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B Stea

Publications and source records attributed to B Stea.

At least 37 records · Page 2Linked to original sources
PubMed1994

The effect of the number of computed tomographic slices on dose distributions and evaluation of treatment planning systems for radiation therapy of intact breast.

PURPOSE: This study was undertaken to answer the following questions in breast irradiation: (a) How many calculation planes are sufficient for three-dimensional (3-D) treatment planning? (b) Is pseudo-3-D planning system sufficiently accurate for 3-D treatment planning of a breast? METHODS AND MATERIALS: We carried out dose calculations and differential dose-volume analysis on three representative patients covering the range of breast size encountered in a clinic. The breast volumes were reconstructed from computed tomography (CT) scans using three slices, five slices and the full CT scan respectively. An established 3-D dose algorithm and two pseudo-3-D commercial systems were used in the calculations. Comparison of isodose distributions were made between the central axis plane, a cephalic and a caudal plane 6 cm above or below the central axis respectively. RESULTS: When comparing isodose distributions generated with conventional two-dimensional treatment planning with 3-D dose calculations, the former underestimated the size and magnitude of the hot spots in the medial and the lateral subcutaneous (SC) regions. When comparing the three-slice with the full CT model, while the three-slice model was found to be adequate for the "small" and the "medium" size patients, the full CT model provided a more accurate representation of dose distributions for the "large" patient. Comparison of a true 3-D algorithm with pseudo-3-D algorithms showed that while the latter systems were adequate for the "small" and the "medium" patients, significant differences were noted between the true 3-D and the pseudo-3-D algorithms for the "large" patient. CONCLUSION: For patients whose breast contours vary slowly within the tangential fields, a three-slice CT scan as well as a pseudo-3-D approach appears to be adequate for clinical decision. However, for patients with large variation of contours within the tangential fields, a full scale CT scan with a true 3-D dose algorithm is more accurate than either the three-slice or the five-slice model.

Breast↗
PubMed1994

A comparison of survival between radiosurgery and stereotactic implants for malignant astrocytomas.

The purpose of this paper is to compare the survival of three groups of patients with high grade supratentorial gliomas who were treated on three sequential protocols with surgical resection, external beam fractionated radiotherapy and a boost to the residual contrasting enhancing mass by either interstitial brachytherapy (IB, n = 33), by interstitial thermoradiotherapy (IT, n = 25) or by stereotactic radiosurgery (SRS, n = 19). The primary aim of this study was to evaluate the role of different boosting techniques in the initial management of primary brain tumors. External beam radiotherapy doses were escalated from one study to the next so that the median doses given to the IB, the IT, and the SRS groups were 41.4 Gy, 48.4 Gy, and 59.4 Gy, respectively. The median dose of interstitial irradiation or stereotactic radiosurgery, were 40 Gy, 32.2 Gy and 10 Gy, respectively, for the same groups. Follow-up was such that all living patients had been followed for a minimum of 30, 27, 4 months in the IB, IT, and SRS groups, respectively; hence, twelve-month survival was 52% (95% CI: 34%-69%), 80% (95% CI: 64%-96%), and 51% (95% CI: 24%-78%) in the same respective groups. Using a multivariate Cox proportional hazards model, treatment with IT conferred a survival advantage over IB (p = 0.029). Furthermore, survival of patients treated with SRS did not significantly differ from that of patients treated with an implant with or without hyperthermia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Interstitial thermoradiotherapy with ferromagnetic implants for locally advanced and recurrent neoplasms.

