PALM BEACH, FLA. The presence of microscopic or even submicroscopic melanoma in a sentinel lymph node may be clinically relevant, a retrospective study has shown.
"We believe patients with microscopic deposits of metastatic melanoma have biologically relevant, potentially life-threatening disease," Dr. David W. Ollila said at the annual meeting of the Southern Surgical Association.
Although other investigators have proposed that submicroscopic disease (a sentinel node tumor that is less than 0.1 mm) is not associated with a significantly increased risk of recurrence or death (Br. J. Surg. 2007;94:12939), Dr. Ollila and his associates hypothesized that any sentinel node evidence of metastatic melanoma, regardless of size or stage, may be a cause for concern.
He and his associates retrospectively studied 586 patients (mean age, 55 years) with invasive melanoma and a sentinel node biopsy from 1998 to 2007 in a prospectively maintained database. They classified the 322 men and 264 women as node negative or as having a tumor burden of less than 0.1 mm, 0.11.0 mm, or greater than 1.0 mm.
The investigators found a statistically significant difference in recurrence of any type between node-negative patients and those with a tumor burden less than 0.1 mm. During a mean follow-up of 2.7 years, 57 (11%) of the 496 node-negative patients had a recurrence, compared with 8 (24%) of the 33 patients with a sentinel node tumor less than 0.1 mm.
"We [also] found a significant difference in disease-free survival between sentinel node-negative [patients] and the submicroscopic group. They cannot be considered equivalent," said Dr. Ollila, director of the sentinel node program and codirector of the multidisciplinary melanoma program at the University of North Carolina at Chapel Hill.
In the node-negative group, 51 patients (10%) died, as did 5 (15%) of those with a tumor burden less than 0.1 mm, 6 of 27 patients (22%) in the 0.1- to 1.0-mm group, and 12 of 30 patients (40%) who had tumors larger than 1.0 mm.
Dr. Ollila pointed out that the stepwise decrease in survival with increasing diameter of the metastatic deposit was statistically different among the four groups. "This is an interesting [finding], contrary to Rotterdam criteria. I submit to you that these patients are on a continuum, and this is clinically relevant disease," he said.
An increased sentinel node tumor burden was also associated with a greater risk of metastatic disease in other nodes. A total of 7% of node-negative patients had distant recurrence, as did 15% of those with tumors less than 0.1 mm, 22% of the 0.1- to 1.0-mm group, and 47% of those with tumors larger than 1.0 mm.
Dr. Marshall M. Urist, professor of surgery, University of Alabama at Birmingham, commented that this is an excellent study and asked, "Why did you measure these metastases in a two-dimensional way for a three-dimensional process?"
Dr. Ollila replied: "Point well taken. It's a volume disease. It would be more representative if we could do volumetric measures." The two-dimensional measurement was a limitation of the database used in the study, he said.