Omission of 5-Fluorouracil Bolus From Multidrug Regimens for Advanced Gastrointestinal Cancers: A Multicenter Cohort...

5-Fluorouracil (5-FU) is a major component of gastrointestinal cancer treatments. In multidrug regimens such as FOLFOX, FOLFIRI, and FOLFIRINOX, 5-FU is commonly administered as a bolus followed by an infusion. However, the pharmacologic rationale for incorporating the 5-FU bolus in these regimens is unclear, and there are other effective regimens for gastrointestinal cancers that do not include the bolus. The purpose of this study was to determine whether omission of the 5-FU bolus was associated with a difference in survival and toxicity.

A real-world database from Flatiron Health was queried for patients with advanced colorectal, gastroesophageal, and pancreatic cancers who received first-line FOLFOX, FOLFIRI, and FOLFIRINOX regimens. Cox proportional hazards and Kaplan-Meier analyses were performed to compare survival outcomes between patients who received the 5-FU bolus and those who did not. Inverse probability of treatment weighted (IPTW) analysis was performed to adjust for treatment selection bias.

This study included 11,765 patients with advanced colorectal (n=8,670), gastroesophageal (n=1,481), and pancreatic (n=1,614) cancers. Among all first-line 5-FU multidrug regimens, 10,148 (86.3%) patients received a 5-FU bolus and 1,617 (13.7%) did not. After IPTW analysis, we found that omitting the bolus was not associated with a decrease in overall survival (hazard ratio, 0.99; 95% CI, 0.91-1.07; P=.74). However, omitting the bolus was associated with reductions in neutropenia (10.7% vs 22.7%; P<.01), thrombocytopenia (11.2% vs 16.1%; P<.01), and use of granulocyte colony-stimulating factors after treatment (19.6% vs 29.1%; P<.01).

After adjusting for baseline clinical factors, we found that omission of the 5-FU bolus from FOLFOX, FOLFIRI, and FOLFIRINOX regimens was not associated with decreased survival, but resulted in decreased toxicity and possible health care savings.