Hormone Contraception before the First Birth and Ovarian Cancer Risk

Introduction: Combined oral contraceptive (OC) use strongly and consistently reduces the risk for epithelial ovarian cancer (EOC); longer durations of use and more recent use are associated with the strongest reductions in risk. However, it is unknown if exclusive OC use before the first birth is associated with a reduction in EOC risk many years later. Therefore, we investigated the risk for EOC among parous women associated with exclusive OC use before the first birth. Methods: From a population-based case-control study in Alberta and British Columbia, Canada, 2001–2011, we included 1144 invasive EOC cases and 2513 controls who were >40 years at diagnosis/reference date. Participants reported OC use and all pregnancies via a telephone interview or self-administered questionnaire (in the early years of the study). Duration of OC use was evaluated as a continuous variable and by categories: non-users (never use or <6 months of use), <5, 5–<10, >10 years, unknown. Using logistic regression, we estimated adjusted odds ratios (aORs) and 95% confidence intervals (CI), controlling for study site, age, parity, breastfeeding, first degree family history of breast/ovarian cancer, tubal ligation, and BMI. Results: OC use at any time during reproductive life was associated with a 42% reduced risk for EOC relative to non-users (aOR = 0.58, 95% CI, 0.49–0.69). Among parous women, each additional year of exclusive OC use before the first birth conferred an 11% risk reduction relative to non-users (aOR = 0.89 95% CI, 0.86–0.94, linear trend p-value <0.01). Results were similar when we restricted to cases with high grade serous cancers (aOR = 0.90 95% CI, 0.84–0.95, linear trend p-value <0.01) and for cases with endometrioid/clear cell cancer (aOR 0.88 95% CI, 0.80–0.95, linear trend p-value < 0.01). Discussion: Among parous women, exclusive use of OCs before the first birth was associated with a strong reduction in EOC risk many years later. Because OCs stop ovulation, this reduced risk may be due to a reduction in lifetime ovulatory cycles. However, it is also possible that OC use at younger ages, before the first birth, represents a window of opportunity to have a substantial impact on reducing risk that remains for many years, informing possible prevention strategies.

Histotype predicts the curative potential of radiotherapy: the example of ovarian cancers

BACKGROUND

To explore the influence of ovarian cancer histotype on the effectiveness of adjuvant radiotherapy (RT).

METHODS

A review of a population-based experience included all referred women with no reported macroscopic residuum following primary surgery who underwent adjuvant platin-based chemotherapy (CT), with or without sequential RT, and for whom it was possible to assign histotype according to the contemporary criteria.

RESULTS

Seven hundred and three subjects were eligible, of these 351 received RT. For those with apparent stage I and II tumors, the cohort with clear cell (C), endometrioid (E), and mucinous (M) disease who additionally received RT exhibited a 40% reduction in disease-specific mortality and a 43% reduction in overall mortality.

CONCLUSIONS

The curability of those with stage I and II C-, E-, and M-type ovarian carcinomas was enhanced by RT-containing adjuvant therapy. This benefit did not extend to those with stage III or serous tumors. These findings necessitate reassessments of the role of RT and of the nonselective surgical and CT approaches that have characterized ovarian cancer care.

Incidence and spectrum of non-Hodgkin lymphoma in Chinese migrants to British Columbia

The incidence and spectrum of non-Hodgkin lymphoma (NHL) differ between the Chinese and Caucasian populations. Using population-based registries, we studied the pattern of NHL in Chinese migrants to British Columbia (BC). The records of all NHL cases of Chinese descent diagnosed between 1980 and 1997 were retrieved. Age-standardized incidences were calculated by 5-year intervals in terms of age and calendar years and the relative rates were compared between the migrant, Hong Kong and BC populations. The histological distribution of NHL was compared with 4500 consecutive NHL cases diagnosed in the two populations. A total of 211 cases of migrant NHL were identified, with an age-standardized incidence rate of 7.11 per 100 000 per year, compared with the Hong Kong and BC rates of 7.91 [standardized incidence ratio (SIR) = 0.86, P = 0.01] and 11.88 (SIR = 0.56, P < 0.01). The standardized rates of follicular lymphoma remained low, but the incidence of gastric and nasal natural killer/T lymphomas in migrants were lower than expected. Genetic factors appeared to be stronger than environmental factors in governing the overall incidence of NHL in Chinese. However, certain subtypes of lymphoma may show decreased rates in migrants because of environmental factors.

