Altered fractionated radiotherapy in the management of head and neck carcinomas: advantages and limitations

The renaissance of anti-neoplastic immunity from tumor cell demise

Cancer therapies can temporarily reduce tumor burdens by inducing malignant cell death. However, cancer cure is still far from realization because tumors often gain resistance to current treatment and eventually relapse. Accumulating evidence suggests that successful cancer interventions require anti-tumor immunity. Therapy-induced cell stress responses ultimately result in one or more cell death modalities, including apoptosis, autophagy, necroptosis, and pyroptosis. These irreversible dying processes are accompanied by active or passive release of cell death-associated molecular patterns (CDAMPs), which can be sensed by corresponding pattern recognition receptors (PRR) on tumor-infiltrating immune cells. This crosstalk with the immune system can reawaken immune surveillance in the tumor microenvironment (TME). This review focuses on immune-modulatory properties of anti-cancer regimens and CDAMP-mediated communications between cell stress responses and the immune contexture of TME. In addition, we describe how immunogenic cell death can elicit strong and durable anti-tumor immune responses.

Long-Term Results of Conventional Radiotherapy versus Accelerated Hyperfractionated Radiotherapy versus Concomitant Radiotherapy and Chemotherapy in Locoregionally Advanced Carcinoma of the Oropharynx

AIMS AND BACKGROUND

To compare conventional fractionation (CF) radiation therapy (RT), arm A, versus a split-course accelerated hyperfractionated schedule (S-AHF), arm B, versus CFRT plus concomitant chemotherapy (CT), arm C, in terms of five-year survival and toxicity for squamous cell tumors of the oropharynx.

METHODS AND STUDY DESIGN

Between January 1993 and June 1998, 192 previously untreated patients with stage III and IV oropharyngeal carcinoma (excluding T1N1 and T2N1) were enrolled in a multicenter randomized phase III trial (ORO 93-01). In arms A and C, 66 to 70 Gy in 33 to 35 fractions was administered five days a week for six and a half to seven weeks. In arm B, the dose delivered was 64 to 67.2 Gy in two fractions of 1.6 Gy every day, five days a week, with a planned two-week split at 38.4 Gy. In arm C the CT regimen consisted of three cycles of carboplatin and 5-fluorouracil (CBDCA 75 mg/m2 on days 1 to 4 and 5-FU 1000 mg/m2 i.v. on days 1 to 4 every 28 days).

RESULTS

No statistically significant difference was found in five-year overall survival (P = 0.39): 21% for arm A, 21% for arm B, and 40% for arm C. Similarly, there was no statistically significant difference in terms of five-year relapse-free survival: 15% for arm A, 17% for arm B, and 36% for arm C. There was a slight trend towards better five-year locoregional control (P = 0.07) for the combined arm: patients without locoregional relapse were 48% in arm C, 21% in arm A and 18% in arm B. Locoregional control was significantly better when arm C was compared with arms A and B combined (P = 0.02; arm A+B 20%; arm C 48%). Distant metastases were fairly balanced in the three arms (A: 14; B: 9; C: 11), with a tendency towards more frequent isolated distant metastasis development in arm C (8 of 11 [72%] versus 7 of 23 [30%] in arms A+B). Five-year second-tumor-free survival was 85%. The 13 second tumors were equally distributed and were mainly correlated with tobacco and alcohol consumption (five lung, two esophagus, two oral cavity, one larynx, one pancreas, one hepatocarcinoma, one myeloma). Arm C showed slightly more G3+ late side effects involving subcutaneous tissues and mucosa, although significant late sequelae were relatively uncommon and the mucosal side effects were mostly transient. The occurrence of persistent G3 xerostomia was comparable in the three treatment arms.

CONCLUSIONS

The results obtained with the combination of CT and RT compared with RT alone did not reach statistical significance, but combined treatment almost doubled the five-year overall survival, relapse-free survival and locoregional control rate. Patients with advanced squamous cell carcinomas of the oropharynx who are medically suitable for the combined approach should be treated with a combination of radiotherapy and chemotherapy. The occurrence of second tumors is relatively common in these patients and may contribute substantially to the causes of death.

