Influence of interfraction interval on local tumor control in patients with limited-disease small-cell lung cancer treated with radiochemotherapy.

Abstract

To investigate the influence of interfraction interval (IFI) on local recurrence-free survival (LRFS) in patients with limited-disease small-cell lung cancer (LD SCLC) treated with accelerated hyperfractionated radiotherapy (Acc Hfx RT) and concurrent cisplatin and etoposide (PE). A total of 103 patients were treated with either "early" (Cycle 1) or "late" (Cycle 4) concurrent Acc Hfx RT/PE. Two daily fractions were nonrandomly given using an IFI of either 4.5-5.0 h ("shorter") (n = 52) or 5.5-6.0 h ("longer") (n = 51). The median LRFS and 5-year LRFS rate for all 103 patients were 52 months and 48%, respectively. Besides gender, Karnofsky performance status, and treatment group, IFI also influenced LRFS, whereas age and weight loss did not. When a multivariate model was used, IFI was marginally insignificant (p = 0.0770) as a predictor of LRFS. In terms of individual treatment groups, IFI was not significant in "early" Acc Hfx RT/PE but showed a strong trend in a "late" Acc Hfx RT/PE regimen. Although a shorter IFI led to a higher incidence of high-grade (>or=3) esophagitis, leukopenia, and infection, a correlation analysis of toxicities with all potential prognostic factors showed that a shorter IFI was not an independent predictor of any acute high-grade toxicity. "Shorter" IFI had a marginally insignificant influence on LRFS. A strong trend favoring it was observed in patients treated with "late" concurrent Acc Hfx RT/PE. This may be of interest because it could contribute to further understanding of potential biologic parameters influencing treatment outcome.