Prognosis of Merkel Cell Carcinoma
Merkel cell carcinoma has a poor prognosis with 5-year survival rates ranging from 30% to 64% overall, and mortality rates that exceed melanoma. 1
Overall Survival by Stage
The prognosis varies dramatically by stage at presentation:
- Stage I disease: 5-year survival of approximately 87% 2
- Stage II disease: 5-year survival drops to 63% 2
- Stage III disease: 5-year survival further declines to 42% 2
- Stage IV (metastatic) disease: 5-year survival is essentially 0%, with estimates of less than 15% 3, 2
Tumor size is a critical prognostic factor—death from disease occurs in only 10% of patients with T1 lesions but in 50% of those with larger tumors. 2
Patterns of Disease Progression
MCC demonstrates aggressive metastatic behavior that directly impacts survival:
- Local recurrence develops in 25-30% of all cases despite treatment 1, 4
- Regional lymph node metastases occur in 52-59% of cases, with one-third of patients presenting with nodal disease at diagnosis 1, 4
- Distant metastatic disease develops in 34-36% of all MCC cases 1, 4
Systemic disease is nearly uniformly fatal regardless of subsequent therapy and is almost always preceded by nodal metastases, suggesting an orderly "cascade" pattern of spread. 5
Timing and Location of Recurrence
Half of all patients who recur do so within a median of 9 months, and regional nodal involvement typically appears within 2 years of diagnosis in 87% of cases where it occurs. 2, 5
The first site of recurrence is most commonly:
High-Risk Populations
Immunosuppressed patients have significantly worse survival, including those with organ transplants, lymphoproliferative malignancies, or HIV infection. 1, 6
Patients with clinically positive lymph nodes at presentation have markedly worse prognosis compared to those with negative nodes. 5
Sentinel Lymph Node Status
Sentinel lymph node biopsy identifies micrometastases in approximately 33% of early-stage patients who appear clinically node-negative. 4, 2
- SLNB-positive patients have a 56% recurrence rate 2
- SLNB-negative patients still have a 39% recurrence rate, indicating that negative SLNB predicts improved but not favorable outcomes 2
Favorable Prognostic Factors
Head and neck primary site location is associated with improved survival compared to other anatomic locations. 5
MCC in situ has an excellent prognosis with minimal mortality risk and very low risk of dermal invasion or recurrence when treated with wide local excision alone. 7
Modern Treatment Era Outcomes
With the advent of PD-1/PD-L1 immunotherapy for advanced disease, response rates of 33-40% have been achieved in metastatic MCC, with median duration of response exceeding 18-40 months in responders. 8
However, one-third of all MCC patients ultimately die from their disease despite available treatments, underscoring the need for more effective adjuvant therapies and better biomarkers for recurrence prediction. 2