Validation of a semi-quantitative job exposure matrix at a Söderberg aluminum smelter

OBJECTIVES

We tested the validity of a job exposure matrix (JEM) for coal tar pitch volatiles (CTPV) at a Söderberg aluminum smelter. The JEM had been developed by a committee of company hygienists and union representatives for an earlier study of cancer incidence and mortality. Our aim was to test the validity and reliability of the expert-based assignments.

METHODS

Personal CTPV exposure measurements (n = 1879) overlapped 11 yr of the JEM. The arithmetic mean was calculated for 35 job/time period combinations (35% of the exposed work history), categorized using the original exposure intervals, and compared with the expert-based assignments.

RESULTS

The expert-based and the measurement-based exposure assignments were only moderately correlated (Spearman's rho = 0.42; weighted kappa = 0.39, CI 0.10-0.69). Only 40% of the expert-based medium category assignments were correctly assigned, with better agreement in the low (84%) and high (100%) categories. Pot operation jobs exhibited better agreement (rho = 0.60) than the maintenance and pot shell repair jobs (rho = 0.25). The mid-point value of the medium category was overestimated by 0.3 mg/m(3).

CONCLUSIONS

The expert-based exposure assignments may be improved by better characterizing the transitions between exposure categories, by accounting for exposure differences between pot lines and by re-examining the category mid-point values used in calculating the cumulative exposure. Lack of historical exposure measurements often requires reliance on expert knowledge to assess exposure levels. Validating the experts' estimates against available exposure measurements may help to identify weaknesses in the exposure assessment where improvements may be possible, as was shown here.

Oral topical doxepin rinse: analgesic effect in patients with oral mucosal pain due to cancer or cancer therapy

Oral mucositis is a treatment limiting toxicity of cancer therapy. The purpose of this study was to assess the impact of doxepin oral rinse in the management of oral mucosal pain in cancer patients. Forty-one cancer patients with oral mucosal pain were provided a solution of doxepin (0.5%) for oral rinsing. Oral pain was assessed prior to rinsing, and following rinsing for 4 h using a visual analogue scale (VAS). Adverse effects were recorded. Doxepin rinse resulted in a reduction of pain intensity of more than 50%, with pain relief extending for more than 3 h with pain not returning to baseline 4 h after rinsing. The rinse was tolerated by patients with mucosal damage, and had acceptable taste, and infrequent mucosal stinging with use. Some patients reported sedation after use, likely due to systemic absorption. The results of this single dose trial suggest that topical doxepin rinse has significant ability to provide clinically significant pain relief in patients with mucosal damage with an extended duration of effect.

Characteristics of oral and paraoral malignant lymphoma: a population-based review of 361 cases

BACKGROUND

Lymphoma is the second most common neoplasm of the head and neck; almost 50% of all lymphomas occur in this region. Waldeyer's ring is the most common site of lymphomas involving the oral region. The purpose of this study was to review the characteristics of a large series of malignant lymphoma of the oral region.

METHODS

Three hundred sixty-one consecutive cases of malignant lymphoma of the oral region were identified in the Tumor Registry between 1969 and 1998.

RESULTS

The 361 cases (200 males and 161 females) of malignant lymphoma of the oral region accounted for 3.5% of all oral malignancies. The mean age was 62.5 years and the most prevalent site of involvement was the tonsil (32.7%), followed by the parotid gland (16.1%). Sixty-five percent of the lesions were diagnosed as large-cell (38%) or small-cell (27%) lymphoma. One quarter of the patients died of the disease in a mean of 2.78 years after diagnosis. Of a total 26 patients who died from other causes, 12 died because of other cancers, including 7 (27%) with leukemia and 5 (19%) with oral carcinoma. The prognosis is based, at least partially, on the histologic grading (low, intermediate, or high) and the anatomic stage of the disease. Localized low-grade lymphomas have a more favorable prognosis compared with those that are disseminated and/or have high-grade cellular changes.

CONCLUSION

Lymphoma is the second most common malignant oral disease. Thorough head and neck and oral examination is necessary to identify lesions that may represent lymphoma.

