A Two-Stage Surgical Approach for Extensive PMP

Based on research published by Sgarbura et al., Montpellier Cancer Institute (original study)

Why This Research Matters to Our Community

For patients with extensive PMP, getting a complete cytoreduction in a single surgery is sometimes not possible. This study offers a look at a different path forward: a planned, two-stage approach that preserves the bowel, uses HIPEC at both stages, and resulted in complete macroscopic removal and complete pathological response in this small cohort. In a recent post, we explored an uncomfortable reality in cytoreductive surgery: even when surgeons achieve what appears to be a “complete” resection, disease can still be missed. You can read that here: “Did They Get It All? What a New Study Reveals About Cytoreductive Surgery and the Limits of Human Vision”

The Challenge: When PMP Has Spread Too Far

Pseudomyxoma peritonei (PMP) is a rare cancer that almost always starts with a perforated mucinous tumor of the appendix. As it spreads, it deposits mucin-producing cells across the lining of the abdomen. When caught early, the standard treatment combines cytoreductive surgery (CRS) with heated intraperitoneal chemotherapy (HIPEC), and it can be very effective.

For some patients, though, the disease has spread so far by the time of diagnosis that complete removal in a single operation is not realistic. Surgeons face a hard choice: attempt an extremely aggressive surgery that carries serious complication risks, or perform a less complete removal that leaves disease behind and typically leads to worse long-term outcomes.

A surgical team in France decided to ask a different question. What if, for the right patients, two planned surgeries were better than one?

What the Researchers Did

This study from the Montpellier Cancer Institute enrolled 8 patients with extensive PMP who were not good candidates for a complete one-stage cytoreduction. All 8 patients had:

• A Peritoneal Cancer Index (PCI) above 20, indicating widespread disease throughout the abdomen
• Mucin deposits on the small intestine or colon that would have required three or more bowel resections to remove
• Low-grade or acellular PMP histology
• Many had compromised nutritional status, which increased their surgical risk

Stage 1: Remove What You Can, Protect the Bowel

The first surgery focused on removing the largest deposits of disease, with priority given to areas at risk of causing obstruction. Rather than resecting sections of bowel to get every last deposit, surgeons deliberately left thin residual disease (under 5mm thick) on the intestinal surface. HIPEC with oxaliplatin was delivered at the end of this stage.

The thinking behind this was based on what we know about how far HIPEC penetrates into tissue, which is roughly 3 to 5mm. Leaving very thin residual disease and then bathing it with heated chemotherapy was a deliberate strategy: use the chemotherapy to target what surgery did not remove, without the risks that come with major bowel resections.

Stage 2: Check Everything and Finish the Job

About four months later, patients returned for the second surgery. The surgical team explored the entire abdomen, removed any remaining visible disease, and took biopsies from the sites where tumor had been intentionally left behind after Stage 1.

What they found was not what anyone could have guaranteed going in.

The Results

Patients	Deaths	Complete Response	Recurrence
8 of 8 completed	0	100%	0 (29.5 mo. follow-up)

In every single patient, the biopsy samples from previously diseased areas showed only fibrosis, which is scar tissue left behind after cells have been destroyed. There were no living cancer cells. This outcome is called a complete pathological response, and it is the best possible finding at the second stage.

At a median follow-up of nearly two and a half years, all 8 patients were alive with no signs of recurrence. There were no deaths. Serious complications were limited to one grade 3 event per stage, which is a low rate for surgery of this complexity. The authors also raise an intriguing question for future research: given that the residual disease was completely gone by the time of the second surgery in every patient, is the second surgery even necessary? They suggest that if response can eventually be confirmed through less invasive means, a single-stage approach with HIPEC may be sufficient for some patients. That question has not been answered yet, but it points to where the research may go next.

What Is a Complete Pathological Response? When the surgeons biopsied the sites where tumor had intentionally been left after Stage 1, the tissue showed only fibrosis. The residual disease was no longer viable, likely reflecting the combined effects of the initial surgery, HIPEC, and the biology of low-grade PMP itself. No living cancer cells were found in any of the 8 patients.

