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Management of Small Bowel Adenocarcinoma

Management of Small Bowel Adenocarcinoma

Malignant small bowel tumors
are extremely rare, accounting for 0.1% to 0.3% of all malignancies. Fewer than 2,400 new cases of small
bowel malignancy are reported in the United States each year.[1] Malignant
tumors, which account for about two-thirds of all primary small bowel tumors,
consist of four primary subtypes: adenocarcinoma, carcinoid tumor, lymphoma, and
sarcoma (or gastrointestinal [GI] stromal tumor). Each malignancy is
characterized by unique predisposing factors, anatomy, and biology. The
prevalence, pattern, and relevance of both regional lymph node and distant
metastases differ. As a result, the study of malignant small bowel tumors, taken
as an aggregate, is fraught with difficulty.

Data Limitations

Although retrospective data offer some insight into the natural history of
this group of diseases, there are many limitations. Single-center reviews often
describe experience spanning many decades, during which the spectrum of the
disease must inevitably change (as, for example, refinements in imaging and
improvements in treatment and treatment-related morbidity evolve). Large
multi-institutional data sets such as the National Cancer Data Base[2] are
limited by internal consistency of data entry from multiple sources, details of
treatment, and consistent long-term follow-up.

These sources of information are the best we have to define the demographics
and natural history of these rare diseases. However, they cannot define the
impact of any given treatment on outcome. This can only be accomplished by
carefully controlled prospective trials. Given the rarity of these tumors and
the enormous resources involved in the successful completion of such trials, it
is unlikely that they will ever be conducted. Rather, many of our treatment
paradigms will evolve as extrapolations from similar, more common tumors in
other locations.

Alternatively, it is conceivable that we may be able to discern unique
biologic susceptibilities of these tumors by genetic fingerprinting of
individual tumors. At present, however, that possibility remains within the
realm of medical speculation rather than reality.

Therapeutic Options

It is against this background that Kummar and associates present a
well-written, concise review of one of the more common small bowel malignancies,
small bowel adenocarcinoma. The authors have included in their review
adenocarcinoma of the duodenum, a site that accounts for over half of all small
bowel adenocarcinomas. These tumors are often included in series reporting
peripancreatic malignancy, although it appears clear that their biology is
different, ie, consistent with other enteric tumors. Surgical resection—with
either segmental duodenectomy or pancreaticoduodenectomy (depending on anatomic
considerations)—is appropriate. Local resection is inadequate as it is
associated with a high rate of subsequent local recurrence. As there is
significant long-term survival in the setting of node-positive disease, regional
lymphadenectomy in patients with this type of adenocarcinoma may, in fact, be
therapeutic in some patients.

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