Prognosis and survival in peritoneal carcinomatosis

Before any figure: what a median is

Almost all survival data is reported as a median. A median of twenty-two months does not mean “you have twenty-two months”. It means that, in that group of patients, half went past it and half did not.

Where you fall on that curve is not something the number can tell you. There are patients at the long end of every one of these series, and there are patients at the short end. The median is where the group splits, not a date.

The second figure you will see is five-year survival, as a percentage: out of a hundred patients in that group, how many were alive five years later. It is more informative than the median where there is a long tail of survivors — which is exactly what happens in some of these diseases.

What weighs most, in order

Three factors explain most of the difference between one patient and another, and only the third depends on a decision.

• The tumour of origin. An appendiceal pseudomyxoma is not a gastric adenocarcinoma; the distance between the two ends of this page is measured in years, not months.
• The specific biology of the tumour. Within the same origin, histology changes the prognosis: signet-ring cells, for instance, worsen the outcome even with little disease and a flawless operation.
• Whether the cytoreduction is complete. This is the factor that does lie with the team and with when surgery happens, and it typically doubles or triples median survival.

The weight of complete versus incomplete cytoreduction as an independent predictor: set out in the author's monograph, drawing on the series cited below.

The figures, with their labels attached

Appendiceal origin and pseudomyxoma peritonei. The best scenario, by some distance. With complete cytoreduction and low-grade histology, five-year survival was 86%. In a pooled analysis of 2,298 patients from sixteen centres, median survival was 196 months — over sixteen years — and 63% were alive at ten.

Peritoneal mesothelioma. With systemic treatment alone, the historical median is six to twelve months. In the international registry of 405 patients treated with cytoreduction and intraperitoneal chemotherapy, the median was 53 months and 47% were alive at five years. With one condition: epithelioid subtype. In the sarcomatoid variant the median is under twelve months with any treatment.

Colorectal origin. The trial that opened the field gave 22.4 months with cytoreductive surgery against 12.6 with systemic treatment and palliative surgery. Later series, with better selection, give medians around 30 months and 27% at five years. In the most recent trial, with every patient operated on until the abdomen was clear, both arms reached about 41 months.

Ovarian origin. In stage III interval surgery, adding heated intraperitoneal chemotherapy moved the median from 33.9 to 45.7 months, and ten-year survival from 10.9% to 16.1%.

Gastric origin. This is the hardest scenario and it is better said plainly. In the trial comparing surgery against systemic treatment in limited peritoneal disease, the results were 15.7 against 16.6 months, with serious adverse events in 44% of the surgical arm against 6%, and the study closed early for futility.

Appendiceal: Sugarbaker PH, Chang D. Ann Surg Oncol 1999; pooled analysis of 2,298 patients across 16 centres. Mesothelioma: Yan TD, et al. J Clin Oncol 2009. Colorectal: Verwaal VJ, et al. J Clin Oncol 2003; Elias D, et al. J Clin Oncol 2010; Quénet F, et al. Lancet Oncol 2021. Ovarian: van Driel WJ, et al. N Engl J Med 2018 and Aronson SL, et al. Lancet Oncol 2023. Gastric: Quik JSE, et al. Lancet Oncol 2026.

The figure that best explains the difference

Of all the numbers on this page, one deserves a second look. In the European series of 506 patients with colorectal peritoneal carcinomatosis, median survival was 32.4 months where the cytoreduction was complete and 8.4 months where visible disease was left behind.

The same disease, the same surgeons, the same year. The only thing that differed was what stayed inside at closure. Which is why the deciding question in clinic is not how much disease there is, but whether all of it can be removed.

Glehen O, et al. Journal of Clinical Oncology, 2004 (506 patients, 28 institutions).

What happens without surgery

It is the question almost nobody asks out loud, and it deserves an answer.

In colorectal cancer, the group treated with systemic chemotherapy and palliative surgery in the landmark trial had a median of 12.6 months. In the pre-oxaliplatin era, peritoneal disease carried the worst prognosis of any metastatic site, with medians of five to seven months.

In peritoneal mesothelioma, the historical median with systemic treatment alone is six to twelve months. In gastric cancer, with modern regimens, around sixteen months in the control arm of the most recent trial.

Systemic treatment has improved since, and any individual case has to account for that improvement. But the order of magnitude is what it is, and it is the reason this surgery exists.

Verwaal VJ, et al. J Clin Oncol 2003 (control arm). Historical and modern-era series as recorded in the author's monograph. Gastric: control arm of PERISCOPE II, Lancet Oncol 2026.

What can be moved, and what cannot

The tumour of origin cannot be changed, nor can its biology. Where and when it is treated can, and two further things depend on decisions and appear repeatedly in the data.

The first is reaching a high-volume unit before the disease progresses: a complete cytoreduction is more achievable the earlier it is considered. The second is the condition in which a patient arrives at surgery: sarcopenia and malnutrition consistently predict more complications and a worse recovery, and they are among the few variables on this list that can be changed in the weeks beforehand.

Sarcopenia and hypoalbuminaemia as modifiable predictors of major morbidity: the author's monograph.

What this page does not do

None of these figures is your prognosis. They all describe selected groups of patients, treated in experienced centres, under criteria that may not be yours.

An individual prognosis can only be given after seeing the pathology, the imaging and the person. If you came here looking for a date, the honest answer is that the number does not exist: there is a curve, and there is room to move within it.