PURPOSE: The University of Arizona, University of California at San Francisco, City of Hope Medical Center, and University of Wisconsin participated in a Phase I/II protocol to assess the heating ability and the toxicity of interstitial thermoradiotherapy using ferromagnetic implantation. METHODS AND MATERIALS: Forty-four patients with advanced primary or recurrent extra-cranial solid malignancies were enrolled in this study. Fourteen gauge catheters were implanted into tumors and, once in the department of Radiation Oncology, loaded with ferromagnetic seeds to deliver a 60 min hyperthermia treatment. Multi-point thermometry was continuously used throughout the heating sessions for all patients, sampling the periphery as well as the core of the tumor. After 192Iridium brachytherapy, 18 patients then had an additional treatment. The mean radiation dose while on protocol was 50.0 Gy, with total doses (including prior radiotherapy) ranging from 20.3-151.8 Gy (median = 88.7 Gy). Response and toxicity were assessed by inspection, palpation, and/or radiologic studies. Forty-one patients were evaluable for response, and there were 55 analyzable hyperthermia treatment sessions. RESULTS: The complete response rate was 61% (25/41). The partial response rate was 31.7% and only 7.3% failed to respond. Median duration of local control has not yet been reached. The mean maximum, minimum, and mean time-averaged temperatures for all in-tissue sensors were 43.7 degrees C, 38.7 degrees C, and 41.0 degrees C, respectively. Tumor size was the only factor significantly correlated with temperatures or with complete response rate; larger tumors attained higher temperatures but smaller tumors had a higher response probability. Nineteen patients (43%) experienced toxicities, however there was only a 7% (3/44) rate of serious complications (Grade 3 or 4). Prior treatment with hyperthermia was the only factor significantly correlated with serious toxicity. CONCLUSION: These results, a 93% total response with only 7% serious toxicity, are encouraging especially in the context of the patient population treated. Phase II/III studies involving ferromagnetic implantation are warranted.

Adult↗
PubMed1993

Feasibility and toxicity of transrectal ultrasound hyperthermia in the treatment of locally advanced adenocarcinoma of the prostate.

PURPOSE: This Phase I trial tests the ability of a new hyperthermia device, the transrectal ultrasound probe, to heat the prostate gland, and evaluates the toxicity of transrectal ultrasound hyperthermia (TRUSH) given with concurrent standard external beam irradiation in the treatment of locally-advanced adenocarcinoma of the prostate. METHODS AND MATERIALS: Between June, 1990 and August, 1991, 14 patients with American Urological Society Stage C2 or D1 adenocarcinoma of the prostate were treated with TRUSH concurrently with standard external beam radiotherapy to the prostate. Twenty-two heat treatments were delivered in 14 patients; 8 patients received two TRUSH procedures, each separated by 1 week. Patient age ranged between 53-86 (mean: 72) years. Three patients had well-, 6 patients had moderately-, and 5 patients had poorly-differentiated adenocarcinoma of the prostate. Karnofsky status ranged from 70-90. Standard radiotherapy to the prostate and periprostatic tissues was delivered using a four-field approach with 1.8-2 Gy daily fractions delivered 5 x/week to a total dose of 67-70 Gy calculated to the minimum tumor volume. TRUSH was delivered after transperineal placement of multipoint thermometry probes by a urologist, under transrectal ultrasound guidance. Two to three thermocouple probes containing seven sensors each were placed in the prostate in an attempt to sample temperatures throughout the gland. The sensor depth from the rectal wall ranged from 5-25 mm. RESULTS: Thirty-six percent of all sensors were heated above 42.5 degrees C averaged over 30 min; and all patients had at least some sensors within the prostate heated to temperatures > or = 42.5 degrees C. The average temperature of all sensors of all sensors (T(ave) +/- s.d.) over all treatments, however, was only 41.9 degrees C +/- 0.9 degrees C over 30 min. The maximum temperature for normal tissues outside the gland was 41.1 degrees C +/- 1.3 degrees C. Treatments have been well-tolerated with few complications. Tolerance has been "good" in 17/22, "fair" in 3/22, and "treatment limiting" in 2/22 treatments secondary to position intolerance and/or pain. There has been one episode of hypotension related to narcotic administration and three episodes of rapidly resolving pain during hyperthermia treatment. Mild hematuria has occurred in 5/22, and moderate hematuria has occurred in 2/22 transperineal thermometer catheter placements. CONCLUSION: In conclusion, TRUSH is well-tolerated and has great potential for consistently heating the prostate gland. We anticipate that further equipment modifications will improve our ability to heat the entire prostate to temperatures > 42.5 degrees C.

