Trends in colon cancer surgery in Ontario: 2002-2009.

AIM: The safety and efficacy of laparoscopic surgery for colon cancer is well established but its uptake in the province has not been previously explored. We report an investigation of the trends of open and laparoscopic surgery for colon cancer in Ontario, Canada. METHOD: A retrospective cross-sectional time-series analysis examining population-based rates of elective surgery for colon cancer among 10.5 million adults in Ontario was conducted from 1 April 2002 to 31 March 2009. Databases were linked to assess quarterly elective procedure rates over time. RESULTS: During the study period, 3950 laparoscopic and 13 048 open elective colon cancer operations were performed in Ontario. The overall quarterly rate of colon cancer surgery remained stable at an average of 5.8 per 100000 population (P=0.10). From the first and last quarter, the rate of laparoscopic operations increased nearly threefold from 0.8 to 2.2 per 100000 population with a notable increase after 2005 (P<0.01). In contrast, open surgery decreased by more than 30% from 5.3 to 3.5 per 100 000 population (P<0.01). If current trends continue, the projected proportion of laparoscopic colon operations is estimated to reach 41% by 2015. Patients receiving open surgery had a significantly higher preoperative comorbidity (Charlson comorbidity score≥3) than those having laparoscopy (47.8%vs 39.1%, standardized difference 0.26). CONCLUSION: Trends in Ontario of laparoscopic colon cancer surgery show an increase between 2002 and 2009, but the incidence remains lower than for open surgery.

Changing trends in rectal cancer surgery in Ontario: 2002-2009.

AIM: The safety and efficacy of laparoscopic surgery for colon cancer have been demonstrated in large, multicentre clinical trials. The study aimed to determine the use of laparoscopic surgery for rectal cancer in Ontario over a 7-year period. METHOD: We conducted a retrospective study examining rates of elective rectal cancer surgery among 10.5 million adults in Ontario, Canada, from 1 April 2002 to 31 March 2009. We linked the Canadian Institute for Health Information Discharge Abstract Database, the Registered Persons Database and the database of the Ontario Cancer Registry to assess procedures used over the period. Data on demographics were collected. Trends were assessed using time series analysis. RESULTS: Over the 7-year period, 8189 open and 1079 laparoscopic elective operations for rectal cancer were identified. The annual rate of laparoscopic rectal cancer procedures increased from 0.60 per 100,000 population in 2003 to 2.24 per 100,000 population in 2008 (P < 0.01). Laparoscopic patients were similar to open with respect to age (66.5 ± 11.8 vs 66.2 ± 12.1 years; standardized difference 0.02), gender (63.2%vs 59.4%; standardized difference 0.08), Charlson Comorbidity Index score (standardized difference < 0.1) and socioeconomic status (standardized difference < 0.1). CONCLUSION: Laparoscopic rectal cancer surgery rates are increasing in Ontario. Ongoing research regarding the long-term safety and effectiveness of the laparoscopic approach for rectal cancer surgeries may lead to greater increases in its utilization.

Biopersistence of synthetic vitreous fibers and amosite asbestos in the rat lung following inhalation.

Fiber biopersistence as a major mechanism of fiber-induced pathogenicity was investigated. The lung biopersistence of 5 synthetic vitreous fibers (SVFs) and amosite asbestos was evaluated using the rat inhalation model. In contrast to several previous studies, this study examined fibers that dissolve relatively slowly in vitro at pH 7.4. Fisher rats were exposed for 5 days by nose-only inhalation to refractory ceramic fiber (RCF1a), rock (stone) wool (MMVF21), 2 relatively durable special application fiber glasses (MMVF32 or MMVF33), HT stonewool (MMVF34), amosite asbestos, or filtered air. Lung burdens were analyzed during 1 year post-exposure. Fiber aerosols contained 150-230 fibers/cc longer than 20 micrometer (>20 micrometer). On post-exposure Day 1, long-fiber lung burdens for the 6 test fibers were similar (12-16 x 10(5) fibers/lung >20 micrometer). After 1 year, the percentage of fibers >20 micrometer remaining in the lung was 0.04-10% for SVFs but 27% for amosite. Lung clearance weighted half-times (WT1/2) for fibers >20 micrometer were 6 days for MMVF34, 50-80 days for the other 4 SVFs, and >400 days for amosite. This study and 3 previous studies demonstrate a broad range of biopersistences for 19 different SVFs and 2 asbestos types. Ten of these fibers also have been (or are being) tested in chronic inhalation studies; in these studies, the very biopersistent fibers were carcinogenic (amosite, crocidolite, RCF1, MMVF32, and MMVF33), while the more rapidly clearing fibers were not (MMVF10, 11, 21, 22, and 34). These studies demonstrate the importance of biopersistence as an indicator of the potential pathogenicity of a wide range of fiber types.

Biopersistence of man-made vitreous fibers and crocidolite asbestos in the rat lung following inhalation.

