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Lawrence W Davis

Publications and source records attributed to Lawrence W Davis.

12 recordsLinked to original sources
PubMed2005

Intracranial arteriovenous malformations treated utilizing a linear accelerator-based patient rotator or commercially available radiosurgery system.

PURPOSE: To report a single-institution experience with intracranial arteriovenous malformations (AVMs) treated utilizing a linear accelerator-based patient rotator (PR) or BrainLAB (BL) radiosurgery system (BrainLAB AG, Heimstetten, Germany). METHODS AND MATERIALS: Since 1989, 84 evaluable patients were treated. PR patients (n = 45) were planned/localized on the basis of biplane angiography and treated between 1989 and 2000. BL patients (n = 39) were planned/localized on the basis of CT/MRI and treated since 2000. Kaplan-Meier analyses of survival, nidus obliteration (NO), and any radiographic improvement were undertaken with Cox regression of dose and volume effects. RESULTS: No significant complication, survival, previous embolization incidence, AVM location or size differences existed between BL/PR patients. The groups differed significantly in prescribed dose (PR: 16.2 Gy, BL: 17.3 Gy, p = 0.004) and isodose (PR: 62%, BL: 79%, p < 0.0001). Estimated 2-year NO rate was 87% for BL patients, 12% for PR patients (p < 0.0001). Ultimate PR NO rate was 67% at 6 years. Dose (p = 0.037) and isodose (p = 0.014) significantly affected PR NO outcome; volume was of borderline significance (p = 0.069). No factors significantly affected BL outcome. Analyses of small (< or = 4.0 cm3), high-dose (> or = 17.0 Gy) PR patients (PR1 group) vs. BL patients still demonstrated greater NO (p = 0.04) and radiographic improvement (p = 0.0004) rates for the BL group. PR1 patients had a 76% 3-year NO rate. CONCLUSIONS: BL-based radiosurgery achieved a high NO rate, the PR method did not. Differences in outcomes between PR/BL groups may be due to localization methods or an inherent advantage with the BL system.

Adult↗
PubMed2005

Comparison of CT- and FDG-PET-defined gross tumor volume in intensity-modulated radiotherapy for head-and-neck cancer.

PURPOSE: To compare the gross tumor volume (GTV) identified on CT to that obtained from fluorodeoxyglucose (FDG) positron emission tomography (PET) and determine the differences in volume and dose coverage of the PET-GTV when the CT-GTV is used for radiotherapy planning. METHODS AND MATERIALS: A total of 40 patients with intact squamous cell carcinoma arising in the head-and-neck region underwent intensity-modulated radiotherapy (IMRT) at one department. All patients underwent CT simulation for treatment planning followed by PET-CT in the treatment position. CT simulation images were fused to the CT component of the PET-CT images. The GTV using the CT simulation images was contoured (CT-GTV), as was the GTV based on the PET scan (PET-GTV). The IMRT plans were obtained using the CT-GTV. RESULTS: The PET-GTV was smaller, the same size, and larger than the CT-GTV in 30 (75%), 3 (8%), and 7 (18%) cases respectively. The median PET-GTV and CT-GTV volume was 20.3 cm(3) (range, 0.2-294) and 37.2 cm(3) (range, 2-456), respectively. The volume of PET-GTV receiving at least 95% of the prescribed dose was 100% in 20 (50%), 95-99% in 10 (25%), 90-94% in 3 (8%), 85-89% in 1 (3%), 80-84% in 2 (5%), 75-79% in 1 (3%), and <75% in 3 (8%) cases. The minimal dose received by 95% of the PET-GTV was >/=100% in 19 (48%), 95-99% in 11 (28%), 90-94% in 5 (13%), 85-89% in 2 (5%), and <75% in 3 (8%) cases. CONCLUSION: The PET-GTV was larger than the CT-GTV in 18% of cases. In approximately 25% of patients with intact head-and-neck cancer treated using IMRT, the volume of PET-GTV receiving at least 95% of the prescribed dose and minimal dose received by 95% of the PET-GTV were less than optimal.

Adult↗
PubMed2005

F-18 FDG PET-CT fusion in radiotherapy treatment planning for head and neck cancer.

