Prognosis and survival outcomes in melanoma patients with unknown primary site (MUP)

Abstract

7544 Background: Metastatic melanoma in lymph nodes (LN) in the absence of a known primary site (MUP) can be accurately diagnosed with current histologic methods. However, the true incidence, stage, prognostic factors, treatment, and long-term outcomes of this clinical entity are poorly defined. Methods: A retrospective analysis was performed of 820 consecutive melanoma patients diagnosed between 1990 and 2001 at a tertiary cancer center with melanoma metastatic to regional LN. Of these, 71 patients (8.7%) were confirmed to have MUP without distant metastatic disease. Clinicopathologic and treatment factors were analyzed to determine their impact on long-term disease-free outcome. Results: The most common presentation was a palpable mass in the axillary nodal basin (76%) in a male patient (72%) with a median age of 51 years. Following completion LN dissection (average 22 LN removed), AJCC 2002 (N) category was identified as N1, N2 or N3 in 34 (46%), 11 (16%) and 26 (38%) patients, respectively. Forty-three patients (61%) received additional systemic therapy and 17 patients (24%) were treated with postoperative adjuvant radiotherapy (XRT). With a median follow-up of 7.6 years, the overall 5- and 10-year disease-free survival rates were 53% and 41%, respectively. Five-year regional control was accomplished in 82% of patients. The median times to distant failure and death were 3.03 and 6.05 years, respectively. Male gender and N3 disease were significant predictors of disease-free survival by univariate analysis, while multivariable analysis revealed that gender was the only significant negative prognostic factor. Conclusions: MUP is not an uncommon clinical entity. The relatively favorable long-term survival of these patients supports the premise that MUP with nodal disease represents a manifestation of stage III melanoma rather than stage IV (M1a) subcutaneous/distant nodal disease. Therefore, patients with MUP should be treated with aggressive surgical approaches with curative intent and also be offered participation in adjuvant therapy protocols. No significant financial relationships to disclose.