The authors concluded that observational studies showed some encouraging long-term results for cytoreductive surgery plus peri-operative intraperitoneal chemotherapy for patients with pseudomyxoma peritonei. The review appears to support the authors' cautious conclusions, but the reliability of the
evidence was weakened by the use of observational data with no comparison groups.

To evaluate the efficacy of cytoreductive surgery (CRS) combined with peri-operative intraperitoneal chemotherapy (PIC) in patients with pseudomyxoma peritonei (PMP).

MEDLINE, PubMed, EMBASE, the Cochrane CENTRAL Register, the Cochrane Database of Systematic Reviews and DARE were searched for 1966 to March 2006 for relevant reports published in peer-reviewed journals; the search terms were not reported. In addition, reference lists of retrieved studies were screened and expert academic surgeons in Washington, DC were contacted for details of unpublished data. Abstracts were excluded.

Study designs of evaluations included in the review

Experimental and observational studies were eligible for inclusion. All of the included studies were observational case series without control groups.

Specific interventions included in the review

Studies of CRS in combination with PIC (administered within 7 days of surgery) as described by Sugarbaker (reference given) were eligible for inclusion. Studies that evaluated surgical debulking alone for PMP were excluded. CRS comprised various peritonectomy procedures and visceral resections. PIC regimens included intraperitoneal hyperthermic chemotherapy and/or early post-operative intraperitoneal chemotherapy. All of the included studies were set in tertiary referral centres.

Participants included in the review

Studies of patients with PMP were eligible for inclusion. Studies in patients with peritoneal surface malignancy but not specifically PMP were excluded. PMP was defined clinically on the basis of intra-operative findings of localised or generalised accumulations of mucinous tumours in the peritoneal cavity. In the included studies, PMP originated from exclusively or mainly appendiceal epithelial neoplasms; 2 studies did not report the origin of PMP.

Outcomes assessed in the review

Studies that assessed survival, disease status, morbidity and mortality, or quality of life were eligible for inclusion. In the review, outcomes that were reported in more than one trial were assessed. The review assessed survival (median and at 1, 2, 3, 5 and 10 years), disease status (no evidence, alive with disease or died from disease), morbidity, haematological toxicity, blood loss, duration of operation, reoperation rate, mortality and duration of hospital stay. None of the included studies evaluated quality of life among patients with PMP only.

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Two reviewers independently assessed the studies for representativeness of sample, specificity of inclusion criteria, similarity of disease status at baseline, completeness of follow-up, objectivity of outcome measures and sub-series analysis.

Two reviewers independently extracted the data and resolved any disagreements through consensus. A third reviewer then checked the data. For each study, percentages of patients with each dichotomous outcome of interest were tabulated, together with mean or median values for continuous outcome measures.

How were the studies combined?

The studies were grouped by outcome and combined in narrative.

How were differences between studies investigated?

Differences between the studies were discussed in the text.

Thirty-seven case series met the inclusion criteria. Publications reporting accumulating numbers of patients or longer follow-up were identified and the 10 most recent case series or updates were included in the review (n=863 from 8 institutions).

None of the 9 studies that only included patients with PMP indicated how representative the samples were. Seven studies specified inclusion and exclusion criteria. All studies included patients at different stages of the disease. The duration of follow-up ranged from 22 to 35 months in 8 studies; 2 studies
followed up patients for 48 and 52 months. None of the studies were considered to have adequate follow-up.

Survival.

Median survival ranged from 51 to 156 months (3 studies). One-year survival rates ranged from 80 to 100% (5 studies), 2-year survival from 76 to 96% (4 studies), 3-year survival from 59 to 96% (6 studies), 5-year survival from 52 to 96% (6 studies) and 10-year survival was 55% (1 study).

Recurrence.

Forty-seven per cent to 74% of patients were reported to have no evidence of disease, 5 to 15% were alive with the disease, and 0 to 32% had died of the disease (3 studies).

Peri-operative outcomes.

Morbidity rates ranged from 33 to 56% (8 studies), haematological toxicity from 4 to 9% (3 studies), blood loss was 2,100 and 8,000 cm3 (2 studies), mean duration of operation ranged from 6 to 12.6
hours (5 studies), reoperation rates were 11% and 21% (2 studies), mortality ranged from 0 to 18% (7 studies), and hospital stay ranged from a median of 16 to 21 days (2 studies) or a mean of 26 to 29 days ( 2 studies).

Observational studies showed some encouraging long-term results for CRS plus PIC in patients with PMP, compared with historical controls.

The review addressed a clear question that was defined in terms of the participants, intervention, outcomes and study design. Several relevant sources were searched and attempts were made to
minimise publication bias. However, the search terms were not reported. Methods were used to minimise reviewer error and bias in the assessment of validity and extraction of data, but it was not clear whether similar steps were taken at the study selection stage. Validity was assessed using specified criteria and the results of the assessment reported. The narrative synthesis was appropriate in view of the nature of the evidence. The review appears to support the authors' cautious conclusions, but no data from historical controls were presented for comparison and the reliability of the evidence was weakened by the use of
observational data with no comparison groups.

Practice: The authors did not state any implications for practice.

Research: The authors stated that a well-designed prospective multisite study is required to evaluate intraperitoneal hyperthermic chemotherapy (IPHC); they suggested a randomised controlled trial comparing CRS plus IPHC versus CRS alone following complete cytoreduction. There is also a need for more information about the histopathology of PMP/peritoneal mucinous carcinomatosis and a need for standardisation of the histopathological classification for pseudomyxoma peritonei, perhaps based on Ronnett criteria.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.