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Biomedical subjects

M Goitein

Publications and source records attributed to M Goitein.

At least 37 records · Page 2Linked to original sources
PubMed1989

The risk of enucleation after proton beam irradiation of uveal melanoma.

Enucleation after proton beam irradiation of uveal melanomas occurred in 64 (6.4%) of 994 eyes with a median follow-up time of 2.7 years. The median time between irradiation and enucleation in the 64 enucleated eyes was 13 months. The probability of retaining the eye was 95 and 90%, 2 and 5 years postirradiation, respectively. Three percent of eyes were enucleated during posttreatment year 1, and the yearly rate was 1% by the fourth year. No patient had enucleation later than 5 1/2 years posttreatment. The complication most likely to result in enucleation was neovascular glaucoma although this was frequently managed without enucleation. Other common reasons for enucleation were documented or suspected tumor growth and complete retinal detachment with associated loss of vision. The leading risk factors for enucleation were anterior tumor margin involving the ciliary body, tumor height greater than 8 mm, and proximity of the tumor to the fovea. Based on the presence or absence of these factors, 5-year eye retention rates were 99, 92, and 76% for low-, moderate-, and high-risk groups, respectively. Thus, the probability of eye retention after proton beam irradiation is high even among those at greatest risk of enucleation.

Eye Enucleation↗
PubMed1989

Fractionated proton radiation therapy of chordoma and low-grade chondrosarcoma of the base of the skull.

Sixty-eight patients with chordoma or low-grade chondrosarcoma at the base of the skull received fractionated high-dose postoperative radiation delivered with a 160-MeV proton beam. Protons have favorable physical characteristics which allow the delivery of high doses of radiation to these critically located tumors. The methods employed for these treatments are described. These patients have been followed for at least 17 months and for a median of 34 months. The median tumor dose was 69 CGE (cobalt Gy equivalent): CGE is the dose in proton Gy multiplied by 1.1, which is the relative biological effectiveness for protons compared to cobalt-60. The daily dose was 1.8 to 2.1 CGE. For this group the 5-year actuarial local control rate is 82% and disease-free survival rate is 76%. The incidence of treatment-related morbidity has been acceptable.

Adolescent↗
PubMed1988

Potential for improvement in radiation therapy.

A successful strategy for improving the efficacy of radiation therapy has been to improve dose distribution, that is, reduce treatment volume toward target volume. This is so as the smaller treatment volume has permitted a higher dose to the target (hence a high tumor control probability) and a lesser volume of non-target tissues being irradiated (consequently a reduced frequency and severity of treatment related morbidity). There are in place several important means for further improvements in dose distributions. These include: (a) 3D graphic reconstruction of the affected part with definition of the position of the tumor vis-a-vis the adjacent normal structures; (b) explicit inclusion in the treatment plan of the uncertainty band around each isodose contour; (c) on-line contrast enhanced visual monitoring of the target tissue during the individual treatment session; (d) gating of treatment so as to reduce the impact of patient motion on the needed treatment volume; (e) use of computer control systems to execute the treatment; and (f) use of treatment methods which achieve a reduced treatment volume. In an examination for sites for which treatment volumes might be decreased by a substantial factor we have compared treatment volumes for radical surgical and radiation therapy. Results are presented for carcinomas of the cervix (Stage IB), breast (Stage II), floor of mouth (Stage II). We describe a system developed here for on-line visual monitoring of the tissues covered by the treatment field. Brief descriptions are given of results of low LET charged particle radiation therapy and of intraoperative electron beam therapy. Also, the program developed here to use computer graphic techniques to display tumor and normal structures and isodose countours with uncertainty bands around each contour is mentioned.

Combined Modality Therapy↗
PubMed1988

Endocrine function following high dose proton therapy for tumors of the upper clivus.