Impact of localized treatment in reducing risk of progression of low-grade oral dysplasia: molecular evidence of incomplete resection

Currently, there is no consensus on the appropriate treatment for low-grade oral dysplasia. This is mainly due to the difficulty in predicting outcome for this heterogeneous group of lesions. In this study, we constructed a detailed clinical history of 66 mild and moderate dysplasias in order to determine how treatment affected outcome, and to evaluate the effect of treatment on lesions with different genetic profiles, which are defined by patterns of loss of heterozygosity (LOH) associated with low, intermediate and high risk of progression [Clin. Cancer Res., 6, 357-62, 2000]. The results showed that although treatment guided by clinical removal of leukoplakia reduced cancer progression risk in all three risk groups, the amount of reduction in our study group did not reach statistical significance. To assess whether completeness of lesion removal was a major factor in recurrence, repeat biopsies at the primary sites were analyzed for persistent LOH status on chromosomes 3p, 4q, 8p, 9p, 11q, 13q and 17p. Strikingly, eight of 17 cases judged clinically removed contained the same molecular clones in the initial and subsequent biopsies, suggesting incomplete removal. When molecular information was included in the assessment of lesion removal, treatment significantly reduced the risk of progression for cases with intermediate (P=0.043) and high risk (P=0.001) genetic profiles, but not cases with low-risk profiles. A 9.1-fold decrease in progression risk was observed for those with high-risk profile. Altogether, these data suggest the use of molecular profiles to guide the treatment of low-grade dysplasia. Our data also suggest that currently an inadequate margin may in part be responsible for the high rate of recurrence, especially in high-risk lesions.

Case-control analysis with partial knowledge of exposure misclassification probabilities

Consider case control analysis with a dichotomous exposure variable that is subject to misclassification. If the classification probabilities are known, then methods are available to adjust odds-ratio estimates in light of the misclassification. We study the realistic scenario where reasonable guesses, but not exact values, are available for the classification probabilities. If the analysis proceeds by simply treating the guesses as exact, then even small discrepancies between the guesses and the actual probabilities can seriously degrade odds-ratio estimates. We show that this problem is mitigated by a Bayes analysis that incorporates uncertainty about the classification probabilities as prior information.

Increased genetic damage in oral leukoplakia from high risk sites: potential impact on staging and clinical management

BACKGROUND

Two staging systems for oral leukoplakias have been proposed to better predict prognosis. Although one system includes site as an independent determinant, its use is controversial.

METHODS

Recent studies have shown that loss of heterozygosity (LOH) in oral premalignancies is associated with risk of progression. The authors analyzed 127 oral dysplasias for LOH on 3 chromosome arms (3p, 9p, and 17p). The lesions included 71 from the floor of mouth, ventrolateral tongue, and soft palate complex (designated high risk [HR] sites) and 56 from the rest of the oral cavity (low risk [LR] sites).

RESULTS

Dysplasias from HR sites contained significantly higher LOH frequencies than LR sites (percentage with any loss, P = 0.0004; percentage with multiple losses, P = 0.0001; percentage loss on each of the arms, P < 0.05). Loss on 3p and/or 9p, a pattern associated with a 24-fold increased risk of progression (Rosin MP, Cheng X, Poh C, Lam WL, Huang Y, Lovas J, et al. Use of allelic loss to predict malignant risk for low-grade oral epithelial dysplasia. Clin Cancer Res 2000;6:357-62) was more frequent among HR lesions (P = 0.0005). Loss of heterozygosity frequencies were elevated at HR sites among both genders and among smokers and nonsmokers. For different histologic groups, LOH frequencies were elevated for HR sites in mild dysplasias (P < 0.05) and moderate dysplasias (marginal significance, P = 0.06), but not in severe dysplasias/carcinoma in situ.

CONCLUSIONS

Anatomic location of mild and moderate oral dysplasias in Western populations may be an important diagnostic indicator because lesions at HR sites have a greater tendency to include genetic alterations associated with elevated risk of progression.

Cohort cancer incidence among pulp and paper mill workers in British Columbia

OBJECTIVES

A study was conducted to investigate cancer risks in a cohort of pulp and paper workers.

METHODS

All male workers with > or =1 years of employment in 14 pulp and paper mills in 1950-1992 were studied. Standardized incidence ratios (SIR) were used to compare the cancer incidence of the cohort with that of the Canadian male population. Record linkage with the National Cancer Registry was performed using the generalized iterative record linkage method.

