Management of Metastatic Gastric Cancer

The approval of pembrolizumab was based on the positive findings from the recent KEYNOTE-059 trial.³⁸ The study included 259 patients who had previously received either fluoropyrimidine, cisplatin, or anti-HER2 therapy, with 148 patients (55%) of these patients having PD-L1−positive tumors. The PD-L1 status was determined using a pharmDx Kit, which is now approved by the US Food and Drug Administration to select patients who could benefit from pembrolizumab treatment. CPS was calculated as the number of PD-L1−staining cells divided by the total number of evaluated cells. The study included patients with microsatellite stable (MSI-S), undetermined, or deficient MMR status. The overall response rate to pembrolizumab across all patients was 11.6%, median PFS was 2 months, and the 12-month OS rate was 23.4%. In the subset of patients with MSI-H tumors, the overall response rate was 57.1%, with a complete response rate of 14.3%; in those with MSI-S tumors, the overall response rate was 9% and the complete response rate was 2.4%. Among patients with PD-L1–positive tumors, the overall response rate was 15.5% (95% CI 10.1% to 22.4). Common adverse events included fatigue, hypothyroidism, nausea, diarrhea, and arthralgia.³⁸

CASE CONCLUSION

This patient with metastatic gastric cancer receives second-line chemotherapy with ramucirumab and paclitaxel. Follow-up imaging shows persistent liver metastases and new lung metastasis. Because the tumor is PD-L1–positive, the patient receives 4 cycles of pembrolizumab, with no significant change noted in disease burden. He notes a significant decline in functional status with increased weight loss, nausea, emesis, and fatigue. The patient opts to forego any further therapy and instead chooses to pursue supportive care only.

SUMMARY

Gastric cancer is the third most common cause of cancer death worldwide. Common risk factors for developing gastric cancer include H. pylori infection, smoking, alcohol abuse, radiation exposure, high-fat diet, and obesity. Patients presenting with alarm symptoms of nausea, emesis, early satiety, abdominal pain, or weight loss should be fully evaluated with upper GI endoscopy. If there is suspicion for metastatic disease, CT evaluation of the chest, abdomen, and pelvis with oral and intravenous contrast should be obtained. Treatment of patients with metastatic gastric cancer is guided by their performance status at presentation. For patients with good performance status, a combination of platinum and fluoropyrimidine therapy, such as FOLFOX, can be considered. Doublet chemotherapy regimens are preferred over triplet chemotherapy regimens given their better tolerability. For patients with HER2-positive disease, the addition of trastuzumab to the platinum and fluoropyrimidine backbone is the standard of care in the first line.

Several targeted agents have been studied in patients progressing on initial therapy, with ramucirumab and paclitaxel being considered the regimen of choice in the second line. No anti-HER2 therapy has been approved for patients who are refractory to trastuzumab. Pembrolizumab is approved for use in patients who are PD-L1–positive and have previously progressed on at least 2 lines of chemotherapy. Pembrolizumab is also approved for the treatment of patients with unresectable or metastatic, MSI-H or MMR-deficient gastric cancers that have progressed after prior treatment and who have no satisfactory alternative treatment options.