Because pemetrexed is primarily cleared through the kidneys, its use in patients with impaired renal function can be problematic and as such the package insert sets the limit for normal dosing at ≥45 mL/min. However, we all recognize that oncology is as much an art as it is a science, especially when it comes to effective and tolerable agents, and for this reason we wanted to see how closely clinicians adhered to this guideline. Although many oncologists fall on both sides of the fence, both Drs Wakelee and Ramalingam are willing to go a bit lower and will still give pemetrexed a careful try in patients with creatinine clearance as low as 
40 mL/min.

Mita AC et al. Phase I and pharmacokinetic study of pemetrexed administered every 3 weeks to advanced cancer patients with normal and impaired renal function. J Clin Oncol 2006;24(4):552-62. Abstract

US Food and Drug Administration. Highlights of prescribing information [pemetrexed disodium]. Available at: http://www.accessdata.fda.gov/drugsatfda_docs/label/2009/021462s021lbl.pdf.