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Biomedical subjects

G S Bauman

Publications and source records attributed to G S Bauman.

At least 19 recordsLinked to original sources
PubMed2005

Dosimetric impact of image-guided 3D conformal radiation therapy of prostate cancer.

The goal of this work is to quantify the impact of image-guided conformal radiation therapy (CRT) on the dose distribution by correcting patient setup uncertainty and inter-fraction tumour motion. This was a retrospective analysis that used five randomly selected prostate cancer patients that underwent approximately 15 computed tomography (CT) scans during their radiation treatment course. The beam arrangement from the treatment plan was imported into each repeat CT study and the dose distribution was recalculated for the new beam setups. Various setup scenarios were then compared to assess the impact of image guidance on radiation treatment precision. These included (1) daily alignment to skin markers, thus representing a conventional beam setup without image guidance, (2) alignment to bony anatomy for correction of daily patient setup error, thus representing on-line portal image guidance, and (3) alignment to the 'CTV of the day' for correction of inter-fraction tumour motion, thus representing on-line CT or ultrasound image guidance. Treatment scenarios (1) and (3) were repeated with a reduced CTV to PTV margin, where the former represents a treatment using small margins without daily image guidance. Daily realignment of the treatment beams to the prostate showed an average increase in minimum tumour dose of 1.5 Gy, in all cases where tumour 'geographic miss' without image guidance was apparent. However, normal tissue sparing did not improve unless the PTV margin was reduced. Daily realignment to the tumour combined with reducing the margin size by a factor of 2 resulted in an average escalation in tumour dose of 9.0 Gy for all five static plans. However, the prescription dose could be escalated by 13.8 Gy when accounting for changes in anatomy by accumulating daily doses using nonlinear image registration techniques. These results provide quantitative information on the effectiveness of image-guided radiation treatment of prostate cancer and demonstrate that the dosimetric impact is patient dependent.

Artifacts↗
PubMed2005

Validation of contour-driven thin-plate splines for tracking fraction-to-fraction changes in anatomy and radiation therapy dose mapping.

The goal of this study is to validate a deformable model using contour-driven thin-plate splines for application to radiation therapy dose mapping. Our testing includes a virtual spherical phantom as well as real computed tomography (CT) data from ten prostate cancer patients with radio-opaque markers surgically implanted into the prostate and seminal vesicles. In the spherical mathematical phantom, homologous control points generated automatically given input contour data in CT slice geometry were compared to homologous control point placement using analytical geometry as the ground truth. The dose delivered to specific voxels driven by both sets of homologous control points were compared to determine the accuracy of dose tracking via the deformable model. A 3D analytical spherically symmetric dose distribution with a dose gradient of approximately 10% per mm was used for this phantom. This test showed that the uncertainty in calculating the delivered dose to a tissue element depends on slice thickness and the variation in defining homologous landmarks, where dose agreement of 3-4% in high dose gradient regions was achieved. In the patient data, radio-opaque marker positions driven by the thin-plate spline algorithm were compared to the actual marker positions as identified in the CT scans. It is demonstrated that the deformable model is accurate (approximately 2.5 mm) to within the intra-observer contouring variability. This work shows that the algorithm is appropriate for describing changes in pelvic anatomy and for the dose mapping application with dose gradients characteristic of conformal and intensity modulated radiation therapy.

Algorithms↗
PubMed2004

Tracking the dose distribution in radiation therapy by accounting for variable anatomy.

The goal of this research is to calculate the daily and cumulative dose distribution received by the radiotherapy patient while accounting for variable anatomy, by tracking the dose distribution delivered to tissue elements (voxels) that move within the patient. Non-linear image registration techniques (i.e., thin-plate splines) are used along with a conventional treatment planning system to combine the dose distributions computed for each 3D computed tomography (CT) study taken during treatment. For a clinical prostate case, we demonstrate that there are significant localized dose differences due to systematic voxel motion in a single fraction as well as in 15 cumulative fractions. The largest positive dose differences in rectum, bladder and seminal vesicles were 29%, 2% and 24%, respectively, after the first fraction of radiation treatment compared to the planned dose. After 15 cumulative fractions, the largest positive dose differences in rectum, bladder and seminal vesicles were 23%, 32% and 18%, respectively, compared to the planned dose. A sensitivity analysis of control point placement is also presented. This method provides an important understanding of actual delivered doses and has the potential to provide quantitative information to use as a guide for adaptive radiation treatments.

