What is the most important prognostic variable for melanoma?

Breslow's Thickness is the Most Important Prognostic Variable for Melanoma

The most important prognostic variable for melanoma is Breslow's thickness (answer d), which has been established as the most powerful and commonly used prognostic factor with level of evidence A. 1

Importance of Breslow's Thickness

• Breslow's thickness demonstrates a close correlation with survival and serves as the foundation for melanoma staging and treatment planning 1
• It is used to determine surgical excision margins, with specific recommendations based on thickness measurements (e.g., 1 cm for ≤1 mm, 2 cm for 2-4 mm, 3 cm for >4 mm) 1
• Breslow's thickness has been validated in multiple studies as the single most important prognostic factor for patients with localized melanoma 2

Comparison with Other Prognostic Variables

Clark's Level

• Clark's level (answer c) has prognostic value primarily for thin melanomas (Breslow thickness <1 mm) but is less predictive than Breslow's thickness overall 1
• In the AJCC staging system, Clark level was considered a strong independent predictor only for melanomas less than 1 mm thick 1
• Measuring tumor thickness (Breslow) has been demonstrated to be more predictive than assessing level of invasion (Clark) 2

Age and Gender

• Age (answer b) and gender (answer a) do have prognostic value (level of evidence C) 1
• However, these clinical parameters have complex inter-relations and their prognostic value is low compared to Breslow's thickness 1
• Studies show that while age and gender correlate with melanoma thickness, they are not independent predictors of survival when Breslow thickness is considered 3

Complexion

• Complexion (answer e) is not identified as a major prognostic factor in any of the guidelines 1

Prognostic Factors by Disease Stage

• For localized melanoma (stages I-II): Breslow thickness and ulceration are the two most important characteristics predicting outcome 1
• For regional disease (stage III): The number of involved nodes becomes the most important prognostic factor 1
• For metastatic melanoma (stage IV): The number of metastatic sites and time interval between primary tumor and metastases are the most important prognostic factors 1

Clinical Implications of Breslow's Thickness

• Thin melanomas (<0.76 mm) are associated with localized disease and excellent survival rates 2
• Intermediate thickness melanomas (0.76-4.00 mm) have increasing risk of harboring regional/distant metastases 2
• Thick melanomas (≥4.00 mm) have high risk of occult distant metastases at initial presentation 2
• Sentinel lymph node biopsy decisions are guided by Breslow thickness, with recommendations varying based on thickness categories 1

Pitfalls in Breslow Thickness Measurement

• Imprecision in Breslow thickness measurements can significantly impact staging and treatment decisions 4
• Terminal digit bias (clustering of measurements at certain values like 1.0 mm) has been identified as a problem that can affect staging accuracy 4
• Clinicians should be aware of the inevitable margin of error in Breslow thickness measurements when making management decisions 4