Gastric Cancer, Complete Surgeon's Guide

Diagnosis and Staging 

Initial Assessment: 

1. Full history & physical examination.
2. Labs: blood count and differential, full liver and renal function tests.
3. Endoscopy.
4. Contrast-enhanced computed tomography (CT) scan of the thorax and abdomen ± pelvis.

Diagnosis should be made from a gastroscopic or surgical biopsy reviewed by an experienced pathologist, and histology should be reported according to the World Health Organization criteria.

Ninety percent of gastric cancers are adenocarcinomas, and these are sub-divided according to histological appearances into diffuse (undifferentiated) and intestinal (well differentiated) types.

Work up:

• Endoscopy + biopsy to obtain tissue for diagnosis, histological classification and molecular biomarkers, e.g. HER-2 status.

• Contrast enhanced CT thorax + abdomen + pelvis staging of tumour: particularly to detect local/distant lymphadenopathy and metastatic disease sites.

• Endoscopic ultrasound (EUS): Accurate assessment of T and N stage in potentially operable tumors. Determine proximal and distal extent of the tumour.

The TNM classification:

The TNM stage should be recorded according to the 8th edition of the AJCC/UICC staging manual. 

TX	Main tumor cannot be assessed due to lack of information
T0	No evidence of primary tumor
Tis	Carcinoma in situ: intraepithelial tumor without invasion of the lamina propria
T1	Tumor invades lamina propria, muscularis mucosae, or submucosa
T1a	Tumor invades lamina propria or muscularis mucosae
T1b	Tumor invades submucosa
T2	Tumor invades muscularis propria
T3	Tumor penetrates sub serosal connective tissue without invasion of visceral peritoneum or adjacent structures. T3 tumors also include those extending into the gastrocolic or gastrohepatic ligaments, or into the greater or lesser omentum, without perforation of the visceral peritoneum covering these structures
T4	Tumor invades serosa (visceral peritoneum) or adjacent structures
T4a	Tumor invades serosa (visceral peritoneum)
T4b	Tumor invades adjacent structures such as spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine, and retroperitoneum Tumor invades adjacent structures such as spleen, transverse colon, liver, diaphragm, pancreas, abdominal wall, adrenal gland, kidney, small intestine, and retroperitoneum
NX	Regional lymph nodes cannot be assessed due to lack of information
N0	No regional lymph node metastasis
N1	Metastasis in 1 to 2 regional lymph nodes
N2	Metastasis in 3 to 6 regional lymph nodes
N3	Metastasis in 7 or more regional lymph nodes 7 to 15 nearby lymph nodes (N3a)  16 or more nearby lymph nodes (N3b)
M0	No distant metastasis
M1	Distant metastasis

For detailed illustration, please follow the link: (https://www.cancerresearchuk.org/about-cancer/stomach-cancer/stages/tnm-staging) 

Staging According to AJCC: 

AJCC Stage	Stage grouping
	T	N	M
0 “Carcinoma in Sito”	Tis	0	0
IA	1	0	0
IB	1	1	0
	2	0	0
IIA	1	2	0
	2	1	0
	3	0	0
IIB	1	3a	0
	2	2	0
	3	1	0
	4a	0	0
IIIA	2	3a	0
	3	2	0
	4a	1 or 2	0
	4b	0	0
IIIB	1 or 2	3b	0
	3 or 4a	3a	0
	4b	1 or 2	0
IIIC	3	3b	0
	4a	3b	0
	4b	3a or 3b	0
IV	Any	Any	1

·         Any T1 or T2 & up to N1 is stage I

·         Any T1 or T2 & N2 is stage II

·         Any T3 & up to N1 is stage II

·         Any T4 & N1 or more is stage III

·         Any M1 is stage IV 

Treatment

UPFRONT SURGERY

Indication: Stage 1A

        I-    Endoscopic Resection:

For T1a if they are clearly:

1-      Confined to the mucosa

2-      Well differentiated (G1-2)

3-      ≤ 2 cm

4-      Non-ulcerated

Endoscopic resection can be done primarily for diagnostic purpose with aiming for no tumor at the margins. Endoscopic submucosal dissection with en bloc removal of the neoplasm and its lateral and deep margin, is recommended for diagnostic and curative intents.

        II-     Surgical Resection:

-    For T1a tumors that did not meet the criteria for endoscopic resection.

-    Extent of the resection depends on tumor location, TNM category and histological subtype.

-    D1+ lymph node dissection to be done for T1 tumors, which include removal of the peri-gastric lymph nodes plus those along the left gastric artery and include local N2 nodes according to tumor location.

PERIOPERATIVE THERAPY

Indications: Stages 1B-III disease.

Contraindications: Stage 0 and stage 1A. (Tis & T1 No)

For complete gastric cancer regimens, please visit the following link: https://emedicine.medscape.com/article/2005831-overview 

POST CHEMOTHERAPY SURGERY

Indications: Stages 1B-III disease (T2, ≥N0, M0)

• Radical gastrectomy although partial gastrectomy can be done in selected cases if an adequate proximal resection margin is achievable. 
• A proximal margin of ≥ 3 cm is recommended for tumors with an expansive growth pattern (including intestinal histotypes) and ≥ 5 cm for those with an infiltrative growth pattern (including poorly cohesive/diffuse histotypes).
• Frozen sections of proximal margin could be done intraoperatively when margin extent can't be satisfied intraoperatively. 
• D2 lymphadenectomy is recommended, which includes removal of D1+ with additional lymph nodes along the proper or common hepatic artery, splenic artery or coeliac axis. 
• Excision of a minimum of 15 lymph nodes is recommended for comprehensive staging.