Adenocarcinoma↗
PubMed1992

Treatment of malignant gliomas with interstitial irradiation and hyperthermia.

A Phase I study of interstitial thermoradiotherapy for high-grade supratentorial gliomas has been completed. The objective of this trial was to test the feasibility and toxicity of hyperthermia induced by ferromagnetic implants in the treatment of intracranial tumors. The patient population consisted of 16 males and 12 females, with a median age of 44 years and a median Karnofsky score of 90. Nine patients had anaplastic astrocytoma while 19 had glioblastoma multiforme. Twenty two patients were treated at the time of their initial diagnosis with a course of external beam radiotherapy (median dose 48.4 Gy) followed by an interstitial implant with Ir-192 (median dose 32.7 Gy). Six patients with recurrent tumors received only an interstitial implant (median dose 40 Gy). Median implant volume for all patients was 55.8 cc and median number of treatment catheters implanted per tumor was eighteen. A 60-minute hyperthermia treatment was given through these catheters just before and right after completion of brachytherapy. Time-averaged temperatures of all treatments were computed for sensors located within the core of (> 5 mm from edge of implant), and at the periphery of the implant (outer 5 mm). The percentage of sensors achieving an average temperature > 42 degrees C was 61% and 35%, respectively. Hyperthermia was generally well tolerated; however, there have been 11 minor toxicities, which resolved with conservative management, and one episode of massive edema resulting in the death of a patient. In addition, there were three major complications associated with the surgical implantation of the catheters. Preliminary survival analysis shows that 16 of the 28 patients have died, with a median survival of 20.6 months from diagnosis. We conclude that interstitial hyperthermia of brain tumors with ferromagnetic implants is feasible and carries significant but acceptable morbidity given the extremely poor prognosis of this patient population.

Adult↗
PubMed1992

Template-guided stereotactic implantation of malignant brain tumors for interstitial thermoradiotherapy.

A phase I trial of 25 patients with anaplastic astrocytoma or glioblastoma multiforme is described. Hyperthermia and radiation were delivered stereotactically by means of template-guided interstitial catheters loaded with ferromagnetic wires and then 192Ir seeds. Implant volumes ranged from 15 to 113 ml (mean 54 ml) involving 9-38 catheters (mean 18); parallel catheters used hexagonal spacing of 1.0-1.5 cm. Patient tolerance of these procedures was excellent. Postoperative morbidity due to additional mass effect or edema was low, but there has been one death and one complication of hydrocephalus, bleeding and symptomatic pneumocephalus, each.

Adult↗
PubMed1991

Development of scanned focussed ultrasound hyperthermia: clinical response evaluation.

Selective heating of irregularly shaped tumors at depth can now be accomplished through focussing and controlled scanning of energy deposition patterns by ultrasound. A scanned focussed ultrasound (SFUS) hyperthermia system developed at the University of Arizona has been used to deliver 220 treatments to 87 tumors in 71 patients with extracranial malignancies between October 1986 and May 1990. Patients received an average of three SFUS hyperthermia treatments, spaced weekly, during ongoing fractionated radiotherapy. The most common anatomic sites treated were the pelvis (22 patients), chest wall or breast (14), neck (8), and axilla (7), while the most common histologies were adenocarcinoma (36), squamous cell carcinoma (11), and melanoma (10). Concurrent radiotherapy was delivered (range 1000-7640 cGy, mean 4320 cGy) to 67 SFUS hyperthermia patients; 4 received concomitant chemotherapy. Tumor volumes ranged from 1-2100 cubic centimeters (mean 325 cc), and 75% were located at depths greater than 3 cm from skin. A 62% overall response rate was observed, with 22% of treated tumors demonstrating a complete response (defined as complete disappearance of treated tumor), and 40% exhibiting a partial response (defined as greater than or equal to 50% reduction in tumor volume). Dramatic local pain reduction was achieved in 42% of the tumors treated. The acute tolerance of SFUS hyperthermia was quite good, and chronic toxicities (persistent skin blisters/burns) were identified in two patients. The versatility of the SFUS system is discussed, as well as its future potential for improving control of advanced loco-regional malignancies treated with curative intent.