RESULTS

Altogether 1756 cancer cases were observed in the entire cohort. For > or =15 years of work, the entire cohort had significantly increased SIR values for pleural and prostate cancer and skin melanoma; there was also a significantly increased risk for skin melanoma among workers in the kraft process only, rectal cancer among workers in the sulfite process only, and stomach and prostate cancer and all leukemias combined among workers in both the kraft and sulfite processes. A separate analysis comparing workers in pulping and papermaking with those in the pulping process only did not reveal any difference in cancer risk and hence did not modify the results. The SIR values for skin melanoma were not significantly increased in a comparison using the British Columbia male population. Nine of 10 pleural cancers were mesotheliomas, which likely reflect past asbestos exposure.

CONCLUSIONS

The results suggest that long-term work in the pulp and paper industry is associated with excess risks of prostate and stomach cancers and all leukemias for work in both kraft and sulfite processes and of rectal cancer for work in the sulfite process only.

A survey of antibiotic use in dentistry

BACKGROUND

Antibiotics are important in the management and prophylaxis of infection in patients at risk of experiencing microbial disease. As a result of the increase in antimicrobial resistance, the authors conducted a survey to assess current antibiotic use in dental practice.

METHODS

The authors mailed a two-page, pretested survey to all licensed dental practitioners in British Columbia, Canada. A total of 2,542 surveys were mailed; 19.9 percent were returned by fax or mail. The authors examined an association between factors analyzed using a chi 2 test.

RESULTS

Respondents were demographically consistent with all registered dentists in British Columbia. They reported writing an average of 4.45 prescriptions per week. Antibiotics prescribed after treatment primarily were penicillin and its derivatives. Recommended adult doses of penicillin were prescribed by 59.2 percent of respondents; recommended daily doses of amoxicillin were prescribed by 72.2 percent of respondents. The average prescription duration was 6.92 days. Respondents prescribed prophylactic antibiotics an average of 1.15 times per week for prophylaxis of bacterial endocarditis; 17.5 percent reported postoperative dosing for prophylaxis, ranging from a one- to seven-day prescription with an average of 6.91 postoperative doses. Preoperative antibiotics were prescribed for patients with a history of rheumatic fever or any heart murmur or prosthetic hip. Antibiotics were prescribed more frequently for surgical procedures and patients with acquired immunodeficiency syndrome than for other circumstances.

CONCLUSIONS

More than 80 percent of respondents reported that they followed current American Heart Association prophylaxis guidelines. The authors, however, noted discrepancies in prophylactic use of antibiotics for bacterial endocarditis and for patients with large joint prostheses, as well as in prescribing antibiotics in the presence of clinical infection. In therapeutic use, approximately 85 percent of respondents followed appropriate prescription guidelines for dosing and duration of therapy.

CLINICAL IMPLICATIONS

Appropriate and correct use of antibiotics is essential to ensure that effective and safe treatment is available and that practices that may enhance microbial resistance are avoided. To improve standards of care, dentists need up-to-date pharmacology in dental education, as well as continuing education, further outcome studies and continuous assessment of dental practices.

Methodological issues in the development of the Canadian Cancer Incidence Atlas

The Canadian Cancer Incidence Atlas is among recent national atlases using incidence rather than mortality data. Methods used to assess the significance and spatial correlation of the age-standardized rates (ASIRs) for the 290 census divisions are described. The expected number of cases by area was used to determine cancer sites with sufficient cases to be mapped. ASIR significance was assessed using a simulation based on a Poisson distribution. The consistency of the observed case distributions with the Poisson distribution was examined. The bootstrap confidence interval (CI) for the ASIR developed by Swift was used in the atlas. Spatial correlation was assessed with Moran's I/I(max) and the significance determined by a simulation in order to allow for area population variation. Data quality indicators typically used for cancer registries were presented, supplemented by a registry questionnaire.

