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Biomedical subjects

J R Castro

Publications and source records attributed to J R Castro.

At least 73 records · Page 4Linked to original sources
PubMed1982

Molecular and cellular radiobiology of heavy ions.

Quantitative studies at the BEVALAC have demonstrated some of the physical and radiobiological factors that promise to make accelerated heavy ions important for the therapy of cancer. The measured physical dose-biological effect relationships allow the safe and effective delivery of therapeutic schedules of heavy ions. Among the charged particle beams available, carbon, neon and helium ions in the "extended Bragg peak mode" have optimal physical and biological effectiveness for delivery of therapy to deep seated tumors. The depth-dose profiles of these beams protect intervening and adjacent tissues as well as tissues beyond the range of the particles. For the treatment of hypoxic tumors, silicon and argon beams are being considered because they significantly depress the radiobiological oxygen effect in the region of the extended Bragg ionization peak. The depth-effectiveness of the argon beam is somewhat limited, however, because of primary particle fragmentation. Silicon beams have a depth-dose profile which is intermediate between that of neon and argon, and are candidates to become the particle of choice for maximizing high LET particle effects. Heavy accelerated ions depress enzymatic repair mechanisms, decrease variations of radiosensitivity during the cell division cycle, cause greater than expected delays in cell division, and decrease the protective effects of neighboring cells in organized systems. Near the Bragg peak, enhancement of heavy particle effects are observed in split dose schedules. Late and carcinogenic effects are being studied. With the newly developed Repair-Misrepair theory we can quantitatively model most observations.

Animals↗
PubMed1982

Treatment of cancer with heavy charged particles.

A clinical radiotherapeutic trial using heavy charged particles in the treatment of human cancers has accrued over 400 patients since 1975, 378 of whom were treated with particles and 28 with low LET photons as control patients. Heavy charged particle radiotherapy offers the potential advantages of improved dose localization and/or enhanced biologic effect, depending on particle selected for treatment. Target sites have included selected head and neck tumors, ocular melanomata, malignant gliomata of the brain, carcinoma of the esophagus, carcinoma of the stomach, carcinoma of the pancreas, selected juxtaspinal tumors and other locally advanced, unresectable tumors. A Phase III prospective clinical trial has been started in carcinoma of the pancreas using helium ions. Phase I-II studies are underway with heavier particles such as carbon, neon and argon ions in order to prepare for prospective Phase III trials. Silicon ions are also under consideration for clinical trial. These studies are supported by the United States Department of Energy and National Institutes of Health.

Adult↗
PubMed1982

Clinical problems in radiotherapy of carcinoma of the pancreas.

Since 1975, 94 patients with localized unresectable carcinoma of the pancreas have been irradiated using helium and heavier particles at the University of California Lawrence Berkeley Laboratory. Despite surgical exploration and an extensive diagnostic workup including radiological, nuclear medicine, and computer-assisted tomographic studies, many patients proved to have occult liver metastases manifested within 9 months post treatment. In addition, local and regional control of the primary neoplasm (approximately 20%) has been difficult to obtain even with doses of 6000 equivalent rad in 7 1/2 weeks. Gastric and biliary obstruction have required surgical bypass procedures since irradiation has not been successful in relieving obstructive symptoms. Evidence of gastrointestinal injury has been present in postradiation therapy in approximately 10% of patients, a figure which might be higher if more patients had a longer survival (average 10 months). Some patients require pancreatic enzyme supplementation because of pancreatic deficiency either secondary to tumor or treatment. Further improvement in local control and survival requires better diagnostic methods for evaluation of local and metastatic spread, improved therapy for local and regional disease, as well as therapy directed at occult liver metastases that are frequently present.

Adenocarcinoma↗
PubMed1980

Current status of clinical particle radiotherapy at Lawrence Berkeley Laboratory.

Clinical experience with charged particle irradiation of human cancers has been underway at the University of California Lawrence Berkeley Laboratory. Over 150 patients have been irradiated with heavy charged particle beams including helium, carbon, neon, and argon ions. Pilot studies have included such tumor sites as glioma of the brain, carcinoma of the esophagus, carcinoma of the pancreas, carcinoma of the stomach, ocular melanoma, and carcinoma of the uterine cervix. Prospective studies are planned to investigate the improved dose localization potential (helium) and the enhanced biologic and physical dose potential (carbon, neon) in a controlled trial against the best available megavoltage irradiation techniques.

Argon↗
PubMed1980

Helium ion charged particle therapy for choroidal melanoma.

