The mechanism of action of radiosensitization of conventional chemotherapeutic agents

Hyperthermia, cisplatin and radiation trimodality treatment: a promising cancer treatment? A review from preclinical studies to clinical application

This review discusses available clinical and experimental data and the underlying mechanisms involved in trimodality treatment consisting of hyperthermia, cisplatin and radiotherapy. The results of phase I/II clinical trials show that trimodality treatment is effective and feasible in various cancer types and sites with tolerable toxicity. Based on these results, phase III trials have been launched to investigate whether significant differences in treatment outcome exist between trimodality and standard treatment. In view of the clinical interest, it is surprising to find so few preclinical studies on trimodality treatment. Although little information is available on the doses of the modalities and the treatment sequence resulting in the largest degree of synergistic interaction, the results from in vivo and in vitro preclinical studies support the use of trimodality treatment for cancer patients. Animal studies show an improvement in treatment outcome after trimodality treatment compared with mono- and bimodality treatment. Studies in different human tumour cell lines show that a synergistic interaction can be obtained between hyperthermia, cisplatin and radiation and that this interaction is more likely to occur in cell lines which are more sensitive to cisplatin.

Evidence-based radiation oncology in head and neck squamous cell carcinoma

BACKGROUND AND PURPOSE

Historically, radiation therapy (RT) has been an available treatment option for patients with early resectable head and neck squamous cell carcinoma (HNSCC) and the sole therapy for those with unresectable or inoperable disease. Recently, four noteworthy strategies have emerged for the improvement of therapeutic outcome in the curative treatment of HNSCC: they include the development of altered fractionation radiotherapy, integration of chemotherapy with radiotherapy, incorporation of intensity-modulated radiotherapy and the introduction of targeted biological therapy. These strategies are briefly reviewed in an effort to help interpret evidence-based data and to facilitate clinical-decision making in a clinical context.

MATERIALS AND METHODS

For patients with early stage HNSCC no level 1 study exists in which radiation therapy is compared with conservative surgery for the evaluation of local control or survival. Only evidence from prospective and retrospective cohort studies is available to evaluate the role external radiotherapy and/or brachytherapy currently play in limited disease. For patients with locally advanced HNSCC the recommendations to address the questions about better treatment in resectable and unresectable tumors are based on more than 100 randomized Phase III trials included in six meta-analyses on chemo-radiotherapy and/or altered fractionation. Data from phase II trials and cohort studies help interpret the advances in intensity-modulated radiotherapy.

RESULTS

External radiotherapy and/or brachytherapy are crucial treatment options in patients with early stage HNSCC. For patients with locally advanced HNSCC, where outcome with conventional radiotherapy is poor, meta-analyses and collective data showed that loco-regional control may be improved at high level of evidence by altered fractionation radiotherapy, chemo-radiotherapy with concomitant approach or association of selected hypoxic cell radiosensitizer with radiotherapy. For these patients, overall survival may be improved at high level of evidence by concomitant chemo-radiotherapy or hyperfractionated RT delivered with increased total dose. Also EGFR-inhibitors (cetuximab)-radiotherapy strategy offers at a lower level of evidence better loco-regional control and overall survival than radiotherapy alone. Chemo-radiotherapy programs can achieve an improved larynx-function preservation program without the risk of overall survival reduction, for patients with larynx or hypopharynx tumors who are candidates to radical surgery followed by radiotherapy. Recently, strong evidence for an improved outcome for high-risk resected patients has been shown by the use of adjuvant concomitant chemo-radiotherapy. Despite improved results, a higher severe toxicity has been largely evidenced with concomitant chemo-radiotherapy by reducing the gain in the therapeutic index with new treatment strategies. Three-dimensional conformal radiotherapy is the minimal standard of technique in HNSCC: however, as advances are promising, intensity-modulated radiotherapy should be largely implemented.

CONCLUSIONS

Stepwise improvements in HNSCC non-surgical therapy have shown favorable impact on loco-regional control and overall survival. However, despite hundreds of clinical trials in patients with advanced disease, there is no absolute consensus about patient selection for altered fractionation regimens, type of chemo-radiotherapy association, radiation or chemotherapy dose schedule. Nevertheless, many well-conducted clinical studies have expanded therapy options besides standard radiotherapy and have contributed to defining the evolving standard of care for patients with HNSCC.

