http://repub.eur.nl/res/aut/9752/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/10708/ 2006-07-14T00:00:00Z Objectives: Surgical resection of postchemotherapy retroperitoneal lymph nodes is often performed in patients with advanced nonseminomatous testicular germ cell cancer. We previously developed a model to predict the probability that the lymph nodes contain only necrotic or fibrotic (benign) tissue versus mature teratoma and viable cancer (tumour) to identify patients who actually need resection. The present study used an updated model with new patient data and studied the validity of the updated model across various settings. Methods: We combined data of 544 patients from the original model with data of 550 new patients and performed a new logistic regression analysis, which included the same six predictors: histology of the primary tumour, prechemotherapy serum levels of a-fetoprotein, human chorionic gonadotropin, lactate dehydrogenase, residual mass size measured on computed tomography, and change in mass size. The validity of the updated model was studied in individual centres. Calibration of the predicted probabilities was assessed graphically and with the Hosmer-Lemeshow test. Discrimination was studied with the concordance (c)-statistic. Results: The updated model had slightly different, although more precise, regression coefficients. Statistically nonsignificant Hosmer-Lemeshow tests confirmed good calibration in most centres. The c-statistic for all centres except one exceeded 0.80. The updated model was valid over the complete range of predicted probabilities across a broad spectrum of centres. Conclusions: This finding gives confidence in the applicability of the model to select patients for resection, particularly patients with small residual masses and low predicted probabilities of benign tissue (i.e., substantial predicted risks of residual tumour). http://repub.eur.nl/res/pub/9359/ 2000-01-01T00:00:00Z PURPOSE: To determine the relative importance of computed tomographic (CT) measurements for the prediction of histologic findings in residual masses in patients with nonseminomatous testicular cancer. MATERIALS AND METHODS: Measurements of the maximum transverse size of retroperitoneal metastases before and after chemotherapy were available in 641 patients who underwent resection after chemotherapy while their levels of tumor markers were normal. Radiologic measurements of mass size and clinical characteristics (histologic findings in primary tumor and levels of alpha-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase before chemotherapy) were related to histologic findings in the residual mass with logistic regression analysis. RESULTS: At resection, 302 patients had benign tissue, and 339 had residual tumor (mature teratomas or cancer). Tumor was more frequent in larger masses after chemotherapy but was unrelated to mass size before chemotherapy. Inclusion of the reduction in size significantly improved the logistic regression model, which included mass size after chemotherapy. This model was further improved with the addition of clinical characteristics. Areas under the receiver operating characteristic curves increased from 0.74 to 0.77 and 0.83 with these models. CONCLUSION: A small retroperitoneal mass after chemotherapy is an important predictor of benign histologic findings in residual masses in patients with nonseminomatous testicular cancer. However, better predictions can be made when the reduction in size and clinical characteristics are considered as well. Decisions regarding resection should be based on the combination of these characteristics rather than on only mass size after chemotherapy. http://repub.eur.nl/res/pub/10632/ 1995-05-01T00:00:00Z PURPOSE: To develop a statistical model that predicts the histology (necrosis, mature teratoma, or cancer) after chemotherapy for metastatic nonseminomatous germ cell tumor (NSGCT). PATIENTS AND METHODS: An international data set was collected comprising individual patient data from six study groups. Logistic regression analysis was used to estimate the probability of necrosis and the ratio of cancer and mature teratoma. RESULTS: Of 556 patients, 250 (45%) had necrosis at resection, 236 (42%) had mature teratoma, and 70 (13%) had cancer. Predictors of necrosis were the absence of teratoma elements in the primary tumor, prechemotherapy normal alfa-fetoprotein (AFP), normal human chorionic gonadotropin (HCG), and elevated lactate dehydrogenase (LDH) levels, a small prechemotherapy or postchemotherapy mass, and a large shrinkage of the mass during chemotherapy. Multivariate combination of predictors yielded reliable models (goodness-of-fit tests, P > .20), which discriminated necrosis well from other histologies (area under the receiver operating characteristic (ROC) curve, .84), but which discriminated cancer only reasonably from mature teratoma (area, .66). Internal and external validation confirmed these findings. CONCLUSION: The validated models estimate with high accuracy the histology at resection, especially necrosis, based on well-known and readily available predictors. The predicted probabilities may help to choose between immediate resection of a residual mass or follow-up, taking into account the expected benefits and risks of resection, feasibility of frequent follow-up, the financial costs, and the patient's individual preferences.