Stomach cancer is the most common source of peritoneal cancer among all the gastrointestinal cancers
The stomach is a sac-like organ which is a part of the digestive system. It lies just under the diaphragm or the sheet of muscle under the lungs. The top of the stomach is connected to the esophagus or the food pipe and the other end of it is connected to the duodenum which is the first part of the small intestine.
When cancer cells form in the inner lining of the stomach, it is known as stomach cancer or gastric cancer. It is a very aggressive form of cancer, which grows rapidly over few months and usually gets diagnosed at an advanced stage. About 8 out of 10 (80%) people who are diagnosed with stomach cancer are in the fourth stage. Over 50% of the patients with stomach cancer have cancer spread to the peritoneum or peritoneal cancer. In medical terms, this is called gastric peritoneal metastases.
Peritoneal Cancer Developing from Stomach Cancer
Of all the cancers arising from the gastrointestinal tract, stomach cancer is the most common cause of peritoneal spread. 60% of the patients with more advanced cancer of the stomach despite will have peritoneal recurrence. 20 to 40% of all gastric cancer patients die as a direct result of peritoneal dissemination. Patients who have advanced cancer breaching all the layers of the wall of the stomach, those with tumor spread to the lymph nodes or lymph glands around the stomach and those with the aggressive type of stomach cancer (signet ring cell cancer or poorly differentiated cancers) are more prone to developing cancer spread to the peritoneum. In some patients, the peritoneal fluid shows the presence of free cancer cells and these patients are also more prone to developing peritoneal cancer spread.
Treatment of Peritoneal Cancer Developing from Stomach Cancer
Conventionally, patients suffering from peritoneal cancer spread from stomach cancer are treated with chemotherapy alone. Though there are few targeted therapies that are effective in stomach cancer, none are effective on the signet ring cell type.
A recent study showed that the combination of cytoreductive surgery and HIPEC can prolong the survival of some of these patients that have a low PCI and complete tumor removal. The survival is better compared to intravenous chemotherapy and also cytoreductive surgery alone.
In order to treat the peritoneal spread in the stomach, Hyperthermic Intraperitoneal Chemotherapy or HIPEC can be used in 2 ways.
At the time of initial surgery: In patients undergoing curative surgery for stomach cancer, there are certain high risk factors for peritoneal spread. These are patients with tumor spread to lymph nodes (glands), T3/T4 tumors (tumors that involve the full thickness of the stomach wall), high grade tumors, and patients with a positive fluid cytology (where the fluid in the peritoneal cavity shows the presence of cancer cells).
Studies have shown that when HIPEC is performed at the time of initial surgery in these patients it is helpful in preventing peritoneal spread. This approach however, is investigational and is done in the setting of clinical trials only.
Patients with peritoneal spread: This may be at the time of initial presentation or in case of recurrence. Chemotherapy is required foremost. For certain patients in whom the disease is limited or can be completely removed, Cytoreductive Surgery and HIPEC is an option. The outcomes in terms of long term survival are not as good as the other cancers for which CRS and HIPEC is used.
When it comes to the treatment of stomach cancer, the disease extent or peritoneal cancer index is very important. Only patients with a low PCI benefit from cytoreductive surgery and HIPEC. In others, even if the tumor is completely removed during surgery, the chances of the tumor coming back are very high.
Another option for advanced peritoneal cancer is the combination of systemic chemotherapy and PIPAC which is described in the section on PIPAC