Biomedical subjects

Alan W Yasko

Publications and source records attributed to Alan W Yasko.

25 records · Page 2Linked to original sources

PubMed2002

Surgical management of soft tissue sarcomas of the hand and foot.

BACKGROUND: Soft tissue sarcomas of the hand and foot present unique management challenges. The purpose of the current study study was to determine oncologic outcome, particularly with respect to factors affecting local recurrence, distant recurrence, and disease-specific survival. METHODS: A retrospective study was performed on 115 patients with soft tissue sarcomas of the hand or foot who were evaluated, treated, and followed at the authors' institution between 1980 and 1998. The medical records and radiographs were reviewed. Kaplan-Meier analysis was used to assess patient survival. RESULTS: Most patients (95%) were referred after previous surgery. The majority of tumors (75%) were T1 lesions (less than 5 cm), and most tumors (81%) were high grade. Patients who were treated by definitive, wide re-excision (n = 43) had a 10 year local recurrence-free survival of 88%, which was significantly better than the corresponding rate of 58% for patients who did not have re-excision (n = 40, P = 0.05). Radiation improved local control in patients who did not undergo re-excision (n = 17, P = 0.02). However, radiation did not improve local control in patients who had definitive re-excision with negative margins (n = 13, P = 0.51). The disease-specific survival at 5 and 10 years was 76% and 65%, respectively, for patients who presented with localized disease. Disease-specific patient survival was significantly worse for patients who had regional or distant metastasis. Radical amputation as initial surgical treatment did not decrease the likelihood of regional metastasis and did not improve disease-specific patient survival. The presence of distant metastasis at presentation was an independent predictor of local recurrence. CONCLUSION: Limb sparing treatment is possible in many patients with soft tissue sarcomas of the hand and foot. Re-excision to achieve microscopically negative surgical margins is an effective method of achieving a high rate of local control in appropriately selected patients who present after unplanned excision of the primary tumor. There does not appear to be a survival benefit to immediate radical amputation, which should be reserved for cases where surgical excision or re-excision with adequate margins cannot be performed without sacrifice of functionally significant neurovascular or osseous structures.

Adolescent↗

PubMed2002

Extraosseous osteosarcoma: response to treatment and long-term outcome.

PURPOSE: To evaluate the clinicopathologic features of extraosseous osteosarcoma (EOO), a rare soft tissue form of osteosarcoma, and to examine its response to multimodality therapy. PATIENTS AND METHODS: The medical records of all patients with EOO evaluated at The University of Texas M.D. Anderson Cancer Center between 1960 and 1999 were reviewed for clinicopathologic factors, treatment, and outcome. RESULTS: Sixty consecutive patients with EOO were identified, including 38 patients with localized (American Joint Committee on Cancer stages I to III) disease. The majority of patients presented with T2 tumors (n = 35, 58%), and 90% of tumors were located beneath the investing fascia. Twenty-seven patients with measurable and assessable disease were treated with doxorubicin-based chemotherapy (median doxorubicin starting dose, 75 mg/m(2); median number of cycles, four). The overall response rate was 19%, with two complete and three partial responses; one (6%) of 18 doxorubicin-treated patients who underwent subsequent surgery had a pathologic complete response. For the subset of 30 patients with localized disease treated at M.D. Anderson, the 5-year actuarial local recurrence-free, distant recurrence-free, event-free, and disease-specific survival rates were 82% (95% confidence interval [CI], 70% to 98%), 64% (95% CI, 43% to 93%), 47% (95% CI, 30% to 70%), and 46% (95% CI, 26% to 80%), respectively. CONCLUSION: EOO should be considered clinically and therapeutically distinct from osseous osteosarcoma. Radiographic response rates and pathologic complete response rates to doxorubicin-based systemic therapy are low.

Adolescent↗

PubMed2002

Giant cell tumor of bone.

Giant cell tumor of bone is an enigmatic osseous neoplasm that is histologically benign but clinically shows local aggression and metastatic potential. The absence of clinical, radiographic, or pathologic features that are predictive of tumor behavior and patient outcome has resulted in recent attention to the pathobiology of giant cell tumor of bone. In this report, the clinicopathologic features of and current treatment approaches to giant cell tumor of bone are reviewed. Recent investigations of the specific role of the cell populations present in giant cell tumor of bone that influence tumor proliferation, bone resorption, and its clinical behavior are described.

Angiogenesis Inhibitors↗

PubMed2002

Development of an injectable, in situ crosslinkable, degradable polymeric carrier for osteogenic cell populations. Part 1. Encapsulation of marrow stromal osteoblasts in surface crosslinked gelatin microparticles.