Partial-Body Irradiation in Patients with Prostate Cancer Treated with IMRT Has Little Effect on the Composition of Serum Proteome

Partial body irradiation during cancer radiotherapy (RT) induces a response of irradiated tissues that could be observed at the level of serum proteome. Here we aimed to characterize the response to RT in group of patients treated because of prostate cancer. Five consecutive blood samples were collected before, during, and after the end of RT in a group of 126 patients who received definitive treatment with a maximum dose of 76 Gy. Serum peptidome, which was profiled in the 2000–16,000 Da range using MALDI-MS. Serum proteins were identified and quantified using the shotgun LC-MS/MS approach. The majority of changes in serum peptidome were detected between pre-treatment samples and samples collected after 3–4 weeks of RT (~25% of registered peptides changed their abundances significantly), yet the intensity of observed changes was not correlated significantly with the degree of acute radiation toxicity or the volume of irradiated tissues. Furthermore, there were a few serum proteins identified, the abundances of which were different in pre-RT and post-RT samples, including immunity and inflammation-related factors. Observed effects were apparently weaker than in comparable groups of head and neck cancer patients in spite of similar radiation doses and volumes of irradiated tissues in both groups. We concluded that changes observed at the level of serum proteome were low for this cohort of prostate cancer patients, although the specific components involved are associated with immunity and inflammation, and reflect the characteristic acute response of the human body to radiation.

Effects of age and radiation treatment on function of extrinsic tongue muscles

Background

Radiation treatment for head and neck cancer often results in difficulty swallowing. Muscle weakness and fibrosis have been identified clinically as possible etiologies for swallowing problems following radiation. Aging may compound the effects of radiation on swallowing because radiation-induced damage to muscles and other tissues critical for the oropharyngeal swallow is overlaid on a declining sensorimotor system. However, there have been no investigations of the manner in which aging and radiation treatment effects combine to impact tongue muscles, which are critical effectors of the oropharyngeal swallow.

Methods

Thirty-seven male Fisher 344/Brown Norway rats were divided into four groups; young adults (9 month old), old (32 months old), young radiation (9 months), and old radiation (32 months old). Two fractions of 11 Gy on consecutive days was delivered by external beam radiation to the ventral side of the rat’s body over the anterior portion (20 X 30 mm area) of the anterior digastric muscle. Two-way analysis of variance (ANOVA) was used to examine the effects of age and radiation and their interaction on muscle contractile properties. Post-hoc testing was completed using Fisher’s least significant differences (LSD).

Results

Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction. However, radiation treatment did not lead to muscle atrophy and fibrosis formation in the GG muscle. Radiation treatment did not exacerbate atrophic changes observed with aging, or lead to additional fibrosis formation in the GG muscle from that observed in the other groups.

Conclusions

The purpose of this research was to determine the effect of radiation on muscles of the tongue and to determine whether aging altered the extent of radiation injury to tongue muscles. Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction, and the reduction in the speed of tongue muscle contraction was exacerbated in the aged-rat tongue. This work provides a foundation for future investigations of treatments for concurrent effects of aging and radiation on muscles of the tongue and swallowing.

The potential of proton beam radiation therapy in head and neck cancer

A group of Swedish oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In head and neck cancer, including thyroid cancer, it is assessed that at least 300 patients annually will gain sufficiently from proton beam therapy, both to improve tumour control and to decrease toxicity to compensate for the increased treatment costs using protons.

Reduction of oral mucositis by palifermin (rHuKGF): Dose-effect of rHuKGF

PURPOSE

The aim of the present study was to determine the dose effect of palifermin (recombinant human keratinocyte growth factor, rHuKGF) for reduction of the response of oral mucosa to fractionated radiotherapy in a mouse model.

MATERIAL AND METHODS

Ulceration (confluent mucositis) of mouse tongue epithelium was analysed as the clinically relevant endpoint. Palifermin at doses from 1 - 30 mg/kg was administered before the onset (day -3), at the end of the first (day +4) or the second week of irradiation (day +11) with 5 x 3 Gy/week. Each protocol was terminated by graded radiation test (top-up) doses. In a further experiment, optimally effective doses were given on days -3 and +4, or -3, +4 and +11.

RESULTS

Single dose irradiation of mouse mucosa yielded an ED50 (dose inducing ulcer in 50% of the mice) of 10.7 +/- 1.0 Gy. With fractionated irradiation for 1 week an ED50 for test irradiation (day +7) of 5.1 +/- 1.9 Gy was observed. After 2 weeks (day +14), the ED50 was 7.3 +/- 1.9 Gy. Palifermin significantly increased the ED50 values in all protocols tested. Maximally effective doses for single injections were 15.0 mg/kg (day -3, +11) or 22.5 mg/kg (day +4), which yielded ED50 values of 12.1 +/- 1.3 Gy, 13.7 +/- 1.5 Gy and 14.4 +/- 1.3 Gy, respectively. Higher palifermin doses did not further increase the ED50. Repeated injections on days -3 and +4 did not increase the ED50 beyond the value obtained with injections on day +4 alone. An additional injection on day +11 increased the ED50 further to 15.1 +/- 0.1 Gy.

