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Biomedical subjects

S H Levitt

Publications and source records attributed to S H Levitt.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of Fluosol DA 20% and carbogen on the radioresponse of SCK tumors and skin of A/J mice.

The effect of Fluosol DA 20%, an emulsion of perfluorochemicals, in combination with carbogen (95% O2 and 5% CO2) breathing on the response of mouse tumors to radiation was studied. When A/J mice bearing SCK tumors in the right hind limb were injected iv with Fluosol DA 20% at 12 ml/kg and exposed to carbogen for 1 h before and during the irradiation of tumors, the response of tumors to a single dose of X irradiation was significantly enhanced. The dose modification factors for growth delay and cure of SCK tumors were 2.10 +/- 0.01 (SE) and 1.86 +/- 0.18 (SE), respectively. Such a treatment slightly increased the radiation-induced skin damage by a factor of 1.17 +/- 0.02 (SE), resulting in a therapeutic gain of 1.79 +/- 0.01 (SE) for the growth delay and 1.59 +/- 0.09 (SE) for the curability. Carbogen breathing alone also increased the response of tumor and skin to radiation, but it was far less effective than the combination of Fluosol DA 20% and carbogen breathing. It was concluded that iv injection of Fluosol DA 20% in conjunction with carbogen breathing significantly increased the O2 transport to hypoxic areas in the SCK tumors and thus significantly enhanced the tumoricidal effect of radiation on SCK tumors.

Administration, Inhalation↗
PubMed1986

The effect of definitive irradiation on local control and disease free survival in breast cancer.

The prognostic factors important in determining local regional control or failures can be divided into two groups. The first, the intrinsic factors, relate to the initial inherent condition of the tumor, that is, the tumor labeling index, progesterone receptors, the degree of involvement of the lymph nodes in he area, the size of the tumor, etc. The second, extrinsic factors, relate to type and adequacy of treatment. The presentation demonstrates that the most critical factors in determining failure and patterns of failure are the intrinsic factors, that is, histologic grade tumor labeling index, number of nodes involved, progesterone receptors and size, and that the adequacy of treatment affects failure and patterns of failure in patients treated. This paper shows that adequate radiation reduces local recurrence and, consequently, increases the survival rate; it also demonstrates that inadequate radiation will lead to increased local recurrence and decreased survival. The factors involved in determining the adequacy of irradiation are discussed.

Breast Neoplasms↗
PubMed1986

Capacitive heating of phantom and human tumors with an 8 MHz radiofrequency applicator (Thermotron RF-8).

The thermal profile was investigated in agar phantoms and in human tumors heated capacitively with 8 MHz RF. Deep and homogeneous heating could be achieved in a large homogeneous phantom of 25 cm diameter and 24 cm thick when heated with a pair of 25 cm diameter electrodes, coupled to both bases of the phantom. When the size of the two electrodes was not the same, the region near the smaller electrode was preferentially heated. It was, therefore, possible to control the depth of heating by choosing properly sized electrodes. Therapeutic temperature (greater than 42 degrees C) could be obtained in 7 out of 9 small, as well as, bulky superficial human tumors as large as 8 X 8 X 10 cm. Indications are that heating of some deep-seated human tumors might be achieved by the capacitive method, provided that subcutaneous fat layer is cooled by temperature controlled bolus and large electrodes are used. The effect of the anatomical structure on the power deposition in the human body during capacitive heating should be further investigated.

Adenocarcinoma↗
PubMed1986

Effect of cis-platinum on tolerance to radiation therapy in advanced cervical cancer.

Women with advanced carcinoma of the uterine cervix are at high risk for the development of local, regional, and distant metastases. Thus, both effective systemic agents and radiosensitizers could be useful adjuvants. However, because a substantial fraction of women with advanced cervical neoplasms are cured with radiation therapy, such experimental agents must not compromise the administration of conventional therapy. Cis-platinum is particularly appealing as it has both radiosensitizing properties and activity in metastatic cervical cancer. The present study examined the effect of weekly cis-platinum on radiation tolerance in 29 women with advanced cervical cancers. Although toxicity was acceptable, no marked enhancement in survival could be demonstrated.

Adult↗
PubMed1985

Primary treatment of early breast cancer with conservation surgery and radiation therapy. The effect of adjuvant chemotherapy.

