cancer.

Forty-three previously untreated patients, all of whom had poor-prognosis small cell lung cancer and/or were greater than 65 years old, received treatment with vindesine and VP16-213. Thirteen patients had limited disease and 30 extensive disease. Response rates (CR + PR) of 86% (CR 29%) and 66% (CR 17%) were seen in patients with limited and extensive disease, respectively. Time to relapse was short in those responding (4-4.5 months), and most responders required additional treatments. The overall toxicity was minimal and patient compliance was high. This combination is useful for the palliative treatment of small cell lung cancer when aggressive chemotherapy is inappropriate.

Adult↗
PubMed1984

Malignant mesothelioma of the pleura: a study of 52 treated and 64 untreated patients.

We have carried out sequential prospective studies of treatment with surgery alone, chemotherapy, and radiotherapy in malignant mesothelioma of the pleura. The survival of treated patients was contrasted with that of 64 contemporary untreated patients whose clinical condition at presentation was comparable with that of the treated patients. Non-radical surgery alone (28 patients) was of palliative benefit, particularly for the control of recurrent pleural effusions, and may have prolonged survival in one patient with localised malignant mesothelioma. Chemotherapy with doxorubicin, vincristine, and cyclophosphamide (12 patients, with preceding surgery in eight) was without objective benefit. Megavoltage radiotherapy by an off axis beam rotational technique (12 patients, with preceding surgery in eight) abolished pain and dyspnoea and may have prolonged survival in one patient and terminated recurrent pleural effusions in three, but it was of no value in the other patients. There was no significant difference in survival between treatment groups or between treated and untreated patients, and no difference when mesotheliomas of epithelial, sarcomatous, and mixed cell types were examined separately. Treatment of this disease appeared to fail because of the unresponsiveness of the tumour to existing forms of treatment and the advanced stage of the disease at clinical presentation.

Adult↗
PubMed1984

The function and morphology of the liver in porphyria cutanea tarda.

The aminopyrine breath test, postprandial serum bile acids, and routine liver tests were assessed as indicators of liver dysfunction in 38 patients with porphyria cutanea tarda. In 17 patients needle biopsy specimens of the liver were obtained. Bile acids were increased in almost all the patients studied (97%) but impairment of aminopyrine demethylation was found in only 45%. More than 50% of cases had elevated activities of serum alanine aminopeptidase, leucine aminopeptidase, gammaglutamyl transpeptidase (GGTP), and alanine aminotransferase (ALAT). All liver biopsy specimens showed fluorescence characteristic of porphyrins. Histologic examination of biopsy material revealed cellular lesions in all cases, the most common pathological findings being fatty degeneration of varying degree and iron accumulation. The most frequent electronmicroscopic changes in the liver were fat droplets, granules containing bile material, and siderosomes in the cytoplasm of hepatocytes. However, there was no evident relationship between morphological and functional liver changes.

Adult↗