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Biomedical subjects

G M Thomas

Publications and source records attributed to G M Thomas.

At least 55 records · Page 3Linked to original sources
PubMed1993

An essential role for phosphatidylinositol transfer protein in phospholipase C-mediated inositol lipid signaling.

Transmembrane signaling by the phospholipase C-beta (PLC-beta) pathway is known to require at least three components: the receptor, the G protein, and the PLC. Recent studies have indicated that if the cytosol is allowed to leak out of HL60 cells, then G protein-stimulated PLC activity is greatly diminished, indicating an essential role for a cytosolic component(s). We now report the complete purification of one component based on its ability to reconstitute GTP gamma S-mediated PLC activity and identify it as the phosphatidylinositol transfer protein (PI-TP). Based on the in vitro effects of PI-TP, we surmise that it is involved in transporting PI from intracellular compartments for conversion to PI bisphosphate (PIP2) prior to hydrolysis by PLC-beta 2/PLC-beta 3, the endogenous PLC isoforms present in these cells.

Amino Acid Sequence↗
PubMed1993

Results of a policy of surveillance in stage I testicular seminoma.

PURPOSE: To determine what proportion of patients with Stage I testicular seminoma will be cured with orchidectomy alone. METHODS AND MATERIALS: From August 1984 to December 1991 148 patients with Stage I testicular seminoma were entered on a prospective study of surveillance following orchidectomy. The eligibility criteria included a normal chest X ray, lymphogram, computed tomography (CT) of the abdomen and pelvis, and normal post-orchidectomy tumor markers (AFP and BHCG). Patients were followed with a clinical assessment (markers, chest X ray and CT abdomen and pelvis) at 4 to 6 monthly intervals. RESULTS: With a median follow-up of 47 months (range 7-87 months), the actuarial relapse-free rate was 81% at 5 years. Twenty-three patients have relapsed with a median time to relapse of 15 months (range 2-61 months). Four patients (17%) relapsed at 4 or more years from diagnosis. Twenty-one of the 23 relapses occurred in the paraaortic lymph nodes, one patient relapsed in the mediastinum and ipsilateral inguinal nodes and one patient had an isolated ipsilateral inguinal node relapse. Nineteen patients were treated for relapse with external beam radiation therapy of which three developed a second relapse and were salvaged with chemotherapy. Four patients were treated for first relapse with chemotherapy and one developed a second relapse and died of disease. Age at diagnosis was the only prognostic factor for relapse, with patients age < or = 34 having an actuarial relapse-free rate at 5 years of 70% in contrast to a 91% relapse-free rate in those > 34 years of age. CONCLUSIONS: We recommend that surveillance in Stage I testicular seminoma should only be performed in a study setting until further data regarding the risk of late relapse and the efficacy of salvage chemotherapy is available.

Adult↗
PubMed1993

Results of a randomized phase-III trial to evaluate the efficacy of strontium-89 adjuvant to local field external beam irradiation in the management of endocrine resistant metastatic prostate cancer.

PURPOSE: A large proportion of the practice of radiotherapy in the management of metastatic adenocarcinoma of the prostate is associated with palliation of pain from osseous metastases and improving quality of life. Radiation therapy is well known to be effective in treating painful sites and may also be effective in reducing the propensity for adjuvantly treated disease to become symptomatic. Strontium-89 is a systemic radionuclide that has clinical efficacy in the palliation of pain from bony metastases. METHODS AND MATERIALS: The study was a Phase-III randomized placebo control trial performed in eight Canadian Cancer Centers to evaluate the effectiveness of strontium-89 as an adjunct to local field radiotherapy. Patients with endocrine refractory metastatic prostate cancer received local field radiotherapy and either strontium-89 as a single injection of 10.8 mCi or placebo. RESULTS: One hundred twenty-six patients were recruited. No significant differences in survival or in relief of pain at the index site where noted. Intake of analgesics over time demonstrated a significant reduction in the arm treated with strontium-89. Progression of pain as measured by sites of new pain or the requirement for radiotherapy showed statistically significant differences between the arms in favor of strontium-89. Tumor makers including prostate specific antigen, acid phosphatase, and alkaline phosphatase were also reduced in patients receiving strontium-89. A Quality-of-Life analysis was performed as a multivariate data set and demonstrated an overall superiority of strontium-89 with alleviation of pain and improvement in physical activity being statistically significant. Toxicity was evaluated and demonstrated increased hematological toxicity in the group receiving strontium-89. CONCLUSIONS: It is concluded that the addition of strontium-89 is an effective adjuvant therapy to local field radiotherapy reducing progression of disease as evidenced by new sites of pain and the requirement of further radiotherapy and improving quality-of-life and need for analgesic support in this group of patients.

