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Upper Gastrointestinal (lips to ileocecal valve, including esophagus and stomach)

P67: Long-Term Outcomes in Patients with Gastric Cancer after Conversion from Positive to Negative Peritoneal Cytology

Introduction: Positive peritoneal cytology classifies patients as having metastatic gastric cancer and is associated with a poor prognosis. Long-term outcomes of patients that convert to negative cytology with systemic therapy are poorly characterized.

Methods: Retrospective review of a prospectively maintained single institution database. Patients from March 1993 to December 2020 who had positive peritoneal cytology without gross metastatic disease (M1Cyt+) at diagnostic laparoscopy (DL) were included. Factors associated with conversion to negative cytology were identified using logistic regression, and factors associated with disease specific survival (DSS) were assessed by logrank testing.

Results: Of 2,692 patients with gastric cancer undergoing DL, 186 (6.9%) were M1Cyt+. Among M1Cyt+ patients, 65 (34.9%) were selected for second DL after systemic therapy, 46 of which (24.7%) had converted to negative cytology. On multivariable analysis of those undergoing second DL, women were less likely to convert to negative cytology (adjusted odds ratio [aOR]: 0.32; 95%CI 0.14-0.76, P=0.01), while those treated with combination taxane and platinum chemotherapy were more likely to convert to negative cytology (aOR: 3.46 vs platinum only; 95%CI 1.19-10.1, P=0.02). Conversion to negative cytology was associated with improved DSS (median 43 months [mo], range: 10-186 mo) compared to those with persistently positive cytology (median 14 mo, range: 2-47 mo) and those not selected for second DL (median 12 mo, range: 1-88 mo; P< 0.01). Of 46 patients that cleared their cytology, 36 (78.2%) underwent resection. The median DSS was not significantly different between resected (median 43 mo, range: 10-186 mo) and unresected (median 41 mo, range: 20-89 mo; P=0.47) patients. There was no difference in DSS among resected patients treated with adjuvant intraperitoneal chemotherapy (n=11, median 43 mo, range: 16-71 mo) compared to those without (n=25, median 47 mo, range 10-186 mo). Among 36 resected patients, 12 were disease free at last follow up (6.5% of initial M1Cyt+ cohort; median follow up 59 mo), with the most common site of recurrence being the peritoneum (n=9, 25.0%). Five-year DSS was observed in thirteen patients (7% of the M1Cyt+ cohort) that converted to negative cytology.

Conclusions:

Conversion to negative cytology is feasible with modern systemic therapy combinations. Long-term survival is achievable in select patients after conversion to negative cytology and this event may represent true downstaging. The impact of subsequent locoregional therapies on outcomes remains undefined.

Learning Objectives:

  • Upon completion, participants will be able to list factors associated with conversion from positive to negative peritoneal cytology in patients with gastric cancer.
  • Upon completion, participants will be able to describe the frequency of five year survival in patients with initially positive cytology after conversion to negative cytology.
  • Upon completion, participants will be able to describe recurrence patterns in patients who undergo resection after conversion from positive to negative peritoneal cytology.