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Biomedical subjects

S H Levitt

Publications and source records attributed to S H Levitt.

At least 145 records · Page 8Linked to original sources
PubMed1980

Radiation therapy for advanced head and neck squamous-cell carcinoma using twice-a-day fractionation.

Fifteen patients with massive advanced squamous-cell carcioma of the head and neck received radiation therapy under the twice-a-day fractionation regimen. The purpose was to increase the therapeutic ratio by minimizing sublethal radiation damage to normal tissue while allowing reoxygenation of radioresistant hypoxic tumor cells. Results demonstrated better local control than can be achieved through once-a-day fractionation, with 53% of the patients showing no evidence of primary tumor at the end of therapy, and 60% showing complete regression of cervical lymphadenopathy.

Carcinoma, Squamous Cell↗
PubMed1980

The effect of hyperthermia on vascular function, pH, and cell survival.

Blood flow in rat skin and muscle increased three- to fourfold during heating at 43 degrees C for one hour, while that in Walker tumors did not change significantly; however, blood flow in the tumors decreased a few hours after heating at 45 degrees C. The temperature of Walker tumors was significantly higher than in the muscle during heating, probably due to inefficient heat dissipation caused by the sluggish blood flow. Severe vascular occlusion occurred in SCK tumors in mice after heating at 41.5-45.0 degrees C. Upon heating, the pH in the tumors significantly decreased, while that in the muscle increased. The clonogenic cell number continuously decreased when SCK tumors were left in situ after hyperthermia. The vascular occlusion and increase in acidity may account for the progressive death of tumor cells after heating.

Animals↗
PubMed1980

Blood flow in normal tissues and tumors during hyperthermia.

The effect of hyperthermia on the blood flow was studied in skin, muscle, and Walker 256 carcinoma implanted in the legs of SD rats. The radioactive microsphere method was used to measure the blood flow. Hyperthermia for 1 hour with water at 43 degrees C increased the blood flow in skin and muscle by about threefold to fourfold. On the contrary, hyperthermia had no appreciable effect on the blood flow in tumors. Consequently, during hyperthermia blood flow in the skin and muscle surrounding the tumors was greater than that in tumors larger than about 2 g. Despite the apparent increase in heat dissipation by the increased blood flow, the temperature of the skin was 42.6-42.8 degrees C, and the temperature at the core of tumors larger than 2 cm in diameter was 42.3-42.7 degrees C during the hyperthermia. The lower temperature in the muscle could be attributed to an increase in heat dissipation as a result of the increased blood flow. This differential rise in temperature by heating may account in part for the differential effect of hyperthermia on tumors and normal tissues in vivo.

Animals↗
PubMed1980

Total lymphoid irradiation and cyclophosphamide as preparation for bone marrow transplantation in severe aplastic anemia.

A new combination of total lymphoid irradiation and cyclophosphamide was used prior to bone marrow transplantation in an attempt to achieve decreased rejection rates and graft-versus-host disease. Nine previously transfused patients with severe aplastic anemia received marrow from an HLA-identical, MLC-compatible sibling following this preparative regimen. There were no episodes of graft rejection, and only one patient developed graft-versus-host disease. Of the 9 patients, 7 (78%) are surviving with a median follow-up of 400 days. The excellent results of this pretransplant combination of total lymphoid irradiation and cyclophosphamide warrants application of this regimen to a larger series of patients.

Adolescent↗
PubMed1980

Curative radiotherapy for localized diffuse histiocytic lymphoma.

Ten newly diagnosed patients, with localized diffuse histiocytic lymphoma classified according to the Lukes-Collins classification, were evaluated for response to treatment with extended-field radiation. All classified tumors were of follicular center cell type (four large cleaved, four large noncleaved, and one small noncleaved). There were nine patients with stage I disease and one with stage II disease. The patient with stage II disease had only two sites of involvement. The disease was nodal in six patients and extranodal in four. All patients are alive without evidence of disease recurrence from 19 to 102 months since diagnosis (median survival, 58 + months). No differences were found in response or survival rates between histologic categories. No significant immediate or long-term complications have occurred. These results suggest that radiotherapy alone is curative for localized diffuse histiocytic lymphoma and may be superior to recently advocated chemotherapeutic approaches.