The endocrine status of patients receiving proton radiation for tumors of the upper clivus was reviewed to evaluate the effect of high dose treatment on the pituitary gland. The fourteen patients had chordomas or low grade chondrosarcomas and were all treated by the same techniques. The median tumor dose was 69.7 Cobalt Gray Equivalent (CGE) with a range from 66.6 to 74.4 CGE. (CGE is used because modulated protons have an RBE of 1.1 compared to 60Co). The daily fraction size was 1.8-2.1 CGE. The median follow-up time is 48 months, ranging from 30 to 68 months. All treatments were planned using a computerized multi-dimensional system with the position of the pituitary outlined on the planning CT scan. Review of the dose distribution indicated that the dose to the pituitary ranged from 60.5 to 72.3 CGE, with a median of 67.6 CGE. One female patient had decreased thyroid and gonadotropin function at the time of diagnosis and has been on hormone replacement since that time. The other three females were all pre-menopausal at the time of radiotherapy. At this time four patients (3 males and 1 female) have developed endocrine abnormalities 14 to 45 months after irradiation. All four had evidence of hypothyroidism and two have also developed corticotropin deficiency. The three males had decreased testosterone levels; the female patient developed amenorrhea and hyperprolactinemia. All four are asymptomatic with ongoing hormone replacement.

Adolescent↗
PubMed1988

Metastasis from uveal melanoma after proton beam irradiation.

The incidence of metastasis and prognostic factors for metastasis in 780 consecutive patients with uveal melanomas treated with proton beam irradiation were evaluated. Metastasis developed in 64 patients (8%). The median time from treatment to the diagnosis of metastasis was 2.1 years (range, 3 months to 7.3 years). The liver was primarily involved in 58 (90%) patients. The 5-year cumulative probability of metastasis developing was 20%. Prognostic factors for metastasis developing were quite comparable to those found for patients treated by enucleation and included largest tumor diameter, involvement of the ciliary body, older age, and extrascleral extension. Surgical localization, tumor height, and elevated liver enzymes before treatment were not important factors in the development of metastasis.

Adolescent↗
PubMed1987

The effect of the respiratory cycle on mediastinal and lung dimensions in Hodgkin's disease. Implications for radiotherapy gated to respiration.

Changes in mediastinal and lung dimensions during respiration were studied to assess the potential of radiotherapy gated to respiration to minimize normal tissue irradiation. Twelve patients with mediastinal Hodgkin's disease were assessed using chest radiographs and thoracic computed tomography (CT) scans both during quiet breathing and at maximum inspiration in the standing, supine, and prone positions. A simple measure of the bulk of mediastinal disease, the ratio of the width of mediastinal mass to thoracic diameter, was determined from posteroanterior (PA) chest radiographs. The volumes of mediastinum, irradiated and protected lung if anteroposterior (AP) and PA mantle fields were used were determined from sequential thoracic CT scans and three-dimensional treatment planning and compared at quiet breathing and deep inspiration. The mediastinal width to thoracic diameter ratio decreased from quiet breathing to deep inspiration an average of 3%, 9%, and 11% for the standing, supine, and prone positions, respectively. Lung volumes as measured from the thoracic CT scans showed that on average, 8% more lung was protected at deep inspiration than at quiet breathing, independent of treatment position. The maximum increase in the percentage of protected lung from quiet breathing to deep inspiration was seen in patients with extensive mediastinal adenopathy suggesting that radiotherapy gated to respiration may be most advantageous in the subset of patients.

Hodgkin Disease↗
PubMed1987

Uveal melanomas near the optic disc or fovea. Visual results after proton beam irradiation.

Proximity to the disc and fovea is a risk factor for visual loss after proton beam irradiation of uveal melanomas. Of 562 eyes treated over a 10-year period with pretreatment visual acuity of 20/200 or better, 363 (64.6%) contained tumors within 2 disc diameters (DD) of the disc or fovea. Rates of visual loss after treatment to worse than 20/200 and causes of visual decline were evaluated using Kaplan-Meier analysis. Cumulative rates of visual loss among subjects with tumors near the disc or fovea were 33 and 47% 1 and 2 years after treatment compared to 17 and 28%, respectively, for subjects with tumors located farther from both structures. The leading cause of visual loss in the first year among eyes with tumors near the disc or fovea was retinal detachment. Controlling for other predictors of visual loss to worse than 20/200, location near the disc or fovea was independently related to visual loss primarily due to retinal detachment, cataract, and radiation retinopathy. Despite the unfavorable location of these tumors, over half of patients with 20/200 or better pretreatment visual acuity had useful vision 2 years after treatment.