CONCLUSIONS

A significant palifermin dose-effect was seen at doses below 15 mg/kg. However, a significant increase in oral mucosal radiation tolerance by palifermin over untreated control tissue was observed already with low doses of 1 mg/kg. This indicates that in clinical studies with palifermin, the dose of the growth factor may be of minor relevance over a wide dose range.

Effects of dexpanthenol with or without Aloe vera extract on radiation-induced oral mucositis: Preclinical studies

PURPOSE

To define the effect of dexpanthenol with or without Aloe vera extract on radiation-induced oral mucositis.

MATERIALS AND METHODS

Mouse tongue mucosal ulceration was analysed as the clinically relevant endpoint. Graded single or fractionated dose irradiation (10 x 3 Gy/2 weeks, graded test doses on day 14) were combined with topical administration of dexpanthenol or a base, with or without Aloe vera extract. The formulations were applied for 14 days (single dose) or 24 days after the first fraction.

RESULTS

Single dose irradiation resulted in an ED50 (dose at which a positive mucosal response was expected in 50% of the animals irradiated) of 11.9+/-1.2 Gy. None of the formulations yielded a significant change in incidence or time course of ulceration. Test irradiation after 10 x 3 Gy gave an ED50 of 9.0+/-0.1 Gy. Base treatment increased the ED50-values to 10.5+/-0.8 Gy (p = 0.0095) and 9.9+/-0.7 Gy (p = 0.0445) without or with Aloe vera. Dexpanthenol resulted in ED50 values of 9.5+/-0.1 Gy without Aloe vera (p > 0.05), and of 10.9+/-0.9 Gy (p = 0.0035) with Aloe vera. The latent time to ulceration was prolonged, compared to the control (6.3 days) without Aloe vera (8.0-8.2 days, p < 0.001) and with dexpanthenol and Aloe vera (7.3 days, p = 0.0239).

CONCLUSIONS

With single dose irradiation, neither dexpanthenol nor Aloe vera extract significantly changed the oral mucosal radiation response. With fractionated irradiation, drug administration significantly increased the isoeffective radiation doses, independent of dexpanthenol or Aloe vera content. Neither dexpanthenol nor Aloe vera display a prophylactic potential.

Is There an Optimum Overall Time for Head and Neck Radiotherapy? A Review, with New Modelling

AIMS

To test by modelling whether a non-standard fractionated schedule giving optimum log cell kill could be expected, between short (accelerated) and longer multiple fraction/day schedules.

MATERIALS AND METHODS

Linear quadratic modelling was carried out for many schedules, with biologically effective doses converted to normalised total doses (NTDs; in 2 Gy fractions). Late complication and acute mucosal NTDs were calculated as constraint doses for each schedule, and the highest tumour NTDs and log cell kill values within both constraints were calculated. This modelling is robust and agrees with conclusions in a very recent meta-analysis (Bourhis J, Overgaard J, Audry H, et al. Hyperfractionated or accelerated radiotherapy in head and neck cancer: a meta-analysis. www.thelancet.com. Published online August 17, 2006).

RESULTS

The six schedules that gave the highest tumour log cell kill deliver a narrow range of 11.1-11.2 log10 cell kill in the present parameters. Other regularly used schedules give closer to 10 log10. Using one fraction/day fails to achieve the highest therapeutic ratios. Suggestions are made for escalating certain UK schedules. Fractionated radiotherapy results in a nearly constant tumour cell kill if the acute mucosal NTD is held constant. However, a small (3%) gain in tumour cell kill occurs from 3 weeks to 73 fractions of 1.15 Gy in 7 weeks. That is how fractionation works, within both acute and late constraints. Short accelerated schedules enable fewer late complications, but do not do as well for the minority of head and neck tumours that repopulate slowly.

CONCLUSIONS

Schedules of 4-6 weeks overall time could be chosen to give at least 11 log10 cell kill, which are safe. Most tumours would require two fractions/day, until routine monitoring of repopulation rates becomes feasible to select individual tumours. There is no 'optimum schedule', but each chosen schedule can be balanced against its own risk of excessive acute or late complications, as shown in these examples.

