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Biomedical subjects

L B Marks

Publications and source records attributed to L B Marks.

At least 91 records · Page 5Linked to original sources
PubMed1994

A simple device to position large/flaccid breasts during tangential breast irradiation.

PURPOSE: It is technically difficult to irradiate large pendulous or flaccid breasts with tangential photon fields because they often lie very high or lateral on the chestwall. We, therefore, designed a device to reposition the breast on the chestwall to facilitate treatment. METHODS AND MATERIALS: A device to aid in repositioning the breast on the chestwall has been designed. The device consists of a reinforced polyvinylchloride tube formed into a ring that is placed around the breast. A strap around the patient's chest holds the ring in place. The breast tissue is manually moved to the desired position on the chestwall, whereafter the strap is tightened to maintain the position. Treatment setup marks are placed on the skin peripheral to the breast and on the immobilization mold. RESULTS: Twelve patients with large/flaccid breasts were successfully treated with this device. The technical and physician staff find the reproducibility and acute treatment reactions to be acceptable. Anatomically, the use of this device reduces the volume of lung tissue otherwise included in the tangential fields in patients where the breast lies far lateral. In patients where the breast lies too far cephalad on the chestwall for tangential fields to clear the arm, repositioning of the breast with this device makes tangential fields possible. CONCLUSION: This repositioning appliance aids in the radiation treatment of patients with large or flaccid breasts and, in some instances, renders otherwise nontreatable patients treatable with radiation therapy.

Breast↗
PubMed1994

To treat or not to treat the internal mammary nodes: a possible compromise.

PURPOSE: A method for designing partly wide tangential fields that irradiate the superiorly placed internal mammary nodes, yet exclude the inferiorly placed internal mammary nodes and the cardiac tissue, is described for patients receiving tangential radiation for breast cancer. METHODS AND MATERIALS: Patients are immobilized in hemibody foam cradles. A CT study is performed with a series of fiducial markers. The CT data set can then either be transferred to the three-dimensional treatment planning computer for sophisticated treatment planning, or can be viewed to design partly wide tangential fields "by hand." This latter method is far less time consuming and, we believe, usually adequate, given the uncertainties in identifying the location of the internal mammary nodes. RESULTS: This technique has been implemented in our clinic and has been used to treat approximately 15 patients. In four of these patients, a formal dose-volume histogram analysis revealed that these partly wide tangential fields can adequately exclude the cardiac volume and include the superiorly placed internal mammary nodes. Modest reductions in the pulmonary volume that is incidentally irradiated are seen compared to conventional wide tangents that irradiate the entire length of the internal mammary chain. CONCLUSION: While controversy remains regarding the appropriateness of internal mammary nodal irradiation for patients with breast cancer, the technique described represents an attractive compromise. Selective irradiation of the superiorly placed internal mammary nodes (which are those at greatest risk for involvement) with customized "partly wide" tangential fields is possible. This treatment technique may provide the survival advantage that might be seen with internal mammary node irradiation, yet avoid the possible cardiac morbidity.

Breast Neoplasms↗
PubMed1994

Radiosurgery dose distributions: theoretical impact of inhomogeneities on lesion control.

OBJECTIVE: To develop a mathematical model to predict the impact of dose heterogeneities on tumor/lesion control during radiosurgery. It is necessary to be able to estimate these effects in order to quantitatively and objectively assess competing treatment plans. METHODS: Target cells are assumed to be uniformly distributed throughout the lesion. The control rate for the entire lesion is assumed to be the product of the control probabilities for each subregion within the target volume. The lesion control probability (LCP) for each region is assumed to equal EXP (the number of surviving target cells within the subregion), as predicted by Poisson statistics. Subregions of variable size are assumed to receive variable doses, and the impact of this dose heterogeneity on the LCP is calculated based on the single-fraction radiation cell survival curve predicted by the single-hit multitarget model. RESULTS: The impact of a dose heterogeneity on LCP is related to three variables: the LCP predicted with uniform irradiation, the volume of the lesion that is irradiated to a new dose, and the magnitude of the dose change relative to the slope of the single-fraction radiation cell survival curve of (delta D/Dzero). The calculations predict that the detrimental effect of underdosing regions of the lesion can, in some instances, be offset by escalating the dose to other subregions within the target volume. In this regard, the "average" dose delivered to the lesion rather than the minimum dose may be most predictive of the lesion control probability. In some situations, escalating the dose to part of the lesion may improve the lesion control rate. CONCLUSION: These calculations quantify the theoretical impact of dose heterogeneities on lesion control rate and may be very useful when comparing competing treatment plans.

Dose-Response Relationship, Radiation↗
PubMed1994

Correlation of mid-sternum and mid-spine positions in 82 patients irradiated for breast cancer.

The validity of designing anterior internal mammary node (IMN) radiation therapy fields based on vertebral body landmarks was tested by reviewing computer tomography (CT) images in 82 patients treated for breast cancer. The horizontal distance between the geometric center of the sternum and the vertebral body was 0-5, 6-10 and > 10 mm in approximately 30%, 25%, and 45% of patients, respectively. This suggests that using the projection of the vertebral bodies to design an anterior internal mammary node field is frequently inaccurate and may lead to inadequate coverage of these lymph nodes.

