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EDITORIALS |
From the Winship Cancer Institute, Atlanta, Georgia.
Correspondence: Address correspondence to: Grant W. Carlson, MD, Winship Cancer Institute, 1365B Clifton Rd., Atlanta, GA 30322; Fax: 404-778-4255; E-mail: grant_carlson{at}emory.org
Sentinel lymph node (SLN) status has been shown to be the strongest prognostic factor in patients with clinical stage I and II melanoma.1 Age is also an independent prognostic factor for overall survival for patients with melanoma. The mortality from melanoma increases directly with age. Paradoxically, the incidence of SLN metastases appears to vary inversely with age.2,3 Chao et al.4 present data on 3079 patients from the Sunbelt Melanoma Trial, which adds further fuel to this controversy. They stratified their patient population into five age groups: ages 18–30, 31–40, 41–50, 51–60, and 61–70 years. Advanced age was found to be associated with increasing tumor thickness, increasing incidence of tumor ulceration, increased number of male patients, but a decreased incidence of SLN metastases. The overall incidence of SLN metastases was 18.2% but was only 14.4% in the age 61–70 years group. No differences in disease-free survival were seen for the various age groups at a median follow up of 19 months.
Several potential explanations exist why the incidence of SLN metastases decreases with advancing age when other prognostic factors appear to be increased. Age-related differences in lymphatic flow or changes in the density of lymphatic vessels may exist. This could result in a decreased sensitivity of the SLN procedure in older patients. In breast cancer, it has been shown that increasing age is associated with increased failure in SLN mapping.5,6 In the Emory experience of 592 patients who had SLN mapping for melanoma, five of the six failures of SLN mapping occurred in patients older that 60 years.7 No regional failures occurred in these six patients after a mean follow up of 39.6 months. In the Chao et al.4 study, no age-related differences were noted in the success of localization or the false–negative rate (regional recurrences in previously mapped basins) of SLN biopsy. Atrophy of dermal lymphatics can result in preferential spread via the hematogenous route in elderly patients. In the Chao et al.4 study, longer follow up is needed to examine the patterns of recurrence and the overall survival of patients in the various age groups.
Desmoplastic melanoma has been shown to be more common in older individuals. It has a high incidence of local recurrence but rarely recurs regionally. Recent data indicate a low incidence of SLN metastases in this histologic subtype.8 In the Chao et al.4 study, desmoplastic subtypes account for 0.3% of the melanoma cases in the 18–30 age group but 2.9% of melanoma in the 61–70 group. Even if this subtype is removed from analysis, the 61–70 group has a lower incidence of SLN metastases.
The authors offer an intriguing hypothesis that SLN biopsy detects a greater proportion of micrometastases that may not be clinically significant in younger patients. A more competent immune system could eliminate these cells before systemic metastases. To answer this question, they compared the fraction of patients with positive SLN detected by immunohistochemistry only methods and found no significant differences between the age groups.4 The amount of metastatic deposit in each SLN was not quantitated. A recent study found that the presence of macrometastases (>2 mm diameter deposit) in melanoma SLN was the strongest independent prognostic factor for overall survival.9 In that study, age >52 years was prognostic for relapse-free survival but did not reach significance for overall survival. Younger patients did not have a greater proportion of minimal metastases (isolated or small clusters of melanoma cells) than older patients.
Chao et al.4 have published a thought-provoking paper examining the correlation between age and other prognostic factors in melanoma. It is hoped that longer follow up will answer many of the questions raised by these findings.
Received for publication January 8, 2004. Accepted for publication January 19, 2004.
REFERENCES
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  S. Sassen, H. M. Shaw, M. H. Colman, R. A. Scolyer, and J. F. Thompson The Complex Relationships Between Sentinel Node Positivity, Patient Age, and Primary Tumor Desmoplasia: Analysis of 2303 Melanoma Patients Treated at a Single Center Ann. Surg. Oncol., February 1, 2008; 15(2): 630 - 637. [Abstract] [Full Text] [PDF]
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A. Doubrovsky, J.H.W. de Wilt, R.A. Scolyer, W.H. McCarthy, and J.F. Thompson Sentinel Node Biopsy Provides More Accurate Staging Than Elective Lymph Node Dissection in Patients With Cutaneous Melanoma Ann. Surg. Oncol., September 1, 2004; 11(9): 829 - 836. [Abstract] [Full Text] [PDF]
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K. M. McMasters Editorial: What Good is Sentinel Lymph Node Biopsy for Melanoma if it does not Improve Survival? Ann. Surg. Oncol., September 1, 2004; 11(9): 810 - 812. [Full Text] [PDF]
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