10 Impact of hemoglobin (Hgb) level and use of recombinant human erythropoietin (r-HuEPO) on response to neoadjuvant chemoradiation therapy, tumor control, and survival in patients with oral or oropharyngeal squamous cell carcinoma (SCCA)

Erythropoietin as an adjuvant treatment with (chemo) radiation therapy for head and neck cancer

BACKGROUND

Tumour hypoxia increases tumour invasiveness and has a negative impact on response to therapy. Hypoxic tumours are also associated with severely anaemic individuals. It has therefore been hypothesised that correcting anaemia, by increasing haemoglobin levels using erythropoietin, improves tumour oxygenation and consequently the patient's prognosis.

OBJECTIVES

To assess whether combined treatment with radiotherapy and erythropoietin (RT plus EPO) is better than standard radiotherapy (RT alone) for the treatment of head and neck cancer patients.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; mRCT and additional sources for published and unpublished trials. The date of the most recent search was 24 February 2009.

SELECTION CRITERIA

Two independent authors assessed identified studies according to the eligibility criteria: RCTs which delivered radiotherapy combined with or without erythropoietin, in patients of any age with head and neck cancer of any stage or type. In addition, trials administering concomitant iron therapy among one or both arms were also eligible.

DATA COLLECTION AND ANALYSIS

For statistical analysis of survival data, we computed a weighted estimate of the typical treatment effect across studies. We used Chi(2) heterogeneity tests to test for statistical heterogeneity among trials and performed the statistical analyses using Review Manager 5.0.

MAIN RESULTS

Five RCTs with a total of 1397 patients were included. Pooled data yielded a significantly worse overall survival (OS) for RT plus EPO as compared to RT alone (Peto odds ratio 0.73; 95% confidence interval (CI) 0.58 to 0.91; P = 0.005, five trials). For local regional tumour control (LRTC) analyses resulted in a small but non-significant difference between the RT alone group and the RT plus EPO group (RR 0.92; 95% CI 0.81 to 1.03; P = 0.15, four trials). In addition, the local regional progression free survival (LRPFS) measured in four studies was significantly different between groups (Peto odds ratio 0.63; 95% CI 0.49 to 0.80; P = 0.0002, four trials), in favour of the RT alone group. Two studies used supplemental iron in the RT plus EPO group and not in the RT alone group. When excluding these studies from the analyses, the statistically (non-) significant differences in OS, LRTC and LRPFS are maintained.

AUTHORS' CONCLUSIONS

There are strong suggestions that RT plus EPO has a negative influence on outcome as opposed to RT alone. However, the target haemoglobin concentration, which was higher than recommended in four of the five included RCTs, may have had a significant role. Nevertheless, based on these findings EPO should not be administered as an addition to RT outside the experimental setting for patients with head and neck cancer.

Darbepoietin Alfa Potentiates the Efficacy of Radiation Therapy in Mice with Corrected or Uncorrected Anemia

Darbepoietin alfa (DA) is a long-acting analogue of erythropoietin that has reduced receptor affinity and enhanced biological activity. Experiments were done to test the hypothesis that correction of anemia in tumor-bearing mice by DA would increase tumor oxygenation and potentiate radiation-induced tumor cell killing. A SCC VII tumor model was used to study tumor responses to fractionated radiation therapy in mice with anemia induced by total body irradiation. Administration of DA reduced the extent and duration of anemia and associated tumor hypoxia, protected the bone marrow cells and prevented the body weight loss from the effect of irradiation, and facilitated the recovery in a time-dependent manner, with the administration of DA prior to total body irradiation having the greatest protective effect. When combined with fractionated radiation therapy, DA increased the tumor growth delay time from 2.7 days for irradiation alone to 7.3 to 10.6 days for combination of DA and irradiation. The effect of DA on tumor responses to fractionated radiation therapy was observed when DA was given 18 to 4 days before starting radiation therapy, but DA was also equally effective as a radiosensitizer when given only 2 hours before fractionated irradiation therapy. Weekly dosing of DA was as efficacious for the enhancement of radiation responses of tumors as biweekly dosing. Similar results were obtained in the RIF-1 fibrosarcoma tumor model. These studies show that DA can effectively correct anemia in tumor-bearing mice and sensitize tumor cells to fractionated radiation therapy. Importantly, DA was also able to sensitize tumors to radiation in mice with uncorrected anemia and hypoxia, suggesting that the effect of DA on radiosensitivity was independent of these factors and a different mechanism of action may be responsible for this effect.

