Survival in Patients With Desmoplastic Melanoma
May 28th, 2008 by admin
Helen M. Shaw, Michael J. Quinn, Richard A. Scolyer, John F. Thompson
The Sydney Melanoma Unit,
To the Editor:
The clinical and biologic behavior of desmoplastic melanoma (DM) is a subject of great relevance to those involved in the management of melanoma patients. We therefore read with interest the article by Livestro et al1 on this subject. However, we have concerns about the validity of some of the conclusions that were drawn, particularly the claim that DM patients have survival rates similar to non-DM patients of equivalent tumor thickness. The authors based their conclusions “solely on the basis of the difference in histology.” Accordingly, they compared 89 DM patients with 178 non-DM patients matched for thickness, age, sex, and year of diagnosis. However, it is evident from their Table 1 that there were marked disproportions between key prognostic factors in their DM and non-DM groups, most importantly stage of disease at first presentation. Almost four times as many non-DM as DM patients first presented with advanced disease, mainly due to a much lower rate of sentinel node (SN) positivity in DM patients. Since stage of disease at first presentation is the major determinant of ultimate survival, this must cast considerable doubt on the comparative survival outcomes reported for the two groups. As well, there were major and potentially important differences in other prognostic characteristics between the groups, particularly in tumor mitotic rate2,3 and primary melanoma anatomic site.4
Several additional comparisons from Table 1 deserve mention. The large amount of incomplete data for both tumor mitotic rate and especially neurotropism was overlooked, resulting in artifactually exaggerated differences in significance for these factors. Multiple primary melanomas, more common in DM than non-DM patients, were included in their survival analyses, a crucial factor possibly influencing outcome. Comment was made on the significant excess of DM compared with non-DM patients who had other skin cancers, but this would seem an unremarkable finding considering that most DM patients had their primary melanomas in the head and neck region—a common skin cancer site.
The Sydney Melanoma Unit (SMU) has treated 922 patients with DM since 1971, when Conley et al5 first described this entity. In SMU patients with localized disease, the 5-year survival rate in 280 DM patients (90%)6 was significantly higher than in all 7,767 cutaneous melanoma patients incorporated into the American Joint Cancer Committee on Cancer staging database (82%),4 despite the fact that median tumor thickness in the former group was considerably greater than in the latter (2.5 mm v 1.6 mm, respectively) group. More recently reported7 was another subgroup of 186 DM patients who underwent SN biopsy since 1993; 12 (6.5%) had at least one positive SN (primary tumor thickness range, 1.4 to 6.7 mm). This rate of positivity was considerably lower than the 32% rate of SN positivity in SMU patients with non-DMs of equivalent thickness undergoing SN biopsy. Three of these 12 DMs displayed neurotropism (thicknesses, 1.8, 6.2, and 6.5 mm). Thus our findings, in accord with those of Livestro et al, show a lower rate of SN positivity in DM than in non-DM patients, but neurotropism was not as closely associated with SN positivity as in their study.
It has become clear that DM differs in several major respects from other forms of cutaneous melanoma. However, most series reported to date have been small, and care must be taken to avoid drawing bold conclusions or making important management decisions (such as to withhold SN biopsy) on the basis of incomplete or inappropriate analysis of limited data.
Authors’ Disclosures of Potential Conflicts of Interest
The authors indicated no potential conflicts of interest.
REFERENCES
— Livestro DP, Muzikansky A, Kaine EM, et al: Biology of desmoplastic melanoma: A case-control comparison with other melanomas. J Clin Oncol 23:6739-6746, 2005[Abstract/Free Full Text]
— Azzola MF, Shaw HM, Thompson JF, et al: Tumor mitotic rate is a more powerful prognostic indicator than ulceration in patients with primary cutaneous melanoma. Cancer 97:1488-1498, 2003[CrossRef][Medline]
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— Balch CM, Soong SJ, Gershenwald JE, et al: Prognostic factors analysis of 17,600 melanoma patients: Validation of the American Joint Committee on Cancer melanoma staging system. J Clin Oncol 19:3622-3634, 2001[Abstract/Free Full Text]
— Conley J, Lattes R, Orr W: Desmoplastic melanoma (a rare variant of spindle cell melanoma). Cancer 28:914-936, 1971[CrossRef][Medline]
— Quinn MJ, Crotty KA, Thompson JF, et al: Desmoplastic and desmoplastic neurotropic melanoma. Cancer 83:1129-1135, 1998
— Scolyer RA, Thompson JF, Quinn MJ: Desmoplastic melanoma and sentinel node biopsy. Presented at the
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