What Is a Chemo Wash? Explaining the HIPEC Procedure

A “chemo wash” is the informal name for hyperthermic intraperitoneal chemotherapy, almost always called HIPEC (pronounced “HI-peck”). It is a targeted treatment in which heated chemotherapy solution is circulated directly inside the abdominal cavity immediately after a surgeon has removed all visible cancer from the peritoneal lining. The goal is to kill microscopic cancer cells that the surgeon cannot see or reach with a scalpel.¹ The term “wash” captures the physical reality fairly well: warm, drug-laced fluid is pumped in, swirled around for about 60 to 120 minutes, and then drained out, all while the patient is still under anesthesia. But the simplicity of that image hides a procedure that is one of the longest and most physiologically demanding operations in cancer surgery.

How the Procedure Actually Works

HIPEC is never performed on its own. It is the second half of a two-stage operation. The first stage is cytoreductive surgery, or CRS, in which the surgeon methodically inspects the entire abdominal cavity and removes every visible tumor deposit from the peritoneal surface. That can mean stripping sections of the peritoneum itself, removing portions of the bowel, the spleen, the gallbladder, or other organs where cancer has taken hold. CRS alone can last many hours, depending on how widely the cancer has spread.

Once the surgeon is satisfied that all macroscopic disease has been cleared, the HIPEC phase begins. Catheters and temperature probes are placed inside the abdomen, and a perfusion machine pumps heated chemotherapy solution through the cavity, typically at around 42 °C (about 107–108 °F). The fluid circulates for 60 to 120 minutes, bathing every surface the cancer may have touched.² During this time, the surgical team gently rocks or repositions the patient to help the fluid reach every fold and crevice. Afterward, the solution is drained, the abdomen is irrigated with saline, and the surgeon closes the incision.

Two main techniques exist for the perfusion itself. In the open, or “Coliseum,” technique, the abdomen stays open during the wash and the surgeon can manually spread the solution around the organs. In the closed technique, the abdomen is temporarily sealed shut, which may help maintain more even heat distribution.³ A comparison from a high-volume center found no meaningful difference in complication rates between the two approaches.⁴ No definitive evidence shows one technique is superior overall, and centers tend to use whichever their surgeons have the most experience with.⁵

Why Heat Makes a Difference

Delivering chemotherapy directly into the abdomen already offers an advantage over standard intravenous infusion: the drugs reach the cancer cells at far higher concentrations without flooding the entire bloodstream. But adding heat on top of that creates a synergy that is more powerful than either treatment alone. Heat increases the permeability of cancer cell membranes, meaning the drug molecules can get inside more easily. It also alters cellular metabolism and drug behavior in ways that amplify how toxic the chemotherapy is to cancer cells specifically.⁶ Cancer cells tend to be more vulnerable to heat than healthy tissue, partly because tumors have disorganized blood vessels that cannot dissipate heat as effectively as normal organs do.

This heat-drug combination is the core rationale behind HIPEC. Standard intravenous chemotherapy has always struggled to reach the peritoneal surfaces in meaningful concentrations because the blood-peritoneal barrier limits how much drug crosses over from the bloodstream. By putting the drug directly where the cancer is, at an elevated temperature, the procedure sidesteps that limitation entirely.

Which Cancers HIPEC Treats

HIPEC is used for cancers that spread along the peritoneal surface, the thin membrane lining the inside of the abdomen and covering most abdominal organs. Not all cancers do this. Peritoneal spread is most common in cancers of the appendix, ovaries, colon and rectum, stomach, and the peritoneum itself (peritoneal mesothelioma). The strength of evidence varies considerably by cancer type, and so does how routinely HIPEC is offered.

Appendiceal Cancer and Pseudomyxoma Peritonei

This is where HIPEC has its longest track record and strongest results. Pseudomyxoma peritonei (PMP) is a rare condition in which mucin-producing tumors, usually originating from the appendix, fill the abdominal cavity with a jelly-like substance. Before CRS and HIPEC became available, PMP was effectively untreatable. Today, five-year survival rates after the combined procedure range from roughly 55% for the most aggressive subtypes to over 90% for the least aggressive ones.⁷ Long-term quality of life in patients who achieve complete removal of their disease is excellent and holds up even two decades later.⁸

Even when surgeons cannot remove every last bit of tumor, adding HIPEC appears to help. A study from China comparing outcomes in patients with incomplete tumor removal found that those who received HIPEC had significantly better five-year and ten-year survival than those who had surgery alone.⁹

