WASHINGTONSentinel lymph node (SLN) mapping has been used in
gastrointestinal cancers to identify patients with occult micrometastases who
might benefit from adjuvant chemotherapy. Because rectal lymph drainage is
"less predictable" than colon lymph drainage, the technique had been
considered less suitable for rectal than for colon cancers, said Sukamal Saha,
MD, of the McLaren Regional Medical Center of Michigan State University, Flint.
Now, a prospective study has found that SLN mapping "works
in both colon and rectal cancers in more than 92% of cases," Dr. Saha
reported at the 54th Annual Cancer Symposium of the Society of Surgical
The study involved 214 consecutive colon and rectal cancer
patients (164 colon and 50 rectal), ranging in age from 26 to 97, who underwent
SLN mapping at the time of surgery. Colon cancer patients received injections
of 1 mL to 2 mL of 1% Lymphazurin blue dye circumferentially around their
tumors during exploration of the abdomen (Figure 1). Rectal cancer patients
received the dye by submucosal injection administered sigmoidoscopic-ally. The
first one to four blue nodes found were designated as sentinel nodes and were
marked with sutures (Figure 2).
With success defined as finding a blue node, SLN mapping proved
as statistically successful in rectal as in colon cancers, he said. An SLN was
identified in 99% of colon cases and 92% of rectal cases.
Occult micrometastasis in one solitary SLN was found in 15% of
colon and 10% of rectal cancer patients (Figure 3). Accuracy in identifying the
presence or absence of metastasis in the SLN was 98% in colon and 90% in rectal
cancers. In 5% of patients, the technique leads to a change in the extent of
There were no adverse effects seen in any of these 214
patients, Dr. Saha said. Even in patients who received neoadjuvant radiation
therapy and chemotherapy for rectal cancer, the technique was successful in
more than 92% of cases.
SLN mapping thus appears to permit better identification of
micrometastases than standard methods, he said. "These upstaged patients
may then receive adjuvant chemotherapy, which may affect their long-term
survival," he said.