PRE-TREATMENT TUMOUR EXTENSION (PRETEXT) SYSTEM

General considerations

The system adopted to describe pre-treatment tumour extension has been called PRETEXT. It has been conceived to describe tumour extension before any therapeutic intervention. Such a system is essential for a study such as SIOPEL 3, which is based on pre-operative chemotherapy. It also serves to assign patients to risk categories ('standard' and 'high').

Anatomically and functionally, the right and the left part of the liver are separate (called right hemiliver and left hemiliver). Each part is divided into two sections. The left hemiliver consists of a lateral section (Couinaud segments 2 and 3) and a medial section (Couinaud segments 4 and left part of 1). The right hemiliver consists of a right posterior section (Couinaud segments 6 and 7) and a right medial section (Couinaud segments 5 and 8 and right part of 1). (Note that there is now international agreement that the term 'sector' used in SIOPEL 2 should be replaced by 'section').

Since surgical resection is a crucial prognostic factor, the healthy sections that can be left in place determine the outcome. PRETEXT aims to predict the anatomical configuration of the healthy liver tissue remaining after resection. It is purely descriptive and is derived as follows:

• PRETEXT The PRETEXT number reflects the numbers of sections that are free of tumour (or involved);

It is important to try to distinguish between actual involvement of the section and only compression of the section. The same distinction applies to "extension" into vessels.
• Extent
Extension of the tumour beyond the liver should also be indicated *):

"V": indicates "extension" into the vena cava and/or all three hepatic veins

"P": indicates "extension" into the main and/or both left and right branches of the portal vein

"E": extra-hepatic disease except for P and V is rare and must be biopsy-proven. (NB: enlarged lymph nodes on radiological investigation are not considered reasons for entering the patient in the the high risk study.)

"M": indicates presence of distant metastases

*) Although strictly speaking only the vena cava and portal vein are beyond the liver, the main tributaries within the liver are also included in "VP" since the resection consequences are the same.

• Volume
Calculation of the actual tumour volume will not influence the final allocation of a tumour into one of the four PRETEXT categories. However, this data will be collected to evaluate the possible impact on patient outcome and to try to monitor, as accurately as possible, tumour response to therapy. In SIOPEL 3 the "volume" will be defined, for ease of calculation, as the actual product of the 3 maximum perpendicular diameters.

Thus the definitive tumour group will be expressed in terms of:

When is tumour extension assessed?

Tumour response monitoring can be assessed during therapy, with some accuracy, by routine physical examination, serial serum a-FP assessments and possibly abdominal ultrasound. However, definitive evaluations of tumour extent are required at diagnosis and before delayed surgery.

Pre-operative tumour extension evaluation is primarily to try to predict the surgical findings and the probable extent of necessary hepatic resection.

Note:

I) Pedunculated tumours are considered to be confined to the liver and to occupy only the section from which they originate.

II) Tumour rupture does not automatically assign the patient to the 'high risk' regimen. Patients should be classified according to the PRETEXT category.