Combined Modality Therapy↗
PubMed1990

The crosslinking of nuclear protein to DNA using ionizing radiation.

DNA-protein complexes were generated in intact Chinese hamster ovary (CHO) cells by the use of ionizing radiation. The DNA-protein crosslinks, as measured by a filter-binding assay, occurred immediately following the irradiation, were produced in a dose-dependent manner and were reversible. The reversibility of the crosslinks in the intact cells was dependent upon general protein synthesis. Three proteins that were attached to DNA in unirradiated cells were analyzed according to the presence of DNA attached to the proteins before, during and after exposure to ionizing radiation. All three proteins contained more DNA reversibly attached to the proteins after exposure to 5 Gy ionizing radiation as compared to unirradiated cells. One of the proteins was increasingly attached to DNA using 2.5-50 Gy X-ray. These data suggest that the increased DNA-protein crosslinking observed with ionizing radiation may involve the increase in particular protein(s) crosslinked to DNA as well as an increase in the amount of DNA attached to specific proteins.

Antibodies, Monoclonal↗
PubMed1990

Interstitial thermoradiotherapy of brain tumors: preliminary results of a phase I clinical trial.

A Phase I clinical trial has been initiated to determine the feasibility, tolerance, and toxicity of interstitial thermoradiotherapy in the treatment of high-grade supratentorial brain gliomas. Hyperthermia was delivered by means of thermally-regulating ferromagnetic implants afterloaded into stereotactically placed plastic catheters. Heat treatments were given immediately before interstitial irradiation; in addition, five patients received a second heat treatment at the completion of brachytherapy. The desired target temperature for the 60-minute hyperthermia session was between 42 degrees C and 45 degrees C. Following hyperthermia, the catheters were afterloaded with Ir-192, which delivered a variable radiation dose of 14-50 Gy depending on the clinical situation. Interstitial irradiation was supplemented with external beam radiotherapy (40-41.4 Gy) in patients with previously untreated tumors. A total of 14 patients (4 males, 10 females) have been treated to date on this protocol. Eleven of the patients had a diagnosis of glioblastoma multiforme, whereas three had anaplastic astrocytoma. The mean implant volume was 61.5 cm3 (range: 9-119 cm3); the median number of interstitial treatment catheters implanted was 19 (range: 7-33). Continuous temperature monitoring was performed by means of multisensor thermocouple probes inserted in the center as well as in the periphery of the tumor. Of the 175 monitored intratumoral points, 83 (47%) had time-averaged mean temperatures of greater than 42 degrees C, and only 12 sensors (7%) exceeded a temperature of 45 degrees C. Among the 19 heat treatments attempted, there have been four minor acute toxicities, all of which resolved with conservative medical management and one major complication resulting in the demise of a patient. These preliminary results indicate that ferromagnetic implants offer a promising new approach to treating brain tumors with hyperthermia.

Adult↗
PubMed1990

Treatment planning of template-guided stereotaxic brain implants.

We have initiated a Phase I clinical trial of interstitial hyperthermia induced with inductively heated ferromagnetic implants in combination with Ir-192 implants for glioblastomas and anaplastic astrocytomas of the brain. For speed and accuracy of the implant procedure, and to control the radiation and thermal dose, a stereotaxic frame is used to position a template. We have modified the Brown-Roberts-Wells frame to be used with a variety of templates which we designed. On the morning of the implant procedure, a CT scan is done, and a CT-based treatment plan is then completed before the patient goes to the operating room. We also describe the CT-based treatment planning system developed to accommodate the template-guided implant and illustrate its clinical use.