This study investigated the temporary encapsulation of rat marrow stromal osteoblasts in surface crosslinked gelatin microparticles. Cells were encapsulated in uncrosslinked gelatin microparticles of average diameter of 630 microm containing approximately 53 cells. Gelatin microparticles were crosslinked to shell thicknesses of approximately 75 microm via exposure to 1 mM dithiobis(succinimidylpropionate) (DSP) solution for 15 min or 5 mm DSP solution for 5 min for the production of microparticles dispersing approximately 60 min after placement into a physiologic fluid at 37 degrees C. Formed microparticles were placed into culture wells at a cell seeding density of 5.3 x 10(4) cells/cm2 and, following the degradation and/or dissolution of gelatin, the cells were cultured in the presence of osteogenic supplements for 28 days. Samples were taken at specified time points and analyzed by a DNA assay for cell number and a 3H-thymidine incorporation assay for proliferative potential. Samples were also obtained and analyzed at several time points by alkaline phosphatase, osteocalcin, and mineralization assays for early and late phenotypic expression markers of osteoblastic differentiation. The measurements from the different assays for encapsulated cells (EC) in uncrosslinked and crosslinked gelatin microparticles were normalized with the cell numbers from the DNA assay and compared with those for nonencapsulated control cells. The results demonstrated that the marrow stromal cells survived the encapsulation procedure in uncrosslinked gelatin microparticles and also retained their proliferative potential and osteoblastic phenotype over a 28 day period, although at a slightly lower level than the nonencapsulated cells. The results further showed that the marrow stromal cells survived the encapsulation in crosslinked gelatin microparticles prepared via exposure to 5mm DSP for 5 min and also retained their proliferative potential and osteoblastic phenotype over a 28 day period, but at a slightly lower level than the EC in uncrosslinked gelatin microparticles. In contrast, exposure to 1 mM DSP for 15 min led to severely limited cell viability and phenotypic expression probably due to the increased crosslinking time. These results suggest that temporary encapsulation of cells in gelatin microparticles may protect cells from short-term environmental effects such as those associated with the crosslinking of an injectable polymeric carrier for bone tissue engineering.

Alkaline Phosphatase↗

PubMed2002

Development of an injectable, in situ crosslinkable, degradable polymeric carrier for osteogenic cell populations. Part 2. Viability of encapsulated marrow stromal osteoblasts cultured on crosslinking poly(propylene fumarate).

The effect of temporary encapsulation of rat marrow stromal osteoblasts in crosslinked gelatin microparticles on cell viability and proliferation was investigated in this study for microparticles placed on a crosslinking poly(propylene fumarate) (PPF) composite over a 7 day time period. Encapsulated cells were seeded on crosslinking PPF composites at times up to 10 min following initiation of the crosslinking reaction, and also on fully crosslinked PPF composites and tissue culture polystyrene controls, with a cell seeding density of 5.3 x 10(4) cells/cm2. The crosslinked PPF composite exhibited an average gel point of 10.3 min and an average maximum crosslinking temperature of 47.5 degrees C. Cell viability and proliferation were assessed by DNA and 3H-thymidine assays and the results were compared with those for nonencapsulated cells. The results showed that the addition time of cells to a crosslinking PPF composite had a large effect on cell viability and proliferation for both encapsulated and nonencapsulated cells with more surviving cells added at later time points. Most importantly, the temporary encapsulation of cells significantly enhanced cell viability at earlier time points. The data indicate that the presence of gelatin microparticles does not affect the crosslinking of a PPF composite. They further suggest that the temporary encapsulation of cells in crosslinked gelatin microparticles may preserve the viability of cells contained in an actively crosslinking PPF composite used as an injectable polymeric scaffold serving also as a carrier for osteogenic cell populations.

Alkaline Phosphatase↗

PubMed2002

Development of an injectable, in situ crosslinkable, degradable polymeric carrier for osteogenic cell populations. Part 3. Proliferation and differentiation of encapsulated marrow stromal osteoblasts cultured on crosslinking poly(propylene fumarate).

This study investigated the effect of temporary encapsulation of rat marrow stromal osteoblasts in crosslinked gelatin microparticles on long-term cell proliferation and phenotypic expression for microparticles placed on crosslinking poly(propylene fumarate) (PPF) composites using N-vinyl pyrollidinone (N-VP) as a crosslinking agent over a 28 day time period. Encapsulated cells (ECs) were seeded on actively crosslinking PPF composites 6 min after initiation of the crosslinking reaction, and also on fully crosslinked PPF composites and tissue culture polystyrene controls, with a cell seeding density of 5.3 x 10(4) cells/cm2. Composites prepared with three PPF:N-VP ratios were examined: 1:0.5, 1:0.1, and 1:0.05. Samples were taken at specified time points and analyzed by DNA, 3H-thymidine, alkaline phosphatase, osteocalcin, and calcium assays, and the measurements were compared with those for nonencapsulated cells (NCs). The results showed that encapsulated marrow stromal cells exhibited much higher viability, proliferation, and phenotypic expression when placed on crosslinking PPF composites than NCs. The assay results for ECs on crosslinking PPF composites were also similar to those on fully crosslinked PPF composites. The data further demonstrated that the PPF:N-VP ratio had no effect on the viability, proliferation, or phenotypic expression of the ECs. These results suggest that cells encapsulated in crosslinked gelatin microparticles may be part of an injectable, in situ crosslinkable, biodegradable polymeric composite for bone tissue engineering applications.

Alkaline Phosphatase↗

PubMedDate not supplied

Methods: a comparative analysis of radiography, microcomputed tomography, and histology for bone tissue engineering.

This study focused on the assessment of radiography, microcomputed tomography, and histology for the evaluation of bone formation in a 15.0-mm defect in the rabbit radius after the implantation of a tissue-engineered construct. Radiography was found to be useful as a noninvasive method for obtaining images of calcified tissue throughout the time course of the experiment. With this method, however, image quality was low, making it difficult to obtain precise information about the location and quantity of the bone formed. Microcomputed tomography was used to create three-dimensional reconstructions of the bone (25-microm resolution). These reconstructions allowed for greater spatial resolution than the radiography, but did not allow for imaging of the implanted scaffold material or the surrounding, nonmineralized tissue. To visualize all materials within the defect area at the cellular level, histology was used. Histological analysis, however, is a destructive technique that did not allow for any further analysis of the samples. Each technique examined here has its own advantages and limitations, but each yields unique information regarding bone regeneration. It is only through the use of all three techniques that complete characterization of the bone growth and tissue/construct responses after implantation in vivo.

Acrylates↗