Breast Neoplasms↗
PubMed1994

Connective tissue tumors in patients with cutaneous melanoma.

BACKGROUND: A possible relation between cutaneous melanoma and connective tissue tumors has been described. OBJECTIVE: After the observation that a group of our patients had both cutaneous melanoma and a soft tissue sarcoma, we elected to review this formally. Eleven patients with both diagnoses were identified and are described. METHODS: A computer search through the Medical Records Department and the Tumor Registry of the Massachusetts General Hospital identified seven men and four women with the diagnoses of melanoma and malignant bone or soft tissue sarcoma. The medical records and pathology specimens of all tumors were reviewed. RESULTS: In three patients, the two tumors were diagnosed within 1 year of each other, in seven, the diagnosis of melanoma was made first, and in one, melanoma was diagnosed after the connective tissue lesion. The interval between the two diagnoses ranged up to 13 years. Although the locations and types of melanoma were typical, some of the connective tissue tumors were unusual; there were two sacral chordomas. In two instances, the melanoma and connective tissue tumor were anatomically close; the sarcoma developed at the edge of the resection of the prior melanoma in one patient. None of the tumors developed in previously irradiated tissues, and in no instance did the second tumor appear to be caused by the therapy received for the first. None of the patients had a family history of melanoma. Four patients had other cancers in addition to the melanoma and connective tissue tumor. CONCLUSION: Although these patients were seen in a referral center, it is our impression (based on the total number of patients with connective tissue tumors seen and the incidence of melanoma in the general population) that observing 11 patients with both types of tumors is greater than would be expected by chance.

Adult↗
PubMed1994

The pulmonary effects of thoracic irradiation.

Radiation-induced pulmonary injury is common following treatment for a variety of tumors in and around the thorax. While symptomatic injury is unusual, subclinical injury identified by formal pulmonary function tests and/or radiographs is very common. In this article, the radiologic, symptomatic, and physiologic pulmonary effects of whole and partial thoracic irradiation are summarized from the animal and human data available. The risk of developing significant lung injury appears to be most dependent upon the radiation dose and volume of lung irradiated. Additional studies are needed to develop algorithms to predict the physiologic consequences of a proposed radiation treatment program such that reasonable risk-benefit assessments can be made. This may lead to improvements in the therapeutic ratios that facilitate dose escalation and improve local tumor control and cure rates.

Animals↗
PubMed1993

The utility of SPECT lung perfusion scans in minimizing and assessing the physiologic consequences of thoracic irradiation.

PURPOSE: Three-dimensional single photon emission computed tomography lung perfusion scans (SPECT) provide a unique quantitative 3-dimensional map of the distribution of functioning pulmonary vascular/alveolar subunits, information not provided by other imaging modalities. This report describes our initial experience utilizing these scans to assist in the design of radiation treatment beams and to assess changes in regional lung function following irradiation. METHODS AND MATERIALS: Patients were immobilized and scanned in the treatment position with appropriate fiducial markers. Four millicuries of technetium 99M microaggregated albumin were injected and SPECT images of the lung were generated. Pre-treatment SPECT images were used to help design radiation beams to minimize irradiation of functioning lung. Pre- and post-treatment scans were compared to assess changes in regional function. These changes in function were then correlated with the regional radiation dose. RESULTS: Pre-radiotherapy SPECT scans were obtained in 18 patients (11 with lung cancer). Marked variations in regional function were frequently noted. In patients with primary lung tumors, these variations were not necessarily immediately adjacent to the tumor volume. In general, patients with poor pulmonary function pre-treatment, in whom one would like to spare as much normal lung as possible, had the most non-uniform distribution throughout the lung of functioning vascular/alveolar subunits. In these cases, pre-treatment scans were most useful in designing radiation portals to minimize irradiation of functioning lung. SPECT scans were also used to detect changes in regional lung function secondary to radiotherapy in four patients. With doses in excess of 40 Gy, reductions in regional function were noted 1-6 months following completion of radiotherapy. These reductions were not necessarily accompanied by reductions in conventional pulmonary function tests, which are assessments of whole lung function and may not reflect regional lung injury if the volume affected is small. CONCLUSIONS: SPECT lung scans provide an excellent means of assessing regional lung function, superior to that obtainable with planar images. The functional data provided by the SPECT images is useful in designing "optimal" radiation treatment beams and in assessing the effect of radiotherapy on regional lung functions. Efforts are continuing in our laboratory to develop a dose response curve for regional lung damage using the tools of SPECT scanning and 3-dimensional dose calculations.

Aged↗
PubMed1993

Comparison of serial PET and MRI scans in a pediatric patient with a brainstem glioma.

