BACKGROUND Irinotecan-based chemotherapy is a standard backbone of therapy in patients with metastatic colorectal cancer (CRC) or gastric cancer (GC). However, there is still a paucity of information concerning the efficacy and safety of irinotecan-based regimens in elderly patients.

PATIENTS AND METHODS Using the patient cohort (n = 1,545) from the UGT1A1 genotype study, we compared the efficacy and safety between elderly and nonelderly patients with metastatic CRC (n = 934) or GC (n = 611) who received first- or second-line FOLFIRI (irinotecan, leucovorin, and 5-fluorouracil) chemotherapy.

RESULTS Despite lower relative dose intensity in elderly patients, progression-free survival and overall survival were similar between elderly (age ≥70 years) and nonelderly (<70 years) patients in the CRC cohort (hazard ratio [HR], 1.117; 95% confidence interval [CI], 0.927-1.345; p = .244, and HR, 0.989; 95% CI, 0.774-1.264; p = .931, respectively) and the GC cohort (HR, 1.093; 95% CI, 0.854-1.400; p = .479, and HR, 1.188; 95% CI, 0.891-1.585; p = .241, respectively). In both cohorts, febrile neutropenia (22.1% vs. 14.6% in CRC cohort and 35.2% vs. 22.5% in GC cohort) and asthenia (grade 3: 8.4% vs. 1.7% in CRC cohort and 5.5% vs. 2.9% in GC cohort) were more frequent in elderly patients. In the CRC cohort, mucositis and anorexia were more frequent in elderly patients. In the GC cohort, nausea and vomiting were less frequent in elderly patients.

CONCLUSION The efficacy of the FOLFIRI regimen was similar between elderly and nonelderly patients in both the CRC and the GC cohorts. However, special attention should be paid to elderly patients because of increased risk for febrile neutropenia and asthenia. The Oncologist 2017;22:293-303 IMPLICATIONS FOR PRACTICE: The efficacy of FOLFIRI (irinotecan, leucovorin, and 5-fluorouracil) chemotherapy in elderly patients with metastatic colorectal cancer or gastric cancer was similar to that in nonelderly patients. However, special attention should be paid to elderly patients because of the increased risk for febrile neutropenia and asthenia. These data suggest that the FOLFIRI regimen could be considered as a standard backbone of therapy in elderly patients with metastatic colorectal cancer or gastric cancer and that the clinical decision between doublet and singlet chemotherapy may not be based solely on age. However, the data require further assessment of frailty and performance status.