Peritoneal Surface Malignancy

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DEFINITION

Involvement of peritoneal surface with malignancy is common and outcome varies with origin of malignancy.

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EPIDEMIOLOGY

As per individual conditions
Secondary tumours far exceed primary tumours.
- primary are very uncommon tumours

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AETIOLOGY

Primary
- primary peritoneal carcinoma
- malignant peritoneal mesothelioma

Secondary
- appendiceal cancer
- colorectal cancer
- gastric cancer
- ovarian cancer
- pancreatic cancer
- endometrial cancer
- sarcoma

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BIOLOGICAL BEHAVIOUR

Pathophysiology

There is a very tight correlation between type and grade of tumour and recurrence rate and outcome.

Low grade are treatable
Spread across cavity by direct attachment and proliferation, but not by hematogenous and lymphatic routes
Common for low-grade mucinous peritoneal malignances, e.g. pseudomyxoma peritonei and appendiceal cancers
--> locoregional therapy can effectively eradicate
Up to 50% long term survival for malignant peritoneal mesothelioma, only 15-25% for perimary peritoneal cancers.

High grade are not treatable
E.g. colorectal, pancreatic, gastric cancers; spread by hematogenous and lymphatic routes
Not practical to remove or treat them.

Pseudomyxoma Peritonei Syndrome
Large volumes of mucinous ascites
Treat aggresively with CRS and HIPEC
Long-term survival reasonable

Appendiceal Tumours
Tend to spread to peritoneum before going distant
All should be considered for therapy, if low grade there can be good survival.

Colorectal Cancer
If low-volume disease, should be considered.
Probably most common indication.




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MANIFESTATIONS

Peritoneal tumors
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INVESTIGATIONS

Peritoneal tumour work up
Detailed imaging essential to guide therapeutic planning; below
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MANAGEMENT

Therapeutic Rationale

1. Optimal therapy involves debulking (CRS - cytoreductive surgery)
- with goal of complete removal of all visible disease
- ie generally a long and tedious procedure.

2. This will not eliminate the disease
- accepted that there will be be residual microscopic cancer cells
--> generally there is rapid recurrence and demise after resection.

3. Hence, additional techniques for residual disease management
- HIPEC: Hyperthermic Intraperitoneal Chemotherapy
- in HIPEC, residual cells are exposed to high doses of chemo (i.e. higher than in systemic chemo)
- addition of heat improves penetration into malignant cells
- toxicity is reduced by delivery under general anaesthesia

4. Optimal selection:
- low grade
- tumour does not spread by blood or lymph
--> accepted in noninvasive peritoneal carcinomatosis, malignant peritoneal mesothelioma, invasive colorectal cancer of low volume
--> perhaps noninvasive sarcomatosis
- must be surgically resectable
- patient condition, must withstand massive surgical stress
--> morbidity up to 50% and mortality perhaps 5%
- degree of peritoneal involvement

Operative

1. Only necessary to remove peritoneum;
- tumour does not invade deeper.

2. If CRS is indicated:
- peritoneal stripping of all involved areas
- organ resection of involved areas
--> use traction and electrocautery on high setting
--> peritoneum strips easily as thickened by the malignancy
--> numerous vessels between underlying tissue and peritoneum will bleed extensively; may be enlarged by vascular tumour growth factors

3. Large incision and assess 6 abdominal areas for CRS
i) RUQ and porta
- cells like tracking here; flow in ascitic fluid up gutters
- great care needed around central tendon and hepatic veins
ii) omentum, spleen and lesser sac
- omentum and spleen often removed together as first step, often with pancreatic tail
- often don't to do much in lesser sac.
iii) LUQ and stomach
- lesser omentum removed when involved, preserving L gastric (often only remaining supply)
iv) Colon and colic gutters
- colectomy considered in extensive disease; occasionally subtotal colectomy
v) Small bowel and mesentery
- resect but remember 150cm desirable for adequate nutrition
- sometimes TI en-bloc with R colon
- leaks and fistulas are common complications and care must be tkaen
vi) pelvic peritoneum and organs
- often site of gretest volume, usually sigmoid can go facilitating access
- female pelvic organs often resected.

4. If disease is confluent in an area, complete peritonectomy there is indicated
- meticulous and diligent
- "completeness score" desired is 0 (macroscopically clear) vs I (0.25cm) II (0.25-2.5) III (>2.5)
- where peritoneum removal impractical, remove the organ.
--> commonly gone are spleen, GB, sigmoid, upper rectum, uterus, ovaries, portions of small bowel and colon.
--> where 2mm spots left on small bowel or colon, ablate with diathermy on high, vaporizing.

5. But remember that CRS alone is not curative, so just go for score 0 without being overzealous.

6. Should be done in a specialist referral center where there is adequate volume.

HIPEC

1. Deliver to all at-risk surfaces
2. Expose to heating 5-7o higher then body temp
3. Circulation to expose freely and evenly
- HIPEC unit pump and heat exchanger.

Technique
Temporarily close skin with a running monofilament.
Temp probes
Carrier diasylate solution.
Agitate abdomen constantly and shift table positions while administering.
Pre-op patient cooling recommended.
Generous fluids to maintain u/output 400ml/hr during Rx
Chemo chosen depends on type of cancer; often mitomycin C +/- other like doxorubacin, oxaloplatin, cisplatin.


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REFERENCES

Cameron 10th

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