Peritoneal carcinomatosis

Where carcinomatosis comes from

The peritoneum is most often involved by tumors of the abdominal organs: cancer of the colon, appendix, stomach and ovaries. Separate conditions are pseudomyxoma peritonei — a slow accumulation of mucus containing tumor cells, most often from a mucinous appendiceal tumor — and peritoneal mesothelioma, a tumor of the lining itself.

Carcinomatosis may be found at the same time as the primary tumor or some time after its treatment. In either case, it is important not to remove individual deposits “in passing” during the first operation without a plan: an incomplete procedure makes later complete cytoreduction harder. If carcinomatosis is found unexpectedly, it is better to finish the operation, take a biopsy, document the extent and return to treatment after the MDT.

The effectiveness of cytoreduction depends on the source: results are best in pseudomyxoma, ovarian cancer and limited disease from colorectal cancer; in gastric cancer it is not standard and is possible only in a narrow group of patients, mostly within trials.

Are there symptoms

Early on there may be no symptoms, and carcinomatosis is found on CT or during surgery for another reason. Later, an enlarging abdomen due to ascites, bloating, a feeling of fullness, loss of appetite and weight, and bowel obstruction appear.

With pseudomyxoma, the abdomen may gradually enlarge over years without other complaints.

Examinations needed

• Contrast-enhanced CT of the abdomen, pelvis and chest — peritoneal spread, ascites, metastases outside the abdomen; CT often underestimates small deposits.
• Diffusion-weighted MRI — shows small deposits on the peritoneum and bowel more accurately.
• PET-CT — when indicated, to rule out metastases outside the abdomen.
• Tumor markers — CEA, CA 19-9, CA-125 depending on the source.
• Diagnostic laparoscopy — allows the peritoneum to be seen and the Peritoneal Cancer Index (PCI) to be calculated — from 0 to 39 across 13 regions. Together with small-bowel involvement, histology and general condition, it determines whether complete cytoreduction is possible.
• Histologic confirmation and identification of the tumor’s source.

When surgery is possible

Cytoreduction is considered when all visible tumor deposits can be removed, there are no metastases outside the abdomen or they are limited and resectable, small bowel involvement is not too extensive, and general condition allows a long operation. The acceptable extent depends on the source: in colorectal cancer, results are best with a low PCI, while in pseudomyxoma surgery is performed even with extensive disease.

For most tumors, surgery is combined with systemic chemotherapy before and after; in low-grade pseudomyxoma it is usually not needed. The MDT decides the sequence.

If surgery is not possible now

If complete cytoreduction is not possible, treatment is based on systemic chemotherapy according to the tumor’s source, with targeted drugs or immunotherapy when indicated. After a response to treatment, surgery is sometimes reconsidered.

Increasing ascites is drained; with bowel obstruction, a bypass, stoma or stent is considered to relieve symptoms.

How the operation is performed

Cytoreduction is performed through a midline incision. All visible deposits are removed: the affected areas of peritoneum (peritonectomy), the greater omentum, the lesser omentum if involved, and, if necessary, part of the bowel, the spleen, the gallbladder, the uterus with ovaries. The goal is to leave no visible deposit: the completeness of cytoreduction is one of the most important factors in the outcome. Such an operation may last many hours.

After the tumor is removed, HIPEC — washing the abdomen with a heated chemotherapy solution — is performed in selected cases. Its effectiveness depends on the source: it is part of the standard for pseudomyxoma and is considered in ovarian cancer, while in colorectal cancer a randomized trial showed no advantage of oxaliplatin HIPEC over complete cytoreduction alone. The MDT therefore decides on the indications.

Recovery after surgery

Care follows the enhanced recovery after surgery (ERAS) protocol: early mobilization, early feeding, controlled pain relief. After extensive cytoreduction the first days are usually spent in intensive care and the hospital stay is longer than after standard surgery; sometimes a temporary stoma is created.

A few weeks later, once the patient has recovered, systemic chemotherapy continues where indicated, as decided by the MDT.

Follow-up

CT or MRI and tumor markers every 3–6 months for the first years, then less often; in pseudomyxoma, follow-up is long-term. An enlarging abdomen, bloating or changes in bowel habits should be reported right away.

What to bring to the consultation

• CT or MRI discs with reports — the discs themselves;
• operative and laparoscopy reports describing peritoneal spread;
• the pathology report, tissue blocks and slides;
• tumor markers over time;
• chemotherapy records with regimens and number of cycles.

If some materials are missing, that is no reason to postpone the consultation: some examinations can be done on site.

The consultation is free of charge. How it goes and how long it takes is described on the page “Oncologist Consultation”.