A new scoring system for peritoneal metastasis in gastric cancer

The degree of peritoneal metastasis (PM) of gastric cancer has been classified into four grades (P0, P1, P2, and P3) in the Japanese Classification of Gastric Carcinoma, First English Edition. However, the PM category in this version was so ambiguous in terms of volumetry that it was unlikely to estimate PM status correctly. We have developed a new volume scoring system for PM, modifying Sugarbaker's classification.

Eighty-five patients with gastric cancer with PM underwent surgery and/or laparoscopy at our hospital at Kanazawa University between January 1990 and December 2000. The grading (Gr) by the volume scoring system was decided according to the sum of scores for nine (in male) or ten (in female) abdominopelvic regions. These regions included left subphrenics, right subphrenics, left flank, right flank, pelvis, omenta, mesentery, small and large bowels, ovaries (only for females), and other intraabdominal organs. Volumetry for each region was carried out using the following categories: VS0, indicating the absence of cancer in a particular abdominopelvic region; VS1, indicating that tumor nodules are less than 10 mm in diameter; VS2, indicating tumors between 1 and 5 cm in diameter; and VS3, indicating that tumor is more than 5 cm in diameter or that an organ is coated by a mat of tumor (confluent disease). The scores for VS0, VS1, VS2, and VS3 were 0, 1, 2, and 3 points, respectively. Total scores of 1 to 3 were the equivalent of Gr I, total scores of 4 to 6 were equivalent to Gr II, total scores of 7 to 9 were equivalent to Gr III, and total scores of more than 9 were equivalent to Gr IV.

There was no significant difference between P1 and P2, or between P1 and P3 in survival curves. But the 50% survival times of Gr I, Gr II, Gr III, and Gr IV were 1.23, 0.66, 0.67, and 0.32 years, respectively. The prognosis of Gr I was significantly better than that of any other grades. Eight of the 28 patients (29%) assessed as Gr I survived more than 2 years, whereas only 2 of the 57 (4%) assessed as Gr II, Gr III, or Gr IV did so. Multivariate analysis by Cox's proportional hazard model revealed that the volume scoring, resection of primary tumor, and resection of peritoneal tumor were independent factors to predict prognosis.

These results showed that the volume scoring system was strongly related to the prognosis, and the patients assessed as Gr I had a great probability of cure by surgery.