Tumor platinum concentrations and pathological responses following preoperative cisplatin-containing chemotherapy in gastric or gastroesophageal junction cancer patients

76 Background: Perioperative chemotherapy plus surgical resection is a standard of care for locally advanced gastric or gastroesophageal junction (GEJ) cancers. There is a wide range in tumor response following cisplatin-containing preoperative chemotherapy. We investigated the relationship between tumor platinum levels and pathological tumor responses in gastric or GEJ cancer patients following preoperative chemotherapy. Methods: Tumor and adjacent normal tissues were retrieved. Pathological responses were assessed per standard criteria. Tissue platinum concentrations were determined with high-performance liquid chromatography mass spectrometry. Platinum distribution in tissue components was evaluated with imaging mass cytometry. Tissue collagen content was evaluated using trichrome staining. Results: Ten patients were enrolled in this study. Nine patients received 3 cycles of preoperative chemotherapy and 1 received 2 cycles. The median cumulative cisplatin dose was 166.8 mg/m2 (range: 95.9–181.1 mg/m2). Surgery was performed at a median time of 49 days (range: 28–72 days) after the last cycle of chemotherapy. The mean platinum level in tumor tissue in patients with any response was 893 ± 460 pg, significantly higher than in those with no response [38.8 ± 8.8 pg (p = 0.007)]. The collagen content was significantly higher in patients with any response than in those with no response (37.4 ± 6.8% vs. 11.5 ± 8.6%, p < 0.05). Platinum preferentially bound to collagen. Conclusions: Platinum was detectable in surgical specimens up to 72 days after preoperative chemotherapy. Higher tumor platinum concentration correlated with improved pathological response. Collagen binding potentially explained the high interpatient variability in tumor platinum concentrations.