Revised FIGO staging for carcinoma of the vulva

Abstract

Staging of cancer is designed to allow valid comparison of results between centers, and to divide patients into prognostic groups. Ideally, the survival for the 4 major FIGO stages should be reasonably evenly spread between 0% and 100%. With the FIGO clinical staging system for vulvar cancer, there was a reasonable distribution of prognostic groups, 5-year survivals being 90.4%, 77.1%, 51.3% and 18.0% for Stages I, II, III, and IV, respectively [1]. This distribution reflected the fact that the incidence of lymph node metastases increased with each stage, being 10.7% for Stage I, 26.2% for Stage II, 64.2% for Stage III, and 88.9% for Stage IV [1]. In 1988, the FIGO Committee on Gynecologic Oncology adopted a surgical staging system for vulvar cancer. This change from clinical to surgical staging was logical. Vulvar cancer is usually treated surgically, the status of the regional lymph nodes is the single most important prognostic factor [2]-[4], and the clinical evaluation of the lymph node status is unreliable [5], [6]. In 1991, the Gynecologic Oncology Group (GOG) reported a survival analysis of 588 patients who were available on their database for retrospective staging according to the new system [2]. The 5-year survival was 98% for 154 patients with Stage I disease, 85% for 231 patients with Stage II disease, 74% for 141 patients with Stage III disease, and 31% for 62 patients with Stage IV disease. It became immediately apparent that the first problem with the new staging was that it did not give a good spread of prognostic groupings. The GOG reported that when tumors had negative lymph nodes, even primary lesions up to 8 cm diameter were low risk. Some unpublished Surveillance, Epidemiology, and End Results (SEER) data have confirmed this. For 349 patients with a primary lesion greater than 8 cm diameter and negative nodes seen between 1988 and 2001, the 5-year survival was 88% [7]. We have recently reviewed our own data on 121 patients with FIGO Stages I and II vulvar cancer, and demonstrated no difference in survival between these two stages [8]. A second problem with the 1988 surgical staging, identified by the GOG analysis, was that Stage III represented a heterogeneous group of patients prognostically, with survivals ranging from 100% to 34%. For example, there were 6 patients with tumors 2 cm or less involving the vagina and/or urethra, with negative nodes, and their survival was 100%. There were 47 patients who had a tumor less than 2 cm in diameter with 1 positive node, and they had a survival of 95%. On the other hand, there were 28 patients who had a tumor greater than 8 cm diameter, with 2 positive nodes, and their survival was 34%, yet all of these patients were officially classified as having Stage III disease [2]. The third problem with the surgical staging system is that the number of positive nodes and the morphology of the positive nodes are not taken into account. The GOG study reported a 5-year survival of 90.9% for 385 patients with negative nodes, 75.2% for 125 patients with 1–2 positive nodes, 36.1% for 40 patients with 3–4 positive nodes, 24.0% for 19 patients with 5–6 positive nodes, and 0% for 16 patients with 7 or more positive nodes [2]. Our analysis of the UCLA data revealed a 94% survival for patients with both negative nodes (n = 82) and 1 positive node (n = 16), an 80% survival for patients with 2 positive nodes, and a 12% survival for patients with 3 or more positive nodes [3]. The significance of the morphological characteristics of positive nodes in vulvar cancer was not appreciated until 1991, when Origoni et al. [9] demonstrated survivals of 90.0%, 41.6%, and 20.6% for nodal metastases less than 5 mm, 5–15 mm, and greater than 15 mm diameter, respectively (P = 0.01). They also demonstrated that patients with extracapsular spread had a poor prognosis (25%) compared with patients with disease confined to the node (85.7%; P = 0.001). These data have subsequently been confirmed by others [10], [11]. The importance of positive nodes bilaterally versus the total number of positive nodes has been somewhat more controversial. Although the majority of reports have suggested bilaterality was not an independent prognostic factor [3], [12]-[14], two papers have suggested otherwise [15], [16]. Both papers suggesting that bilaterality of positive nodes was an independent risk factor included patients with 1 positive node in the analysis. This is statistically invalid, because such patients are not at risk for positive nodes bilaterally. The recent paper by Fons et al. [16] of 134 patients with Stages III/IVA vulvar cancer reported that the presence of lymph node metastases bilaterally was not a significant risk factor for survival if correction was made for the number of lymph node metastases. In fact, if extracapsular spread was put into the model, the latter was the only factor of significance in multivariate analysis. In view of the above, major changes have been made to the FIGO staging [17]. Stage IA will remain unchanged because this is the only group of patients with a negligible risk of lymph node metastases, but Stage I and II have been combined. The number and morphology of the involved nodes have been taken into account, and the bilaterality of positive nodes has been discounted. In the future, account may need to be taken of patients having sentinel node biopsies without full groin dissection, and molecular markers may provide even better discrimination between prognostic groups. For the moment, it is hoped that the proposed system will allow better prognostic discrimination between stages and less heterogeneity within stages.