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Biomedical subjects

P F Dixon

Publications and source records attributed to P F Dixon.

At least 19 recordsLinked to original sources
PubMed2001

The role of computed tomography in the T classification of laryngeal carcinoma.

BACKGROUND: The objectives of this study were 1) to describe patterns of use of computed tomography (CT) in laryngeal carcinoma, and 2) to characterize the contribution of CT to the T classification of laryngeal carcinoma. METHODS: The study population comprised 1195 patients with laryngeal carcinoma diagnosed from 1982 through 1995 chosen randomly from the Ontario provincial cancer registry. A chart review was conducted to obtain data on each case. Patient-related, tumor-related, and health-system-related factors were analyzed to identify factors associated with the use of CT. Descriptions of clinical exams and CT reports were reviewed to see how CT information modified T classification. Actuarial local control and cause specific survival curves were plotted by clinical T classification without and with CT to evaluate stage migration. The percentage of the variance in outcome explained by T classification in a Cox analysis was used to evaluate whether the prognostic accuracy of T classification was improved with the use of information from CT. RESULTS: Patients with glottic (20.1%) and supraglottic (41.7%) carcinoma underwent CT. The use of CT increased over time in glottic and supraglottic carcinoma combined from 17.2% in 1982-5 to 33.9% in 1991-5. Computed tomography was used less often in older patients with a 16% (95% confidence interval, 5-27%) decrease in the odds of having CT with each 10-year age increment. Computed tomography use varied considerably across the cancer center regions in Ontario. Computed tomography altered the T classification in 20.2% of those patients who had CT, with most being "upstages." Stage migration due to CT was demonstrated. Using information from CT in the assignment of T classification for 27.8% of this study population did not make a significant contribution to the ability of T classification to predict outcome over the entire group. CONCLUSIONS: There is large variation in the use of CT among different age groups and regions. The ability to compare outcomes by stage across geographic areas is compromised when the use of CT varies.

Analysis of Variance↗
PubMed2000

Cancers of the upper aerodigestive tract in Ontario, Canada, and the United States.

BACKGROUND: Squamous cancers of the upper aerodigestive tract (UADT) are related to the use of tobacco and/or alcohol, and in North America they are more common among the poor. They are usually locoregionally confined at diagnosis, and local treatment with surgery and/or radiation therapy is often curative. This study compares the incidence and survival of this group of diseases in Canada and the U.S., two North American neighbors with many cultural similarities but significant differences in their health care and social programs. METHODS: To describe and compare the case mix, incidence, and outcome of squamous cancers of the UADT in Ontario, Canada, and the U.S., we used the Ontario Cancer Registry (OCR) and the Surveillance, Epidemiology, and End Results (SEER) registries in the U.S. to identify all cases of cancer with International Classification of Disease (ICD) codes 141, 143-9, 160-1, and a subset of 140, which were diagnosed between 1982 and 1994. ICD-O histology codes were placed into clinically relevant groupings, and ICD-9 site codes were grouped into sites as defined by the International Union Against Cancer and the American Joint Committee on Cancer. Age-adjusted incidence rates were calculated for each site. For the SEER registry, race specific incidence rates were also calculated. Observed and expected survival were plotted by site and registry, and from these, relative survival was calculated. Survival was compared during the first 5 years after diagnosis and during the next 5 years among patients who had survived the first 5 years. RESULTS: Of the 16,577 and 42,990 cases identified in the OCR and SEER registries, respectively, squamous cancer was by far the most common histology (94.1% in OCR, 94.6% in SEER) and will form the main subject of this report. The distribution of squamous cancers by site, subsite, age, and gender were remarkably similar in the two populations. Overall, the incidence was about 17% higher in the U.S. than in Ontario, and this difference was seen for all sites except the nasopharynx, which was more common in Ontario. The higher incidence in the U.S. in part reflects the much higher rate for African Americans than for Americans of other ethnic backgrounds. During the first 5 years after diagnosis, when most deaths from UADT cancer occur, there was a significant relative survival difference in favor of the U.S. for cancer of the supraglottis, and in favor of Ontario for cancer of the oral cavity. There was a nonsignificant trend in favor of Ontario for cancer of the nasopharynx. Within the SEER population, for all sites except the nasopharynx, 5-year relative survival was considerably worse for African Americans than for Americans of other ethnic backgrounds. Examination of survival beyond 5 years after diagnosis for patients who had survived the first 5 years revealed that for all sites, the observed survival continued to diverge markedly from the expected survival. The excess mortality ranged from less than 20% for glottic and nasopharyngeal cancers to about 30-40% for oropharyngeal and supraglottic cancers. CONCLUSIONS: Despite remarkable similarities in case mix between the two countries, UADT cancers were more frequent in the SEER population of the U.S. than in Ontario, and this was partly attributable to the much higher incidence among African Americans. Significant differences between the registries in 5-year survival were seen for several sites. African Americans with UADT cancers had much worse prognoses than did Americans of other ethnic backgrounds. Patients who survive their UADT cancer remain at a higher-than-expected risk of death even after they have been cured.