Aged↗
PubMed1993

Integrating radiation therapy into the management of ovarian cancer.

Several studies during the last 15 years have elucidated the role of postoperative external beam radiation therapy as curative management of some subsets of patients with ovarian cancer. Despite this, the use of radiation therapy in patients with ovarian cancer has remained a controversial subject. Substantially improved cure rates have not been realized during the past decade despite the early promise of high response rates to cisplatin chemotherapy. Thus, it is important that all currently effective therapies be used for maximum therapeutic gain. This article will review the evidence that radiation therapy is curative in ovarian cancer and highlight the criteria, including stage and grade of disease and tumor residuum, by which patients suitable for such therapy are selected. The rationale for the use of whole abdominopelvic irradiation rather than pelvic or lower abdominal treatment will be discussed, as will the optimal radiation technique and its attendant morbidity. Limited data pertinent to the controversy over the use of radiation therapy versus chemotherapy in early disease, will be reviewed. The possible benefits of consolidation abdominopelvic radiation therapy after chemotherapy in highly selected patients with well-differentiated microscopic residual disease at second-look laparotomy or with no residual disease but high a risk for relapse will be considered.

Combined Modality Therapy↗
PubMed1993

Is there a role for consolidation or salvage radiotherapy after chemotherapy in advanced epithelial ovarian cancer?

Cure rates following surgery and platinum-containing chemotherapy in advanced epithelial ovarian cancer are only 20-30%. Relapse rates even after complete chemotherapy responses or those leaving only microscopic residual disease are disappointingly high at 30 to 80%. Strategies to improve outcome, consolidate the results of surgery and chemotherapy, or salvage those with residual disease include whole-abdominopelvic irradiation. This paper reviews its usage to date in 28 trials. The results of sequential therapy are generally disappointing, possibly because of inappropriate patient selection, toxic regimens, underlying biological factors, and difficulties interpreting the uncontrolled studies. Tumor residuum appears to be one factor predictive of survival: no residuum, 76%; microscopic or < 5 mm, 49%; macroscopic, 17%. Other factors may be tumor grade and patient age. Appropriate selection of patients for controlled studies of sequential radiotherapy after surgery and chemotherapy include those with negative second-look laparotomy who had large residual Stage III presentations prechemotherapy, are over 50 years of age, or who have grade 3 tumors. Others are those with microscopic residual disease, grade 1 or 2. If therapy is to be successfully completed with minimal morbidity, abdominal radiotherapy should be limited to < or = 25 Gy, initial chemotherapy to six courses, and surgery to initial debulking and second-look laparotomy.

Carcinoma↗
PubMed1993

Surveillance in stage I seminoma of the testis.

In a health care system with adequate personnel and resources, careful surveillance, rigorously performed, following guidelines set out in the prospective trials is an appropriate alternative to adjuvant irradiation for patients with stage i seminoma of the testis.

Dysgerminoma↗
PubMed1992

Analysis of complications in patients treated with abdomino-pelvic radiation therapy for ovarian carcinoma.

Between 1971 and 1985, 598 patients with ovarian carcinoma were treated with abdomino-pelvic radiation therapy. Acute complications included nausea and vomiting in 364 patients (61%) which were severe in 36, and diarrhea in 407 patients (68%), severe in 35. Leukopenia (less than 2.0 x 10(9) cells/liter) and thrombocytopenia (less than 100 x 10(9) cells/liter) occurred in 64 patients (11%) each. Treatment interruptions occurred in 136 patients (23%), and 62 patients (10%) did not complete treatment. In both situations the most common cause was myelosuppression. Late complications included chronic diarrhea in 85 patients (14%), transient hepatic enzyme elevation in 224 (44%), and symptomatic basal pneumonitis in 23 (4%). Serious late bowel complications were infrequent: 25 patients (4.2%) developed bowel obstruction and 16 required operation. Multivariate analysis was unable to determine any significant prognostic factors for bowel obstruction; however, the moving-strip technique of radiation therapy was associated with a significantly greater risk of developing chronic diarrhea, pneumonitis, and hepatic enzyme elevation than was the open beam technique. We conclude that abdomino-pelvic radiation therapy as used in these patients is associated with modest acute complications and a low risk of serious late toxicity.

Abdomen↗
PubMed1992

Complications of whole abdominal and pelvic radiotherapy following chemotherapy for advanced ovarian cancer.

