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According to a study published in the Annals of Oncology, the prognosis of patients with T3 rectal cancer (cancer that has invaded through the bowel muscle but not into adjacent organs) depends not only on lymph node involvement, but also on how far beyond the muscle the tumor extends.

The rectum is part of the digestive system and consists of the final six inches of the large intestine. Current treatments for rectal cancer include surgery, chemotherapy, and radiation.

Determining cancer stage is an important part of making treatment decisions. Rectal cancer staging is based on the extent to which the tumor penetrates through the bowel wall, as well as whether it has spread to lymph nodes.

Patients with T3 rectal cancer have tumors that have spread through the bowel muscle, but have not invaded adjacent organs. Patients with T3 tumors and negative lymph nodes are considered to have stage II rectal cancer. If lymph nodes are involved (but the cancer has not spread to distant parts of the body), the cancer is stage III.

The prognosis of patients with T3 rectal cancer depends on whether or not the lymph nodes are involved, but may also depend on the extent to which the tumor invades the area known as the mesorectum. The mesorectum is fatty tissue that surrounds the rectum; it contains blood vessels and lymph nodes. The extent of mesorectal invasion varies among patients with T3 tumors, but is not taken into account when assigning cancer stage.

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In order to determine whether the extent of mesorectal invasion influences prognosis among patients with T3 rectal tumors (stages II or III), researchers in Japan evaluated two groups of rectal cancer patients. The first group consisted of 196 patients diagnosed between 1980 and 1997, and the second group consisted of 247 patients diagnosed between 1960 and 1969.

The extent of mesorectal invasion was defined as the distance the cancer had spread beyond the bowel muscle.

  • Patients with minimal mesorectal invasion (tumors that extended less than 6 mm beyond the muscle) had better survival. This was true regardless of whether or not lymph nodes were involved.
  • In the first data set (the 196 patients diagnosed between 1980 and 1997), five-year survival was 84% among patients with negative lymph nodes and minimal mesorectal invasion, and 38% among patients with positive lymph nodes and more extensive mesorectal invasion. Patients with extensive mesorectal invasion or positive lymph nodes (but not both) had intermediate survival rates. Similar patterns were observed in the second data set.

The researchers conclude that both lymph node involvement and the extent of mesorectal tumor invasion provide information about the prognosis of patients with T3 rectal cancer. This information may help guide treatment decisions.

Reference: Miyoshi M, Ueno H, Hashiguchi Y et al. Extent of Mesorectal Tumor Invasion as a Prognostic Factor After Curative Surgery for T3 Rectal Cancer Patients. Annals of Surgery. 2006;243:492-498.

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