Biomedical subjects
Publications and source records attributed to K K Ang.
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A modified fractionation schedule was designed with the purpose of reducing the treatment burden. Three fractions of 2 Gy with four hours interval were given during 5 days. The whole scheme was repeated after a rest period of 4 weeks. This makes it possible to deliver a dose of 60 Gy in 10 treatment days and over a total time of 6 weeks. A total of 30 patients, 22 with prostatic cancer and 8 with invasive bladder carcinoma, have been treated. The feasibility has been found to be very good. Forty-seven percent of the patients had acute morbidity, although it was mild in all patients. One patient had a persistent, another had a transient delayed symptom, and one had a severe late complication. The tolerance to this schedule is better than that observed with conventional fractionation schedules. Together with the drastic reduction of the total treatment days, this multiple daily fractionation (MDF) schedule has already been shown to improve the therapeutic ratio by diminishing the burden on the patients. Longer follow-up necessary for the assessment of the efficacy of this schedule for local tumor control. However, with a follow-up period of 7 to 16 months no recurrence of the prostate cancer in the pelvis has been observed. These results warrant further exploration of the possible benefits of modifications in time-dose-fractionation schedules.
An inhalation anesthesia system has been employed to overcome several of the limitations associated with the use of sodium pentobarbital and other i.p. administered anesthetics in experimental radiotherapy. The described method is reliable and time-saving. The depth and duration of anesthesia are easily controllable. Only 4 deaths have occurred with more than 6000 animal exposures. The use of polystyrene jigs is shown to provide adequate thermal isolation. Oxygen as a carrier of the anesthetic agent is expected to prevent a reduced tissue oxygenation and its radiobiological consequences. The whole system is constructed as a mobile unit in which up to 16 mice or rats can be anesthetized simultaneously and irradiated in a single field with clinical treatment equipment during short time intervals between patient irradiations. The described advantages of this method make it specially suited for experiments with protracted fractionation schedules.
Three groups of C57/BL/Ka mice received total lymphoid irradiation (TLI) in a total dose of 34 Gy in three different fractionation schedules. In the first group daily fractions of 2 Gy were given during 3 1/2 weeks. In the second group 4 to 5 fractions with 3 1/2 hr interval were given each day, thus delivering 17 fractions in 4 days. In the third group three fractions were given daily for two consecutive days and was repeated two times after 8 or 9 days interval, resulting in a total treatment time of 3 1/2 weeks. The tolerance of all different schedules was excellent. No difference in the peripheral white blood cell and lymphocyte counts nor the degree of immunosuppression as measured by phytohaemaglutinin or concanavalin A induced blastogenesis and mixed lymphocyte reaction were observed at the end of the treatment and up to 200 days. When bone marrow transplantation was performed one day after the end of each schedule, chimerism without signs of graft versus host disease was induced in all the groups. However, from the results in a limited number of animals it seems that concentrated schedules were less effective for chimerism induction. It has been demonstrated that it is possible to reduce drastically the overall treatment time for TLI before bone marrow transplantation. Further investigations are necessary in order to determine the optimal time-dose-fractionation factors and the different parameters involved in the transplantation.
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Liver scintigraphy demonstrated areas of increased radiocolloid uptake in three cases with obstruction of the superior vena cava and extensive collateral circulation through the veins of the thoracic wall. The pattern of the hyperactive zones is indicative of predominant vascularization of the liver via the umbilical vein, with high colloid particle deposition in the quadrate lobe and adjacent part of the right lobe. These liver regions vascularized by the first intrahepatic branches of the umbilical vein as demonstrated by postmortem angiography, probably extract a great portion of the tracer dose, resulting in localized hyperactivity. An identical liver scan image was, however, found in a fourth case without evident superior vena cava syndrome. In this patient, presenting with a bronchus carcinoma with paratracheal metastatic lymph nodes, there is no explanation metastatic lymph nodes, there is no explanation (collateral circulation without vena cava obstruction?) for the abnormal tracer distribution within the liver.
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BACKGROUND: This retrospective study analyzes the outcome of treatment of a cohort of patients with hypopharyngeal tumors staged T1 or T2 treated with curative radiation alone to the primary tumor. The potential influence of advances in technology and radiobiology are studied. METHODS: Eighty-two patients with early-stage (T1, 19 patients; T2, 63 patients) hypopharyngeal squamous cell carcinomas treated between 1976 and 1992 at the University of Texas M.D. Anderson Cancer Center completed a course of definitive radiotherapy to their primary tumors. Forty-three patients (52%) were node positive, of which 23 (28%) had surgery to their involved necks in addition to radiation. Thirty-six patients (44%) had computerized tomography (CT) as part of the staging workup. Doses to the primary ranged from 60 to 79 Gy. Forty-four patients (54%) in this study were treated with twice-daily radiation (BID). Boosts to gross disease using off spinal cord fields were treated with Co60 gamma rays in 40 patients (49%); 34 (41%) with 6-25 MV x-rays (X), and 8(10%) with an ipsilateral electron beam field. RESULTS: The 2-year actuarial local control rates for patients with T1 and T2 disease were 89% and 77%, respectively. Subgroup analysis of T2 patients showed the following differences in actuarial local control rates at 2 years: BID, 86%; no BID, 60% (p, .004%); CT, 83%; no CT, 71% (p, .1); X boost, 88%; no X boost, 67% (p, .04). The actuarial 2- and 5-year survival rates for all patients were 72% and 52%, respectively. CONCLUSIONS: A majority of patients with early hypopharyngeal lesions are radiocurable. Patients treated with hyperfractionated radiotherapy and off spinal cord fields with 6 MV (or higher energy) x-ray beams had improved local control rates. CT scans assisted in appropriate patient selection for definitive treatment with radiation.
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Clinical investigations for cancer of the head and neck, primarily tumors of the upper respiratory and digestive tracts, have been one of the most important components of the Radiation Therapy Oncology Group (RTOG) since its inception 30 years ago. Emphasis from the very beginning to the present time has been on altered fractionation. Studies of hypoxic cell sensitizers were also explored for many years. More recently, combinations of radiation therapy with cytotoxic chemotherapeutic agents, either sequentially or concurrently, have been a major focus. Although the majority of the trials have been for unresectable tumors, surgical adjuvant radiation therapy alone or combined with chemotherapy has also been an important activity. Combined modality trials emphasizing organ conservation have been carried out within the last decade. The RTOG represents a national and international resource for studies of cancer of the head and neck. Its results influence the care of patients and the clinical research environment.