Ovarian Cancer

Ovarian cancer frequently spreads to the peritoneum, making it a natural candidate for HIPEC. A landmark Dutch trial published in the New England Journal of Medicine compared surgery alone to surgery plus HIPEC in women with advanced ovarian cancer who had already received initial chemotherapy. The group that received HIPEC lived a median of about 46 months compared to roughly 34 months in the surgery-only group, and the time before cancer came back was also longer.¹⁰ A subsequent meta-analysis pooling data from randomized trials confirmed a meaningful improvement in both overall survival and disease-free survival when HIPEC was added to interval surgery for primary ovarian cancer.¹¹

Despite these encouraging findings, adoption has been uneven. A national-level analysis found that HIPEC use in ovarian cancer is still relatively uncommon, though the three-year survival trend favored patients who received it.¹² Some of the hesitation stems from the fact that a few later European trials have produced less dramatic results, and oncologists remain divided on which patients benefit most. The current consensus is that HIPEC should be seriously considered for women undergoing interval surgery after initial chemotherapy for advanced-stage disease, but it has not yet become universal standard of care.

Colorectal Cancer

For colorectal cancer that has spread to the peritoneum, the picture is more complicated. The large French PRODIGE 7 trial randomized patients to CRS with or without HIPEC and found no difference in overall survival between the two groups after more than five years of follow-up. Late complications were also somewhat more common in the HIPEC group.¹³ The trial’s authors concluded that CRS alone should be the main treatment approach for these patients. This was a significant shift; many centers had been offering HIPEC routinely for colorectal peritoneal disease before PRODIGE 7 published. The result remains debated, and some subgroup analyses hint that certain patients might still benefit, but the overall evidence does not support adding HIPEC to CRS as a blanket strategy in colorectal cancer.

Peritoneal Mesothelioma

Malignant peritoneal mesothelioma is rare, and randomized trials are difficult to conduct in small patient populations. Observational data consistently suggests CRS with HIPEC is the only treatment that meaningfully extends survival. A large multi-center study reported a median survival of about 53 months and a five-year survival rate around 47% in patients who underwent the combined procedure.¹⁴ A single high-volume center reported median overall survival of about 3.3 years across all patients, with those who survived the first year seeing their projected median survival improve to nearly five years.¹⁵ Without CRS and HIPEC, survival for this disease has historically been much shorter.

Who Is a Good Candidate

Not everyone with peritoneal cancer is a fit for this procedure. Two factors matter above all else: how much cancer is present and whether it can be completely removed.

The extent of disease is scored using the peritoneal cancer index (PCI), which divides the abdomen into 13 regions and assigns each a score based on how much tumor is found there. The total gives a rough map of disease burden. In colorectal peritoneal cancer, a PCI above 20 has traditionally been considered a contraindication because the survival benefit of CRS and HIPEC appears to diminish significantly at that point.¹⁶ That said, some recent work suggests PCI should not be the sole deciding factor; other variables, like tumor biology and the patient’s overall fitness, deserve weight too.¹⁷

The second factor, completeness of cytoreduction, is arguably even more critical. Experts broadly agree that CRS and HIPEC should only proceed if the surgeon believes a complete or near-complete removal of all visible tumor is achievable.¹⁶ If too much disease remains behind, the heated chemotherapy wash alone is unlikely to compensate. In practice, about half of the patients who are taken to surgery but turn out to be unsuitable are closed back up because the disease is more widespread than imaging had predicted.¹⁸

General fitness matters too. The combined operation typically lasts anywhere from 6 to 12 hours, involves significant fluid shifts, and demands intensive care afterward. Patients with very poor baseline health, significant heart or lung disease, or liver cirrhosis at an advanced stage are generally not offered the procedure, though limited data suggests mild cirrhosis does not necessarily rule someone out if the disease burden is low and complete resection is feasible.¹⁹

Which Drugs Are Used in the Wash

The specific chemotherapy agent pumped into the abdomen varies by cancer type and center preference. Cisplatin is the most commonly used drug overall and is particularly prominent in ovarian cancer and mesothelioma protocols. Mitomycin C (often abbreviated MMC) is widely used for appendiceal and colorectal cancers, and oxaliplatin is another option for colorectal disease.²⁰ Some protocols combine cisplatin with doxorubicin (also called Adriamycin), though this combination carries a higher complication rate than cisplatin alone.²⁰

A typical MMC-based HIPEC regimen involves dissolving about 40 mg of the drug in a large volume of warmed saline, perfusing it at 42 °C for 90 to 120 minutes. The dose is often split, with the larger portion given at the start and a smaller booster added partway through.² Because the drug stays mostly inside the abdomen, blood levels remain relatively low compared to intravenous chemotherapy, which spares the rest of the body from many of the usual side effects like severe nausea or immune suppression in the days following surgery.