Chemoradiotherapy for localized esophageal cancer: regimen selection and molecular mechanisms of radiosensitization

Concurrent chemoradiotherapy administered either before surgery or as definitive treatment has a central role in the multimodality treatment of locally advanced esophageal cancer. Initial studies of this combined-modality regimen were based on models of squamous-cell cancers from other primary sites; this approach progressed from use of bleomycin or fluorouracil plus cisplatin concurrent with radiation in early trials, to the integration of taxanes, camptothecins and platinum analogs in recent trials. These trials demonstrated the tumoricidal effect of concurrent chemotherapy and radiotherapy and showed the survival advantages of this approach. Preoperative concurrent chemoradiation is used to downstage the tumor, ideally to a pathological complete response status in which there is no residual tumor in the resected primary and nodal tissues. A pathological complete response is associated with long-term survival but occurs in a minority (30%) of patients. While clinical trials have demonstrated an improvement in survival with concurrent chemoradiotherapy this effect is limited, as indicated by the plateau in survival beyond 5 years of approximately 30% or less. The recent clinical development of biologic, targeted therapies provides a new avenue for the study of chemoradiotherapy and an opportunity to increase long-term survival.

Purvalanol A Enhances Cell Killing by Inhibiting Up-Regulation of CDC2 Kinase Activity in Tumor Cells Irradiated with High Doses of X Rays

To clarify the relationship between CDC2 kinase activity and radiation-induced apoptosis, we examined whether the cyclin-dependent kinase (CDK) inhibitor purvalanol A enhanced radiation-induced apoptosis in gastric tumor cells. MKN45 cells exposed to 20 Gy of X rays increased the CDC2 kinase activity and the expression of regulatory proteins (phospho-CDC2 and cyclin B1) of the G2/M phase, followed by activation of the G2/M checkpoint, whereas the treatment of X-irradiated MKN45 cells with 20 microM purvalanol A suppressed the increase in the CDC2 kinase activity and expression of the G2/M-phase regulatory proteins and reduced the fraction of the cells in the G2/M phase in the cell cycle. Furthermore, this treatment resulted in not only a significant increase in radiation-induced apoptosis but also the loss of clonogenicity in both MKN45 (p53-wild) and MKN28 (p53-mutated) cells. The expression of anti-apoptosis proteins, inhibitor of apoptosis protein (IAP) family members (survivin and XIAP) and BCL2 family members (Bcl-X(L) and Bcl-2), in purvalanol A-treated cells with and without X rays was significantly lower than for cells exposed to X rays alone. These results suggest that the inhibition of radiation-induced CDC2 kinase activity by purvalanol A induces apoptosis through the enhancement of active fragments of caspase 3.

Effects of base excision repair gene polymorphisms on pancreatic cancer survival

To explore the association between single nucleotide polymorphisms of DNA repair genes and overall survival of patients with pancreatic cancer, we conducted a study in 378 cases of pancreatic adenocarcinoma who were treated at The University of Texas M. D. Anderson Cancer Center between February 1999 and October 2004 and were followed up to April 2006. Genotypes were determined using genomic DNA and the MassCode method. Overall survival was analyzed using the Kaplan-Meier plot, log-rank test and Cox regression. We observed a strong effect of the POLB A165G and T2133C genotypes on overall survival. The median survival time (MST) was 35.7 months for patients carrying at least 1 of the 2 homozygous variant POLB GG or CC genotypes, compared with 14.8 months for those carrying the AA/AG or TT/TC genotypes (p = 0.02, log rank test). The homozygous variants of hOGG1 G2657A, APEX1 D148E and XRCC1 R194W polymorphisms all showed a weak but significant effect on overall survival as demonstrated by either log rank test or multivariate COX regression after adjusting for other potential confounders. In combined genotype analysis, a predominant effect of the POLB homozygous variants on survival was observed. When POLB was not included in the model, a slightly better survival was observed among those carrying none of the adverse genotypes than those carrying at least one of the adverse genotypes. These observations suggest that polymorphisms of base excision repair genes significantly affect the clinical outcome of patients with pancreatic cancer. These observations need to be confirmed in a larger study of homogenous patient population.