Humans↗
PubMed2001

Multidisciplinary management of adult anaplastic oligodendrogliomas and anaplastic mixed oligo-astrocytomas.

Once thought to be rare, oligodendroglial tumors might actually represent up to 25% of primary glial neoplasms. In recent years, the histologic criteria for the diagnosis of oligodendroglioma have been broadened to include most small cell, monomorphic glial neoplasms. These refinements have led to an increased recognition of oligodendroglial neoplasms, but uniform definitions of pure versus mixed oligodendroglioma as well as the criteria for high-grade (anaplastic) versus low-grade tumors remain elusive. From a prognostic standpoint, the presence of an oligodendroglial component in a malignant glioma predicts longer survivals times for patients treated with surgery, and radiation therapy with or without chemotherapy. High rates of response to PCV (procarbazine, CCNU and Vincristine) chemotherapy also have been noted among patients with anaplastic oligodendroglial neoplasms. Ongoing prospective trials seek to clarify the role of PCV chemotherapy when added to radiation therapy and surgery. In addition, the role of molecular markers as diagnostic aides and guides to therapy and prognosis are being explored for patients with pure and mixed anaplastic oligodendroglial tumors.

Adult↗
PubMed2001

Nontraumatic osteonecrosis after chemotherapy for testicular cancer: a systematic review.

Nontraumatic osteonecrosis is a well-documented late complication of chemotherapy for hematologic malignancies, with prolonged corticosteroid exposure implicated. Reports of this treatment complication in patients treated with chemotherapy for solid tumors are sparse. We reviewed our institutional experience and the published medical literature to explore an association between chemotherapy for testicular cancer and the occurrence of nontraumatic osteonecrosis. Two databases of men with testicular cancer were reviewed. Search of the medical literature included MEDLINE, CANCERLIT, and EMBASE. Two of 107 men with testicular cancer treated with chemotherapy at our center were identified with nontraumatic osteonecrosis. Literature review identified 14 reports describing patients with 39 solid tumors with osteonecrosis after chemotherapy. Of 38 adults, 28 had testicular cancer and 6 had breast cancer. All patients with testicular cancer had received cisplatin, vinblastine, and bleomycin, or bleomycin, etoposide, and cisplatin. Twenty-seven of 28 had received corticosteroids. Diagnosis was subacute in three and delayed a mean of 26 months (range, 12-47 months) in 26. The femoral head was involved in 26 patients, with bilateral involvement in 18. Crude incidence was 1.5% (95% CI, 0.9-2.1). Nontraumatic osteonecrosis is an infrequent but disabling late complication of cancer chemotherapy reported most commonly in adult patients with testicular cancer. Corticosteroid exposure makes this association plausible.

Adult↗
PubMed2000

Allelic loss of chromosome 1p and radiotherapy plus chemotherapy in patients with oligodendrogliomas.