Identification of occupational cancer risks in British Columbia. A population-based case-control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors

Lifetime occupational histories as well as information on known and suspected breast cancer risk factors were collected by means of a self-administered questionnaire from 1018 women with incident breast cancer ascertained from the British Columbia Cancer Registry, and from 1020 population controls. A matched case-control study design was used. Conditional logistic regression for matched sets data and the likelihood ratio were used in a two-step procedure and were performed separately for pre-menopausal women, post-menopausal women, and for all cases combined. Excess risk was noted for several white-collar occupations. Significantly increased risk was observed: (1) among pre-menopausal women: in electronic data-processing operators; barbers and hairdressers; in sales and material processing occupations; and in the food, clothing, chemical and transportation industries; (2) among post-menopausal women: in schoolteaching; in medicine, health, and nursing occupations; in laundry and dry-cleaning occupations; and in the aircraft and automotive, including gasoline service station, industries. Several significant associations were also seen in the combined group of pre- and post-menopausal women, particularly in crop farmers and in the fruit and vegetable, publishing and printing, and motor vehicle repair industries. The results of this study suggest excess breast cancer risk in a number of occupations and industries, notably those that entail exposure to solvents and pesticides.

Use of allelic loss to predict malignant risk for low-grade oral epithelial dysplasia

One of the best approaches to identifying genetic changes critical to oral cancer progression is to compare progressing and nonprogressing oral premalignant lesions. However, such samples are rare, and they require long-term follow-up. The current study used the large archive network and clinical database in British Columbia to study loss of heterozygosity (LOH) in cases of early oral premalignancies, comparing those with a history of progression to carcinoma in situ or invasive cancer and those without a history of progression (referred to as nonprogressing cases). Each of 116 cases was analyzed for LOH at 19 microsatellite loci on seven chromosome arms (3p, 4q, 8p, 9p, 11q, 13q, and 17p). The progressing and nonprogressing cases showed dramatically different LOH patterns of multiple allelic losses. An essential step for progression seems to involve LOH at 3p and/or 9p because virtually all progressing cases showed such loss. However, LOH at 3p and/or 9p also occurred in nonprogressing cases. Individuals with LOH at 3p and/or 9p but at no other arms exhibit only a slight increase of 3.8-fold in relative risk for developing cancer. In contrast, individuals with additional losses (on 4q, 8p, 11q, or 17p), which appeared uncommon in nonprogressing cases, showed 33-fold increases in relative cancer risk. In conclusion, analysis of LOH at 3p and 9p could serve as an initial screening for cancer risk of early premalignancies. Follow-up investigation for additional losses would be essential for predicting cancer progression.

Measuring and modelling pollution for risk analysis

The great scale and complexity of environmental risk analysis offers major methodological challenges to those engaged in policymaking. In this paper we describe some of those challenges from the perspective gained through our work at the University of British Columbia (UBC). We describe some of our experiences with respect to the difficult problems of formulating environmental standards and developing abatement strategies. A failed but instructive attempt to find support for experiments on a promising method of reducing acid rain will be described. Then we describe an approach to scenario analysis under hypothetical new standards. Even with measurements of ambient environmental conditions in hand the problem of inferring actual human exposures remains. For example, in very hot weather people will tend to stay inside and population levels of exposure to e.g. ozone could be well below those predicted by the ambient measurements. Setting air quality criteria should ideally recognize the discrepancies likely to arise. Computer models that incorporate spatial random pollution fields and predict actual exposures from ambient levels will be described. From there we turn to the statistical issues of measurement and modelling and some of the contributions in these areas by the UBC group and its partners elsewhere. In particular we discuss the problem of measurement error when non-linear regression models are used. We sketch our approach to imputing unmeasured predictors needed in such models, deferring details to references cited below. We describe in general terms how those imputed measurements and their errors can be accommodated within the framework of health impact analysis.

Identification of occupational cancer risks in British Columbia. Part II: A population-based case-control study of 1516 Prostatic cancer cases

We have, as part of a program aimed at detecting occupational risk factors in British Columbia, collected lifetime occupational histories from 15,643 incident cancer cases, of whom 1519 had a diagnosis of prostate cancer. Occupational risks for this cancer site are examined using this large data set, and the results are presented in this report.

Identification of occupational cancer risks in British Columbia. Part I: Methodology, descriptive results, and analysis of cancer risks, by cigarette smoking categories of 15,463 incident cancer cases

To identify occupational cancer risk factors, lifetime occupational, smoking, and alcohol-consumption histories were collected by means of a self-administered questionnaire from 15,463 male cancer patients aged 20 years and over as ascertained from the British Columbia population-based cancer registry; all cases were histologically confirmed. The study methodology, descriptive results, and cancer risks from cigarette smoking are reported. Assessment of questionnaire validation and reliability showed very high correlations between all variables analysed. Non-response bias, assessed among 221 non-responders and 432 matched controls, revealed no statistically significant differences for smoking status, education, or for 11 usual (longest-held job) occupational groups, except for managerial occupations and for four pooled groups that represented 6.7% of all occupations. Except for pancreatic cancer, a significant relationship was found for all cancer sites known to be strongly associated with cigarette smoking.