Cataract↗
PubMed1987

Long-term results of proton beam irradiated uveal melanomas.

The first 128 consecutive patients with uveal melanomas treated with proton beam irradiation were studied in order to evaluate survival and visual acuity status of patients with relatively long-term follow-up. The median follow-up was 5.4 years, and no patient was lost to follow-up. All tumors showed regression. The most recent visual acuity was 20/40 or better in 35% and 20/100 or better in 58%. Eight eyes were enucleated because of complications. Metastasis developed in 26 patients (20.5%) from 3 months to 7 years after treatment. Results indicate that proton irradiation is quite successful for achieving local control of uveal melanomas. A large proportion of the treated eyes maintained useful vision. Five-year follow-up data indicate that proton irradiation has no deleterious effect on the likelihood of the development of metastasis.

Eye Diseases↗
PubMed1987

[Fractionated proton radiotherapy].

Investigations in proton beam therapy of cancer patients have been initiated at the Cyclotron Laboratory, Harvard University, Cambridge, USA, since 1974 using a proton beam with the energy of 160 MeV for fractionated irradiation of uveal melanoma (899 cases), chordoma and chondrosarcoma of the base of the skull (96), sarcoma of the soft tissues and bones (79), prostatic cancer, head and neck tumors, etc. (altogether 1331 patients had been irradiated by June, 1986). To stop a beam in the target computer-assisted three-dimensional design and heterogeneity calculations were performed; computed compensatory boles were produced. Proton beam therapy is used alone or in combination with proton beam irradiation, routine radiotherapy. Areas of particular interest are ocular melanoma, chordoma and chondrosarcoma of the base of the skull, paraspinal sarcomas. Investigations in the field of proton beam therapy of malignant meningioma, metastases to the paraaortic lymph nodes hold promise.

Humans↗
PubMed1986

Causes and consequences of inhomogeneous dose distributions in radiation therapy.

Reasons for delivering a non-uniform dose to the target volume are discussed. These include deliberate tailoring of dose to a non-uniform tumor burden or to a non-uniform expectation of the presence of disease, and undesired but unavoidable non-uniformities due to: technical factors; set-up uncertainty; and the need to avoid sensitive organs abutting the target volume. The consequences of non-uniform dose distributions are reviewed and it is suggested that: tumor control may be better characterized by the mean rather than the minimum target absorbed dose when the dose non-uniformity is not too great; modest dose deficits to small sub-volumes of the target volume may not be too deleterious; and modest dose increments to substantial sub-volumes of the target volume may be advantageous. Further modeling, and animal experiments in which tumors are non-uniformly irradiated are required to validate these hypotheses.

Humans↗
PubMed1986

Prognostic factors for metastasis following proton beam irradiation of uveal melanomas.

Prognostic indicators for the development of metastasis following proton beam irradiation of uveal melanomas were evaluated for 510 patients treated from 1975 to 1984. Thirty-three patients developed metastasis (6.5%) from 3 to 51 months following treatment. The primary site of metastasis was the liver in 28 cases (85%). Both demographic and clinical factors were considered. The three leading predictors of survival without metastasis after proton beam irradiation in order of importance were: (1) largest diameter of the tumor; (2) location of the anterior margin of the tumor; and (3) age at treatment. Worse prognosis was associated with largest tumor diameter greater than 15.0 mm, tumor involvement of the ciliary body and age at treatment older than 59 years.

Adult↗
PubMed1986

Visual outcome after proton beam irradiation of uveal melanoma.