INTRODUCTION: Allelic loss of the short arm of chromosome 1 predicts radiographic response to chemotherapy and long overall survival times in patients with anaplastic oligodendrogliomas. Using a database of patients with oligodendrogliomas in whom chromosome 1p status was known, we explored whether allelic loss of 1p also predicted longer duration of tumor control when radiotherapy was part of the initial treatment of these patients. MATERIALS AND METHODS: We measured progression-free survival following radiotherapy in a cohort of patients with World Health Organization (WHO) Grade II and WHO Grade III oligodendrogliomas. The effects on progression-free survival of patient age, Karnofsky performance score (KPS), tumor grade when irradiated and chromosome 1p status were examined by univariate and multivariate statistical analyses. For the subset of patients with newly diagnosed anaplastic oligodendrogliomas, relationships between use of chemotherapy, chromosome 1p status and progression-free survival were also examined. RESULTS: Fifty-five patients (29 male, 26 female; ages 18-75 years; median, 44 years; KPS 50-90, median 80) were irradiated for either a WHO Grade II (n = 19) or Grade III (n = 36) oligodendroglioma. Twenty-eight patients had chemotherapy immediately prior to radiotherapy, and 27 had chemotherapy at progression following radiotherapy. The median radiation dose was 54 Gy in 30 fractions. Loss of heterozygosity (LOH) at chromosome 1p was evident in 36 tumors and absent in 19. Overall median progression-free survival after radiotherapy was 40.4 months. Median progression-free survival was 55.0 months for patients whose tumors harbored 1p loss vs. 6.2 months for those patients whose tumors retained both copies of chromosome 1p (p < 0.001). On both univariate and multivariate analyses, chromosome lp loss was the principal independent predictor of longer progression-free survival for patients with Grade II and III oligodendrogliomas. For Grade III oligodendrogliomas, chemotherapy as an adjunct to radiotherapy prolonged tumor control for those patients whose tumors harbored allelic loss of chromosome 1p (p = 0.004). CONCLUSION: These data suggest allelic loss of chromosome 1p in patients with oligodendroglial neoplasms predicts longer progression-free survival among patients receiving radiotherapy +/- chemotherapy as part of their initial treatment. Chromosome 1p loss may be an important stratification variable in future therapeutic trials of oligodendroglioma.

Adolescent↗
PubMed2000

Simulation for localized prostate cancer: a comparison of urethrography techniques.

Forty-five patients having conventional fluoroscopic, or CT scan simulation of the prostate gland from January 1999 to June 1999 were studied. Patients were consecutively assigned (not randomized) in groups of 15 to 3 different urethrography techniques: air contrast alone (group 1), hypaque contrast alone (group 2), and xylocaine jelly and hypaque contrast (group 3). Outcome measures were pain scores, visualization of the apex (indicated by urethrogram tip), and frequency of corrections necessary on the basis of verification port films. Group 3 patients had the lowest mean pain score and required fewer lateral setup corrections at the time of portal imaging on the first day of treatment. A comparison of radiographs also revealed that group 2 and 3 patients (hypaque contrast) had better delineation of the prostatic anatomy than group 1 patients (air contrast). We found that of the 3 techniques tested, urethrography utilizing xylocaine jelly and hypaque was associated with the least amount of pain, least amount of corrective shifts, and best quality in defining the prostatic anatomy.

Contrast Media↗
PubMed2000

Palliative chemoirradiation for transitional carcinoma of the bladder: a case report.

Palliation of locally advanced transitional carcinoma of the bladder is a major problem that has not been well investigated. Recent reports from the curative literature suggest improved tumor response rates using platinum based chemoirradiation over radiotherapy alone. Because of the poor symptomatic responses seen with conventional palliative radiotherapy, we have been treating selected cases of locally advanced bladder carcinoma palliatively with low dose chemoirradiation. We present a case of an elderly female treated this way with an excellent clinical response.

Aged↗
PubMed1999

Analysis of the clinical benefit of 5-fluorouracil and radiation treatment in locally advanced pancreatic cancer.