A double-blind crossover trial of Oral Balance gel and Biotene toothpaste versus placebo in patients with xerostomia following radiation therapy

Following therapeutic irradiation of the head and neck, patients with profound xerostomia have complaints associated with oral dryness, effects upon use of oral prosthesis, speech, and taste. In addition, xerostomia may lead to risk of oral infections and rampant demineralization of teeth. The use of topical Oral Balance gel and Biotene toothpaste (Laclede Professional Products, Gardena, CA) versus carboxymethylcellulose gel and commercial toothpaste applications was assessed in a 2-week double-blind, crossover design. The palliative effects of Oral Balance gel and Biotene toothpaste were superior to the effects of a placebo. No effect on oral colonization by Candida species and cariogenic oral microflora was seen with use of the topical agents.

Occupational risk factors for prostate cancer mortality in British Columbia, Canada

BACKGROUND

Although prostate cancer is the most common life-threatening cancer among males in North America, relatively little is known about its etiology. We have conducted a proportional mortality study to generate hypotheses concerning occupational risk factors for the disease.

METHODS

Age standardized proportional mortality ratios (PMR) for prostate cancer were calculated for a total of 216 occupations and 88 industries. Separate calculations were done for all male deaths age 20 and up and for deaths that occurred during men's working lifetime (age 20-65).

RESULTS

Elevated mortality from prostate cancer was seen among business owners and managers (PMR = 110; 95% CI = 101-118), brokers (PMR = 184; 95% CI = 122-266), farmers and farm managers (PMR = 112; 95% CI = 105-120), and school teachers (PMR = 133; 95% CI = 101-174). Evaluation by industry shows elevated prostate cancer mortality in agriculture (PMR = 110; 95% CI = 103-118), financial institutions (PMR = 138, 95% CI = 112-170), and transportation equipment manufacture (PMR = 136; 95% CI = 109-168).

CONCLUSIONS

The findings suggest that workers in a number of occupations have elevated risks of prostate cancer including farmers and teachers. More detailed cohort and case-control studies, evaluating specific exposures are required before primary prevention programs in the workplace are feasible.

Quality of life and oral function following radiotherapy for head and neck cancer

BACKGROUND

Multiple oral complaints occur following radiotherapy for oropharyngeal cancer, but the frequency and severity of symptoms of dysfunction and discomfort are not well understood. The purpose of this investigation was to assess the quality of life, oral function, and oral symptoms following radiotherapy.

METHODS

A general quality of life survey (the European Organization for Research and Treatment of Cancer [EORTC] Quality of Life Questionnaire QLQ-C30), with an added oral symptom and function scale was mailed to 100 patients more than 6 months following radiotherapy.

RESULTS

Sixty-five patients responded. Difficulty chewing or eating was reported by 43% of respondents. Dry mouth was reported by 91.8%, change in taste by 75.4%, dysphagia by 63.1%, altered speech by 50.8%, difficulty with dentures by 48.5%, and increased tooth decay by 38.5% of dentate patients. Pain was common (58.4%) and interfered with daily activities in 30.8%. Mood complaints were reported by approximately half the patients. Interference of the physical condition social activities was reported by 60%. The frequency of oral side effects correlated with radiation treatment fields and dose.

CONCLUSION

Oral complications following radiotherapy for head and neck cancer are common and affect quality of life. Use of a general function scale such as the EORTC questionnaire with the addition of disease/site specific scales may provide useful data on outcome of therapy and upon the complications associated with therapy and impact upon the quality of life.