Gemcitabine radiosensitizes multiple myeloma cells to low let, but not high let, irradiation

The radiosensitizing properties of gemcitabine in relation to low Linear Energy Transfer (LET) particles (Cobalt 60) and high-LET particles (alpha-RIT (213)Bi-radiolabeled CHX-DTPA-B-B4) were analyzed. Three multiple myeloma cell lines (LP1, RPMI 8226, U266) were irradiated with or without 10 nM gemcitabine 24 h prior to radiation. Gemcitabine led to radiosensitization of LP1 and U266 cells with low-LET (Radiation Enhancement Ratio: 1.55 and 1.49, respectively) but did not radiosensitize any cell line when combined with high-LET.

Rationale and clinical application of alkylphospholipid analogues in combination with radiotherapy

Concurrent treatment with radiotherapy and chemotherapy has emerged as an effective strategy to improve clinical outcome of cancer. In addition to combining radiation with classical anticancer agents, several new biological response modifiers are under investigation in pre-clinical and clinical studies. Synthetic alkylphospholipids are anticancer agents that in contrast to most anticancer drugs, do not target DNA, but insert in the plasma membrane and subsequently induce a broad range of biological effects, ultimately leading to cell death. Alkylphospholipids kill tumor cells directly by induction of both apoptotic and non-apoptotic cell death, and indirectly by interference with critical signal transduction pathways involved in phospholipid metabolism and survival. Due to their distinct mode of action, these drugs are considered as attractive candidates to combine with radiotherapy. In this review, we will discuss several alkylphospholipids that reached clinical application. These include first-generation alkyl-lysophospholipids edelfosine and ilmofosine, second-generation alkylphosphocholine-prototype miltefosine and more recently developed analogues perifosine and erucylphosphocholine. We focus on mechanisms of action and the rationale to combine these agents with radiotherapy. The preclinical results on molecular targeting underlying this approach will be reviewed, concluded with first clinical data on combined treatment of radiotherapy with perifosine.

The concurrent chemoradiation paradigm—general principles

During the past 20 years, the advent of neoadjuvant, primary, and adjuvant concurrent chemoradiotherapy has improved cancer care dramatically. Significant contributions have been made by technological improvements in radiotherapy, as well as by the introduction of novel chemotherapy agents and dosing schedules. This article will review the rationale for the use of concurrent chemoradiotherapy for treating malignancies. The molecular basis and mechanisms of action of combining classic cytotoxic agents (e.g. platinum-containing drugs, taxanes, etc.) and novel agents (e.g. tirapazamine, EGFR inhibitors and other targeted agents) with radiotherapy will be examined. This article is part one of two articles. In the subsequent article, the general principles outlined here will be applied to head and neck cancer, in which the impact of concurrent chemoradiotherapy is particularly evident.

Suicide genes for cancer therapy

The principle of using suicide genes for gene directed enzyme prodrug therapy (GDEPT) of cancer has gained increasing significance during the 20 years since its inception. The astute application of suitable GDEPT systems should permit tumour ablation in the absence of off-target toxicity commonly associated with classical chemotherapy, a hypothesis which is supported by encouraging results in a multitude of pre-clinical animal models. This review provides a clear explanation of the rationale behind the GDEPT principle, outlining the advantages and limitations of different GDEPT strategies with respect to the roles of the bystander effect, the immune system and the selectivity of the activated prodrug in contributing to their therapeutic efficacy. An in-depth analysis of the most widely used suicide gene/prodrug combinations is presented, including details of the latest advances in enzyme and prodrug optimisation and results from the most recent clinical trials.

Combining cisplatin and mitomycin with radiotherapy in anal carcinoma

PURPOSE

The European Organization for Research and Treatment of Cancer (EORTC) phase II study No. 22953 demonstrated the feasibility of reducing the overall treatment time of chemoradiation, delivering mitomycin C twice rather than once and fluorouracil during the whole treatment. We tested the feasibility of chemoradiation in anal carcinoma with mitomycin and cisplatin in a phase II study.