PURPOSE: To assess the palliative benefit of 5-fluorouracil (5-FU) and radiotherapy in patients with surgically unresectable localized pancreatic cancer. METHODS AND MATERIALS: Twenty-five patients with locally advanced surgically unresectable symptomatic pancreatic cancer received 5-FU chemotherapy and local radiation therapy. They were retrospectively reviewed in regard to their clinical benefit response (a composite of measurement of pain assessment, weight, and Karnofsky performance status [KPS]), as well as radiological response, time to progression, and overall survival. RESULTS: Median survival for the 25 patients was 9 months and median progression-free survival was 6 months. Thirty-two percent of patients survived in excess of 1 year. Analgesic requirements increased >50% in 2 patients and KPS deteriorated in 10 patients. Of the 13 remaining patients, 2 sustained a >7% weight loss and 2 gained weight post-treatment. Six patients improved in one parameter of analgesic consumption, weight loss or KPS without deteriorating in any others. Thus, the clinical benefit response index for 5-FU-radiation was 6/25 (24%). In terms of tumor response, 8 patients (44%) demonstrated a reduction in tumor volume post-treatment, 4 of whom (22%) experienced a >50% reduction. Four additional patients had radiologically stable disease. CONCLUSION: In this retrospective analysis, the clinical benefit response index for 5-FU-radiation was 24%, a value similar to the 23.8% reported for single agent gemcitabine. The median survival of 7 months was also similar to the 5.65 months reported for gemcitabine. The radiological partial response rate of 22% and the 1-year survival of 32% were higher for 5-FU-radiation than the reported values for gemcitabine. A randomized trial would be necessary to compare 5-FU-radiation to gemcitabine directly; however, from this review it did not appear that the overall palliative benefit of 5-FU-radiation was inferior to gemcitabine.

Adult↗
PubMed1999

Effects of radiation on a model of malignant glioma invasion.

We sought to characterize the effects of radiation alone and in combination with BCNU and dexamethasone on malignant glioma invasion. A model of malignant glioma invasion into a gel matrix of collagen type I was used to characterize response to radiation treatment for four malignant glioma cell lines (C6, U251, U373, A172) and nine primary human glioblastoma explants. A radiation dose dependent inhibition of invasion was noted for the C6 astrocytoma cell line but not the other cell lines or explants. Addition of BCNU and dexamethasone to radiation produced additional inhibition of invasion among the cell lines and explants but could not suppress invasion entirely.

Antineoplastic Agents, Alkylating↗
PubMed1998

Preoperative radiation with concurrent 5-fluorouracil continuous infusion for locally advanced unresectable rectal cancer.

BACKGROUND AND PURPOSE: To determine the percentage of complete responders and the resectability rate for patients with locally advanced carcinoma of the rectum treated by 5-fluorouracil (5-FU) infusional chemotherapy and pelvic radiation. MATERIALS AND METHODS: Between October 1992 and June 1996, 29 patients with a diagnosis of locally advanced unresectable rectal cancer received preoperative 5 FU by continuous intravenous infusion at a dose of 225 mg/m2/day concurrent with pelvic radiation (median 54 Gy/28 fractions). All patients were clinical stage T4 on the bases of organ invasion or tumor fixation. Median time for surgical resection was 6 weeks. RESULTS: Median follow-up for the group was 28 months (range 5-57 months). Six patients were felt to be persistently unresectable or developed distant metastases and did not undergo surgical resection. Of the 29 patients, 23 proceeded to surgery, 18 were resectable for cure, 13 by abdominoperineal resection, 3 by anterior resection and 2 by local excision. Of the 29 patients, 4 (13%) had a complete response, and 90% were clinically downstaged. Of the 18 resected patients, 1 has died of his disease, 17 are alive, and 15 disease-free. The regimen was well tolerated; there was only one treatment-related complication, a wound dehiscence. CONCLUSION: The combination of 5 FU infusion and pelvic radiation in the management of locally advanced rectal cancer is well tolerated and provides a baseline for comparison purposes with future combinations of newer systemic agents and radiation.

Adenocarcinoma↗
PubMed1998

Postoperative radiotherapy for Stage I/II seminoma: results for 212 patients.

