Cáncer Gástrico

Gastric
A d e n o c a rc i n o m a
S u r g e r y an d
Adjuvant Therapy
Sameer H. Patel,

MD,

David A. Kooby,

MD*

KEYWORDS
 Gastric cancer  Gastric resection  Adjuvant therapy
 Gastric adenocarcinoma

Although the incidence of gastric cancer in the United States has steadily declined
since the 1930s, globally it remains the second leading cause of cancer-relatedmortality.1 This ominous diagnosis affected approximately 21,000 individuals in the
United States in 2010 and, despite existing treatments, an estimated 10,570 (50%)
of those patients succumbed to the disease.2 The incidence of gastric cancer varies
substantially worldwide, with the highest rates (>20 per 100,000) occurring in Japan,
China, eastern Europe, and South America.1 By contrast, the lowestrates (.05).41–43 Several studies suggest that MRI may improve
detection of metastatic disease compared with CT, especially when the contrast
ferumoxtran-10 is used (sensitivity 100%, specificity 92.6%).41–44 18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) is increasingly used and can
provide additional staging information, especially for metastatic disease; however, it
isinferior to CT and MRI for screening (sensitivity 10.0%, specificity 99.2%).45 For
assessing depth of invasion, endoscopic ultrasonography (EUS) remains the primary
choice for determining T staging.46–49
A large systematic review examining 31 studies conducted by Kwee and Kwee50
evaluated the usefulness of using abdominal ultrasonography (AUS), EUS, multidetector computed tomography (MDCT), MRI,FDG-PET, and FDG-PET/CT fusion in
assessing lymph node status in gastric cancer. They found that there was no imaging
modality that consistently achieved both high sensitivity and high specificity in the
detection of lymph node metastasis. Despite these disappointing findings, it is necessary to determine the extent of disease so that the appropriate surgical resection can
take place.
It is theauthors’ practice to use EUS selectively to assess the depth of invasion
(T staging) and regional node involvement (N staging) when the tumor is small, and
the information guides the treatment approach. CT is preferred, rather than MRI, for
staging, and FDG-PET is selectively used as an adjunct if there is high suspicion of
distant metastatic disease in higher risk patients.

Gastric CancerNODAL STAGING

The current AJCC tumor-node-metastasis (TNM) staging classification remains the
best prognostic system for assessing survival from gastric adenocarcinoma (see
Table 2). In 1997, nodal classification changed from using the location of the involved
lymph nodes to the number (pN1, 1–6 nodes; pN2, 7–15 nodes; pN3, >15 nodes). For
an adequate sampling, 15 lymph nodes need to beremoved to accurately differentiate
between pN2 and pN3 disease. However, several studies confirmed that the average
number of nodes evaluated is close to 10, and that only about 30% of patients have at
least 15 nodes evaluated.51–53 This is an issue of both adequate dissection and thorough pathologic assessment. As a result of the routine inadequate nodal evaluation,
the N stage was furthermodified. In the revised seventh edition of the AJCC staging,
a minimum of 7 nodes are needed, and this is today’s current classification system
(pN1, 1–2 nodes; pN2, 3–6 nodes; pN3, !7 nodes).
More recent studies propose examining the metastatic lymph node ratio (MLR; the
ratio between metastatic lymph nodes and total evaluated lymph nodes) as opposed
to the total number of positive nodes.Autopsy studies have shown that, on average,
D1 dissections can provide an average of 15 nodes, D2 dissections can produce 27
nodes, and 42 nodes may come from a D3 dissection.54 MLR may be more valuable
in cases in which inadequate node evaluation has been performed. Several groups
have found MLR to be one of the strongest negative prognostic factors for survival
on multivariate analyses,...