What's the Meaning of Positive Peritoneal Cytology in Gastric Cancer

Orlando, FL—In patients with locally advanced gastric cancer who have positive peritoneal cytology but no other evidence of metastatic disease (M0Cyt), those who convert to negative cytology after systemic chemotherapy have a significant improvement in disease-specific survival (DSS), according to Memorial Sloan-Kettering Cancer Center investigators who presented findings at the 2010 Gastrointestinal Cancers Symposium.

Lead author James Mezhir, MD, commented, “Cytology is an important prognostic factor, even in the absence of visible M1 disease.” Patients with cytology-only disease are now considered to have M1 disease, he noted.

The study of 1241 patients, 93 of who had positive cytology without visible visceral or peritoneal metastases, there was a trend toward better DSS when patients had gastric resection, although peritoneal recurrence was common after surgery, he said.

Positive peritoneal cytology is a negative prognostic factor in gastric cancer patients treated with resection, and in some patients this may be the only evidence of metastatic disease. The study examined the natural history of patients with positive cytology as the only sign of metastases.

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Patients underwent diagnostic laparoscopy for primary gastric cancer, which found positive cytology in 291 (23%), which was classified as M1Cyt in 196 (68%) and M0Cyt in 93 (32%).Among the 291 with positive cytology, worse DSS (time from first laparoscopy) was associated with poor performance status, presence of M1 disease and diffuse tumor. By M stage, median DSS was 1.3 years for the M0Cyt patients versus 0.8 years for the M1Cyt group ( < .0001), Mezhr reported.

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Among the M0Cyt patients, performance status was also predictive of DSS in the multivariate analysis, which was 1.4 years in patients with good performance status but just 0.5 years in sicker patients ( < .003). There was also a trend for resection status to be predictive, with more favorable outcomes observed in patients who underwent surgery ( =.06). Of the 93 M0Cyt patients, 31% received immediate gastrectomy, while 69% underwent systemic chemotherapy, followed by gastrectomy in 36% or no gastrectomy in 64%. Data on site of recurrence were available for 26 resected patients, showing that vast majority (69%) were local or peritoneal recurrences, he said.

Repeat cytology informative

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Forty-eight patients initially treated with chemotherapy had repeat staging laparoscopy with washings, of which 22 had low-volume M1 disease at initial laparoscopy (no visceral metastases). Altogether 27 (56%) of the patients converted to negative cytology, and these patients had significantly improved DSS: 2.5 years compared with 1.4 years for positive repeat cytology ( =.0003), Mezhir reported.

“Although long-term survival in patients with positive cytology is extremely uncommon, those who convert to negative cytology after chemotherapy exhibit significant improvement in disease-specific survival,” he said.

What is the role of surgery?

Kevin C. Conlon, MD, professor of surgery at the University of Dublin and Trinity College, Ireland, discussed the findings of Trinity College Dublin, Ireland, noting the poor prognosis of gastric cancer and the paucity of good treatment options. He said that the benefit of gastrectomy in these patients remains unknown, and the current study would have been more informative had it compared the patients who had immediate gastrectomy versus chemotherapy, and those who had chemotherapy plus gastrectomy versus chemotherapy alone.

“Here, resection appeared to improve survival, but this may reflect lead time bias, the underlying biology of the disease or the performance status of the patients,” he suggested. He found the conversion to negative cytology on repeat testing to be interesting, but wondered if resection in this particular group might provide a survival benefit. “Our anecdotal experience in these patients,” he said, “is that surgery has a limited role. The majority still die of peritoneal disease.”

2010 GI Symposium Abstract 5