PURPOSE: A retrospective review of patients with Stage I and II seminoma treated at a regional cancer center was performed to assess the long term efficacy and toxicity associated with post operative radiotherapy. METHODS AND MATERIALS: Between 1950 and 1995, 212 patients seen at the London Regional Cancer Centre received adjuvant radiotherapy following orchiectomy for Stage I (169) and II (43) seminoma. Median follow-up for the group was 7.5 years. RESULTS: Progression free, cause specific, and overall survival were 95%, 98%, and 95% at 5 years, and 94%, 98%, and 94% at 10 years respectively. An increased risk of failure was noted among patients with bulky Stage II disease. No other prognostic factors for relapse were identified. Late toxicity was uncommon with only 12/212 (6%) developing any late GI toxicity potentially attributable to radiotherapy. The incidence of second malignancies (excluding second testicular tumors) was 6/212 (actuarial:1%, 1%, 6% at 5,10,15 years respectively). There was a trend toward increased acute complications for patients treated with larger volumes of radiation. No prognostic factors associated with increased risk of late toxicity or second malignancy were identified, likely a consequence of the small number of these events. CONCLUSION: Survival and toxicity were comparable to that reported in the literature. Post-operative radiotherapy remains a safe and efficacious adjuvant treatment for Stage I and early Stage II seminoma.

Adolescent↗
PubMed1998

Low-grade gliomas in children: tumor volume response to radiation.

Object. The authors conducted a retrospective review to examine and document the frequency, degree, and timing of the radiologically confirmed response to radiotherapy of low-grade gliomas in children. Methods. Between 1963 and 1995, 80 patients 17 years of age or younger were referred to the London Regional Cancer Centre in London, Ontario, after diagnosis of a low-grade glioma. All patients underwent surgical resection or biopsy procedures and 47 underwent radiotherapy (40 postoperatively and seven at the time of tumor progression). Nineteen patients with residual measurable lesions who received radiation therapy were selected for volumetric analysis of tumor response to this treatment. The extent and timing of response to radiation were determined by the process of comparing postoperative, preirradiation computerized tomography (CT) scans with postirradiation, follow-up CT scans. For one patient the comparison was made by using serial magnetic resonance images. Residual tumor was found on postoperative CT scans in all cases. The mean preradiotherapy tumor volume was 17.1 cm(3), and the postradiotherapy volume was reduced to a mean of 11.5 cm(3). A reduction in tumor was demonstrated in eight patients by the time of their first postirradiation follow-up CT scan and in two patients a slower reduction in volume over time was shown, bringing the total number of "responders" to 10. In five of these 10 patients the tumor had shown a maximum response by the time of the first postirradiation CT scan; the median time to response was 3.3 months. A 25% or greater reduction in tumor volume was seen in eight (42%) of the 19 patients. A 50% or greater reduction was noted in five (26%) of the patients. A complete response was demonstrated at 7, 12, and 15 months, and 5 years, respectively, in four patients (21%). One responder's tumor eventually increased in size after radiotherapy and he died of his disease. The magnitude of the radiographically demonstrated response to radiation did not correlate significantly with clinical outcome (that is, survival or symptom improvement). Conclusions. On the basis of this CT scan analysis of the response of low-grade gliomas in children to radiotherapy, the authors suggest that these lesions respond to radiation, as demonstrated by tumor shrinkage on serial imaging. Major or complete responses occur occasionally. However, low-grade gliomas in children mimic other benign brain tumors such as pituitary adenomas and meningiomas in that, although growth is frequently arrested after radiotherapy, residual tumor can persist for many years, illustrating that tumor shrinkage may not be a good measure of treatment efficacy. Nevertheless, radiation therapy can result in improvement of clinical symptomatology in association with or independent of visible tumor reduction. As radiation treatment techniques become increasingly conformal and because studies indicate that lower doses of radiation may be equally effective, improvement of symptoms may be an important consideration when weighing treatment options, particularly in patients with residual or unresectable disease.

Journal Article↗
PubMed1998

Bihemispheric malignant glioma: one size does not fit all.