Early experience with a hybrid accelerated radiotherapy schedule for locally advanced head and neck cancer

BACKGROUND

Our aim was to determine feasibility and efficacy of a hybrid radiotherapy schedule in locally advanced head and neck cancer.

METHODS

Seventy-three patients with locally advanced head and neck cancer were irradiated according to a hybrid accelerated schedule consisting of 20 fractions of 2 Gy (once daily), followed by 20 fractions of 1.6 Gy (twice daily), to a total dose of 72 Gy.

RESULTS

Locoregional control was 55% after 2 years. Overall survival was 59%, disease-specific survival was 63%, and disease-free survival was 46%. Acute toxicity was prospectively scored in all 73 patients: the most frequent toxicities were mucositis (50.7%, grade 3), dysphagia (47.9%, grade 3), and dermatitis (34.5%, grade 3). All patients were treated to full dose, without treatment interruption.

CONCLUSION

With this regimen, acceptable locoregional control and survival rates are achieved. Toxicity was well manageable, suggesting that a combination of this schedule with concomitant chemotherapy is possible and could lead to further improvement in the treatment of locally advanced head and neck cancer.

Laryngeal preservation in head and neck cancer: multidisciplinary approach

Since the first total laryngectomy was undertaken, efforts have been made to avoid removing the entire larynx. For a long time, partial surgery and radiotherapy were the only options that could preserve the larynx. Development of active chemotherapy regimens has prompted an era of intensive clinical research. Induction chemotherapy followed by radiotherapy in patients with objective responses has been shown to allow conservation of the larynx in nearly two-thirds of individuals, without any effect on survival; concurrent chemoradiotherapy also provides high rates of laryngeal preservation, again without affecting survival; and induction chemotherapy followed by concurrent chemoradiotherapy is under investigation. In the meantime, partial open surgery and endoscopic carbon dioxide laser procedures are feasible in selected moderately advanced laryngopharyngeal cancers as an alternative to destructive surgery. Altered fractionation radiotherapy can also be used in management of these tumours, and targeted treatments have opened a new area of clinical research. Findings of basic research and modern imaging should provide useful approaches for selection of patients for various strategies.

American Society of Clinical Oncology Clinical Practice Guideline for the Use of Larynx-Preservation Strategies in the Treatment of Laryngeal Cancer

Purpose

To develop a clinical practice guideline for treatment of laryngeal cancer with the intent of preserving the larynx (either the organ itself or its function). This guideline is intended for use by oncologists in the care of patients outside of clinical trials.

Methods

A multidisciplinary Expert Panel determined the clinical management questions to be addressed and reviewed the literature available through November 2005, with emphasis given to randomized controlled trials of site-specific disease. Survival, rate of larynx preservation, and toxicities were the principal outcomes assessed. The guideline underwent internal review and approval by the Panel, as well as external review by additional experts, members of the American Society of Clinical Oncology (ASCO) Health Services Committee, and the ASCO Board of Directors.

Results

Evidence supports the use of larynx-preservation approaches for appropriately selected patients without a compromise in survival; however, no larynx-preservation approach offers a survival advantage compared with total laryngectomy and adjuvant therapy with rehabilitation as indicated.

Recommendations

All patients with T1 or T2 laryngeal cancer, with rare exception, should be treated initially with intent to preserve the larynx. For most patients with T3 or T4 disease without tumor invasion through cartilage into soft tissues, a larynx-preservation approach is an appropriate, standard treatment option, and concurrent chemoradiotherapy therapy is the most widely applicable approach. To ensure an optimum outcome, special expertise and a multidisciplinary team are necessary, and the team should fully discuss with the patient the advantages and disadvantages of larynx-preservation options compared with treatments that include total laryngectomy.

Concurrent weekly docetaxel and concomitant boost radiation therapy in the treatment of locally advanced squamous cell cancer of the head and neck

PURPOSE

In a Phase I/II trial, we investigated concurrent weekly docetaxel and concomitant boost radiation in patients with locally advanced squamous cell cancer of the head and neck (SCCHN) after induction chemotherapy.

PATIENTS AND METHODS

Patients presented with American Joint Committee on Cancer Stage III/IV and were treated initially with induction chemotherapy using cisplatinum/5-fluorouracil (PF), carboplatinum-5-FU, or docetaxel-PF. Patients then received docetaxel four times weekly with concomitant boost (CB) radiation (1.8 Gy once-daily X20, 1.8/1.5 Gy twice a day). Fifteen patients each received 20 mg/M2 and 25 mg/M2.

