Colon cancer lymph node target ‘overambitious’ for rectal disease

The lymph node (LN) yield needed during rectal cancer surgery following long-course radiotherapy may be considerably less than that recommended for colon cancer, say the authors of a systematic review.

"[Our findings] may force clinicians to re-adjust their expectations of what an appropriate LN harvest is especially in radiation treated rectal cancer," say George Awwad (Royal Adelaide Hospital, Australia) and colleagues.

The authors, reporting in Colorectal Disease, reviewed 11 cohort studies of patients with rectal cancer who received long-course radiotherapy in a dose of 45.0-50.4 Gy prior to surgery.

In accordance with previous findings, seven of the studies showed that long-course radiotherapy reduced the LN yield. The same proportion of studies also confirmed that patients with node-positive disease had poorer prognosis than those with node-negative disease.

While current guidelines for colon cancer recommend an LN yield of 12, the authors identified only one study that showed that an LN yield greater than 11 led to a statistically significant survival benefit over those with a lower LN yield.

This study included 210 patients with node-positive or locally advanced rectal cancer. Recurrence was significantly higher at 15.1% in patients with an LN yield less than 11 compared with 7.4% in patients with a yield greater than 11. Five-year cancer-specific survival was significantly greater in the high-yield group at 69.6% compared with 48% in the low-yield group.

Another included study of 372 patients with node-negative rectal cancer showed that patients with an LN yield greater than seven had a 61% lower risk for relapse and a 55% lower risk for death from rectal cancer compared with patients with a LN yield lower than seven.

Interestingly, a further study indicated that an LN yield as low as three may be sufficient to improve survival compared with lower yields.

Awwad and colleagues conclude that, while they were not able to establish conclusively whether LN yield affects prognosis, several studies demonstrated that a yield of less than 12 was sufficient to improve survival.

The authors say that a lack of randomized data limit the ability to provide a specific number for LN yield target and suggest that other markers of prognosis, such as LN ratio, should be used to determine staging and management in rectal cancer.

"What is certain is that further and more rigorous studies are required to answer the question of the prognostic significance of LN yield in patients with RC [rectal cancer] receiving long course preoperative RT [radiotherapy]," the authors conclude. They add: "Until this time RC will rely on staging, appropriate use of RT, competent surgery and adequate pathological analysis of specimens."

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