Difluorodeoxyuridine plasma concentrations after low-dose gemcitabine during chemoradiation in head and neck cancer patients

Gemcitabine-Based Chemoradiation in the Treatment of Locally Advanced Head and Neck Cancer: Systematic Review of Literature and Meta-Analysis

BACKGROUND

Platinum-based concurrent chemoradiation (CCRT) improves locoregional control and overall survival of locoregionally advanced (LA) squamous cell carcinoma of the head and neck (SCCHN) when compared to radiotherapy alone, but this approach is hampered by significant toxicity. Therefore, alternative ways to enhance the radiation effects are worth investigating. Gemcitabine (2',2'-difluorodeoxycytidine), in addition to its activity against a variety of solid tumors, including SCCHN, is one of the most potent radiosensitizers, and it has an overall favorable safety profile. In this paper, the clinical experience with gemcitabine-based chemoradiation in the treatment of patients with LA-SCCHN is reviewed.

METHODS

We conducted a review of the literature on the clinical experience with radiotherapy combined with either single-agent gemcitabine or gemcitabine/cisplatin-based polychemotherapy for the treatment of patients with LA-SCCHN. We also searched abstracts in databases of major international oncology meetings from the last 20 years. A meta-analysis was performed to calculate pooled proportions with 95% confidence intervals (CIs) for complete response rate and grade 3-4 acute mucositis rate.

RESULTS

A total of 13 papers were eligible for the literature review. For schedules using a gemcitabine dose intensity (DI) below 50 mg/m(2) per week, the complete response rate was 86% (95% CI, 74%-93%) with grade 3-4 acute mucositis rate of 38% (95% CI, 27%-50%) and acceptable late toxicity. In one of the studies employing such low DIs, survival data were provided showing a 3-year overall survival of 50%. Compared with DI ≥50 mg/m(2) per week, there was no difference in the complete response rate (71%; 95% CI, 55%-83%; p = .087) but a significantly higher (p < .001) grade 3-4 acute mucositis rate of 74% (95% CI, 62%-83%), often leading to treatment interruptions (survival data provided in 8 studies; 3-year overall survival, 27%-63%). Late toxicity comprising mainly dysphagia was generally underreported, whereas information about xerostomia and skin fibrosis was scarce.

CONCLUSION

This review highlights the radiosensitizing potential of gemcitabine and suggests that even very low dosages (less than 50 mg/m(2) per week) provide a sufficient therapeutic ratio and therefore should be further investigated. Refinements in radiation schemes, including intensity-modulated radiation therapy, in combination with low-dose gemcitabine and targeted agents, such as cetuximab, are currently being investigated.

IMPLICATIONS FOR PRACTICE

Cisplatin-based concurrent chemoradiation (CCRT) has become the standard treatment of locally advanced head and neck cancer (LAHNC). This approach is hampered by significant toxicity. This paper reviews the studies using gemcitabine as an alternative radio-sensitizer for CCRT in patients with LAHNC. In this capacity, despite its mild intrinsic toxicity, gemcitabine comes with high rates of severe mucositis when used in dosages exceeding 50 mg/m(2) per week. CCRT with low-dose gemcitabine provides a sufficient therapeutic ratio, combining clinical activity, similar to the higher-dose regimens, with lower toxicity. Further investigation is warranted.

The radiosensitising effect of gemcitabine and its main metabolite dFdU under low oxygen conditions is in vitro not dependent on functional HIF-1 protein

Background

Regions within solid tumours often experience oxygen deprivation, which is associated with resistance to chemotherapy and irradiation. The aim of this study was to evaluate the radiosensitising effect of gemcitabine and its main metabolite dFdU under normoxia versus hypoxia and to determine whether hypoxia-inducible factor 1 (HIF-1) is involved in the radiosensitising mechanism.

Methods

Stable expression of dominant negative HIF-1α (dnHIF) in MDA-MB-231 breast cancer cells, that ablated endogenous HIF-1 transcriptional activity, was validated by western blot and functionality was assessed by HIF-1α activity assay. Cells were exposed to varying oxygen environments and treated with gemcitabine or dFdU for 24 h, followed by irradiation. Clonogenicity was then assessed. Using radiosensitising conditions, cells were collected for cell cycle analysis.

Results

HIF-1 activity was significantly inhibited in cells stably expressing dnHIF. A clear radiosensitising effect under normoxia and hypoxia was observed for both gemcitabine and dFdU. No significant difference in radiobiological parameters between HIF-1 proficient and HIF-1 deficient MDA-MB-231 cells was demonstrated.

Conclusions

For the first time, radiosensitisation by dFdU, the main metabolite of gemcitabine, was demonstrated under low oxygen conditions. No major role for functional HIF-1 protein in radiosensitisation by gemcitabine or dFdU could be shown.