Brachytherapy↗
PubMed1990

Possible relationship between chromosome alterations and in vitro cellular radiosensitivity of human malignant melanoma.

In the present study, in vitro radiation survival analysis was performed on 8 human malignant melanoma cell lines with defined karyotypes. Exponentially growing cells were irradiated to doses of 0 to 8 Gy and examined for soft agar clonogenicity. Two groups emerged from this analysis: 4 cell lines with a small shoulder (extrapolation number, n less than 2) and 4 cell lines with a large shoulder (n greater than 2). Of possible significance, 4/4 cell lines with extrapolation numbers greater than 2 demonstrated clonal structural abnormalities of chromosome 7. In contrast, 3/4 cell lines with extrapolation numbers less than 2 had no structural abnormalities of chromosome 7. These very preliminary results suggest that structural alterations of chromosome 7 may be associated with melanoma tumors with high extrapolation numbers.

Cell Line↗
PubMed1988

Small-cell osteosarcoma: correlation of in vitro and clinical radiation response.

Small-cell osteosarcoma is an entity which shares some clinical and pathological features with both classic osteosarcoma and Ewing's sarcoma of bone. While noted to be "not radiosensitive" when first described, a retrospective review the National Cancer Institute experience of five patients with small-cell osteosarcoma treated with radiation therapy following biopsy (three pts) or limited excision (two pts) showed local control in all five patients with two long-term disease-free survivors (12, 18 years). This compares to three patients treated with surgery alone where one patient failed locally and one patient is a long-term disease-free survivor (7 years). We have studied the in vitro radiation response of a recently established small-cell osteosarcoma cell line (TC-252) and compared its response with that of a classic osteosarcoma cell line (U2-OS) and an Ewing's sarcoma cell line (5838). The small-cell osteosarcoma line responded with a similar Do and extent of PLDR compared to the Ewing's line and was different from the in vitro radiation response of classic osteosarcoma. Based on this small clinical series and the in vitro radiation studies, we conclude that small-cell osteosarcoma is a radioresponsive tumor. Definitive radiation therapy or conservative surgery plus radiation therapy are effective alternative therapeutic options, compared to ablative surgery, for the local treatment of this uncommon bone tumor of children and young adults.

Adolescent↗
PubMed1987

Treatment of pelvic sarcomas in adolescents and young adults with intensive combined modality therapy.

Adolescent and young adult patients with pelvic sarcomas continue to have a poor prognosis with standard combination chemotherapy and local irradiation. In addition to a significant risk of local failure, these patients are at high risk for systemic relapse. Twenty-three consecutive patients with Ewing's sarcoma, alveolar rhabdomyosarcoma, undifferentiated sarcoma, or malignant peripheral neuroepithelioma originating in the pelvis were treated with short, intensive combined modality therapy. This approach integrates 5 cycles of VADRIAC chemotherapy (Vincristine, Adriamycin, Cyclophosphamide) with high dose irradiation to the primary lesion (55-60 Gy) and sites of gross metastatic disease (45-50 Gy). Following achievement of a complete response, intensification therapy consisting of total body irradiation (TBI) (8.0 Gy), high dose VADRIAC chemotherapy, and autologous bone marow transplantation is given. All therapy is completed within 6-7 months. No maintenance chemotherapy is given; no surgery is intended. Of the twenty-three patients with pelvic sarcomas treated on this combined modality protocol, 22 achieved a complete remission. Local control was achieved and maintained in all twenty-three patients. With a median follow-up of 21 months since initiation of treatment, there have been nine relapses (all systemic). Seven relapses occurred among the thirteen patients who presented with overt metastatic disease and the other two relapses were among the ten patients with localized disease at presentation. All seven metastatic patients who relapsed have died, whereas both of the relapsed localized patients remain alive. Acute and late toxicities have been acceptable using this aggressive combined modality approach. Induction chemotherapy had a significant impact on reduction of the typically large (greater than 10 cm diameter) soft tissue mass associated with these pelvic tumors, thus facilitating achievement of local control by high dose irradiation. Of 18 patients with measureable soft tissue tumor, all experienced a partial response (greater than 50% reduction in size) following the initial two cycles of chemotherapy given prior to local irradiation. In conclusion, this short, intensive chemoradiotherapeutic regimen is highly effective in controlling the primary lesion (100% local control) and inducing a complete response in a high proportion (96%) of these high risk pediatric and young adult patients with pelvic sarcomas. The role of TBI as "systemic" adjuvant therapy to control micrometastatic disease is discussed as still under investigation.