RESULTS

Thirty-one patients were enrolled and 30 were evaluable for response and toxicity. Median follow-up was 42 months (range, 27-63 months). Primary sites were: oropharynx 19, oral cavity 2, larynx/hypopharynx 5, and unknown primary 4. Eighty-seven percent of patients had N2/N3 disease; 60% had T3/T4 disease. Twenty percent of patients had a complete response (CR) to induction chemotherapy. After chemoradiotherapy, 21 of 30 patients had a CR, 2 had progressive disease, and 7 had partial response (PR). Nineteen of 26 patients presenting with neck disease had neck dissections, and 7 of 19 were positive. Ninety-three percent of all patients were rendered disease-free after all planned therapy. Treatment failed in 8 patients, and 7 have died of disease. An additional patient died with no evidence of disease. Twenty-one patients (70%) are currently alive with no evidence of disease. No acute dose-limiting toxicity was observed at either dose level.

CONCLUSIONS

This intensive treatment regimen of concurrent docetaxel/concomitant boost radiation and surgery after induction chemotherapy in poor prognosis patients yields good local regional control and survival. Docetaxel/CB chemoradiotherapy represents an aggressive alternative regimen to platinum-based chemoradiotherapy or surgery in patients who have a poor response to induction chemotherapy.

Radiotherapy for head and neck cancer: latest developments and future perspectives

PURPOSE OF REVIEW

Despite recent advances in multimodality management the prognosis of patients with stage III-IV squamous cell head and neck cancer remains disappointing. The objective of this review is to identify how, within the main axes of the current translational and clinical research and in an attempt to improve treatment outcome, a number of institutions and cooperative groups have embarked on systematic investigations of novel strategies for radiotherapy delivery and for combining radiation with systemic treatments.

RECENT FINDINGS

Four domains of translational and clinical researches can be identified in head and neck radio-oncology: altered fractionation, concurrent delivery of chemotherapy and radiotherapy, combination of targeted therapies with radiation, and high-conformality radiotherapy.

SUMMARY

Here we provide a critical appraisal of recent strategies allowing an increase in dose intensity for treatments based on radiotherapy and drug-radiation interactions, and revisit the potential opportunities they offer as well as the possible caveats they may present in patients with locally advanced head and neck cancers.

French multicenter phase III randomized study testing concurrent twice-a-day radiotherapy and cisplatin/5-fluorouracil chemotherapy (BiRCF) in unresectable pharyngeal carcinoma: Results at 2 years (FNCLCC-GORTEC)

BACKGROUND

Unresectable carcinomas of the oropharynx and hypopharynx still have a poor long-term prognosis. Following a previous phase II study, this phase III multicenter trial was conducted between November 1997 and March 2002.

METHODS

Nontreated, strictly unresectable cases were eligible. Twice-daily radiation: two fractions of 1.2 Gy/day, 5 days per week, with no split (D1-->D46). Total tumor doses: 80.4 Gy/46 day (oropharynx), 75.6 Gy/44 day (hypopharynx). Chemotherapy (arm B): Cisplatin 100 mg/m2 (D1, D22, D43); 5FU, continuous infusion (D1-->D5), 750 mg/m2/day cycle 1; 430 mg/m2/day cycles 2 and 3.

RESULTS

A total of 163 evaluable patients. Grade 3-4 acute mucositis 82.6% arm B/69.5% arm A (NS); Grade 3-4 neutropenia 33.3% arm B/2.4% arm A (p < 0.05). Enteral nutrition through gastrostomy tube was more frequent in arm B before treatment and at 6 months (p < 0.01). At 24 months, overall survival (OS), disease-free survival (DFS), and specific survival (SS) were significantly better in arm B. OS: 37.8% arm B vs. 20.1% arm A (p = 0.038); DFS: 48.2% vs. 25.2% (p = 0.002); SS: 44.5% vs. 30.2% (p = 0.021). No significant difference between the two arms in the amount of side effects at 1 and 2 years.

CONCLUSION

For these unresectable cases, chemoradiation provides better outcome than radiation alone, even with an "aggressive" dose-intensity radiotherapy schedule.