Profound clinical deficits may be associated with insults to the brainstem, making management of patients with brainstem gliomas very complex. Small changes in the radiographic appearance of a brainstem tumor may be associated with significant clinical deterioration. Furthermore, both magnetic resonance imaging and computed tomography are frequently unable to differentiate between therapy-related tissue reactions and progressive tumor. Two clinical scenarios particularly difficult to resolve include: (1) transient radiographic and clinical deterioration following hyperfractionated radiotherapy, and (2) clinical deterioration in a patient who has failed initial therapy, but has stable radiographic findings following a second therapy. We report a child with a pontine glioma whose tumor progression was demonstrated more convincingly with a 18F-deoxyglucose positron emission scan than with magnetic resonance imaging. PET scans may be helpful in confirming that tumor progression is responsible for clinical deterioration in a patient whose MRI scans remain stable.

Brain Neoplasms↗
PubMed1993

Conventional fractionated radiation therapy vs. radiosurgery for selected benign intracranial lesions (arteriovenous malformations, pituitary adenomas, and acoustic neuromas).

Despite growing interest in radiosurgery, the precise role of radiosurgery relative to that of conventional fractionated external-beam radiation therapy is not fully clear. A critical review of the available data suggests that radiosurgery is both a safe and effective treatment for small arteriovenous malformations, pituitary adenomas and acoustic neuromas. For arteriovenous malformations, the effectiveness of radiosurgery is clearly reduced as the size of the malformation increases. Conventional external-beam radiation therapy is also an effective treatment for pituitary adenomas and acoustic neuromas, while the results for arteriovenous malformations are less encouraging. However, most arteriovenous malformations that have been treated with fractionated radiation therapy were large and received relatively low doses of radiation. One can speculate that high doses (> or = 50 Gy) of fractionated radiation therapy may be effective in the treatment of small arteriovenous malformations. Differences in the apparent effectiveness of radiosurgery and conventional fractionated radiation therapy are partly due to patient selection. A single fraction of approximately 20 Gy (a dose frequently used during radiosurgery) is probably 'biologically equivalent' to approximately 50 to 110 Gy of fractionated radiation therapy (at 2 Gy/fraction based on the linear quadratic model). In this regard, radiosurgery may be just a means of dose escalation. It remains to be shown that the possible benefit of radiosurgery could not be achieved by simply escalating the doses of fractionated radiation. Further clinical experience is needed to better define the role of radiosurgery. Randomized trials comparing conventional fractionated radiation vs. radiosurgery at approximately equal complication levels may be possible.

Adenoma↗
PubMed1993

Craniospinal irradiation for trilateral retinoblastoma following ocular irradiation.

A case study is presented. Craniospinal radiotherapy and a three-fold pineal boost for trilateral retinoblastoma were delivered to a patient previously irradiated for ocular retinoblastoma. The availability of CT-based three-dimensional treatment planning provided the capability of identifying the previously irradiated volume as a three-dimensional anatomic structure and of designing a highly customized set of treatment beams that minimized reirradiation of that volume.

Brain Neoplasms↗
PubMed1993

High-dose chemotherapy and autologous bone marrow support as consolidation after standard-dose adjuvant therapy for high-risk primary breast cancer.

PURPOSE: We studied high-dose cyclophosphamide, cisplatin, and carmustine (CPA/cDDP/BCNU) with autologous bone marrow support (ABMS) as consolidation after standard-dose adjuvant chemotherapy treatment of primary breast cancer involving 10 or more axillary lymph nodes. PATIENTS AND METHODS: One hundred two women with stage IIA, IIB, IIIA, or IIIB breast cancer involving 10 or more lymph nodes at surgery were registered; 85 were eligible, treated, and assessable. Patients were treated with four cycles of standard-dose cyclophosphamide, doxorubicin, and fluorouracil (CAF), followed by high-dose CPA/cDDP/BCNU with ABMS. RESULTS: Actuarial event-free survival for the study patients at a median follow-up of 2.5 years is 72% (95% confidence interval, 56% to 82%). Comparison to three historical or concurrent Cancer and Leukemia Group B (CALGB) adjuvant chemotherapy trials selected for similar patients showed event-free survival at 2.5 years to be between 38% and 52%. Therapy-related mortality was 12%; pulmonary toxicity of variable severity occurred in 31% of patients. Quality-of-life evaluations indicate that patients are functioning well without major impairments. CONCLUSION: High-dose consolidation with CPA/cDDP/BCNU and ABMS after standard-dose CAF results in a decreased frequency of relapse in patients with high-risk primary breast cancer compared with historical series at the median follow-up of 2.5 years. Evaluation in a prospective, randomized trial is warranted and currently underway.

Adult↗
PubMed1992

Reversal of radiation-induced neutropenia by granulocyte colony-stimulating factor.

Myelosuppression is a common sequelae of radiotherapy, occasionally delaying the completion of treatment. In this report, we describe successful reversal of radiation-induced neutropenia in a child receiving craniospinal irradiation by granulocyte colony-stimulating factor (G-CSF). We suggest that G-CSF be considered as supportive care in patients in whom neutropenia develops during radiotherapy.

Cerebellar Neoplasms↗