Impact of tumor hypoxia and anemia on radiation therapy outcomes

Local recurrence remains a major obstacle to achieving cure of many locally advanced solid tumors treated with definitive radiation therapy. The microenvironment of solid tumors is hypoxic compared with normal tissue, and this hypoxia is associated with decreased radiosensitivity. Recent preclinical data also suggest that intratumoral hypoxia, particularly in conjunction with an acid microenvironment, may be directly or indirectly mutagenic. Investigations of the prognostic significance of the pretreatment oxygenation status of tumors in patients with head and neck or cervical cancer have demonstrated that increased hypoxia, typically designated in these studies as pO(2) levels below 2.5-10 mm Hg, is associated with decreased local tumor control and lower rates of disease-free and overall survival. Hypoxia-directed therapies in the radiation oncology setting include treatment using hyperbaric oxygen, fluosol infusion, carbogen breathing, and electron-affinic and hypoxic-cell sensitizers. These interventions have shown the potential to increase the effectiveness of curative-intent radiation therapy, demonstrating that the strategy of overcoming hypoxia may be a viable and important approach. Anemia is common in the cancer population and is suspected to contribute to intratumoral hypoxia. A review of the literature reveals that a low hemoglobin level before or during radiation therapy is an important risk factor for poor locoregional disease control and survival, implying that a strong correlation could exist between anemia and hypoxia (ultimately predicting for a poor outcome). While having a low hemoglobin level has been shown to be detrimental, it is unclear as to exactly what the threshold for "low" should be (studies in this area have used thresholds ranging from 9-14.5 g/dl). Optimal hemoglobin and pO(2) thresholds for improving outcomes may vary across and within tumor types, and this is an area that clearly requires further evaluation. Nonetheless, the correction of anemia may be a worthwhile strategy for radiation oncologists to improve local control and survival.

The negative impact of anemia on radiotherapy and chemoradiation outcomes

In cancer patients, anemia is common and has been found to impair quality of life and reduce locoregional disease control conferred by radiotherapy. The prognostic importance of anemia in the radiation oncology setting may be related to a reduction of molecular oxygen levels, thereby attenuating radiation-induced damage and ultimate cell death. Substantially higher doses of radiation are required to eradicate malignant cells under the hypoxic conditions commonly identified in solid tumors. Consistent with this, patients with hypoxic solid tumors have been found to have shorter postradiation disease-free survival rates relative to patients with well-oxygenated tumors. An attempt to enhance intratumoral oxygenation via correction of anemia, a highly prevalent but modifiable condition, is therefore a reasonable approach to optimize radiotherapy and chemoradiation outcomes. Clinical studies investigating recombinant human erythropoietin (epoetin alfa) as an adjunct to radiotherapy have demonstrated its ability to increase and maintain hemoglobin (Hb) levels during the course of radiotherapy. In a study involving anemic patients undergoing chemoradiation for head and neck cancer, epoetin alfa extended locoregional control and survival to rates reported for patients with normal pretreatment Hb levels. Given the high prevalence and prognostic significance of anemia during radiotherapy, strategies that safely and effectively increase Hb levels may be of value for optimizing radiotherapy and chemoradiation outcomes.

Cancer therapy. New strategies and treatment modalities for optimizing patient outcomes

In the postgenome era, development of novel targeted therapeutics is anticipated to accelerate, with the promise of specifically tailored strategies to treat specific molecularly characterized disease entities. Greater understanding of disease pathophysiology and pharmacologic actions at the molecular, cellular, and tissue levels have provided the basis for expanding the clinical application of available therapies such as recombinant human erythropoietin (r-HuEPO, epoetin alfa). The role of epoetin alfa in anemic cancer patients receiving chemotherapy has grown as our understanding of the relationship between anemia and quality of life in this patient population has evolved. With anemia and tumor hypoxia associated with poorer outcomes in various solid tumors, the potential impact of epoetin alfa on outcomes, as well as quality of life, in patients undergoing radiation or chemoradiation is of considerable interest. Anemia occurs almost universally in critically ill patients, resulting in substantial transfusion requirements. In this setting, the anemia appears to be consistent with anemia of chronic inflammatory disease and is potentially treatable by epoetin alfa. Recent preclinical studies indicate that erythropoietin exhibits neuroprotective effects in models of central nervous system injury, suggesting additional potential novel clinical applications for epoetin alfa worthy of careful investigation. Advances in the understanding of the ras genes and their functional proteins in signaling pathways involved in the development of cancer, particularly hematologic malignancies, over the last decade have prompted development of a new class of agents, farnesyl protein transferase inhibitors (FTIs), designed specifically to inhibit the initial step in Ras protein activation. Initial clinical evaluation of FTIs is ongoing, and preliminary results demonstrate antitumor activity in hematologic malignancies. Further identification and understanding of the function and complex interactions of proteins involved in diseases holds the promise of targeted therapies and improved patient outcomes.