Nine patients with choroidal melanomas were treated with helium ion charged particle irradiation. No patient demonstrated tumor enlargement, and most lesions followed for more than five months have demonstrated tumor shrinkage. The most effective method of choroidal melanoma management is unclear. Heavy charged particle irradiation may be more applicable and have less ocular morbidity associated with it in either radioactive plaques or photocoagulation.

Adult↗
PubMed1980

Radiotherapy with heavy charged particles at Lawrence Berkeley Laboratory.

Since July 1975, 157 patients have been irradiated with heavy charged particles at the Lawrence Berkeley Laboratory in a Phase I-II clinical trial to study the usefulness of these particles in the irradiation of human cancers. The particles utilized have included helium, primarily of interest because of improved dose distributions with reduction of dose to adjacent normal tissues, and heavier particles such as carbon, neon and argon ions which have the additional potential of increased biologic effectiveness against the tumor, especially hypoxic tumor cells. Initial results with helium particles have been sufficiently good to warrant a Phase III randomized trial in carcinoma of the pancreas; in other tumor sites, and with other particles, Phase I -- Phase II studies are in progress. Although follow-up is short, control within the irradiated area in this heterogeneous group of patients appears at least as good as with current megavoltage irradiation and complications to date are acceptably low, warranting further studies with heavy charged particles.

Argon↗
PubMed1980

Computerized tomography in the quantitative assessment of tumour response.

While Computerized Tomographic (CT) scans have been a valuable asset to radiotherapy treatment planning, their role in the critical assessment of tumour response has been less well defined. Recent refinements in radiotherapy treatment techniques have intensified the need for non-invasive methods to evaluate the local control of inaccessible neoplasms. In this study, 20 cases in which both pre- and post-treatment CT scans were available up to 27 months post-therapy were reviewed. The majority of the patients had pancreatic carcinoma. In both pre- and post-therapy scans, the tumour volume was calculated from contours outlined on sequential CT slices. These interpretations were compared with surgical findings, clinical course and patient survival. The rate of the primary tumour regression had little bearing on the clinical outcome. However, there was CT scan evidence of initial local tumour stabilization or regression in > 80% of the cases. In addition, CT scan evidence of tumour progression was correlated with clinical progression in > 90% of the patients. This suggests that a growth delay analysis might be possible with the use of CT scans, at least for the evaluation of pancreatic carcinoma.

Humans↗
PubMed1979

The use of 2450 megahertz of microwave in cancer therapy; a pilot study.

Contraindications to microwave diathermy traditionally include malignant tumors. This paper describes a pilot study of tissue hyperthermia treatment (average 42.5 degrees C, 108.5 degrees F) for superficial cancers, using 2450 megahertz of microwave diathermy. Tissue temperatures were recorded for prolonged periods of time, and tumor responses to heat alone, or to heat combined with radiation therapy, were observed. Such treatments were tolerated by the patients, but were not without side effects. Preliminary results of this pilot study, as well as those of other investigators, showed that tissue hyperthermia would be a useful treatment modality for cancer therapy. The familiarity of physical therapists with microwave diathermy may be an asset to them as clinicians. Physical therapists, however, should not attempt to treat cancer patients alone. Further clinical research in the area should be conducted in the proper setting under the guidance of an oncologist.

Body Temperature↗
PubMed1978

137Cs afterloading intrauterine packing for stage I and stage II adenocarcinoma of the endometrium.

Eleven patients with Stage I or Stage II adenocarcinoma of the endometrium were treated with 137Cs afterloading intrauterine packing. Treatment results and complications were similar to those obtained with radium afterloading tandems and colpostats (20 patients) and Heyman packing (2 patients). 137Cs is preferable in patients with roomy or irregular intrauterine cavities and also offers reduced radiation exposure to personnel.

Adenocarcinoma↗
PubMed1975

Evaluation of time-dose factors in glottic tumors.

Sixty patients with localized squamous cell carcinoma of the vocal cord without nodal or metastatic disease were treated with four fractions per week. No serious complications occurred with the dose and fractionation schedule as outlined. Voice quality after treatment has been satisfactory. After a minimum of two years follow-up the control rates for T1 and T2 tumors are 80% and 81.5%, respectively. All radiation therapy failures were cured surgically. A dose-response curve was constructed for T1 lesions, utilizing the Ellis' formula to derive the NSD, from data from different therapy centers. There appears to be no differences in the parameters studied between four and five fractions per week treatment schedules. A ret dose of approximately 1800 appears somewhat low for optimal control rates in T1 and T2 tumors.

Carcinoma, Squamous Cell↗