METHODS

Twenty-one patients with locally advanced anal carcinoma (15 women, 6 men) were treated. The first sequence of radiotherapy consisted of 36 Gy over four weeks. After a gap interval of 16 days, a second sequence of radiotherapy was given, delivering 23.4 Gy over 2.5 weeks. Mitomycin C was delivered at 10 mg/m(2) day 1 of each sequence and cisplatin was delivered at 25 mg/m(2)/week of each sequence.

RESULTS

The compliance rates for the first sequence with radiation, mitomycinm, and cispaltin (dose and timing) were 100 percent. The median duration gap was 16 days (14-30 days). The compliance rates for the second sequence with radiation, mitomycin, and cisplatin (dose and timing) were 100, 76.2, and 85.7 percent, respectively. Grade > or = 2 acute toxicities of 62, 29, 25, and 5 percent were observed for skin, diarrhea, hematologic, and renal toxicities, respectively. Nineteen patients were in complete response (90.5 percent).

CONCLUSIONS

Combining radiation with mitomycin and cisplatin in patients with locally advanced anal cancer is feasible. The results are promising. The EORTC is currently comparing this combination with mitomycin and 5-fluorouracil in a large phase II-III trial.

Concurrent chemoradiation for locally advanced oropharyngeal cancer

PURPOSE

The aim of this study was to assess the survival, pattern of failure, morbidity, and prognostic factors of concurrent chemoradiation for locally advanced oropharyngeal cancer.

MATERIALS AND METHODS

A retrospective survey of patients who underwent chemotherapy and radiation for locally advanced oropharyngeal carcinoma at the Veteran Affairs North Texas Health Care System, Dallas, Tex.

RESULTS

Between December 1999 and September 2004, 48 patients with locally advanced oropharyngeal cancer underwent concurrent chemotherapy and radiation. At a median follow-up of 23 months, the 3- and 5-year survival for the whole group were, respectively, 52% and 41%. Seventeen patients (35%) developed recurrences. There were 12 (25%) locoregional failures (6 local failures alone and 6 local and regional failures). Distant metastases developed in 8 patients (5 alone, 3 associated with locoregional failures). Four patients (8%) developed second primaries. No difference was observed in survival between base of tongue and tonsillar carcinoma (P = .32). The 5-year survival for T1-T2 and T3-T4 tumors was, respectively, 84% and 27% (P = .01). No patient with T1-T2 tumors developed distant metastases (P = .04). Forty-five patients (94%) developed toxicity grade 3 to 4 (40 mucositis and 26 hematological). The median weight loss was 18 lb (range, 0-47 lb). Eight patients (16%) developed aspiration pneumonia during and after treatment. Five patients (10%) died of aspiration (2 during and 3 post treatment). Four patients (8%) developed esophageal strictures requiring repeated dilatations post treatment. Two patients had radionecrosis (1 soft tissue and 1 bone) requiring hyperbaric oxygen. Eighteen patients (37%) had prolonged tube feedings (>3 months) after treatments because of severe dysphagia or aspiration.

CONCLUSION

Concurrent chemoradiation provided good locoregional control for locally advanced oropharyngeal carcinoma. Patients with small tumors (T1-T2) had excellent survival. The poor prognosis associated with large tumors may be due to the risk of developing distant metastases. Acute and late toxicities remained significant. Aspiration pneumonia and severe dysphagia were the most prevalent complications of the combined modality approach.

Real-time evaluation of p53 oscillatory behavior in vivo using bioluminescent imaging

p53 is a key mediator of cellular response to stress, and, although its function has been carefully evaluated in vitro, noninvasive evaluation of the transcriptional activity of p53 in live animals has not been reported. To this end, we developed a transgenic mouse model wherein the firefly luciferase gene expression was dependent on the p53-responsive P2 promoter from the murine double minute 2 (MDM2) gene. Bioluminescence activity following ionizing radiation was shown to be dose, time, and p53 dependent. In addition, expression of both p53 and its activated form as well as the expression of p53 target genes (MDM2 and p21) correlated with bioluminescence activity. Temporal evaluation of p53 activity following ionizing radiation showed a distinct oscillatory pattern, which confirmed the oscillations observed previously in cultured cells. In addition, the kinetics of oscillations were altered by pretreatment with radiation-modifying agents. These results show the use of this mouse model in enhancing our understanding of the transcriptional role of p53 in vivo.

