The prognostic index: a useful pathologic guide for prediction of nodal metastases and survival in penile squamous cell carcinoma

Abstract

A concern of surgical oncologists has been to find a method to select patients for groin dissection in penile carcinomas considering the high morbidity of this procedure. A promising methodology, in the identification of early metastatic foci by the sentinel lymph node technique (initiated in Paraguay in the 1970s), was found, using a static anatomic approach, to be associated with a recurrence rate of 30%. Later, a dynamic method using radioactive tracers and peritumoral dye injection was introduced with an improvement in patients' outcome. Recurrences, however, remained high in most studies at a rate of about 15% to 20% except in few highly specialized centers with failure rates of 5%. The technical sophistication, lack of multicenter reproduction, and cost of dynamic sentinel node biopsies preclude their routine implementation in developing countries and other approaches are necessary. Because histologic grade, depth of tumor infiltration, and perineural invasion (PNI) are considered among the most important pathologic prognostic parameters in penile cancer, we devised a Prognostic Index combining these 3 factors. In this study, we are evaluating the incidence of nodal metastasis according to the Prognostic Index score. Pathologic materials from 193 patients with penectomy/circumcision and bilateral groin dissections for invasive squamous cell carcinoma were analyzed. The Prognostic Index (ranging from 2 to 7) consisted in the addition of numerical values given to histologic grade (1 to 3), deepest anatomic level involved by cancer (1 to 3), and presence of PNI (0 or 1). Histologic grades were defined as follows: grade 1, carcinomas with minimal to no atypias; grade 3, tumors showing any proportion of anaplastic cells; and grade 2, the remainder tumors. The anatomic levels and their numerical values were: in glans, lamina propria, 1; corpus spongiosum, 2; and corpus cavernosum, 3. In foreskin they were: lamina propria, 1; dartos, 2; and skin, 3. PNI was evaluated as follows: absence of PNI, 0; presence of PNI, 1. Penile intraepithelial neoplasia (carcinoma in situ), or index 1, was excluded from the study. Mean follow-up obtained in all patients was of 81 months. The distribution of cases and rate of metastasis according to index scores were: 2 (1 case), no metastasis; 3 (17 cases), no metastasis; 4 (35 cases), 20% of metastasis; 5 50 cases), 50% of metastasis; 6 (47 cases), 66% of metastasis; and 7 (43 cases), 79% of metastasis. On logistic regression analysis evaluating various pathologic factors, Prognostic Index scores were found as the best predictors of inguinal node metastasis and patients' survival. Inguinal node dissections might not be necessary for patients with low indices (2 and 3). Nodal dissections might be formally indicated for high-grade indexes (5 to 7). Patients with index 4 should be individually assessed for nodal dissection. If sentinel node biopsy cannot be performed for various reasons the Prognostic Index might represent a useful pathologic guide to the clinicians in the often difficult decision to perform an inguinal dissection or not.