Prognostic factors for visual loss following proton irradiation of uveal melanoma were evaluated for 440 eyes treated from 1975 to 1984, with visual acuity 20/200 or better before treatment. Analysis involved Kaplan-Meier survival curves and Cox proportional hazards analysis with visual outcome defined as worse than 20/200. Prognostic factors were tumor height: rate ratio (ratio of rate of visual loss for one category of the variable relative to the rate of visual loss for a reference category of that variable) of 5.26 (95% confidence interval, 2.66-10.39) for tumors greater than 5 mm compared to tumors 3.0 mm or less in height; distance of tumor from the optic disc and fovea: rate ratio 2.59 (1.63-4.11) for tumors 2DD or less from both the optic disc and fovea compared to those greater than 2 DD from these structures. Also predictive of visual loss were tumor location close to disc only, or close to fovea only, macular detachment, worse pretreatment vision, and higher radiation doses delivered to both the disc and fovea, and lens. Regression analysis using a visual acuity scale gave similar results.

Adolescent↗
PubMed1986

Degradation of the Bragg peak due to inhomogeneities.

The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles.

Humans↗
PubMed1985

The effects of pre-enucleation irradiation on the development of metastases from intraocular Greene melanoma in hamsters.

Using intraocular Greene melanoma in a hamster model, we studied the effect of pre-enucleation irradiation on the development of melanoma metastases. One group (No. = 111) was treated with 1,210 to 1,600 rads of cobaltous chloride Co 60 gamma irradiation before enucleation and the second group (No. = 100) received no irradiation. The groups did not differ with respect to presence of metastases in the 106 days after tumor implantation (chi 2 = 3.05; P = .08). However, Kaplan-Meier survival curves gave a longer time to melanoma-related death in the irradiated animals compared with the controls (log rank test, P = .0008).

Animals↗
PubMed1985

Future prospects in planning radiation therapy.

Recent advances in imaging, especially computed tomography and magnetic resonance imaging, and in the power and capabilities of reasonably priced computers and image display devices will permit a substantial extension of the scope of computer programs designed to help plan cancer therapy. All available diagnostic studies could be incorporated into the process of assessing the patient's disease, picking a treatment modality, and determining details of the selected treatment. Fully three-dimensional simulation of any possible treatment will be possible and methods for comparing and choosing between possible rival plans will be developed. Monitoring of the treatment machine and verification of the adequacy of the delivered treatment will be facilitated, and the follow-up of the patient and statistical analysis of the results of treatment can be incorporated into the overall programming system.

Humans↗
PubMed1985

Accuracy of radiation field alignment in clinical practice.

We present an analysis of simulator and portal films of 71 patients. Twenty-five were analyzed retrospectively, 39 prospectively, but without changing routine filming practice, and 7 had daily portal films taken. Treatment-to-treatment variations in anatomy with respect to the field were determined by comparing sequential portal films. The standard deviation of the variations was approximately normally distributed with an average value of 3 mm independent of site and field shaping technique. Discrepancies between the portal and simulator films were greater and depended on the site of treatment. The mean worst-case discrepancy averaged over all sites was 7.7 mm; the lowest value was 3.5 mm in the head and neck region; the highest value was 9.2 mm in the thorax.

Humans↗
PubMed1985

A diagnostic X ray field verification device for a 10 MV linear accelerator.

The quality of portal films taken at megavoltage energies is frequently poor, despite the use of various techniques such as lead screens to improve the image. When critical structures, such as the spinal cord, are to be blocked out of the treatment field, it is frequently difficult to determine whether the block is correctly placed. To solve this problem, a diagnostic X ray source has been mounted on the side of a 10 MV linear accelerator to provide accurate verification of patient positioning and location of shielding blocks. The coincidence between the mechanical, 10 MV and diagnostic X ray isocenters is about 1 mm. The system has been designed so that procedures to monitor this coincidence, and adjustment procedures to maintain it, are easily performed.

Humans↗