Promising new advances in head and neck radiotherapy

Efforts to improve the efficacy of treatment for SCCHN have led to the use of multimodality approaches with combinations of surgery, radiotherapy and chemotherapy. Conventional head and neck radiotherapy, a standard approach for locoregionally advanced disease, is associated with a variety of well-known acute and long-term toxicities. These chronic toxicities (i.e. xerostomia, dysphagia, fibrosis) can impact negatively on patient quality of life. Altered radiation fractionation regimens that incorporate acceleration and/or hyperfractionation can improve locoregional control but also increase acute toxicities for head and neck cancer patients. Intensity modulated radiation therapy (IMRT) has emerged as a promising method for delivering effective radiation dose to head and neck tumour targets while reducing exposure of surrounding healthy tissue. Another method for improving head and neck cancer outcome with conventional radiotherapy is with the concurrent addition of chemotherapy. Indeed, chemoradiotherapy is now a standard treatment approach for locoregionally advanced disease. Molecular targeted agents, such as the epidermal growth factor receptor (EGFR) antagonist, cetuximab (Erbitux), have recently been shown to enhance the effects of radiotherapy, and reports to date suggest that this potentiation occurs without an increase in the characteristic toxicities associated with head and neck radiation.

Salvage surgery after failure of very accelerated radiotherapy in advanced head-and-neck squamous cell carcinoma

PURPOSE

To assess the efficacy and toxicity of salvage surgery for local or cervical nodal recurrence after accelerated radiotherapy for locally advanced head-and-neck squamous cell carcinoma (HNSCC).

METHODS AND MATERIALS

We reviewed the medical records of the 136 patients with HNSCC who had been treated in three consecutive clinical trials at the Institut Gustave-Roussy using a very accelerated radiotherapy regimen (62 to 64 Gy with 2 daily fractions of 1.8 to 2 Gy over 3.5 weeks). Sixty-nine patients of the 136 initial patients (51%) had local or neck lymph nodes relapse, or both.

RESULTS

Sixteen of these 69 patients (23%) had undergone salvage surgery for recurrence locally (n = 8) or in the cervical nodes (n = 8). All 16 had initially been diagnosed with locally advanced oropharyngeal carcinoma (T4, 11 patients; T3, 5 patients), and 13 had initially had cervical node involvement. After salvage surgery, 6 patients had had a local recurrence; 7, cervical node recurrence; and 3, distant metastasis. Thus, salvage surgery had been successful only in 3 patients. The 3- and 5-year overall actuarial survival rates were 20% and 11%, respectively. Eight patients had major postoperative wound complications, including carotid rupture in three cases.

CONCLUSION

Salvage surgery for relapse after very accelerated radiotherapy for advanced HNSCC is infrequently feasible and is of limited survival benefit. It should be used only in carefully selected cases.

Effects of keratinocyte growth factor (palifermin) administration protocols on oral mucositis (mouse) induced by fractionated irradiation

BACKGROUND AND PURPOSE

Aim of this study was to assess the impact of the administration protocol of palifermin on amelioration of oral mucositis after fractionated irradiation.

MATERIALS AND METHODS

Mouse tongue ulceration was analysed as the clinically relevant endpoint. Daily fractionated irradiation (5 x 3 Gy/week, days 0 to +4, +7 to +11, with a weekend gap on days +5 and +6) was followed by graded test doses on day +14, i.e. after a second weekend gap. Palifermin (5 mg/kg) was injected subcutaneously. In the first series of experiments, the effect of three daily injections (days -3, -2 and -1) was compared with a single administration either on day -2 or -1; all animals received a further injection on day +4. In the second series, a single or three injections were given in the weekend gap between fractionated irradiation (days +5 to +6), with an additional administration on day +11. In a final protocol, single weekly injections of palifermin were given either on days -3, +4 and +11, days +4, +11 and +18, or on days -3, +4, +11 and +18.

RESULTS

The ED50 (dose after which ulcer induction is expected in 50% of the mice) to single dose irradiation was 11.5+/-0.7 Gy. The ED50 for test irradiation after 10 x 3 Gy was 5.7+/-1.6 Gy. Palifermin administration before the start of fractionated irradiation and on day +4 increased the ED50 to 10-12 Gy, administration over the first weekend and on day +11 to 11-15 Gy. Administration over three consecutive weekends, starting on day -3 or day +4, increased the ED50 to 13.0+/-0.1 and 14.9+/-0.3 Gy. Single weekly KGF administrations over four weekends, including the weekend prior to and after completion of radiotherapy, showed no further increase in ED50.

CONCLUSIONS

A single palifermin injection during the weekend gap before or during fractionated irradiation is as effective as three applications. Onset of the palifermin treatment during the first weekend gap between fractionated irradiation is more effective than during the weekend before radiotherapy. The effect of palifermin on oral mucositis can be increased by three weekly injections, while four injections do not yield a further increase in ED50.