Dysphagia severity following chemoradiation and postoperative radiation for head and neck cancer

OBJECTIVE

The purpose of the study is to evaluate dysphagia severity following chemoradiation and postoperative radiation for head and neck cancer, and particularly the aspiration risk because of its potential life-threatening consequence.

MATERIALS AND METHODS

We reviewed retrospectively the modified barium swallow (MBS) results in 110 patients who complained of dysphagia following chemoradiation (57) and postoperative radiation (53) of their head and neck cancer. Patients were selected if they were cancer free at the time of the swallowing study. Dysphagia severity was graded on a scale of 1-7. Patients were grouped according to the dysphagia severity: mild (grades 2-3), moderate (grades 4-5), and severe (grades 6-7).

RESULTS

Mean and median dysphagia grades were 4.84/5 and 4.12/4 for chemoradiation and postoperative radiation respectively. The mean difference between the two groups is statistically significant (p=0.02). Mild dysphagia occurred in 13 patients (22%) of the chemoradiation group and 17 (32%) of the postoperative group. Corresponding number for the moderate group was 25 (43%) and 25 (48%), respectively. Severe dysphagia was significant in the chemoradiation group (34%) compared to the postoperative group (19%). However, the difference was not statistically significant (p=0.29). There was a higher proportion of patients with large tumor (T3-T4) in the chemoradiation group who developed severe dysphagia.

CONCLUSION

Dysphagia remained a significant morbidity of chemoradiation and postoperative radiation for head and neck cancer. Dysphagia may be more severe in the chemoradiation group because of the higher proportion of patients with large tumor, the high radiation dose, and a high number of oropharyngeal tumors. Aspiration occurred in both groups. Diagnostic studies such as MBS should be part of future head and neck cancer prospective studies to assess the prevalence of aspiration, as it may be silent.

New and emerging radiosensitizers and radioprotectors

The combination of chemotherapy and radiation has led to clinical breakthroughs in several disease sites, and current work continues to define optimum combinations of proven chemotherapy as well as more recently available, noncytotoxic agents. Administration of systemic therapies allows modulation of radiation response to improve tumor control (radiosensitization) or to prevent normal tissue toxicity (radioprotection). Substantial progress has been made in identifying the targets of standard chemotherapeutic radiation sensitizers and protectors as well as in the introduction of a new generation of molecularly targeted therapies in combination with radiation. We have reviewed the most recent, predominantly early phase clinical trials combining systemic agents with radiation. Although the proof of an improved schedule ultimately needs to come from well-run Phase III trials, the search among schedules could be shortened by the use of surrogate endpoints such as presence of active drug metabolites in the tumor. This has been accomplished only in a few cases and needs to become a more standard part of radiation sensitizer and protector trials.

Aspiration rate following chemoradiation for head and neck cancer: an underreported occurrence

BACKGROUND AND PURPOSE

We would like to assess the prevalence of aspiration before and following chemoradiation for head and neck cancer.

PATIENTS AND METHODS

We reviewed retrospectively the Modified Barium Swallow (MBS) in 63 patients who underwent concurrent chemotherapy and radiation for head and neck cancer. MBS was performed prior to treatment to determine the need for immediate gastrostomy tube placement. MBS was repeated following treatment to assess the safety of oral feeding prior to removal of tube feeding. All patients were cancer free at the time of the swallowing study. No patient had surgery. Dysphagia severity was graded on a scale of 1-7. Tube feedings were continued if patients were diagnosed to have severe aspiration (grade 6-7) or continued weight loss. Patients with abnormal swallow (grade 3-7) received swallowing therapy following MBS.

RESULTS

Before treatment, there were 18 grade 1, 18 grade 2, 9 grade 3, 8 grade 4, 3 grade 5, 3 grade 6, and 4 grade 7. Following chemoradiation, at a median follow-up of 2 months (1-10 months), one patient had grade 1, eight patients had grade 2, nine patients had grade 3, eight patients had grade 4, 13 patients had grade 5, seven patients had grade 6, and 11 patients had grade 7. Six patients died from aspiration pneumonia (one before, three during, and two post-treatment), and did not have the second MBS. Overall, 37/63 (59%) patients developed aspiration, six of them (9%) fatal. If we excluded the 10 patients who had severe aspiration at diagnosis and the six patients who died from pneumonia, the prevalence of severe aspiration was 33% (21/63).

