If left untreated, the five-year survival rates of gastric cancer range from almost no survival for patients with disseminated disease to almost 50% survival for patients with localized distal gastric cancers confined to resectable regions. Higher recurrence rates are seen in those who have piecemeal or incomplete resections. Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as poor. Complications of gastric cancer are ascites, gastrointestinal bleeding, distant metastasis to other organs, weight loss, recurrence of cancer, and treatment complications. The prognosis of patients with gastric cancer is related to tumor extent that includes direct tumor extension and lymph nodes involvement. The five-year survival rate for treated early gastric cancer is over 90 percent; nearly 100 percent for mucosal tumors, and 80 to 90 percent for submucosal tumors.

The symptoms of gastric cancer usually develop in the fifth decade of life, and start with loss of appetite and loss of weight. The symptoms of gastric cancer typically progress to dysphagia, abdominal pain, and vomiting. Without treatment, 63 percent of patients with early gastric cancer will progress to advanced disease within five years. Metastasis occurs in 80-90% of individuals with stomach cancer.^[1]

Complications of gastric cancer include the following:

• Ascites
• Gastrointestinal bleeding
• Distant metastasis to other organs
• Weight loss

• Recurrence following curative resection was local or regional in 40 % and systemic in 60%.
• Regional recurrences may be more frequent in patients treated with surgery alone or surgery plus postoperative chemotherapy without radiotheapy, and among those who have a fewer number of negative resected lymph nodes.^[2]
• Sites of regional recurrence include the luminal margins, the resection bed, and the regional nodes.^[3]
• The predominant sites of systemic recurrence are the liver and peritoneum.^[4]
• Metastatic disease beyond the abdomen is uncommonly the first site of recurrence aside from the supraclavicular nodes.^[5]
• In a Japanese series, 9.2 % with early gastric cancers had a second cancer within the first year after therapy.^[6]
• The overall incidence of recurrence is 9.5 %t at five years, 13.1 % at seven years, and 22.7 % at 10 years.^[7]

• Anastomotic leakage^[8]
• Anastomotic strictures^[9]
• Obstruction
• Dumping syndrome: Dumping is a phenomenon caused by the destruction or bypass of the pyloric sphincter. Dumping symptoms include gastrointestinal discomfort, abdominal pain, flushing, nausea and diarrhea.^[10]
• Gastric stasis may develop as a result of post-surgical atony, vagal denervation, or from a small gastric remnant following surgical resection.
• Symptoms consist of epigastric fullness with meals, often followed by emesis of undigested food, abdominal pain, and weight loss^[11]

• Neutropenia 
• Anemia 
• Gastrointestinal side effects:
  • Nausea and vomiting 
• Mucositis 
• Weight gain
• Alopecia 
• Fatigue 
• Sexual and reproductive side effects

• The prognosis of patients with gastric cancer is related to tumor extent that includes direct tumor extension and lymph node involvement.
• The five-year survival rate for treated early gastric cancer is over 90 percent; nearly 100 percent for mucosal tumors, and 80 to 90 percent for submucosal tumors.^[12]
• Survival rates are similar between patients who undergo endoscopic resection and those who undergo surgical resection.^[13]
• For advanced cases, the five-year survival rate ranges from almost no survival for patients with disseminated disease to almost 50% survival for patients with localized distal gastric cancers confined to resectable regions.
• The 5-year survival rate of patients with proximal gastric cancer is only 10% to 15%.
• The recurrence rate after surgery is approximately 1 to 5 percent in reports from Korea and Japan and 5 to 15 percent in studies from Western centers.^[14]
• These variable recurrence rates partially reflect differences in length of follow-up, but may also be due to differences in the pathologic diagnosis of malignancy.^[15]
• Among patients undergoing endoscopic resection, recurrence rates have been reported to be between 0 and 30%.^[16]
• Higher recurrence rates are seen with those who have piecemeal or incomplete resections.

Prognosis with lymph node involvement

• Long-term survival was 95 percent in patients with no lymph node involvement, 88 percent in those with one to three nodes involved, and 77 percent in those with more than three nodes involved.^[17][18]

• Between 2004 and 2010, the 5-year relative survival of patients with stomach cancer was 29%.^[19]

• The 5-year relative survival of patients with stomach cancer was 31.4% and 26% for patients <65 years.^[19]

• The survival of patients with stomach cancer varies with the stage of the disease. Shown below is a table depicting the 5-year relative survival by the stage of stomach cancer:^[19]

• Shown below is an image depicting the 5-year conditional relative survival (probability of surviving in the next 5-years given the cohort has already survived 0, 1, 3 years) between 1998 and 2010 of stomach cancer by stage at diagnosis according to SEER. These graphs are adapted from SEER: The Surveillance, Epidemiology, and End Results Program of the National Cancer Institute.^[19]