BACKGROUND: The fusion of fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) with CT scans has been shown to improve diagnostic accuracy and staging in non-small cell lung cancer. We report on the influence of PET-CT fusion on the management of patients with head and neck cancer. METHODS: Thirty-six patients with intact primary head and neck cancers treated with radiation therapy (RT) received PET-CT as part of treatment planning. Workup before PET-CT included a contrast-enhanced CT scan of the head and neck and chest X-ray; patients with nasopharyngeal and paranasal sinus primary tumors also underwent MRI. RESULTS: Changes in TNM score and American Joint Committee on Cancer stage occurred in 13 patients (36%) and five patients (14%), respectively, based on PET-CT. RT volume and dose were altered in five patients (14%) and four patients (11%), respectively. Five patients initially were seen with carcinoma of unknown primary, and PET-CT confirmed oropharyngeal primary tumors in two. PET-CT data also detected a synchronous lung cancer in one patient. CONCLUSION: PET-CT fusion may have a significant impact on staging and determination of RT treatment volume and dose.

Adult↗
PubMed2005

Measurements of secondary neutron dose from 15 MV and 18 MV IMRT.

Secondary neutron dose-equivalents were determined for conventional and intensity modulated radiation therapy (IMRT) prostate treatments for 15 and 18 MV X-ray beams. Conventional and IMRT treatment plans were generated to deliver 45 Gy to the prostate, seminal vessicles and external and internal iliac lymph nodes. Neutron spectra were determined by unfolding measurements from a TLD-based Bonner sphere system. Treatments using 18 MV IMRT and conventional plans result in neutron ambient dose-equivalents of 687 and 112 mSv, respectively. Delivery of the 15 MV IMRT and conventional plans results in neutron ambient dose-equivalents of 327 and 52 mSv, respectively. The data illustrate that using lower photon energies for IMRT reduces the secondary neutron dose, while still achieving comparable treatment volume coverage and sparing critical normal tissue.

Body Burden↗
PubMed2004

Extra-target doses in children receiving multileaf collimator (MLC) based intensity modulated radiation therapy (IMRT).

PURPOSE: To investigate the extra-target doses using intensity modulated radiation therapy (IMRT). MATERIALS AND METHODS: Thirteen children underwent multileaf collimator (MLC)-based IMRT. Treatment site was head and neck or brain in eight (Group I), trunk in two (Group II), and abdomen/pelvis in three (Group III). Thermoluminescent dosimeters (TLD) were placed at the thyroid gland, breast, and testis. A control group of seven children received conventional RT and TLD measurements. RESULTS: For the eight Group I children, the median dose equivalent measurements during the course of IMRT to the thyroid, breast, and testis were 348 mSv, 110 mSv, and 30 mSv, respectively. For the two Group II patients, the measurements to the thyroid ranged from 1,525 to 2,449 mSv while for the testis was 62 mSv. For the Group III patients, the median dose equivalent measurements to the thyroid, breast, and testis were 182 mSv, 406 mSv, and 159 mSv. The median dose equivalent measurements to the thyroid, breast, and testis for Group I children were 300 mSv, 120 mSv, and 75 mSv. The Group II conventional patient had a measurement of 180 mSv, 80 mSv, and 80 mSv to the thyroid, breast, and testis. For the Group III conventional cases, the median dose equivalent measurements were 192 mSv, 496 mSv, and 434 mSv. CONCLUSIONS: No significant difference was seen in the thyroid and breast doses of children receiving MLC-based IMRT compared to conventional RT for the treatment of head and neck/brain and abdominal/pelvic tumors.

Abdominal Neoplasms↗
PubMed2004

Black and white patients fare equally well when treated with postlumpectomy radiotherapy.

PURPOSE: Some previous studies have demonstrated that black patients have inferior local-regional control and disease-free survival when treated with postlumpectomy radiotherapy. The intention of this study was to analyze the same outcomes with a larger series of black patients. METHODS: A retrospective chart review was performed at an academic referral center, a community hospital, and an inner-city public hospital. RESULTS: A total of 270 patients that received postlumpectomy radiotherapy were reviewed. Of those, 102 were black, 162 white, and six nonblack, nonwhite. The black patients were statistically significantly more likely to present with higher-stage disease (Stage II: 43.1% vs. 32.1%), positive lymph nodes (29.4% vs. 14.8%), higher-grade disease (Grade III: 35.3% vs. 24.1%), and age < 45. The actuarial local control at five years in the black patients was 95.5% and in the white patients was 94.8%. The actuarial five-year disease-free survival in the black patients was 90.3% and in the white patients was 91.7%. There was no statistically significant difference in either local control or disease free-survival in the black and white patients when matched by stage. CONCLUSION: At five years, the local control and disease-free survival for black patients are equally as good as white patients.

