Toxicity antagonists in head and neck cancer

A dual mechanism fully blocks ethanol relapse: Role of vagal innervation

Previous studies showed that vagotomy markedly inhibits alcohol self-administration. Present studies hypothesised that vagotomy significantly adds to the inhibition of alcohol relapse induced by drugs that reduce the alcohol-induced hyperglutamatergic state (e.g., N-acetylcysteine + acetylsalicylic acid). The alcohol relapse paradigm tested gauges the elevated alcohol intake observed in animals that had consumed ethanol chronically, were subjected to a prolonged alcohol deprivation and are subsequently allowed ethanol re-access. Ethanol-drinker rats (UChB) were exposed to 10% and 20% ethanol and water concurrently for 4 months, were alcohol deprived for 14 days and were thereafter allowed re-access to the ethanol solutions. An initial binge-like drinking episode is observed upon ethanol re-access, followed by a protracted elevated ethanol intake that exceeds the predeprivation intake baseline. Prior to ethanol re-access, animals were (i) administered N-acetylcysteine (40 mg/kg/day) + acetylsalicylic acid (15 mg/kg/day), (ii) were bilaterally vagotomised, (iii) were exposed to both treatments or (iv) received no treatments. The initial binge-like relapse intake and a protracted elevated ethanol intake observed after repeated ethanol deprivations/re-access cycles were inhibited by 50%-70% by the administration of N-acetylcysteine + acetylsalicylic acid and by 40%-70% by vagotomy, while the combined vagotomy plus N-acetylcysteine + acetylsalicylic acid treatment inhibited both the initial binge-like intake and the protracted ethanol intake by >95% (p < 0.001), disclosing a dual mechanism of ethanol relapse and subsequent inhibition beyond that induced by either treatment alone. Future exploration into the mechanism by which vagal activity contributes to ethanol relapse may have translational promise.

Multivariable analysis of risk factors for enlargement of the tracheoesophageal puncture after total laryngectomy

BACKGROUND

Enlarged tracheoesophageal puncture (TEP) is a challenging complication of surgical prosthetic voice restoration. Prevention of this complication requires identification of high-risk individuals, and surgical and prosthetic correlates of TEP enlargement.

METHODS

Multivariable logistic regression methods were used to analyze preoperative, perioperative, and postoperative risk factors for enlarged TEP in a 5-year retrospective cohort.

RESULTS

Enlarged TEP only occurred in irradiated patients. Adjusting for length of follow-up and timing of TEP, advanced (N2 or N3) nodal disease (odds ratio [OR](adjusted) , 4.3; 95% confidence interval [CI], 1.0-19.1), postoperative stricture (OR(adjusted) , 3.2; 95% CI, 1.2-8.6), and diagnosis of locoregional recurrence or distant metastasis after laryngectomy (OR(adjusted) , 6.2; 95% CI, 2.3-16.4) increased risk of enlarged TEP. Extended resection and preoperative nutritional status were also significantly associated with enlarged TEP. Prosthetic parameters did not significantly correlate with enlargement.

CONCLUSION

Development of enlarged TEP is a multifactorial process related to both baseline and postoperative factors.

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.

Exploitable mechanisms for combining drugs with radiation: concepts, achievements and future directions

Widening indications for combining radiation therapy with cytotoxic or molecular-targeted drugs have mainly been driven by pragmatic clinical trials. With a flurry of novel drugs in various stages of preclinical and clinical development there is a need to revise the framework that has traditionally been used for discussing possible drug-radiation interactions, especially because many of the new drugs are directed at a specific molecular target. Spatial cooperation, cytotoxic enhancement, biological cooperation, temporal modulation and normal tissue protection are proposed as five primary exploitable mechanisms for the rational combination of drugs with radiation for cancer therapy. These five mechanisms produce different clinical outcomes and, therefore, the optimum clinical end point for assessing therapeutic benefit will depend on the mechanism tested. The dependence of outcome on these mechanisms also affects the selection of preclinical models and the optimum scheduling of the two modalities, i.e. the timing and dosing of the drug relative to the radiation dose fractions. These considerations are discussed in some detail for each mechanism and illustrated with specific clinical examples. Multi-modality therapy for head and neck squamous-cell carcinoma is used to illustrate these concepts. Further clinical progress in this field will require hypothesis-driven trials to ensure efficient identification of treatments with the most favorable risk:benefit ratio.

