Prediction models for the histology of residual masses after chemotherapy for metastatic testicular cancer

Abstract

Patients with metastatic non-seminomatous testicular cancer can be cured by cisplatin-based chemotherapy. After chemotherapy, surgical resection is a generally accepted treatment to remove remnants of the initial metastases since residual tumor may still be present (mature teratoma or viable cancer cells). We review here several policies for the selection of patients for retroperitoneal lymph node dissection. We consider one simple policy as a reference, which bases the selection solely on the diameter of the residual mass (≥10 mm). Further, we distinguish 4 rule-based policies, which combine several clinical characteristics (e.g., primary tumor teratoma-positive or insufficient reduction in size), and 2 probability-based policies, where a regression or tree model is used that statistically combines well-known, important clinical predictors for the absence of residual tumor. The policies were evaluated in an international data set containing 716 patients. The reference policy would leave 204 masses < 10 mm unresected, where mature teratoma was present in 50 (25%) and cancer in 11 (5%). Compared with this policy, most of the rule-based policies left fewer patients with residual tumor unresected, at the expense of more resections. The probability-based policies could refine the selection without such an increase in the number of resections. Prediction models for the residual histology therefore merit wider application in clinical practice.