Why This Approach Is Different

The standard in peritoneal surface oncology has long been that complete cytoreduction needs to happen in a single operation. This study pushes back on that assumption for a specific group of patients: those with low-grade, gelatinous PMP that is widespread but not deeply invasive into the bowel wall.

By spreading the surgical work across two planned stages, the team achieved several things:

• More of the small intestine and colon was preserved, which reduces the risk of short bowel syndrome and long-term digestive problems
• HIPEC with oxaliplatin was administered during both surgeries, giving the treatment two chances to work
• Patients had time to recover nutritionally in between, going into the second surgery in better condition
• The final surgical goal, complete removal of visible disease, was ultimately reached by a different route

Who Might Benefit From This Approach?

The researchers note this strategy is most relevant for patients with:

• Low-grade PMP (acellular mucin or low-grade mucinous neoplasm). This is not applicable to high-grade or signet ring cell subtypes
• Very extensive disease (PCI above 20) that cannot be completely removed in one surgery
• Gelatinous implants that sit on the surface of the bowel rather than growing into it
• Nutritional compromise or other factors that make a single aggressive operation especially risky

It is worth emphasizing that patients with high-grade or infiltrative disease were excluded from this study. The biology of low-grade PMP, particularly its tendency to respond well to HIPEC and its relatively non-invasive growth pattern, is almost certainly what made this approach work.

Important Context: Study Size and Research Stage This is a proof-of-concept study with 8 patients at a single expert center. The results are encouraging, but this approach has not yet been tested in larger multi-center trials. It is still considered experimental and is best discussed with a center that has significant experience in peritoneal surface oncology. Ask your care team whether any clinical trials exploring this approach may be available to you.

What This Means for You

If you or a family member has been told that your PMP is too extensive for complete cytoreduction, this research shows that “too extensive for one surgery” does not necessarily mean “too extensive to treat,” at least for patients with low-grade disease.

It also speaks to why choosing a center with real expertise in peritoneal disease matters so much. Decisions like where to leave residual disease, how thick to allow it, and how to sequence HIPEC across two stages require surgeons who have done this many times. This is not a strategy that can be improvised.

Questions to Ask Your Doctor

• What are your thoughts on this study?
• Is my PMP low-grade or high-grade? How does that affect my surgical options?
• What is my PCI score and what does it mean for my treatment plan?
• Has complete cytoreduction in a single surgery been ruled out for my case, and if so, why?
• Is a two-stage cytoreductive surgery approach something your center has experience with?
• Are there clinical trials exploring staged surgical strategies that I might qualify for?
• What role does HIPEC play in each stage, and which chemotherapy agent would be used?
• What nutritional support would you recommend between the two surgeries?

And as always, share these findings with your medical team.

Glossary of Key Terms

Term	What It Means
Pseudomyxoma Peritonei (PMP)	A rare condition where mucus-producing tumor cells spread to the lining of the abdomen, causing a jelly-like substance to build up over time.
Cytoreductive Surgery (CRS)	Surgery to remove as much tumor as possible from the abdomen and its lining.
HIPEC	Hyperthermic Intraperitoneal Chemotherapy. Heated chemotherapy delivered directly into the abdomen at the time of surgery.
Peritoneal Cancer Index (PCI)	A scoring system (0 to 39) that doctors use to measure how extensively the cancer has spread throughout the abdomen. A higher number means more widespread disease.
Complete Pathological Response	When tissue samples taken from areas of prior tumor show only scar tissue, with no living cancer cells remaining.
CCR0/CCR1	Completeness of Cytoreduction scores. These reflect the surgical goal: no visible tumor remaining (CCR0) or only very small deposits under 2.5mm (CCR1).
Oxaliplatin	A chemotherapy drug used in the HIPEC solution in this study.

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This blog post is for educational purposes only and does not constitute medical advice. Always consult with your oncology care team before making treatment decisions.