Adolescent↗
PubMed1981

Urinary excretion levels of unconjugated pterins in cancer patients and normal individuals.

Urinary excretion levels of seven unconjugated pterins in healthy individuals and in cancer patients, most of whom were undergoing chemotherapy, were measured utilizing a newly developed high-pressure liquid chromatographic system. Excretion of pterins in the control group appears to be under strict metabolic control as the values obtained were confined within a small range. When the mean excretion levels in control subjects were compared with those in cancer patients, we found a significant increase in the excretion of xanthopterin, neopterin and pterin and a significant decrease in isoxanthopterin by cancer patients. Biopterin levels, on the other hand, were found only slightly but not significantly increased, whereas pterin-6-carboxylic acid and 6-hydroxymethylpterin were found to be excreted in approximately equal amounts in both groups. Urinary excretion levels of pterins were monitored for a period of nine months in a patient being treated with chemotherapy for metastatic ovarian carcinomatosis. We found that the excretion pattern of pterins appeared to correlate with the clinical status of the patient. These results indicate that a definite imbalance in pterin, and possibly folate metabolism, is associated with the presence of malignant diseases.

Adult↗
PubMed1980

Quantitative determination of pterins in biological fluids by high-performance liquid chromatography.

During our continuing study of pteridine metabolism, the need arose for a more rapid and quantitative determination of pterins in biological fluids. By adopting and modifying previously developed techniques, we have obtained a rapid and sensitive method that allows the simultaneous determination of eight different pterins in human urine and blood. When examined over a 10-day period, the levels of pterins excreted by a normal individual averaged the following values expressed in picomoles per mg of creatinine: biopterin, 9104; neopterin, 6018; xanthopterin, 6561; pterin, 1136; isoxanthopterin, 636; pterin-6-carboxylate, 483; and 6-hydroxymethylpterin, 315. Moreover, 6-hydroxymethylpterin and pterin-6-carboxaldehyde were detected for the first time in the blood of normal individuals.

Chromatography, High Pressure Liquid↗
PubMed1979

Separation of unconjugated pteridines by high-pressure cation-exchange liquid chromatography.

In the course of determining the levels of unconjugated pteridines occurring in various biological fluids, such as urines, plasma and tissue culture media, a method has been developed for the separation and quantitative determination in the picomole range of ten 2-amino-4-hydroxy substituted pteridines. This method involves separation by high-pressure cation-exchange liquid chromatography and fluorescence detection of the eluted compounds at 450 nm. Optimal separation was obtained by isocratic elution with 3 mM phosphoric acid-7% methanol-1% acetonitrile at a flow-rate of 2 ml/min or with 1 mM ammonium dihydrogenphosphate pH 2.8-7% methanol-5% acetonitrile at a flow-rate of 1.5 ml/min. With either solvent, the order of elution of the compounds is: isoxanthopterin, pterin-6-carboxylic acid, xanthopterin, pterin-6-carboxaldehyde, D-erythro-neopterin, L-threo-neopterin, biopterin, 6-hydroxymethylpterin, pterin, 6-methylpterin. In addition, a systemic investigation of the effects of ammonium ion concentration and pH of the solvent as well as column temperature on the separation of these compounds was also conducted.

Cation Exchange Resins↗