This study investigated possible relationships between fiber bio-persistence in the lung and previously observed differences in pulmonary toxicity between asbestos and man-made vitreous fibers (MMVF) following inhalation exposure. Fischer 344/N rats were exposed nose only, 6 hr/day for 5 days to 30 mg/m3 MMVF (two fiberglass compositions, rock wool, or slag wool) or to 10 mg/m3 crocidolite asbestos. At eight time points up to 1 year postexposure, lung fiber burdens were analyzed for number/lung and bivariate dimensions using scanning electron microscopy (SEM) and for chemical composition using SEM energy dispersive spectroscopy. After 365 days, > 95% of long (> 20 microns) MMVFs had disappeared from the lung compared to only 17% of long crocidolite fibers. Longer MMVFs disappeared more rapidly than short MMVFs, suggesting that long fibers were dissolving or breaking. Mean diameters and lengths of the MMVFs decreased with time, while the mean diameter of crocidolite remained unchanged and its mean length showed an apparent increase, probably related to macrophage-mediated clearance of short fibers. Leaching of oxides occurred in the fibrous glasses and slag wool and correlated with morphological changes in the fibers over time. No chemical or morphological changes were observed in crocidolite fibers. These changes in MMVF number, chemistry, and morphology over time in lung tissue compared to crocidolite asbestos demonstrate the relatively low biological persistence of some MMVFs in the lung and may explain why these MMVFs are not tumorigenic in rats, even after chronic exposure at high concentrations.

Biopersistences of man-made vitreous fibers and crocidolite fibers in rat lungs following short-term exposures.

Biopersistence of commercial man-made vitreous fibers (MMVF) and crocidolite were studied in Fischer 344 rats. MMVF used were size-selected to be rat-respirable, and rats were exposed nose-only 6 h/day for 5 days to gravimetric concentrations (30 mg/m3) of two fiber glass compositions--a rockwool, and a slagwool--or to 10 mg/m3 of long-fibered crocidolite, or to filtered air. Animals were sacrificed at 1 hr, 1, 5, 31, 90, 180, 270, 365, and 545 days after exposure stopped. Fibers were recovered from digested lung tissue to determine changes in concentrations (fibers/mg dry lung) and fiber retentions (expressed as percent of day 1 retention [PR]) for selected dimension categories. One-day average concentrations of lung-retained MMVF and crocidolite fibers, of diameter > or = 0.5 micron or > 20 microns in length, were nearly equal, permitting direct comparisons between MMVF and crocidolite. At 270 days average PR for MMVF > or = 0.5 micron in diameter were from 3 to 6 +/- 2% and 27 +/- 9% for crocidolite. For fibers > 20 microns, PR were 1 to 4 +/- 4% for MMVF and 37 +/- 20% for crocidolite. At 545 days, MMVF > 20 microns in length were at background level while concentration of crocidolite fibers > 20 microns in length remained at 2000 +/- 400 f/mg DL (dry lung), or 38 +/- 9% of day-1 retention. These results suggest strongly that MMVF dissolved or fractured in vivo whereas crocidolite fibers did not change.

An epidemiological and toxicological evaluation of the carcinogenicity of man-made vitreous fiber, with a consideration of coexposures.

Exposure to man-made mineral (or vitreous) fiber (MMMF or MMVF) is a potential health concern in both occupational and environmental settings. Previous epidemiologic studies have reported a small increase of lung cancer among workers exposed to MMVF. Most of these studies were cohort studies and lacked information on fiber concentration, occupational coexposures, and cigarette smoking. Some of the coexposures were known human lung carcinogens and could have accounted for the small lung cancer excess. In a recently completed epidemiologic case-control study of lung cancer in MMVF workers exposed to slag wool fibers, we analyzed lung cancer risk in relation to cumulative fiber exposure (concentration and duration) and smoking history and controlled for other coexposures such as asbestos contamination. No increased lung cancer risk with exposure to slag wool fibers was found. As expected, however, we detected a strong confounding effect of smoking. The findings from this epidemiologic study were consistent with the results of recently completed toxicologic studies, which found that slag wool fibers of dimension classically associated with tumor induction ("Stanton" fibers) do not stay in the lung in sufficient quantity or time to induce tumors in animals. In this paper we emphasize the importance of confounding effects due to coexposures and provide guidelines to estimate the magnitude of potential confounding effects of coexposures such as smoking.

Hand-rearing baboons for laboratory investigations.

To conduct laboratory studies in unsedated animals that were similar anatomically and physiologically to man, five full term baboons (four Papio cynocephalus anubis, one Papio cynocephalus cynocephalus) were hand-reared. These infants were used as unsedated animal models in short-term lung clearance studies conducted from birth to 2 years of age. The hand-rearing techniques described here encouraged the formation of an infant-human rearer bond that permitted us to control the level of expressed aggressive behavior as the infant matured. These techniques resulted in baboons which displayed subordinate behavior, showed positive reception to human contact (without evidence of negative stereotypic behavioral anomalies) and remained cooperative subjects for our investigations of short-term pulmonary clearance. The baboons generally were above average in weight in comparison to conspecifically-reared baboons of similar age, sex and species. Representative lung retention curves presented on one baboon demonstrate the feasibility of lung clearance studies in these hand-reared animals. Due to its suitability for unsedated studies, this baboon model may be considered for other types of laboratory investigations.

Unsedated animal models of pulmonary mucociliary transport.

Measurements of the rate of mucociliary transport in the airways of the lower respiratory tract have been shown to be influenced by the techniques and protocols used. To avoid the effects associated with invasive techniques and anesthesia in animal models used to study the effect of maturation, drugs, disease, and inhaled pollutants on mucociliary transport we have developed unsedated dog and baboon models of mucociliary transport using radioaerosol techniques. As far as they have been tested these animal models of mucociliary transport react to drugs such as isoproterenol and atropine in the same manner as in man.