Health & Medical Cancer & Oncology

Adjuvant Treatment for Stage II Colon Cancer?

A 58-year-old woman underwent a left hemicolectomy for a large (5.5 cm) bulky descending, moderately differentiated adenocarcinoma that extended into the pericolic adipose tissue. None of the 15 pericolic lymph nodes was involved with tumor. The surgeon's report indicated that the tumor was densely adherent to the retroperitoneum and to the outer surface of the left ureter, and it was necessary to divide the latter structure in order for all gross tumor to be removed from these surfaces. Would this patient be considered a candidate for standard systemic adjuvant chemotherapy?

The description of the pathologic specimen is that of a T4 lesion that extended beyond the colon wall and adhered to the retroperitoneum and left ureter. The lymph nodes were tumor-free, so the tumor should be classified as stage II.

The need for adjuvant treatment in patients with stage II colon cancer remains a matter of debate since none of the randomized clinical studies conducted in this patient population included enough patients to definitively answer this question. Pooled analyses and meta-analyses of available trials have not conclusively answered the question either, with one analysis indicating no benefit, and another using a rather complex statistical methodology, indicating that the relative benefit derived by patients with stage II cancer is similar to that of patients with stage III tumors for which adjuvant treatments is an accepted option.

Given the lack of definitive data, features suggesting a poor prognosis, such as obstruction, perforation, histologic subtype (eg, mucinous tumor), invasion of adjacent structures, and grade of differentiation, have been used as a basis for recommending treatment. Note, however, that the impact of chemotherapy to change the course of the disease in these patients still remains to be determined.

More recently, the use of novel molecular markers such as loss of heterozygosity in chromosome 18, microsatellite instability, and p53 mutation have been explored as predictors of patients survival after adjuvant treatment. For example, retention of the 18q alleles in microsatellite-stable cancers and mutation of the gene for the type II receptor for TGF-beta-1 in cancers with high levels of microsatellite instability have been linked to a favorable outcome after adjuvant chemotherapy in patients with stage III tumors.

In the patient under discussion, it would be of interest to know the histologic subtype of the tumor and the margins of resection. Based on the T stage and the age of the patient, 6 months of 5-fluorouracil-based chemotherapy could be indicated after the uncertainties regarding efficacy and the potential side effects have been explained and discussed in detail to the patient.

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