Adult↗
PubMed1980

Role of vascular function in response of tumors in vivo to hyperthermia.

The response of SCK tumor cells in vivo and in vitro to heat was compared, and the relationship between the kinetics of cell death and vascular function in tumors in vivo after hyperthermia was studied. The number of clonogenic cells in tumors excised immediately after heating was significantly less than that in the in vitro culture treated with the same heat doses. This suggested that the tumor cells in vivo are far more sensitive to direct damage by heat than are the cells in vitro. When the tumors were left in situ after hyperthermia at 43.5 degrees for 30 min, there was a progressive decrease in cell survival until 6 to 12 hr after the heating. The study of intravascular volume using the 51Cr-labeled red blood cell method indicated that severe vascular occlusion occurs in the tumor after hyperthermia. It therefore appeared that delayed cell death in tumors in vivo after hyperthermia resulted from an insufficient supply of oxygen and nutrients and an increase in acidity due to the vascular occlusion. Both the direct damage to tumor cells and the indirect damage to tumor cells as a consequence of vascular occlusion may play important roles in the eradication of tumors by hyperthermia.

Animals↗
PubMed1979

The management of extratesticular seminoma without gonadal involvement.

Diagnosis, treatment and follow-up of 8 patients from 1955 to 1975 with extratesticular seminoma are presented. In 5 patients, the neoplasm developed in the mediastinum and in 3 in the retroperitoneum. All the patients were treated by radiation therapy after resection or biopsy. In the entire group, no tumor was diagnosed in the testes. Two patients expired with disease, one after 2 months due to pneumonia, and the other 5 years after diagnosis (10 months after treatment) due to cerebral metastases. Two patients died 12 and 16 years after diagnosis and treatment. At death, they were free of seminoma and the cause of death was a second malignancy. Four patients are alive and healthy, free of disease, 5, 10, 13, and 17 years after diagnosis and treatment. In essence, of the 8 patients, only one actually died of disease, and he was not adequately treated. We feel that this is an entity with an excellent prognosis if adequately and appropriately treated with radiation. We recommend not to perform an orchiectomy when the testes are clinically normal, and to follow the patient closely after treatment.

Adolescent↗
PubMed1979

Factors predisposing to radiation-related small-bowel damage.

From 1970 through 1977, 92 patients with ovarian cancer received 20 Gy (2,000 rad) to the abdomen, followed by 30 Gy (3,000 rad) to the pelvis. Small-bowel obstruction developed in 7 (7.6%). The number of previous laparotomies, thin physique, and hypertension were significantly associated with complications. Two patients receiving isoniazid and 2 receiving Premarin had enteric complications. Pre-existing vascular damage may potentiate radiation damage to the small bowel.

Abdomen↗
PubMed1978

Second neoplasms following megavoltage radiation in a pediatric population.

Previous reports of radiation-related neoplasia have relied primarily upon patients treated by orthovoltage to low doses for benign disease. This survey is believed to be the first to assess the incidence of second neoplasms following megavoltage therapy. The source was the records of all long-term pediatric survivors (88 patients) who were treated with megavoltage radiation (cobalt 60) at the University of Minnesota. There was an average follow-up period of 14 years during which 7 second neoplasms were discovered (8%). Five were not associated with prior radiation. Both radiation-related neoplasms were associated with low doses and one was without significant morbidity. Two of the seven neoplasms were malignant; one was not associated with radiation while the other was associated with prolonged chemotherapy and low dose radiation (1%). The only fatal second neoplasm was not associated with radiation but developed 5 years after prolonged chlorambucil treatment. This review reveals the tendency of childhood cancer victims to develop other neoplasms regardless of radiation. The finding of neoplasia induction only at low radiation doses supports the Gray hypothesis of decreased tumor induction at high doses through increased cell killing.

Adolescent↗