Reduction of radiochemotherapy-induced early oral mucositis by recombinant human keratinocyte growth factor (palifermin): Experimental studies in mice

PURPOSE

To study the effect of recombinant human keratinocyte growth factor (rHuKGF or palifermin) on oral mucositis induced by radiochemotherapy in a mouse model.

METHODS AND MATERIALS

Cis-diamminedichloroplatinum (cisplatin) and/or 5-fluorouracil were given before single dose irradiation, combined with palifermin before or after the treatment, or both. Daily fractionated irradiation for 2 weeks was followed by graded test doses. With additional chemotherapy in Week 1, palifermin was given before radiotherapy and at the end of the first week, or additionally at the end of Week 2. Radiochemotherapy in Week 2 was combined with palifermin at the end of Weeks 1 and 2, Weeks 1, 2, and 3, or additionally before radiotherapy. Ulceration of mouse tongue mucosa was analyzed as the endpoint.

RESULTS

The dose associated with ulcer induction in 50% of the mice (ED(50)) for single-dose irradiation was 11.5 +/- 0.7 Gy. Palifermin increased the ED(50) to about 19 Gy in all protocols tested. Similar values were observed when chemotherapy was added before irradiation. With fractionated irradiation, palifermin increased the ED(50) for test irradiation from 5.7 +/- 1.5 Gy to 12-15 Gy, depending on the administration protocol. With chemotherapy in Week 1, two palifermin injections had no significant effect, but a third injection increased the ED(50) to 13 Gy. With chemotherapy in Week 2, all palifermin protocols resulted in ED(50) values of 13-14 Gy.

CONCLUSION

A marked increase in oral mucosal radiation tolerance by palifermin was found, which was preserved in combinations with chemotherapy using cisplatin and/or 5-fluorouracil.

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.

Chemical radioprotection: a critical review of amifostine as a cytoprotector in radiotherapy

The use of chemical radioprotectors represents an obvious strategy to improve the therapeutic index in radiotherapy. Amofostine (WR-2721) has recently been approved for use in head and neck cancer to protect against radiation-induced xerostomia. Currently, the question has arisen whether amifostine could be used for radioprotection in broader terms. Amifostine may have the potential to enable intensified treatment by ameliorating mucosal reactions that are often a limiting factor in accelerated fractionation or concomitant chemoradiation. However, it has as yet not been clarified whether sufficient amifostine to reduce mucositis can be administered before each radiation fraction without causing unacceptable toxicity. Also, the optimal dosage and schedule of amifostine in chemoradiation combinations have not yet been established. The major concern related to radioprotectiors is the potential hazard of collateral tumor protection. A number of clinical studies have concluded that amifostine does not reduce antitumor efficacy. However, not even the largest study conducted, with over 300 patients, has sufficient statistical power to detect a clinically significant reduction in tumor control rate. To put this issue ultimately to a rest, a clinical trial with a sufficient accrual to definitely rule out a tumor protective effect of amifostine needs to be conducted. Substances reducing radiation-induced toxicity by modulating the biological response to radiation injury may represent an alternative concept in radioprotection. However, such agents are still at a developmental stage.

Radiation myelopathy: new perspective on an old problem

This article discusses recent advances in basic research that alter the view of the pathogenesis of radiation myelopathy and summarizes the available data from developmental neurobiology and preclinical studies on demyelinating diseases. These studies have produced interesting insights into oligodendrocyte development, intercellular signaling pathways, and myelination processes. Current findings suggest that administration of cytokines as platelet-derived growth factor and basic fibroblast growth factor could increase proliferation of oligodendrocyte progenitors, enhance their differentiation, up-regulate synthesis of myelin constituents, and promote myelin regeneration in the adult central nervous system (CNS). Other compounds might also be able to modulate the progression of pathogenic processes that lead to myelopathy. In addition, several possible biological prevention or treatment strategies, for example stimulation of endogenous cellular regeneration and glial cell transplantation, are discussed. Rationally designed animal experiments pursuing such strategies could further elucidate the pathogenesis of radiation-induced CNS damage.