Page 31 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors
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Salivary gland pleomorphic adenoma in the Netherlands
excluded primary carcinomas ex pleomorphic adenoma from our database, and counted secondary carcinomas ex pleomorphic adenoma (SGPAs that recurred as malignant tumors) both as malignant transformations and as recurrences. Carcinomas in situ ex pleomorphic adenoma were not considered malignant transformations.
Risk factors for recurrence: We investigated sex, age, tumor site, and margin status. As the type of surgery was not always specified, and reporting practices varied, we decided to exclude this factor for our study.
Statistical analysis: We analyzed our data with SPSS (version 21.0; SPSS Inc., Chicago, III) and R [21,22], taking a p-value of <0.05 to be statistically significant for all purposes. Using linear regression and the natural log rhythm of ESR, we computed annual percent changes (APCs) by sex and overall, and we applied finite mixture models to investigate distribution patterns for age at diagnosis [23]. With the Kaplan-Meier method, we calculated times to recurrence and identified potential predictors for recurrence using multivariate logistic regression analysis. In addition to our analysis of complete cases, we performed missing data analysis and multiple-imputation analysis, imputing missing data by letting the R MICE package generate five imputed datasets and comparing the pooled results to our analysis of complete cases.
Results
Incidence: After data cleaning, 3 504 unique patients remained of a total of 3 948 diagnosed with pleomorphic adenoma (Table 1). Two patients developed a second primary SGPA at a different anatomical site. Overall crude incidence varied from 3.9 to 4.7 per 100 000 person-years (Tables 2a and 2b). ESR ranged between 4.2 and 4.9 per 100 000 person-years. After stratifying for sex, we found a statistically significant annual rise of ESR in women (APC= 1.0% per year; 95% CI: 0.2-1.8), but not in men (APC= 0% per year; 95% CI: -1.0 to 0.9) (Figure 1).
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