Therapeutic Surgical Management of Palpable Melanoma Groin Metastases: Superficial or Combined Superficial and Deep Groin Lymph Node Dissection

Survival in patients with palpable metastatic melanoma to the groin is poor. In the literature, estimated 5-year overall survival (OS) rates vary from 20% to 40%.8,11,13 In our series of 169 patients with palpable nodes in the groin, 5-year estimated OS rates were 33% for CGD and 29% for SGD. Also 5-year DFS rates were virtually identical, i.e., 18% for CGD and 16% for SGD. Patients with CGD with positive deep nodes have the poorest prognosis, with OS ranging from 6% to 34% in the literature.7,8,10,14‐16 (Table 5). In our institute, patients with CGD and positive deep nodes have estimated 5-year OS and DFS rates of 12% and 9%. In contrast, for CGD patients without deep nodal involvement, we observed 40% and 22%, respectively.

There were differences between the CGD and SGD patients. CGD patients had a significantly larger size of involved superficial lymph nodes than SGD patients (Table 1). Moreover, 25% of CGD patients had involved deep lymph nodes, while there was no suspicion and no diagnosis of deep nodal involvement in SGD patients. CGD patients had unfavorable preoperative prognosis, which is apparent since selection for extent of surgery was based on comorbidities and the suspicion of involvement of deep lymph nodes. However, during CGD, more superficial nodes were harvested and the number of positive superficial nodes was not different, resulting in a significant lower superficial lymph node ratio (Table 1). Lower superficial lymph node ratio is a good prognostic factor for survival.17‐19 Based on surgery only, CGD patients were expected to have favorable prognosis. In this study, the outcome of CGD patients was virtually identical to that of SGD patients (Fig. 1c, d). Even comparison of patients with superficial involved nodes only showed no difference, indicating that the extent of groin surgery does not influence outcome (data not shown; p = 0.217). Also in other studies, it has been demonstrated that extent of groin surgery, regardless of presence or absence of deep lymph node involvement in CGD patients, has no effect on survival.8,10,16

Preoperative CT was performed in 61 of 121 patients who underwent CGD. Positive predictive value (PPV) of CT scan was only 59% in our experience, whilst the negative predictive value (NPV) was fairly good at 91%. Sensitivity was 71% and specificity 85% in our group of patients (Table 2). Allen et al. found different results with PPV of 100%, NPV of 86%, specificity of 100%, and sensitivity of 60%, stating that CT scan was not reliable as a tool for preoperatively assessing pelvic lymph node involvement.4 However, both studies show that a CT-based decision on whether or not to perform CGD could be correctly made in 9 out of 10 patients. Thus, CT scan may be used as a tool in the decision on whether or not to remove deep lymph nodes.

Morbidity rates in the present study are divided into short- and long-term morbidities. Underestimation of events in the morbidity data could have occurred due to the retrospective gathering of data from medical records. However, comparison of the two groups of patients in this study remains valid since this presumed underestimation arose in both groups. Neither short- nor long-term morbidities were significantly lower in SGD than in CGD patients, being 39.6% versus 49.6% (p = 0.305) and 16.7% versus 26.5% (p = 0.229), respectively (Table 3). The most debilitating morbidity is chronic lymphedema, which is difficult to define. Some authors have used measurements to define this, whilst others have opted to define chronic lymphedema as edema requiring intervention. Also debated is the minimum period of edema to define it as chronic, which we did when moderate or severe swelling was present (more than) 6 weeks after surgery and required treatment. In any case, it is a widely feared and unpleasant complication.20‐22 There was a trend towards increased chronic lymphedema in patients after CGD (25.6%) than in patients after SGD (14.6%), yet this difference was not statistically significant (p = 0.154). This difference was not the result of an imbalance of additional radiotherapy to the groin, as 10% of SGD patients received radiotherapy versus 9% of CGD patients (p = 0.776). The assessment of one large or two small incisions for CGD has no influence on the rate of lymphedema as well.23 Other reports also indicate that lymphedema rates after CGD (range 23–55%) are greater than after SGD (range 7–29%), albeit not always statistically significantly so.8,11,20,22 Faries et al. recently reported the difference in lymphedema rates between immediate and delayed lymph node dissection. In these data of the Multicenter Selective Lymphadenectomy Trial (MSLT) I, lymphedema rates for SGD patients were 21.4% when undergoing immediate dissection and 22.6% when undergoing delayed dissection (p = 0.9), while CGD patients had higher lymphedema rates of 36.4% for immediate dissection and 34.2% for delayed dissection (p = 0.89).22 Unfortunately, p-values for the difference in lymphedema between SGD and CGD patients were not provided.22

