Tumor Platinum Concentrations and Pathological Responses Following Cisplatin-Containing Chemotherapy in Gastric Cancer Patients

Purpose There is a wide range in tumor response following preoperative chemotherapy in locally advanced gastric or gastroesophageal junction cancers. We investigated the relationship between tumor platinum levels and pathological responses in these patients. 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. Collagen content was evaluated using trichrome staining. Results Surgical specimens from 10 patients were available. Surgery was performed at a median time of 49 days (range: 28–72) after the last cycle of chemotherapy. The mean platinum level in tumor tissue in patients with any response was significantly higher than in those with no response (893 ± 460 vs. 38.8 ± 8.8 pg, P = 0.007), so was the collagen content (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.