Mobility and speciation of geogenic arsenic in bedrock groundwater from the Canadian Shield in western Quebec, Canada.

High arsenic concentrations occur in groundwater collected from a fractured crystalline bedrock aquifer in western Quebec (Canada). Sampling and analysis of water from 59 private wells reveal that more than half of the bedrock wells exceed the Canadian guideline value of 10µg/l for arsenic, whereas shallow wells in unconsolidated surficial deposits are not affected by the contamination. The weathering of arsenic-bearing sulfides present along the mineralized fault zone is considered to be the primary source of arsenic in groundwater. High-arsenic wells are generally characterized by mildly reducing conditions (Eh<250mV), weak alkaline conditions (pH>7.4), low Ca/Na ratios, elevated dissolved Fe and Mn concentrations and high proportions of As(III). Private bedrock wells are open boreholes that likely receive groundwater from multiple contributing fractures. Hence, it is proposed that dissolved arsenic is mainly derived from the contribution to the well discharge of reducing and alkaline geochemically evolved groundwater that contains arsenic as As(III). Geochemically evolved groundwater provides favorable conditions to release arsenic by reductive dissolution of iron and manganese oxyhydroxides and alkaline desorption from mineral surfaces. Thus, high-arsenic wells would contain a high proportion of geochemically evolved groundwater, while oxidizing low-pH recharge water causes dilution and sequestration of arsenic. In relation with the chemical evolution of groundwater along the flow path, most contaminated wells are located in confined areas whereas most of the wells located in unconfined recharge areas are not contaminated. The occurrence of boreholes with high dissolved arsenic as As(V) and oxidizing conditions is attributed to extensive sulfide oxidation and alkaline desorption. This work shows that the determination of arsenic speciation provides a valuable tool to investigate the behavior of arsenic in bedrock groundwater.

Exploring 222Rn as a tool for tracing groundwater inflows from eskers and moraines into slope peatlands of the Amos region of Quebec, Canada.

Peatlands can play an important role in the hydrological dynamics of a watershed. However, interactions between groundwater and peat water remain poorly understood. Here, we present results of an exploratory study destined to test radon (222Rn) as a potential tracer of groundwater inflows from fluvioglacial landform aquifers to slope peatlands in the Amos region of Quebec, Canada. 222Rn occurs in groundwater but is expected to be absent from peat water because of its rapid degassing to the atmosphere. Any 222Rn activity detected in peat water should therefore derive from groundwater inflow. 222Rn activity was measured in groundwater from municipal, domestic wells and newly drilled and instrumented piezometers from the Saint-Mathieu-Berry and Barraute eskers (n = 9), from the Harricana Moraine (n = 4), and from the fractured bedrock (n = 3). Forty measurements of 222Rn activity were made from piezometers installed in five slope peatlands, along six transects oriented perpendicular to the fluvioglacial deposits. The relationship between 222Rn and total dissolved solids (TDS) measured in water from the mineral deposits underlying the peat layer suggests that 222Rn is introduced by lateral inflow from eskers and moraine together with salinity. This input is then diluted by peat water, depleted in both TDS and 222Rn. The fact that a relationship between TDS and 222Rn is visible calls for a continuous inflow of groundwater from lateral eskers/moraines, being 222Rn rapidly removed from the system by radioactive decay. Although more research is required to improve the sampling and tracing techniques, this work shows the potential of 222Rn tracer to identify groundwater inflow areas from granular aquifers found in eskers and moraines to slope peatlands.

Population-based study of perioperative mortality after retroperitoneal lymphadenectomy for nonseminomatous testicular germ cell tumors.

OBJECTIVES: To determine whether retroperitoneal lymphadenectomy (RPLND) perioperative mortality (PM) rates reported from a center of excellence (Indiana University: 0% for primary and 0.8% for postchemotherapy RPLND) are applicable to institutions at large. METHODS: We used the data from 882 assessable patients with nonseminomatous testicular germ cell tumor treated with RPLND from 1988 to 1997 accessed from the Surveillance, Epidemiology, and End Results (SEER) database. These data did not include data from Indiana University. The observed PM rates were stratified according to age and SEER stage. RESULTS: The median age at RPLND was 29 years. Of the 882 cases, 435 (49.3%) were performed for localized (Stage I), 380 (43.1%) for regional (Stage II), and 67 (7.6%) for metastatic (Stage III) SEER stage. Of the 882 patients, 7 patients died during the initial 90 days after RPLND, for a 0.8% PM rate. PM increased with increasing age: < or =29 years, 0.0%; 30-39 years, 1.3%; and > or =40 years, 2.7% (chi(2) trend test, P = .002). PM also increased with increasing stage: 0.0% for localized, 0.8% for regional, and 6.0% for metastatic disease (chi(2) trend test, P < .001). CONCLUSIONS: RPLND is associated with virtually no or low PM in patients with localized and regional disease. The PM rates for these 2 groups replicated those of Indiana University. In contrast, the PM rate of 6% for patients with distant metastases implies that RPLND for these higher risk patients should ideally be performed at centers of excellence, with the intent of reducing the PM rate.