Cohort mortality study of pulp and paper mill workers in British Columbia, Canada

The authors studied a cohort of 30,157 male pulp and paper workers in British Columbia, Canada. Of these, 20,373 worked in kraft mills only, 5,249 in sulfite mills only, and 4,535 in both kraft and sulfite mills. All workers with at least 1 year of employment on January 1, 1950, or thereafter until December 31, 1992, were studied. Standardized mortality ratios (SMRs) were used to compare the mortality rates of the cohort with those of the Canadian male population. Ninety percent confidence intervals (CIs) for the SMRs were obtained. Cancer risks significantly associated with work duration and time from first employment of 15 years or more were observed: 1) total cohort: pleura (SMR = 3.61, 90% CI 1.42-7.58); kidney (SMR = 1.69, 90% CI 1.13-2.43); brain (SMR = 1.51, 90% CI 1.03-2.16); 2) workers in kraft mills only: kidney (SMR = 1.92, 90% CI 1.04-3.26); 3) workers in sulfite mills only: Hodgkin's disease (SMR = 4.79, 90% CI 1.29-12.37); 4) workers ever employed in both kraft and sulfite mills: esophagus (SMR = 1.91, 90% CI 1.00-3.33). These malignancies have been associated with the following known or suspected carcinogens to which pulp and paper workers may have been exposed: asbestos (pleura), biocides (kidney), formaldehyde (kidney, brain, Hodgkin's disease), hypochlorite (esophagus). A nested case-control study with detailed exposure assessment is under way to help determine whether excess risks for specific cancers reflect exposure among subsets of workers.

The reversal of profound mivacurium-induced neuromuscular blockade

PURPOSE

Mivacurium is metabolized by plasma cholinesterase catalyzed ester hydrolysis. Acetylcholinesterase antagonists used in the reversal of muscle relaxation may also inhibit plasma cholinesterase and, therefore, delay the hydrolysis of mivacurium. The clinical interaction between acetylcholinesterase antagonists and mivacurium induced neuromuscular blockade was studied.

METHOD

Intraoperative muscle relaxation was maintained with a mivacurium infusion to achieve a constant intense block (first twitch, T1, 2-3% of control). Patients were randomly divided into three groups. Patients in Group 1 received no anticholinesterase, in Group 2 neostigmine 0.07 mg.kg-1, and in Group 3 edrophonium 1 mg.kg-1. The times between termination of the mivacurium infusion (Group 1) or the administration of the anticholinesterase (Groups 2 and 3) to 25%, 50%, 75% and 95% T1 recovery, and to 50%, 70% and 90% recovery in the ratio, T4/T1 (TR) were recorded.

RESULT

In the neostigmine Group, T1 recovery to 25%, 50% and 75% (2.32 +/- 1.41, 3.90 +/- 1.85 and 6.88 +/- 2.66 min) was accelerated compared with control (3.36 +/- 1.34, 5.78 +/- 2.22, and 8.58 +/- 3.60, and), but recovery to 95% (18.53 +/- 9.09 vs 13.29 +/- 5.24 min) was delayed. Also, TR recovery to 50%, 70%, and 90% was slower (14.47 +/- 8.73, 21.25 +/- 11.06 and 31.37 +/- 12.11 min vs 11.75 +/- 3.74, 13.78 +/- 4.39 and 17.86 +/- 6.44 min). However, all T1 and TR recovery times were decreased in the edrophonium group (0.88 +/- 0.51, 2.00 +/- 1.50, 4.97 +/- 2.96, and 9.35 +/- 5.24 min for T1 and 6.86 +/- 3.93, 9.05 +/- 4.51 and 12.24 +/- 6.66 min for TR).

CONCLUSION

Neostigmine reversal of intense mivacurium neuromuscular block should be avoided, as this may result in prolongation of the block.

Surveillance of clustering near point sources

Health authorities are often alerted to suspected cancer clusters near the vicinity of potential point sources by members of the public. A surveillance system, where administrative regions around the potential point sources are regularly monitored for high disease rates, would allow for responses which are easier to obtain, timelier, and less expensive than individual thorough investigations. The monitoring could be done by using the so-called 'focused' tests for detecting disease clustering. However, these tests, generally designed to detect clusters of a fixed size around the foci, are not particularly effective when dealing with administrative regions with substantial differences in populations. In this work, an approach which overcomes the problem to a certain extent is described. Here the selected cluster sizes are based on the populations of the administrative regions under examination. The approach is used to investigate whether cancer clustering appears in the vicinity of the pulp and paper mills in British Columbia for the years 1983-1989. The results indicate that the approach performs reasonably well in identifying cancer sites for which elevated risks have also been suggested in the epidemiologic literature. Consequently, this methodology could be utilized to provide guidance for further investigation even in the absence of local reports. Similarly, it could be readily utilized to provide timely responses to local reports.

Cohort study of Air Canada pilots: mortality, cancer incidence, and leukemia risk

Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.80-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group.

