ORLANDO-Sentinel lymph node mapping (SLNM) upstaged nodal
metastases in 15% of colon cancer patients in a single-institution
retrospective study of more than 300 colon cancer patients at stages T1 to T4.
Routine pathological examination after conventional surgery understages 15% to
20% of colorectal cancer patients, the researchers said. Thus, SLNM has a
potential survival benefit: "Higher numbers of patients with nodal metastases
in the group that underwent SLNM went on to receive chemotherapy," they
reported. "This may explain the reduced recurrence rates seen in these
patients, which may lead to prolonged survival."
Lead investigator Sukamal Saha, MD, presented the findings
in a poster session at the 41st Annual Meeting of the American Society of
Clinical Oncology (abstract 3567). Dr. Saha, of McLaren Regional Medical Center
and Michigan State University, Flint, noted striking differences in recurrence,
with recurrence rates up to eight times higher in patients managed
conventionally, compared with patients who underwent SLNM.
The study included 315 patients with colon cancer treated
and followed within the same institution. Investigators retrospectively
compared recurrence patterns of patients who underwent either SLNM followed by
standard oncologic resection by one oncologic surgeon (n = 153) or conventional
oncologic resection by six general surgeons (n = 162).
Patients undergoing SLNM were injected with isosulfan blue
dye (Lymphazurin 1%) subserosally and circumferentially around the tumor. The first one to four blue nodes identified within the first 5 to 10
minutes of injection were designated as SLNs.
The focused pathological examination of the SLNs comprised
multilevel sections at intervals of 10 to 40 microns, with four sections
stained for H&E and one section assessed with immunohistochemistry for
cytokeratin. Non-SLNs in the SLNM group and all LNs in the conventional surgery
group were examined by standard methods with H&E.
All patients were followed by the same group of oncologists
(median follow-up, 56 months; minimum follow-up, 29 months). Data were
collected for age, number of LNs, tumor and nodal status, and recurrence
More Node Positives
The average number of LNs studied in the SLNM group was 15.5
vs 11.8 in the conventional surgery group (P = .0001). T-stage distribution in
the SLNM and conventional-surgery groups, respectively, was 11.1% vs 8% at
stage T1, 22.2% vs 14.2% at T2, 62.1% vs 69.2% at T3, and 4.6% vs 8.6% at T4.
SLNM was successful in 100% of patients, with an accuracy of 94.7% and a
sensitivity of 89%.
For all T stages, Dr. Saha said, a greater proportion of
node-positive patients were identified in the SLNM group (51.6% vs 35.6%,
respectively; P = .005).
"SLNM upstaged 15% of patients with micrometastases that
would have been missed by conventional methods," Dr. Saha commented. This
occurred even though more patients in the SLN group were T1/T2 (51 vs 36). The
most striking difference observed was in T3 patients, 67.3% of whom were node
positive in the SLNM group vs 42% in the conventional-surgery group (P =
Fewer Recurrences With SLNM
The recurrence rate was significantly greater for both
node-positive and node-negative patients managed with conventional surgery
(24.6% vs 7.1% with SLNM). Among node-positive patients, an 11.3% recurrence
rate was observed with SLNM vs 36.8% with conventional surgery (P = .0004).
Among node-negative patients, the recurrence rate was 2.7% for SLNM vs 18% for
conventional surgery (P = .0025).
For stage I (T1, T2, N0) patients, recurrence in the SLNM
and conventional-surgery groups, respectively, was 1.96% vs 11.1% (P = .002).
All four recurrences in the conventional group occurred in N0 patients,
"suggesting that there were possible missed and therefore untreated micrometastases, and perhaps explaining the overall increased incidence of
recurrence in the conventional-surgery group vs the SLNM group," Dr. Saha told
ONI. He concluded, "SLNM is simple and accurate in determining nodal
metastases. Compared with conventional surgery, it upstages a significant
number of patients whose disease may remain undetected by conventional methods.
Patients upstaged by SLNM could receive adjuvant chemotherapy, resulting in a
further decrease in recurrence and perhaps prolonged survival."