Gastric (Stomach) Cancer
The cancer of stomach (gastric cancer) is fourth most common cancer in the world and second leading cause of cancer deaths. Recent data from the Indian Council of Medical Research suggests that by the year 2020, approximately 50000 new patients would be detected to have gastric cancer. Even though the age standardized incidence rate of gastric cancer has decreased in India (Lancet Oncology 2018), it ranks second amongst the three most fatal cancers with oral and lung cancers being first and third respectively(Lancet 2012).
Gastric cancer often does not cause any specific symptoms in the early stage. The common symptoms include epigastric pain, fullness after meals and weight loss and are frequently mistaken for more common gastritis. In most instances by the time patient develops symptoms such as difficulty in swallowing (dysphagia associated with proximal gastric cancers) or persistent / recurrent vomiting after meals (gastric outlet obstruction associated with distal gastric cancers), the disease is often in an advanced stage.
However mere presence of these symptoms does not mean that you have cancer stomach. You should consult your doctor so that the cause for these symptoms can be investigated.
Based on your symptoms, other relevant medical history and physical examination your doctor may recommend investigations to reach a diagnosis.
The objectives of investigations for a patient with suspected gastric cancer include:
1. Establish diagnosis
2. Assess fitness for major surgery
3. Meticulous preoperative staging to select patients who are candidates for surgery
Upper GI Endoscopy (UGIE) is an initial and essential investigation for diagnosis of gastric cancer. Biopsies (usually 6-8) are taken from any suspicious mass lesion or ulcer.
In patients where the biopsy is confirmatory of gastric cancer, further investigations are performed to determine the stage of the disease so as to plan appropriate treatment. These would usually include:
1. Abdominal CT scan of the whole abdomen and pelvis (with oral and intravenous contrast) is the preferred imaging investigation to detect spread to other abdominal organs such as the liver. It also provides reasonable information regarding the tumor (T stage) and surrounding lymph nodes (N stage).
2. High resolution CT scan of chest (with or without contrast) is performed to exclude spread of cancer deposits in lungs.
3. Positron emission tomography (PET) scan is recommended in patients with loco-regionally advanced tumors with no evidence of metastatic disease on initial CT scan and in those patients who are planned for chemotherapy prior to definitive surgery.
Upper GI endoscope with mounted ultrasound is used to perform EUS examination. In patients with gastric cancers, EUS provides more accurate information regarding the T (tumor) stage and N (surrounding lymph nodes) stage as compared to abdominal CT scan.
The most widely used staging system for cancer stomach is American Joint Committee on cancer (AJCC) staging system which includes TNM classification of the cancer. The TNM system indicates size of the tumor (T), lymph node involvement (N) and distant metastases to lymph nodes outside specified regional nodes or other organs (M).
The stage of the cancer indicates the likely treatment and survival.
Stage IB, II & III: Disease likely confined to stomach and draining lymph nodes. Survival benefit by surgery ± chemotherapy/chemoradiotherapy
Stage IV: Cancer has spread to distant organs such as liver therefore cure is no longer possible. Such patients are candidates for palliative management only.
a. Curative surgery
D2 radical gastrectomy is the current standard of care and remains the only available potentially curative treatment consistent with long term survival. The surgery can be performed by traditional open surgery or by minimally invasive techniques (laparoscopic or robot assisted). At specialized centers, the procedure can be accomplished with a morbidity (GI bleeding, leak, obstruction and wound related complications) and mortality rate ranging up to 15% and 3% respectively.
b. Chemotherapy and chemoradiotherapy in patients with resectable gastric cancers (Stage IB, II & III)
Pre and postoperative chemotherapy in patients with stage IB, II and III gastric cancers improves survival in patients who undergo D2 radical gastrectomy. In patients who do not receive preoperative chemotherapy, or have microscopic residual disease (R1 resection) and where D2 gastrectomy does not conform to current standards, benefit from addition of radiotherapy to chemotherapy after surgery.
The detailed chemotherapy and chemoradiotherapy protocols are beyond the scope of current discussion
c. Palliative management
Patients with spread of cancer to other organs such as liver or lining of abdominal cavity (peritoneal metastases) where curative surgery is not an option may present with complications of advance disease such as obstruction or bleeding. Such patients benefit from a multidisciplinary consultation / management. The patients fit to undertake major surgical procedure may be considered for palliative gastrectomy. Other options include – endoscopic stenting for proximal gastric cancers with obstruction and surgical gastrojejunostomy or endoscopic stenting for distal gastric cancers with obstruction. For patients who present with persistent / recurrent tumor bleeding the treatment options are endoscopic/ angiographic embolization/ surgery.
Locally advanced gastric cancers (Clinical stage 4b) by direct extension may involve adjacent organs such as spleen, pancreas, colon or liver. In such patients multivisceral resection (radical gastrectomy + involved organ) may be performed with acceptable postoperative morbidity and mortality rates and can have a positive impact on long-term survival.
Five year survival of 33- 45% and 15 year survival of up to 29% has been reported from European centers of excellence following D2 radical gastrectomy.