The combination of radiation therapy (RT) and conservation surgery is appropriate treatment for Stage I and II breast cancer patients, and is equivalent to radical mastectomy in overall survival and recurrence free survival. Moreover, RT and conservation surgery has the advantage over radical surgery of breast preservation (and subsequent psychological advantage). Inherent in the preservation of the breast is the concept of cosmesis. This implies that the treated breast is not retracted or deformed by the surgery and radiation. Current studies indicate that there is an increase in complications and less satisfactory cosmetic effect on patients receiving chemotherapy in conjunction with conservation surgery and RT, but no effect on survival. This raises the question of which patients should receive chemotherapy and what type of chemotherapy should be used. It also raises the question of the initiation timing and dosage of chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Change in fibrinogen turnover in tumors by hyperthermia.

The effect of hyperthermia on the turnover of fibrinogen and albumin in the SCK tumor of A/J mice was studied. Immediately after heating at 43.5 degrees C for 30 min, the content of 131I-labeled fibrinogen in the tumors was about 2.7-fold that in the control tumor and remained elevated for 24 hr. On the other hand, the content of 125I-labeled serum albumin in the tumor immediately after heating was only 1.7-fold that in the control tumor and started to decrease soon after heating. The greater increase in the accumulation and the longer retention of the labeled fibrinogen as compared with the labeled albumin in the heated tumors appeared to be related to the heat-induced vascular damage accompanied by vascular occlusion, fibrination and subsequent thrombus formation.

Animals↗
PubMed1985

Increased radiosensitivity of tumors by perfluorochemicals and carbogen.

The efficacy of an emulsion of perfluorochemicals (Fluosol-DA) to sensitize RIF-1 tumors of C3H mice to radiation was studied. An i.v. injection of 12 ml/kg of Fluosol-DA (20%) to tumor-bearing animals and keeping the animals in an atmosphere of a mixture of O2 (95%) and CO2 (5%) (carbogen) for 1 hr before and during irradiation of s.c. tumors in the thigh significantly enhanced the tumoricidal effect of radiation as measured with growth delay of the treated tumors. A lesser but significant enhancement of radiation damage in the tumors was also observed when the animals were kept in carbogen for 1 hr without injection of Fluosol-DA. It was concluded that Fluosol-DA increased the delivery of oxygen to hypoxic areas in the tumors and enhanced the response of hypoxic cells to radiation.

Animals↗
PubMed1985

Thyroxine administration during radiation therapy to the neck does not prevent subsequent thyroid dysfunction.

In an attempt to reduce the incidence of hypothyroidism following irradiation of the neck, we administered oral L-thyroxine in doses sufficient to suppress serum TSH to 20 patients receiving radiation therapy for Hodgkin's disease or other lymphomas. L-thyroxine was discontinued when radiation therapy was completed. Twenty similar patients who did not receive L-thyroxine during radiation therapy served as a control group. After a mean follow-up period of 33 months, seven patients (35%) in the L-thyroxine group developed elevation of serum TSH and were started on chronic L-thyroxine therapy. In the control group, after mean follow-up of 19 months, five patients (25%) developed elevation of TSH and were started on chronic L-thyroxine. We conclude that suppression of serum TSH during neck irradiation does not prevent subsequent thyroid dysfunction.

Adolescent↗
PubMed1985

Radiation therapy for advanced head and neck squamous cell carcinoma using twice-a-day fractionation. A long-term follow-up.

Twenty-one patients with massive advanced squamous cell carcinoma of the head and neck received radiation therapy under the twice-a-day fractionation regimen. One hundred ten rad tumor dose was delivered twice daily with a 4-hour gap between the fractions, 5 days/week, to a total tumor dose of 7480 rad. The purpose was to increase the therapeutic ratio by minimizing sublethal radiation damage to normal tissue while allowing reoxygenation of radioresistant hypoxic tumor cells. Fifty-three percent of the patients showed no evidence of primary tumor at the end of the therapy and 60% showed complete regression of massive cervical lymphadenopathy. The 2-year recurrent-free rates for patients with tumors of the tonsillar region were 36% of T4 (4/11) and 33% (2/6) of N3a. The experience with conventional fractionation in similar cases was previously reported by others from this institution. They reported 2-year recurrent-free rates of 0% of T4 (0/10) and 17% (1/6) of N3. The higher recurrent-free rates in our series suggests better local and regional tumor control by the twice-a-day fractionation.