Risks and Complications

HIPEC is a major procedure, and serious complications are not uncommon. The most well-studied complication specific to the heated chemotherapy itself, rather than the surgery, is acute kidney injury. The kidneys filter whatever drug does make it into the bloodstream, and cisplatin in particular is hard on the kidneys. Across studies, the overall rate of acute kidney injury after HIPEC ranges from roughly 13% to 32%, with cisplatin-based regimens carrying the highest risk.²¹²² One study found that patients who developed kidney injury after HIPEC were about six times more likely to develop chronic kidney problems down the line.²³ Aggressive fluid hydration and maintaining strong urine output during the perfusion phase are key protective strategies that surgical teams use to reduce this risk.

Beyond kidney injury, the heat itself causes widespread changes in the body during the procedure. Core body temperature rises, blood vessels dilate, and the heart rate speeds up to compensate. The anesthesia team monitors all of this closely, using cooling blankets to keep the patient’s core temperature from climbing too high and adjusting fluid and medication in real time.²⁴ Other common complications stem more from the surgery than the wash: bowel leaks at surgical connection sites, infections, blood clots, and prolonged need for intensive care. Severe complications occur in roughly a third to half of patients, though the definition and grading of “severe” varies between centers.

Recovery and Long-Term Quality of Life

The recovery period is significant. Most patients spend at least a few days in intensive care and remain in the hospital for one to three weeks. During the first three months after surgery, quality of life typically drops: pain, fatigue, and disrupted social functioning are common, and a substantial portion of patients experience depressive symptoms.²⁵ The physical toll of a 6-to-12-hour surgery that may involve removing multiple organs is understandably heavy.

The encouraging news is that most studies show quality of life rebounds to baseline or better by about 12 months after the operation. A systematic review found that the factors most likely to drag recovery down included older age, extensive disease at the time of surgery, complications, and the need for a stoma (an external bag for bowel output).²⁶ Patients who had less extensive surgery and no major complications tend to recover faster and more completely. Emotional well-being, interestingly, sometimes improves even while physical functioning is still lagging, presumably because patients feel relief at having undergone definitive treatment.²⁵

What It Costs

CRS and HIPEC is an expensive undertaking: a long operating room time, multiple surgical specialties involved, days in intensive care, and often weeks of hospitalization. For ovarian cancer, one economic analysis found the addition of HIPEC to interval surgery cost only about $1,000 more than surgery alone while adding roughly half a year of quality-adjusted life, making it highly cost-effective by standard health-economics thresholds.²⁷

For colorectal peritoneal disease, the calculus differs because the upfront cost is higher and survival improvements are less certain. One analysis from Singapore found that CRS-HIPEC patients lived a median of about 47 months at a total cost per life year that was actually lower than palliative chemotherapy, because palliative chemotherapy costs accumulate over repeated cycles and yields far shorter survival.²⁸ A U.S.-based analysis estimated an incremental cost-effectiveness ratio of about $91,000 per quality-adjusted life year gained, which is within the range most health systems consider acceptable.²⁹ The financial picture, in short, depends heavily on the cancer type and how much the HIPEC actually improves survival for that particular disease.

PIPAC and Other Emerging Alternatives

A newer approach called PIPAC, for pressurized intraperitoneal aerosol chemotherapy, has generated interest as a less invasive alternative to HIPEC. Instead of flooding the abdomen with heated fluid, PIPAC sprays chemotherapy as a fine mist through a laparoscopic port under pressure. The idea is that pressurized aerosol might distribute the drug more evenly across the peritoneal surface. In animal comparisons, PIPAC delivered a lower total drug concentration to the tissues than HIPEC but did so more efficiently per milligram of drug used.³⁰

PIPAC is generally not used as a substitute for CRS-HIPEC in patients who are eligible for curative-intent surgery. Instead, it is being explored for patients whose disease is too extensive for surgery or who need tumor reduction before CRS becomes feasible. One important caveat from preclinical research is that PIPAC may carry a higher risk of bowel leak when used alongside any intestinal surgery, suggesting it should be avoided in cases where the bowel has been cut or its surface damaged.³¹ Clinical trials are ongoing to better define where PIPAC fits, but for now it remains complementary to rather than a replacement for HIPEC.

HIPEC and the Immune System

One area of active research is whether the heat and chemotherapy used in HIPEC do more than just poison cancer cells directly. Preclinical work has shown that the combination of heat-killed tumor cells and HIPEC-treated tumor cells can activate immune cells called dendritic cells, which in turn prime the body’s own T cells to recognize and attack cancer. In animal models, mice that received tumor cells treated under HIPEC-like conditions mounted a strong immune response and resisted tumor growth even when re-challenged with live cancer cells weeks later.³² This raises the possibility that HIPEC might prime the immune system to fight leftover cancer in a way that extends beyond the direct drug-and-heat assault during surgery. Whether this immune effect plays a meaningful role in human patients is still being studied, but it has fueled interest in combining HIPEC with immunotherapy drugs in future trials.