Regarding locoregional control in the ilioinguinal region, we found no differences between CGD and SGD, as regional recurrence rates were similar (Table 3). The frequency of pelvic recurrences was equal in both groups. Possible causes for this counterintuitive observation could be the small sample size, patient selection, i.e., SGD patients having occult pelvic disease at time of surgery, and/or the overall worse prognosis of both groups of patients compared with literature. Patients might die of distant visceral metastases before pelvic recurrence has developed. Our results are in line with other reports in the literature. Coit et al. reported similar nodal recurrence rates for SGD and CGD patients, while Singletary et al. reported relatively more nodal recurrence in SGD patients, but attributed that to the extent of tumor burden rather than the extent of surgery. 10,24

Our group of patients has worse survival compared with literature; for example, Balch et al. reported 5-year OS rates of 50% for N1b, 45% for N2b, and 40% for N3 patients in the 2009 AJCC melanoma staging system analysis.25 Patients from our center showed (in the same order) 5-year OS rates of 43%, 26%, and 17%. Because of our relatively small study population compared with the enormous AJCC databases of > 30,000 patients, a single event will have a greater impact on the estimate survival rates in Kaplan–Meier analysis, because the number at risk is smaller. Due to our relatively short median follow-up, we underestimate our long-term survival. Moreover, all patients were operated at the Erasmus University Medical Center – Daniel den Hoed Cancer Center, a tertiary center in The Netherlands for such cases. This implies that a negative selection bias is most likely. More advanced cases might lead to worse survival.

As well as the superficial lymph node ratio, the number of positive superficial nodes was a consistent prognostic variable for OS and DFS (Table 4). This is consistent with the outcome after analysis of stage III melanoma patients by the AJCC.25,26 With an increasing number of positive superficial lymph nodes, the chance of involvement of the deep lymph nodes increased. No patients with 1 involved superficial node showed additional positivity in the pelvic area, while this applied to 32% of patients with 2–3 involved superficial lymph nodes and to 66% of patients with ≥4 involved superficial lymph nodes. A decision on the extent of surgery might be made based on the number of involved superficial lymph nodes. A scenario based on our results of preoperative CT scan and the number of involved superficial lymph nodes could be considered. When preoperative CT is negative for involvement in the pelvic region and only one superficial lymph node is involved, SGD might be performed. When, after pathological analyses of the SGD specimen, more than one involved superficial lymph node is found, additional dissection of the pelvic region could be considered. CGD is performed in case of suspicion of multiple positive superficial lymph nodes and/or positive deep lymph nodes.

We acknowledge that this study is retrospective and has short follow-up time. We selected patients who underwent only therapeutic groin dissection for palpable disease and excluded patients who underwent elective lymph node dissection or sentinel node biopsy. The consequence was that our clean cohort of melanoma patients underwent surgery in a period of time (1991–2009) with evolving practice and imaging. Before applying this scenario in clinical practice, results similar to those of the present study should be reported by other retrospective studies or a randomized controlled trial.

In conclusion, the poor outcome in melanoma patients with palpable nodal disease in the groin after CGD was equal after SGD in our series and in many other reports in the literature. Patients without overt iliac nodes on CT might safely undergo SGD and be spared the greater morbidity of CGD. CGD might be reserved for patients with multiple positive nodes in the SGD and/or positive nodes on CT scan. A prospective randomized controlled trial is the only study that could overcome the classical drawbacks of this and other retrospective studies.