Disease-Free Survival↗
PubMed1999

A real-time audit of radiation therapy in a regional cancer center.

PURPOSE: To report the development, structure, and implementation of a real-time clinical radiotherapy audit of the practice of radiation oncology in a regional cancer center. METHODS AND MATERIALS: Radiotherapy treatment plans were audited by a real-time peer-review process over an 8-year period (1989-1996). The overall goal of the audit was to establish a process for quality assurance (QA) of radiotherapy planning and prescription for individual patients. A parallel process was developed to audit the implementation of intervention-specific radiotherapy treatment policies. RESULTS: A total of 3052 treatment plans were audited. Of these, 124 (4.1%) were not approved by the audit due to apparent errors in radiation planning. The majority of the nonapproved plans (79%) were modified prior to initiating treatment; the audit provided important clinical feedback about individual patient care in these instances. Most of the remaining nonapproved plans were deviations from normal practice due to patient-specific considerations. A further 110 (3.6% of all audited plans) were not approved by the audit due to deviations from radiotherapy treatment policy. A minority of these plans (22%) were modified prior to initiating treatment and the remainder provided important feedback for continuous quality improvement of treatment policies. CONCLUSION: A real-time audit of radiotherapy practice in a regional cancer center setting proved feasible and provided important direct and indirect patient benefits.

Canada↗
PubMed1999

Using TNM staging to predict survival in patients with squamous cell carcinoma of head & neck.

BACKGROUND: There is a need for a classification system for prognosis based on the TNM system for patients with squamous cell carcinoma of the head and neck such that patient groupings are homogeneous within and heterogeneous between. METHODS: Six hundred fifty-five consecutive patients with invasive squamous cell carcinoma of the head and neck followed prospectively are split into a training set and a test set. Using the training set, the Cox Proportional Hazards Model and the outcome of dead with disease, we created homogeneous prognostic levels (PLs) based on RR. Using the test set, we compare our model to others in the literature. RESULTS: Using the training set, we identified five PLs, and using the test set, we demonstrated that our model is superior to others for both within-group homogeneity and between-group heterogeneity. CONCLUSIONS: A simple classification system can be used to group patients for survival and is valid for future study in prognostication.

Adult↗
PubMed1997

Nucleotide sequence of the glycoprotein gene of viral haemorrhagic septicaemia (VHS) viruses from different geographical areas: a link between VHS in farmed fish species and viruses isolated from North Sea cod (Gadus morhua L.).

RT-PCR methods have been applied to the detection and sequencing of the glycoprotein gene of viral haemorrhagic septicaemia virus (VHSV), the rhabdovirus which causes viral haemorrhagic septicaemia (VHS) in farmed salmonid fish. Phylogenetic analysis of a 360 nt region of the glycoprotein gene from a range of marine and fresh water VHSV isolates identified three genogroups, I-III. Significantly, two virus isolates recovered from ulcerated North Sea cod caught off the Shetland Islands, and an isolate recovered from diseased turbot farmed on the island of Gigha, Scotland were assigned to the same genogroup. Moreover, a virus isolated from diseased turbot farmed on the Baltic Sea coast shared 99.4% nucleotide sequence similarity with a virus associated with a VHS outbreak in rainbow trout. This is the first time that a genetic link between a VHS outbreak and natural VHSV infections of marine fish species has been demonstrated.

Amino Acid Sequence↗
PubMed1997

Does TANIS (T And N Integer Score) help predict survival?

OBJECTIVE: This study was conducted to validate the TANIS model as a predictor of survival. DESIGN: Using Cox Proportional Hazards model, we examined the subgroups of the TANIS score levels to see if they were homogeneous on survival. SETTING: The Departments of Otolaryngology and Oncology and the Radiation Oncology Research Unit at Queen's University in Kingston, Ontario. METHODS: Five hundred and ninety-four patients with cancer of the head and neck classified by TNM and TANIS were analyzed for the outcome dead of disease using estimates of relative risk. RESULTS AND CONCLUSION: The stages of TNM and the levels of TANIS contain subgroups of patients with different survival rates.

Adult↗
PubMed1996

Does N stage predict survival?

OBJECTIVE: To examine the relationship between N stage and survival in head and neck cancer to see if N stage has prognostic value. DESIGN: Database analysis using the Cox Proportional Hazards Model. METHOD: Five hundred and twenty-three consecutive patients with squamous cell carcinoma of the head and neck prospectively entered into a clinical database are analyzed for the outcome of dead with disease. RESULTS: There is no difference in survival between some increments of N stage, specifically N1 and N2, controlling for T stage and site. CONCLUSION: A modified N stage system consisting of N0, N(limited), and N(extended) appears to have a better prognostic value.

