HIPEC (hyperthermic intraperitoneal chemotherapy) is a surgical treatment where heated chemotherapy is circulated directly inside the abdomen to kill microscopic cancer cells that remain after tumors have been physically removed. The procedure combines two steps: first, a surgeon removes all visible cancer from the abdominal cavity, then bathes the area in warm chemotherapy solution for 60 to 90 minutes. The entire operation takes roughly 8 to 10 hours and is reserved for cancers that have spread to the lining of the abdomen, known as the peritoneum.
How HIPEC Works
The logic behind HIPEC starts with a simple problem. When cancer spreads across the peritoneal surface, surgeons can cut out every tumor they can see, but invisible clusters of cancer cells almost always remain. Standard intravenous chemotherapy has difficulty reaching these cells because the peritoneum acts as a natural barrier between the abdominal cavity and the bloodstream. HIPEC flips that barrier into an advantage: by delivering chemotherapy directly into the abdomen, drug concentrations in the target area can be far higher than what intravenous treatment achieves, while less of the drug leaks into the bloodstream, reducing side effects throughout the rest of the body.
Heat is the second ingredient. The chemotherapy solution is warmed to about 106 to 109°F (41 to 43°C). At these temperatures, tumor blood vessels become more permeable, allowing drugs to penetrate deeper into cancerous tissue. Heat also loosens the outer membranes of cancer cells, making it easier for drugs to get inside them. Normal tissue tolerates this temperature range better than tumor tissue does, because healthy blood vessels can dissipate heat more effectively. The sweet spot for this heat-drug synergy starts around 102°F (39°C) and drops off above 109°F (43°C).
The Two-Part Procedure
HIPEC is never performed on its own. It always follows a surgery called cytoreductive surgery (CRS), where the surgeon methodically removes every visible tumor from the peritoneal surface. This can involve stripping sections of the peritoneal lining and, in some cases, removing portions of affected organs. The goal is complete macroscopic cytoreduction, meaning no tumor deposits visible to the naked eye remain. Multiple studies have shown that when visible tumor cannot be fully removed, adding HIPEC provides no survival benefit.
Once the cytoreduction is finished, and before the abdomen is closed and the digestive tract reconnected, the surgical team circulates the heated chemotherapy solution throughout the abdominal cavity through a series of tubes. The solution flows for 60 to 90 minutes, reaching surfaces and crevices where microscopic cancer cells may be hiding. After the perfusion is complete, the solution is drained and the surgeon proceeds with reconstruction.
Which Cancers HIPEC Treats
HIPEC targets cancers that have spread to the peritoneal surface. The strongest evidence and most consistent guideline support exists for two conditions: pseudomyxoma peritonei (a rare condition usually originating from the appendix that fills the abdomen with mucus-producing tumor cells) and peritoneal mesothelioma. About 90% of national guidelines worldwide give robust positive recommendations for HIPEC in both diseases.
For colorectal cancer that has spread to the peritoneum, the picture is more nuanced. Cytoreductive surgery itself is widely endorsed, but the added benefit of HIPEC is debated. A major trial found no survival advantage when a specific drug regimen was used, though guidelines note that other drug choices may still be effective. For ovarian cancer, HIPEC added during interval surgery (after initial chemotherapy cycles) showed a survival benefit in one landmark trial, but its role remains controversial, and guidelines for recurrent ovarian cancer largely do not recommend it. Gastric cancer with peritoneal spread is generally not considered a candidate for either cytoreductive surgery or HIPEC.
Who Qualifies
Not everyone with peritoneal cancer is a candidate. Surgeons use the Peritoneal Cancer Index (PCI), a scoring system that divides the abdomen into 13 regions and grades the tumor burden in each on a scale of 0 to 3, producing a total score from 0 to 39. For colorectal peritoneal metastases, patients with a PCI above 20 are generally not offered the procedure, and some research suggests the benefit disappears at scores of 17 or higher.
The single most important criterion is whether the surgeon believes complete visible tumor removal is achievable. If cancer involves so much of the small intestine that removing it would leave too little bowel to absorb nutrients (short bowel syndrome), the procedure is typically ruled out. Patients also need to be in good enough overall health to withstand a lengthy, complex operation. Pre-surgical imaging, diagnostic laparoscopy, and sometimes exploratory surgery help the team make this determination before committing to the full procedure.
Survival Outcomes
Outcomes vary significantly by cancer type and how much disease is present. For colorectal peritoneal metastases, a recent single-center study found that patients with low tumor burden (PCI 0 to 10) had a 3-year survival rate of 69%, while those with moderate burden (PCI 11 to 20) had a 3-year survival of 38%. All patients in the study with a PCI above 20 died within three years.
For peritoneal mesothelioma, 5-year survival reaches about 30% when treatment occurs at specialized academic centers, compared to roughly 18% at community hospitals. These numbers reflect the importance of surgical expertise and case volume, which is a consistent finding across peritoneal surface malignancy research. The difference between a high-volume center and a low-volume one can be meaningful.
Risks and Complications
This is major surgery with significant, though manageable, risks. The 30-day mortality rate is about 1%, and the overall complication rate ranges from 10% to 30%. In a study of over 1,800 patients, the most common complications were abdominal infections (7.2%), the need for a return trip to the operating room (6.8%), wound infections at the incision site (5.4%), and deeper wound infections (1.7%). These rates are comparable to other complex cancer surgeries like major liver or pancreatic operations.
The heated chemotherapy itself can cause side effects that overlap with standard chemotherapy, including nausea, changes in blood cell counts, and kidney stress, though systemic exposure is lower than with intravenous treatment. The length and complexity of the surgery also raise the risk of blood clots, pneumonia, and other complications associated with long operations and extended hospital stays.
Recovery Timeline
Recovery from HIPEC is a long process. Most patients spend the first two days after surgery in the ICU, then move to a regular hospital room for another 6 to 20 days. The total hospital stay typically ranges from about one to three weeks, depending on how the body responds and whether any complications develop.
Full recovery takes at least three months, and many patients describe a gradual return to normal over six months or longer. Common side effects during this period include fatigue, weight loss, digestive issues like bloating, diarrhea, or constipation, difficulty sleeping, nausea, and pain. Depression is also reported frequently, which is not surprising given the physical toll and the emotional weight of a major cancer treatment. Nutritional support is often part of the recovery plan, since portions of the digestive tract may have been removed or temporarily disrupted during surgery.