Development and external validation of a highly accurate nomogram for the prediction of perioperative mortality after transurethral resection of the prostate for benign prostatic hyperplasia.

PURPOSE: Benign prostatic hyperplasia affects 60% of men at the age of 60 years. Transurethral resection of the prostate is the gold standard of therapy. We assessed the 30-day mortality rate after transurethral resection of the prostate for benign prostatic hyperplasia, identified risk factors related to 30-day mortality and developed a model that discriminates among individual 30-day mortality risk levels. MATERIALS AND METHODS: We performed development (7,362) and external validation (7,362) of a multivariable logistic regression model predicting the individual probability of 30-day mortality after transurethral resection of the prostate based on an administrative data set (Quebec Health Plan) of 14,724 patients 43 to 99 years old treated between January 1, 1989 and December 31, 2000. RESULTS: Overall 30-day mortality occurred in 58 patients (0.4%) undergoing transurethral resection of the prostate. On univariable analyses increasing age (p <0.001) and increasing Charlson comorbidity index (p <0.001) were statistically significant predictors of 30-day mortality after transurethral resection of the prostate. Conversely annual surgical volume was not. On multivariable analyses age (p <0.001) and Charlson comorbidity index (p <0.001) reached independent predictor status. The accuracy of the age and Charlson comorbidity index based nomogram that predicts the individual probability of 30-day mortality after transurethral resection of the prostate was 83% in the external validation cohort. CONCLUSIONS: Age and Charlson comorbidity index are important determinants of 30-day mortality after transurethral resection of the prostate. The combination of these parameters allows an 83% accurate prediction of individual 30-day mortality risk after transurethral resection of the prostate. Despite limitations such as the need for additional external validations and possibly the need for inclusion of clinical parameters, the use of the current model is warranted for the purpose of informed consent before transurethral resection of the prostate and/or for patient counseling.

Population-based analysis of normal Total PSA and percentage of free/Total PSA values: results from screening cohort.

OBJECTIVES: To examine the distribution of total prostate-specific antigen (tPSA) and percentage of free/total PSA (%f/tPSA) values in patients undergoing prostate cancer screening in Canada. METHODS: The data from 4 consecutive annual prostate cancer screening events held in Montreal, Canada were examined with respect to age, tPSA, and %f/tPSA in 3222 men. RESULTS: Within the entire cohort, the median PSA level was 1.0 ng/mL and the median %f/tPSA was 26%. Using the interquartile range around the median, the upper bound for tPSA was situated at 1.9 ng/mL and the lower bound for %f/tPSA was at 19%. The 90th percentile for the median tPSA was 3.8, and the 10th percentile for the median %f/tPSA was 14. PSA and %f/tPSA showed a relation with age. The 75th percentile for the median tPSA level in the age category 40-49, 50-59, 60-69, and 70-79 years was 1.1, 1.4, 2.6, and 3.6 ng/mL, respectively. The 25th percentile for the median %f/tPSA level in the age category 40-49, 50-59, 60-69, and 70-79 years was 19, 21, 18 and 19 ng/mL, respectively. CONCLUSIONS: Our results can guide clinicians regarding the population-based distribution of serum tPSA and %f/tPSA values. Those values can be used for the purpose of counseling, as well as in the informed consent process before prostate biopsy.

A simple and accurate model for prediction of cancer-specific mortality in patients treated with surgery for primary penile squamous cell carcinoma.