Carcinoma, Squamous Cell↗
PubMed1994

What we learn from a clinical database.

A clinical database documents caseload, assesses treatments, compares treatments, follows patients, and can be used for effective teaching. The database and software used at Kingston Regional Cancer Clinic are described, and a few pertinent findings are presented.

Database Management Systems↗
PubMed1993

Pulmonary eosinophils express HLA-DR in chronic eosinophilic pneumonia.

BACKGROUND: Chronic eosinophilic pneumonia is a rare idiopathic disorder. role the eosinophil plays in the pathogenesis of this disease is unknown. The recent finding that nature eosinophils can express the class II major histocompatibility complex molecule HLA-DR suggests an immunologic role, perhaps through antigen presentation. The purpose of this research was to determine whether lung-derived eosinophils exhibit in vivo expression of HLA-DR. METHODS: Eosinophils were obtained simultaneously from bronchoalveolar lavage and peripheral blood from a 59-year-old woman with asthma and chronic eosinophilic pneumonia. Eosinophil-enriched aliquots of peripheral blood were cocultured with human lung fibroblasts (with or without additional granulocyte-macrophage colony-stimulating factor). The percentage of cells expressing HLA-DR was quantitated by flow cytometric analysis. RESULTS: Eosinophils derived from bronchoalveolar lavage displayed in vivo expression of HLA-DR (86%) in contrast to those from peripheral blood (7%), suggesting compartmentalization of eosinophil activation within the lung. Peripheral blood eosinophils retained the capacity for HLA-DR expression when coincubated with lung fibroblasts (83%) with augmentation by granulocyte-macrophage colony-stimulating factor (93%). CONCLUSION: These data demonstrate that lung eosinophil HLA-DR expression occurs in vivo; it may contribute to the pathogenesis of inflammatory lung injury.

Bronchoalveolar Lavage Fluid↗
PubMed1988

Superfractionated radiotherapy in grade III, IV intracranial gliomas.

Preliminary results of superfractionation in the treatment of glioblastoma led to a randomized trial consisting of 76 patients. All patients received whole brain irradiation followed by a 1000 cGy boost to the primary site. Thirty-four patients received standard daily treatment to 4000 cGy, whereas 42 patients received superfractionated radiation, treating three times a day to a total dose of 4760 cGy. No significant difference was found between the 5-year survival of the superfractionated group and the standard treatment group. Early reactions were greater for superfractionation whereas late effects were less.

Adult↗
PubMed1986

Nasopharyngeal carcinoma in children.

The results of treatment are reviewed in 18 cases of childhood nasopharyngeal carcinoma. Since 1976 adjuvant chemotherapy with cyclophosphamide, methotrexate, and adriamycin has been used in Manchester and Leeds. The outcome is compared in 9 patients treated with radiotherapy alone and 9 patients treated later with both radiotherapy and adjuvant chemotherapy. Relapse-free survival rates were 0% for those treated with radiotherapy alone and 78% at 13-80 months after diagnosis for those treated with both radiotherapy and chemotherapy. It is concluded that adjuvant chemotherapy improves relapse-free survival in childhood nasopharyngeal carcinoma.

Adolescent↗
PubMed1983

Rapid detection of infectious pancreatic necrosis virus (IPNV) by the enzyme-linked immunosorbent assay (ELISA).

The enzyme-linked immunosorbent assay (ELISA) was used to demonstrate the presence of infectious pancreatic necrosis virus (IPNV) antigen in cell cultures and in fish. Virus antigen could be detected in infected cell cultures before visible cytopathic effect (c.p.e.) was evident and cell cultures showing complete viral c.p.e. produced intense colour reactions. Virus antigen was detected in infected fry during and immediately after an epizootic, but although IPNV-carrier fish could be detected by the ELISA technique, the sensitivity of detection was not as great as that of isolation of the infectious virus in cell culture. The major IPNV serotypes, Sp, Ab and Vr, crossreacted at only a low level and it was shown that the ELISA technique could be used to serotype IPNV strains rapidly. None of 10 other fish pathogenic viruses reacted with plates sensitized for IPNV detection. The time taken to perform the technique was reduced to 1 h 35 min at room temperature and this still allowed the results to be readily assessed visually as antigen-positive or antigen-negative.

Animals↗
PubMed1983

Hypocalcaemia--an unusual complication of successful chemotherapy for metastatic breast cancer.

Three cases of metastatic carcinoma of the breast are described in patients who presented with hypercalcaemia. They achieved an excellent regression of their disease with combination chemotherapy but despite this they clinically deteriorated. Investigation showed them to be hypocalcaemic due to temporary hypoparathyroidism. Correction of their serum calcium resulted in good symptomatic relief. The possible mechanisms for these changes are discussed and we feel that this unusual complication of successful chemotherapy should be remembered when patients fail to improve symptomatically despite a good disease response.

Antineoplastic Agents↗