Carcinoma, Squamous Cell↗
PubMed1985

Effect of fractionation and rate of radiation dose on human leukemic cells, HL-60.

The capacity of HL-60 cells, human acute promyelocytic leukemic cells established in culture, to repair sublethal radiation damage was estimated from the response of the cells to fractionated irradiation or to a single irradiation at different dose rates. The HL-60 cells grown as a suspension culture in RPMI 1640 medium supplemented with 10% calf serum and antibiotics showed a cloning efficiency of about 0.46 in an agar culture bed. After exposure of cells to a single dose of X rays at a dose rate of 78 rad/min, the survival curve was characterized by n = 2.5, Dq = 80 rad, and D0 = 83.2 rad. Split-dose studies demonstrated that the cells were able to repair a substantial portion of sublethal radiation damage in 2 hr. The response of the cells to irradiation at different dose rates decreased with a decrease in the dose rates, which could be attributed to repair of sublethal radiation damage. The radiation response of leukemic cells is only one of the many factors which affect the clinical outcome of total-body irradiation (TBI) followed by bone marrow transplantation. Nevertheless, the possibility that some of the malignant hemopoietic cells, if not all, may possess a substantial capacity to repair sublethal radiation damage should not be underestimated in planning total-body irradiation followed by bone marrow transplantation.

Cell Line↗
PubMed1985

Paraaortic lymph node radiotherapy in cancer of the uterine corpus.

From 1973 through 1982, 48 women received 4500 to 5075 rads to the paraaortic lymph nodes as part of their primary management for cancer of the uterine corpus. One patient developed severe enteric morbidity. Five-year survival rates were 52% in the total group, 57% in clinically staged patients, and 47% in surgically staged patients. Patients with surgically confirmed pelvic lymphatic spread had a five-year survival rate of 67%. Patients with surgically confirmed paraaortic spread alone or pelvic and paraaortic spread had five-year survival rates of 47 and 43%, respectively. Eighty-eight percent of recurrences were outside of the radiation portals. In contradistinction to much of the last decade's literature, radiation therapy has salvaged a substantial fraction of patients with nodal metastases, and morbidity rates have been acceptable.

Adult↗
PubMed1984

The role of luminal contents in radiation enteritis.

A guinea pig model was used to evaluate luminal content as a factor in the development of acute radiation enteritis. Surgical bypass of one half of the small bowel created an isolated segment free of luminal contents. Radiation effects on this empty intestine were compared with effects on bowel in continuity, on intestine containing bile only, and on intestine containing pancreatic enzymes plus food. The animals were subjected to a single dose of 1600 rad via an abdominal port and killed 4 days later. Surviving crypts per circumference provided one index of the severity of the injury. Intestinal damage was further evaluated by histologic grading. Surviving crypts were significantly fewer for irradiated segments of bowel containing any of the components of the intestinal stream compared to either nonirradiated controls or irradiated but empty bowel. Histologic scoring revealed a gradation of injury, with progressively more severe damage in empty irradiated bowel, and in intestine containing only pancreatic secretion, bile, and all components of the luminal stream. We conclude that both bile and pancreatic secretions in the lumen enhance acute radiation-induced small-bowel injury.

Animals↗
PubMed1984

Benefits versus risks in conservation surgery with irradiation for breast cancer.

This report analyzes the survival and complications inherent in the conventional treatment of breast cancer, radical mastectomy, and the more conservative procedure, conservation surgery with irradiation. Both procedures have benefits and risks. The benefits as measured by survivorship appear to be approximately the same. The major benefit of conservation surgery with irradiation is that the breast is left intact. The possible complication of irradiation carcinogenesis is addressed, and the literature analyzed. This review indicates that the absolute risk of breast cancer developing in the second breast is not nearly as great as originally thought. It is concluded that if a woman with breast cancer is a candidate for either mastectomy or the conservative procedure, it is the clinician's obligation to objectively present the evidence regarding the benefits and risks of these procedures.

Breast Neoplasms↗