PURPOSE: Cancer-specific mortality (CSM) of patients with primary penile squamous cell carcinoma (PPSCC) may be quite variable. Recently, a nomogram was developed to provide standardized and individualized mortality predictions. Unfortunately, it relies on a large number (n = 8) of specific variables that are unavailable in routine clinical practice. We attempted to develop a simpler prediction rule with at least equal accuracy in predicting CSM after surgical removal of PPSCC. EXPERIMENTAL DESIGN: The predictive rule was developed on a cohort of 856 patients identified in the 1988 to 2004 Surveillance, Epidemiology and End Results (SEER) database. The predictors consisted of age, race, SEER stage (localized versus regional versus metastatic), tumor grade, type of surgery (excisional biopsy, partial penectomy, and radical penectomy), and of lymph node status (pN0 versus pN1-3 versus pNx). A look-up table based on Cox regression model-derived coefficients was used for prediction of 5-year CSM. The predictive rule accuracy was tested using the Harrell's modification of the area under the receiver operating characteristics curve. RESULTS: SEER stage and histologic grade achieved independent predictor status and qualified for inclusion in the model. The model achieved 73.8% accuracy for prediction of CSM at 5 years after surgery. Both predictors achieved independent predictor status in competing risk regression models addressing CSM, where other cause mortality was controlled for. CONCLUSION: Despite equivalent accuracy, our predictive rule predicting 5-year CSM in patients with PPSCC is substantially less complex (2 versus 8 variables) than the previously published model.

Thirty-day mortality after nephrectomy: clinical implications for informed consent.

BACKGROUND: The existing literature suggests that the surgical mortality (SM) observed with nephrectomy for localised disease varies from 0.6% to 3.6%. OBJECTIVE: To examine age- and stage-specific 30-d mortality (TDM) rates after partial or radical nephrectomy. DESIGN, SETTING, AND PARTICIPANTS: We relied on 24535 assessable patients from the National Cancer Institute (NCI) Surveillance, Epidemiology, and End Results (SEER) database. MEASUREMENTS: In 12283 patients, logistic regression models were used to develop a tool for pretreatment prediction of the probability of TDM according to individual patient and tumour characteristics. External validation was performed on 12252 patients. RESULTS AND LIMITATIONS: In the entire cohort of 24535 patients, 219 deaths occurred during the initial 30 d after nephrectomy (0.9% TDM rate). TDM increased with age (≤49 yr: 0.5% vs 50-59 yr: 0.7% vs 60-69 yr: 0.9% vs 70-79 yr: 1.2% vs ≥80 yr: 2.0%; χ(2) trend p<0.001) and stage (0.3% for T1-2N0M0 vs 1.3% for T3-4N0-2M0 vs 4.2% for T1-4N0-2M1; χ2 trend p=<0.001). TDM decreased in more recent years (1988-1993: 1.3% vs 1994-1998: 0.9% vs 1999-2002: 0.7% vs 2003-2004: 0.6%; χ2 trend p<0.001) and was lower after partial versus radical nephrectomy (RN) (0.4% vs 0.9%; p=0.008). Only age (p<0.001) and stage (p<0.001) achieved independent predictor status. The look-up table that relied on the regression coefficients of age and stage reached 79.4% accuracy in the external validation cohort. CONCLUSIONS: Age and stage are the foremost determinants of TDM after nephrectomy. Our model provides individual probabilities of TDM after nephrectomy, and its use should be highly encouraged during informed consent prior to planned nephrectomy.

A critical assessment of the prognostic value of clear cell, papillary and chromophobe histological subtypes in renal cell carcinoma: a population-based study.

OBJECTIVE To assess the magnitude of the effect of histological subtype (HS, the three most common being clear cell, papillary and chromophobe) on cause-specific mortality (CSM) from renal cell carcinoma (RCC). PATIENTS AND METHODS Univariable and multivariable Cox regression models included data from 11 618 patients treated with nephrectomy between 1988 and 2004 in nine Surveillance Epidemiology and End Results registries. We tested whether HS represents an independent predictor of CSM, and whether HS adds to the ability of other variables to predict CSM. The covariates comprised age, year of surgery, T stage, nodal status, M stage and Fuhrman grade. RESULTS In a multivariable model predicting CSM, HS was an independent predictor (P = 0.03), but failed to improve the accuracy of the model (+0.1% gain when HS was included in the model). CONCLUSION Although we confirmed that HS is an independent predictor for CSM, there was no gain in accuracy when HS was added to standard predictors of CSM. From a practical perspective, this implies that patients with clear cell, papillary and chromophobe HS share similar natural histories after nephrectomy, provided that other cancer characteristics are accounted for. From a statistical perspective, in multivariable models of CSM, the clear cell, papillary and chromophobe HS might be included as a single entity.