We examined the records of 105 patients with advanced ovarian cancer who had been treated with cisplatin combination chemotherapy followed by abdominopelvic radiotherapy. The purpose was to define the morbidity of this approach, and identify those factors predictive of toxicity. Acute toxicity resulting in delay or failure to complete treatment was most commonly due to myelosuppression. Nine of 105 patients (8.6%) required surgery for bowel obstruction that was not due to recurrent disease, 3 had an episode of bowel obstruction that settled conservatively, and a further 5 underwent surgery for obstruction due to recurrent tumor. The presence of both a dose of abdominopelvic radiotherapy over 2250 cGy, as well as a second-look laparotomy prior to radiotherapy, was associated with an increased risk of serious bowel complications. The increased frequency of late bowel morbidity seen in the combined modality group is likely explained by the presence of these two factors, rather than the exposure to chemotherapeutic agents per se. These observations are supported by the published literature.

Abdomen↗
PubMed1992

Borderline epithelial ovarian tumors: a review of 81 cases with an assessment of the impact of treatment.

Optimal management of borderline epithelial ovarian tumors remains controversial because of the lack of clear, universally accepted pathologic criteria for diagnosis, the lack of complete understanding of the significance of intraperitoneal implants, and the desire to employ more limited surgery in young women. We reviewed the experience with borderline epithelial ovarian tumors at Princess Margaret Hospital in order to assess the natural history of the disease, to determine prognostic factors that would aid in management decisions, and to determine if adjuvant therapy influenced outcome. Eighty-one patients were analyzed. The mean age was 48 years. Seventy-two percent of tumors were of the serous histologic sub-type and 28% were mucinous. Seventy-eight percent were Stage I, 11% Stage II, and 11% Stage III. Peritoneal washings contained malignant cells in 14 of 32 patients (not recorded or obtained in 49), cyst rupture occurred in 25%, surface excrescences in 40%, and adhesions in 46%. None of these factors had a significant effect on recurrence rate or survival. Eleven patients received adjuvant radiation therapy (10 abdomino-pelvic and 1 pelvic alone), four adjuvant chemotherapy, and one both radiation therapy and chemotherapy. The rest (65) received no adjuvant therapy. Due to the small numbers and infrequent events, it was not possible to analyze and thus draw valid conclusions regarding the effect of adjuvant therapy on survival or recurrence. The overall survival (OS) and cause specific survival (CSS) were 85% and 96% at 10 years, respectively. No Stage I patient died of tumor. OS for Stage I patients was 90% at 10 years, the majority of whom (61 of 63) received no adjuvant therapy, and is thus unnecessary in Stage I disease. The adequacy of unilateral oophorectomy or ovarian cystectomy could not be confirmed because of small numbers. The 10 year OS and disease-free survival in Stage II and III were 75% and 50%, respectively, despite the use of adjuvant radiation therapy, chemotherapy, or both. It is necessary to create a multi-center tumor registry in order to acquire a prospective data base from which to develop sound therapeutic decisions.

Adolescent↗
PubMed1991

Identification of a novel cytosolic poly-phosphoinositide-specific phospholipase C (PLC-86) as the major G-protein-regulated enzyme.

Activation of phosphoinositide-specific phospholipase C (PLC) generates two intracellular signals which play major roles in many cellular processes including secretion, proliferation and contraction. PLC activation by many receptors occurs via a guanine nucleotide regulatory protein, Gp. PLCs are found predominantly in the cytosolic fraction though some activity is membrane-associated. At least four families of iso-enzymes of PLC (alpha, beta, gamma and delta) have been identified, but there is only scant evidence to indicate that any of the mammalian cytosolic activities are involved in G-protein-regulated signalling. In this study we demonstrate that the PLC activity from rat brain cytosol can be regulated in a G-protein-dependent manner in a reconstituted system using pre-permeabilized HL60 cells. We identify two enzymes, PLC-beta and a novel 86 kDa enzyme (designated PLC-epsilon) as the G-protein-regulated enzymes. PLC-epsilon was found to be the major G-protein-regulated enzyme.

Animals↗
PubMed1991

Changing concepts in the management of vulvar cancer.

Vulvar carcinoma varies widely in its clinical presentations and prognosis. The reviewed literature outlines the achievements of conventional surgery, radiation, or chemoradiation therapy in its management. Currently therapeutic concepts are evolving. New treatment strategies replacing the uniform use of radical vulvectomy and bilateral groin dissection are proposed. These strategies are tailored to the clinical and pathological disease extent and location and integrate the possible therapeutic advantages of both surgery and chemoradiation. The testing and use of the proposed multimodality therapy protocols require the expertise of gynecologic, radiation, and medical oncologists. This approach should lead to improved anatomic and functional preservation in early disease and improved locoregional in advanced disease.

Algorithms↗