CONCLUSIONS

Aspiration remained a significant morbidity following chemoradiation for head and neck cancer. Its prevalence is underreported in the literature because of its often silent nature. Diagnostic studies such as MBS should be part of future head and neck cancer prospective studies to assess the prevalence of aspiration, and for rehabilitation.

Base excision repair of both uracil and oxidatively damaged bases contribute to thymidine deprivation-induced radiosensitization

PURPOSE

Increased cellular sensitivity to ionizing radiation due to thymidine depletion is the basis of radiosensitization with fluoropyrimidine and methotrexate. The mechanism responsible for cytotoxicity has not been fully elucidated but appears to involve both the introduction of uracil into, and its removal from, DNA. The role of base excision repair of uracil and oxidatively damaged bases in creating the increased radiosensitization during thymidine depletion is examined.

METHODS AND MATERIALS

Isogenic strains of S. cerevisiae differing only at loci involved in DNA repair functions were exposed to aminopterin and sulfanilamide to induce thymidine deprivation. Cultures were irradiated and survival determined by clonogenic survival assay.

RESULTS

Strains lacking uracil base excision repair (BER) activities demonstrated less radiosensitization than the parental strain. Mutant strains continued to show partial radiosensitization with aminopterin treatment. Mutants deficient in BER of both uracil and oxidatively damaged bases did not demonstrate radiosensitization. A recombination deficient rad52 mutant strain was markedly sensitive to radiation; addition of aminopterin increased radiosensitivity only slightly. Radiosensitization observed in rad52 mutants was also abolished by deletion of the APN1, NTG1, and NTG2 genes.

CONCLUSION

These data suggest radiosensitization during thymidine depletion is the result of BER activities directed at both uracil and oxidatively damaged bases.

Scheduling cisplatin and radiotherapy in the treatment of squamous cell carcinomas of the head and neck: a modelling approach

The aim of the present work was to implement the kinetics of cisplatin into a previously developed tumour growth model and to simulate the combined cisplatin-radiotherapy treatment with the emphasis on time sequencing and scheduling of drug and radiation. An investigation into whether the effect of cisplatin-radiation is determined by independent cell kill or by cisplatin-produced radiosensitization was also undertaken. It was shown that cisplatin administered before radiation conferred similar tumour control to the post-radiation sequencing of the drug. The killing effect of the combined modality treatment on tumour increased with the increase in cell recruitment. Furthermore, the individual cell kill produced by the two cytotoxins led to an additive only tumour response when the treatments were given concurrently, suggesting that for a synergistic effect, cisplatin must potentiate the effect of radiation, through the radiosensitizing mechanisms addressed in the literature. It was concluded that the optimal timing of cisplatin should be close to radiation. The model showed that daily administration of cisplatin led to a 35% improvement of tumour control as compared to radiation alone, while weekly cisplatin has improved radiotherapy by only 6%.

Cell death induced in a human glioblastoma cell line by p(65)+Be neutrons combined with cisplatin

High linear energy transfer (LET) radiation have the ability to kill cancer cells resistant to conventional radiotherapy. On the other hand, protocols combining radiotherapy and chemotherapy are effective in eradicating certain inoperable cancers. In this study, we investigated the cytotoxicity of a co-treatment with fast neutrons and cisplatin in a human glioblastoma cell line, U-87. Cells cultured in vitro were irradiated with p(65)+Be neutrons in the presence of cisplatin. Cell survival and the induction of apoptosis and premature senescence were assessed at different time intervals thereafter, using a variety of methods. A marked reinforcement of the cytotoxicity was obtained when irradiation and cisplatin were associated. This reflected both an amplification of the apoptotic process and the induction of premature cell senescence. The efficiency of a combination between fast neutrons and cisplatin in inducing cell death in U-87 is more than additive. The present data concur with those we previously reported in a mouse lymphoma and suggest the potential utility of platinum compounds as adjuncts to future cancer therapy protocols using high-LET radiation.