Adult↗
PubMed2002

Treatment of pancreatic cancer tumors with intensity-modulated radiation therapy (IMRT) using the volume at risk approach (VARA): employing dose-volume histogram (DVH) and normal tissue complication probability (NTCP) to evaluate small bowel toxicity.

The emergent use of a combined modality approach (chemotherapy and radiation) in pancreatic cancer is associated with increased gastrointestinal toxicity. Intensity-modulated radiation therapy (IMRT) has the potential to deliver adequate dose to the tumor volume while decreasing the dose to critical structures such as the small bowel. We evaluated the influence of IMRT with inverse treatment planning on the dose-volume histograms (DVHs) of normal tissue compared to standard 3-dimensional conformal radiation treatment (3D-CRT) in patients with pancreatic cancer. Between July 1999 and May 2001, 10 randomly selected patients with adenocarcinoma of the pancreatic head were planned simultaneously with 3D-CRT and inverse-planned IMRT using the volume at risk approach (VaRA) and compared for various dosimetric parameters. DVH and normal tissue complication probability (NTCP) were calculated using IMRT and 3D-CRT plans. The aim of the treatment plan was to deliver 61.2 Gy to the gross tumor volume (GTV) and 45 Gy to the clinical treatment volume (CTV) while maintaining critical normal tissues to below specified tolerances. IMRT plans were more conformal than 3D-CRT plans. The average dose delivered to one third of the small bowel was lower with the IMRT plan compared to 3D-CRT. The IMRT plan resulted in one third of the small bowel receiving 30.2+/-12.9 Gy vs. 38.5+/-14.2 Gy with 3D-CRT (p = 0.006). The median volume of small bowel that received greater than either 50 or 60 Gy was reduced with IMRT. The median volume of small bowel exceeding 50 Gy was 19.2+/-11.2% (range 3% to 45%) compared to 31.4+/-21.3 (range 7% to 70%) for 3D-CRT (p = 0.048). The median volume of small bowel that received greater than 60 Gy was 12.5+/-4.8% for IMRT compared to 19.8+/-18.6% for 3D-CRT (p = 0.034). The VaRA approach employing IMRT techniques resulted in a lower dose per volume of small bowel that exceeded 60 Gy. We used the Lyman-Kutcher models to compare the probability of small bowel injury employing IMRT compared to 3D-CRT. The BIOPLAN model predicted a small bowel complication probability of 9.3+/-6% with IMRT compared to 24.4+/-18.9% with 3D-CRT delivery of dose (p = 0.021). IMRT with an inverse treatment plan has the potential to significantly improve radiation therapy of pancreatic cancers by reducing normal tissue dose, and simultaneously allow escalation of dose to further enhance locoregional control.

Adenocarcinoma↗
PubMed2002

Breast conservation is an effective option in Black, medically indigent patients.

The purpose of the study was to evaluate the efficacy of lumpectomy and postoperative radiotherapy in an African-American, medically indigent population. From 1980 through 1996, a retrospective chart review was undertaken of the patients treated with radiotherapy after lumpectomy at an inner city hospital, whose patients are primarily African American and uninsured. One hundred and one patients were treated with breast conservation during this time. Of those, 72 were African American and with invasive carcinoma. The data were analyzed using JMP IN (SAS Institute). The study found that African-American patients with invasive carcinoma had 95.2% local control at 5 years and 87.9% at 10 years. The disease-free survival was 84.6% at 5 years and 65.3% at 10 years. Patients that received less than 50 Gray to the tumor bed had inferior local control, disease-free survival, and overall survival (p < 0.0001 for all three). The 5-year and 10-year local control for DCIS, in a limited number of patients, was 95.2%. We conclude that lumpectomy followed by radiotherapy is an effective treatment strategy in the high-risk population of African-American, medically indigent patients. The local control and disease-free survival compare favorably to published controls in this traditionally high-risk patient population.

Black People↗