Compliance with fluoride gel use in irradiated patients

Patients who undergo radiation therapy that includes the salivary glands frequently experience severe xerostomia. The standard of care for these patients who have natural teeth has become daily application of fluoride by means of custom-fabricated carriers. The purpose of this study was to determine patient compliance with fluoride gel application using carriers. Using a structured verbal questionnaire, we interviewed 76 patients who had completed radiation therapy for head and neck cancer. Thirty of these patients were seen regularly in the dental clinic of the Cancer Agency (group 1); the remaining 46 were not seen on a regular basis (group 2). Overall, 43% of patients reported using fluoride gel regularly (once a day). In group 1, 67% of patients used fluoride regularly, as did 28% of patients in group 2 (p = 0.001). There were no significant differences between the groups in frequency of toothbrushing and use of dental floss. Compliance with the use of fluoride in carriers was not associated with differences in other oral care measures in the two groups, which suggests that fluoride application in carriers achieves limited compliance in relation to daily oral health care measures. Regular follow-up of patients after radiation therapy is needed to assess their need for, and compliance with, daily fluoride application.

Assessing viral retention and elimination in rotary dental instruments

The authors of this article used a laboratory model of herpes simplex virus infection to assess the potential for contamination of dental handpieces by a human viral pathogen. They found that although all the handpieces in the study were fitted with anti-retraction valves, it was not until the units were flushed internally and disinfected externally that the pathogens were eliminated.

Topical bleomycin treatment of oral leukoplakia: a randomized double-blind clinical trial

BACKGROUND

Oral leukoplakia and oral erythroplakia may be associated with benign and dysplastic cellular changes, and are at risk of malignant transformation. Additional means of management of these lesions is needed. The results of nonblinded trials using topical bleomycin in oral leukoplakia indicated the need for phase III study.

METHODS

A prospective, double-blind, randomized trial of topical bleomycin versus placebo was conducted. Bleomycin 1% in dimethylsulphoxide (DMSO) or the carrier was applied for 5 minutes for 14 consecutive days. Clinical assessment and pre-application and post-treatment biopsies were conducted.

RESULTS

Twenty-two patients were randomized. Of the patients who received bleomycin, decrease in clinical size of the lesion was achieved (p = 0.001), and histological reduction in dysplasia was seen (p = 0.094).

CONCLUSIONS

The topical application of bleomycin in DMSO may represent an additional approach to management of oral leukoplakia. The treatment is well-tolerated, and may be considered when the location or extent of the lesion may make surgical excision difficult.

A clinical trial of bethanechol in patients with xerostomia after radiation therapy. A pilot study

The effects of bethanechol in the treatment of dry mouth were assessed in patients with xerostomia after radiation therapy to the head and neck. Bethanechol possesses muscarinic and nicotinic-cholinergic activity that likely accounts for its mode of action. Bethanechol (25 mg, three times daily) was not associated with significant side effects. Statistically significant increases in whole resting saliva (p = 0.003) and whole stimulated saliva (p = 0.001) were seen. In patients with pretreatment stimulated saliva volumes greater than resting saliva volumes, a positive response to subsequent use of the sialagogue was seen.

Risk factors for oropharyngeal candidiasis in patients who receive radiation therapy for malignant conditions of the head and neck

Twenty-seven consecutive patients receiving radiation to the head and neck were followed to assess risk factors for the development of candidiasis. One-third of the patients developed oral candidiasis during radiation therapy. Xerostomia was shown to correlate with risk of oropharyngeal infection (p = 0.033). The presence and use of oral prostheses were shown to correlate with oral colonization of Candida albicans before radiation therapy (p = 0.011). Alcohol use and smoking represent risk factors for oral colonization by Candida during radiation therapy (p = 0.023 and p = 0.045 respectively). These factors must be assessed in future studies of oropharyngeal candidiasis in radiation therapy.

Exact likelihood evaluation in a Markov mixture model for time series of seizure counts

This paper provides an alternative to Albert's (1991), Biometrics 47, 1371-1381) approximation to the E-step when using the EM algorithm for parameter estimation in Markov mixture models. Use of a recursive algorithm of Baum et al. (1970, Annals of Mathematical Statistics 41, 164-171) results in exact evaluation of the likelihood, optimal parameter estimates, and very efficient computation. Applications to time series of seizure counts and fetal movements clearly show the advantages of this exact approach.