Journal of Clinical Oncology, Vol 14, 1903-1912, Copyright © 1996 by American Society of Clinical Oncology
Therapeutic monitoring of continuous infusion etoposide in small-cell lung cancer
SP Joel, P Ellis, K O'Byrne, D Papamichael, M Hall, R Penson, S Nicholls, C O'Donnell, A Constantinou, J Woodhull, M Nicholson, I Smith, D Talbot and M Slevin
Department of Medical Oncology, St Bartholomew's Hospital, West Smithfield, London. joel@icrf.icnet.uk
PURPOSE: To investigate the feasibility of therapeutic monitoring of
etoposide at different plasma concentrations of the drug, and the resulting
pharmacodynamic effects of such an approach. PATIENTS AND METHODS:
Forty-nine previously untreated small-cell lung cancer (SCLC) patients
received single-agent etoposide every 3 weeks by continuous infusion over 5
days. Plasma etoposide concentrations were monitored 18 and 66 hours into
the infusion to permit dose modification. The first cohort of 15 patients
began treatment with etoposide 2 micrograms/mL, with dose escalation to 3
micrograms/mL for cycles 3 and 4 and 4 micrograms/mL for cycles 5 and 6,
toxicity permitting. The second cohort of 34 patients commenced at 3
micrograms/mL, with dose escalation to 4 and 5 micrograms/mL on cycles 3
and 5, respectively. RESULTS: Mean plasma etoposide concentration during
the first treatment cycle was 93.4% +/- 26.6% of the target level at 18
hours (57% of patients within +/- 20% of the target) and 98.9% +/- 14.5% of
the target level at 66 hours (82% of patients within +/- 20%). Hematologic
toxicity was more pronounced in those treated with 3 micrograms/mL versus 2
micrograms/mL (median nadir neutrophil count, 1.3 v 2.6 x 10(9)/L, P =
.032). Tumor responses, typically documented by the third cycle, were
similar in each cohort (71% in patients commenced at 2 micrograms/mL and
70% at 3 micrograms/mL). Treatment cohort was not independently predictive
of survival. CONCLUSION: Therapeutic monitoring of infusional etoposide is
feasible and dramatically reduces interpatient pharmacokinetic variability.
Although this was a small nonrandomized trial, the observation of different
hematologic toxicity at the two starting concentrations but similar
antitumor activity further suggests that these effects may be associated
with different plasma etoposide concentrations.