Background:
The optimal surgical margin for removing melanoma, a type of skin cancer, has been a topic of significant research. A landmark study, the Intergroup Melanoma Surgical Trial, initiated in 1983, investigated the effectiveness of different surgical margins for melanomas of intermediate thickness, specifically those between 1 and 4 mm. This study has now reached a median 10-year follow-up, providing valuable long-term insights. When we discuss surgical margins, it’s crucial to understand the scale. Often, measurements are discussed in centimeters (cm), but in detail, especially in pathology and surgical planning, millimeters (mm) become essential. For clarity, remember that 1 cm is equal to 10 mm. Thus, a 2 cm margin is the same as a 20 mm margin, and a 4 cm margin equates to 40 mm. This article will delve into the findings of this crucial trial, focusing on the implications of these measurements – millimeters compared to centimeters – in melanoma surgery.
Study Methods and Patient Cohorts:
This prospective multi-institutional trial enrolled two groups of patients. The first group consisted of 468 patients with melanomas located on the trunk or proximal extremities (arms and legs closer to the body). These patients were randomly assigned to receive either a 2 cm (20 mm) or a 4 cm (40 mm) radial excision margin. The second group included 272 patients with melanomas on the head, neck, or distal extremities (hands and feet). This group received a standardized 2 cm (20 mm) radial excision margin. This design allowed researchers to compare the effectiveness of different margin sizes in reducing local recurrence and improving survival rates in different anatomical locations.
Key Results: Local Recurrence and Survival Rates
The study revealed a critical link between local recurrence (LR) – the cancer returning at the original site – and patient survival. Patients who experienced a local recurrence had a significantly lower 5-year survival rate, only 9% if LR was the first relapse, and 11% at any time. This starkly contrasts with an 86% 5-year survival rate for patients without local recurrence (P < .0001). The overall 10-year survival for patients with local recurrence was a concerning 5%.
However, when comparing the 2 cm (20 mm) versus 4 cm (40 mm) excision margins, the 10-year survival rates were not statistically different (70% vs. 77%). Similarly, the management of regional lymph nodes (observation vs. elective node dissection) did not significantly impact 10-year survival. Importantly, the incidence of local recurrence was also similar between the 2 cm (20 mm) and 4 cm (40 mm) margin groups, whether measured as the first relapse (0.4% vs. 0.9%) or at any point during follow-up (2.1% vs. 2.6%).
Anatomical Location and Ulceration: Impact on Recurrence
Analyzing local recurrence rates by anatomical site revealed variations. Melanomas on the proximal extremity had a 1.1% LR rate, the trunk 3.1%, distal extremities 5.3%, and the head and neck region showed the highest LR rate at 9.4%.
The study identified ulceration of the primary melanoma as a profoundly influential factor on local recurrence rates. In the randomized group (trunk and proximal extremity), the LR rate was 6.6% for ulcerated melanomas versus 1.1% for non-ulcerated melanomas. In the non-randomized group (distal extremity and head and neck), the difference was even more pronounced: 16.2% LR for ulcerated versus 2.1% for non-ulcerated melanomas (P < .001).
Multivariate analysis further confirmed ulceration as an independent adverse prognostic factor (P = .0001), along with melanoma location in the head and neck (P = .01). Other factors analyzed were not statistically significant (all with P > .12).
Conclusion: 2cm Margin Safety and Ulceration Significance
This long-term follow-up from the Intergroup Melanoma Surgical Trial provides strong evidence that for patients with intermediate thickness melanoma (1-4 mm), a 2 cm (20 mm) surgical excision margin is safe and effective in terms of local recurrence and survival. The study underscores that local recurrence is a serious event associated with high mortality. Crucially, the presence of ulceration in the primary melanoma emerges as the most significant prognostic factor for predicting an increased risk of local recurrence, outweighing the difference between a 2 cm and 4 cm excision margin in this patient group. Therefore, assessing for ulceration and anatomical location are critical considerations in managing patients with intermediate thickness melanoma.