Recurrence of malignant glioma following radiotherapy most commonly occurs in close proximity to the original contrast enhancing CT/MRI tumor volume. For this reason current radiation planning favors focal radiotherapy fields designed to cover the preoperative tumor contrast enhancing volume +/- surrounding edema with a 2-4 centimetre margin. Two patients with bifrontal malignant gliomas treated with such radiotherapy fields experienced out of field tumor progression while on treatment. Posterior extension along the corpus callosum, not evident on pretreatment imaging, was hypothesized as the cause of the geographic miss. The literature documenting recurrence patterns of malignant glioma following radiotherapy support focal field radiotherapy fields for most patients with malignant glioma. Reporting bias may exist in the literature, however, due to the whole brain radiotherapy used in older series reporting recurrence patterns and exclusion of patients with bihemispheric or more locally extensive tumors in more modern series. Tumor location and pattern of growth at presentation may be important factors in predicting patterns of spread and relapse after radiotherapy.

Adult↗
PubMed1998

Low-grade gliomas in children: tumor volume response to radiation.

OBJECT: The authors conducted a retrospective review to examine and document the frequency, degree, and timing of the radiologically confirmed response to radiotherapy of low-grade gliomas in children. METHODS: Between 1963 and 1995, 80 patients 17 years of age or younger were referred to the London Regional Cancer Centre in London, Ontario after diagnosis of a low-grade glioma. All patients underwent surgical resection or biopsy procedures and 47 underwent radiotherapy (40 postoperatively and seven at the time of tumor progression). Nineteen patients with residual measurable lesions who received radiation therapy were selected for volumetric analysis of tumor response to this treatment. The extent and timing of response to radiation were determined by the process of comparing postoperative, preirradiation computerized tomography (CT) scans with postirradiation, follow-up CT scans. For one patient the comparison was made by using serial magnetic resonance images. Residual tumor was found on postoperative CT scans in all cases. The mean preradiotherapy tumor volume was 17.1 cm3, and the postradiotherapy volume was reduced to a mean of 11.5 cm3. A reduction in tumor volume was demonstrated in eight patients by the time of their first postirradiation follow-up CT scan and in two patients a slower reduction in volume over time was shown, bringing the total number of "responders" to 10. In five of these 10 patients the tumor had shown a maximum response by the time of the first postirradiation CT scan; the median time to response was 3.3 months. A 25% or greater reduction in tumor volume was seen in eight (42%) of the 19 patients. A 50% or greater reduction was noted in five (26%) of the patients. A complete response was demonstrated at 7, 12, and 15 months, and 5 years, respectively, in four patients (21%). One responder's tumor eventually increased in size after radiotherapy and he died of his disease. The magnitude of the radiographically demonstrated response to radiation did not correlate significantly with clinical outcome (that is, survival or symptom improvement). CONCLUSIONS: On the basis of this CT scan analysis of the response of low-grade gliomas in children to radiotherapy, the authors suggest that these lesions respond to radiation, as demonstrated by tumor shrinkage on serial imaging. Major or complete responses occur occasionally. However, low-grade gliomas in children mimic other benign brain tumors such as pituitary adenomas and meningiomas in that, although growth is frequently arrested after radiotherapy, residual tumor can persist for many years, illustrating that tumor shrinkage may not be a good measure of treatment efficacy. Nevertheless, radiation therapy can result in improvement of clinical symptomatology in association with or independent of visible tumor reduction. As radiation treatment techniques become increasingly conformal and because studies indicate that lower doses of radiation may be equally effective, improvement of symptoms may be an important consideration when weighing treatment options, particularly in patients with residual or unresectable disease.

Adolescent↗
PubMed1997

Primary intracerebral osteosarcoma: a case report.

Primary intracerebral sarcomas are rare tumors. Malignant fibrous histiocytoma and fibrosarcoma are the predominant histologies. A 3 year old girl with a primary, intraparenchymal cerebral osteosarcoma, the second case reported in the literature, is described. Partial surgical resection, systemic chemotherapy and radio-surgery has provided tumor control at 18 months. Treatment issues are discussed.

Brain Neoplasms↗