Vascular complications of cranial radiation

OBJECTIVES

Cerebral vascular disease has been reported as a long-term complication of cranial radiotherapy. The purpose of this study was to examine the frequency and risk factors associated with development of cerebral vascular disease in children after cranial radiation.

MATERIALS AND METHODS

A retrospective chart review of all cancer patients treated between 1985 and 2003 who were under the age of 18 years at the time of initial radiotherapy was performed. Variables examined include diagnosis and site of malignancy, age at the time of radiotherapy, sex, total radiation dosage, number of fractions, duration, and whether the patient had proven cerebral vascular event.

RESULTS

Two hundred and forty-four patients met the study criteria. One hundred and 13 cases involved tumors of the central nervous system. The remaining patients had systemic neoplastic disease. Post radiation cerebral vascular disease occurred in 11 (5%) patients, and all but one patient had a tumor involving the central nervous system (mainly in the posterior fossa and supratentorial midline).

CONCLUSION

There is an increased risk of cerebral vascular disease after radiation therapy in childhood, especially in children who received high dose radiation at the posterior fossa and supratentorial axial region.

Preoperative versus postoperative treatment for locally advanced rectal carcinoma

EPIDEMIOLOGY

Overall mortality of rectal cancer at 5 years is approximately 40%. This cancer is commonly diagnosed at an early stage, but because of local relapse and/or metastatic disease, only half of radically resected patients can be considered disease free.

COMMON TREATMENT

The value of adding radiotherapy to surgery in the treatment of patients with resectable rectal cancer has been assessed in trials using either preoperative or postoperative irradiation.

IMPROVEMENTS IN TREATMENT

Preoperative radiotherapy and complete resection are established modalities for Stage II and III rectal cancer whilst data reporting improvement of survival by preoperative chemoradiotherapy are still not available. At present, the improved results reported by Phase II trials in terms of local control, sphincter saving and tumor regression grade make neoadjuvant treatment the 'standard' therapy only in North America and some other countries, but the concept of preoperative combined modality treatment is not supported globally.

Tumor radiosensitizers--current status of development of various approaches: report of an International Atomic Energy Agency meeting

PURPOSE

The International Atomic Energy Agency (IAEA) held a Technical Meeting of Consultants to (1) discuss a selection of relatively new agents, not those well-established in clinical practice, that operated through a variety of mechanisms to sensitize tumors to radiation and (2) to compare and contrast their tumor efficacy, normal tissue toxicity, and status of development regarding clinical application. The aim was to advise the IAEA as to which developing agent or class of agents would be worth promoting further, by supporting additional laboratory research or clinical trials, with the eventual goal of improving cancer control rates using radiotherapy, in developing countries in particular.

RESULTS

The agents under discussion included a wide, but not complete, range of different types of drugs, and antibodies that interfered with molecules in cell signaling pathways. These were contrasted with new molecular antisense and gene therapy strategies. All the drugs discussed have previously been shown to act as tumor cell radiosensitizers or to kill hypoxic cells present in tumors.

CONCLUSION

Specific recommendations were made for more preclinical studies with certain of the agents and for clinical trials that would be suitable for industrialized countries, as well as trials that were considered more appropriate for developing countries.

Significant effect of homologous recombination DNA repair gene polymorphisms on pancreatic cancer survival

Genetic variation in DNA repair may affect the clinical response to cytotoxic therapies. We investigated the effect of six single nucleotide polymorphisms of the RecQ1, RAD54L, XRCC2, and XRCC3 genes on overall survival of 378 patients with pancreatic adenocarcinoma who were treated at University of Texas M.D. Anderson Cancer Center during February 1999 to October 2004 and were followed up to October 2005. Genotypes were determined using the MassCode method. Survival was determined from pathologic diagnosis to death. Patients who were alive at the last follow-up evaluation were censored at that time. Kaplan-Meier plot, log-rank test, and Cox regression were used to compare overall survival by genotypes. A significant effect on survival of all patients was observed for RecQ1 and RAD54L genes. The median survival time was 19.2, 14.7, and 13.2 months for the RecQ1 159 AA, AC, and CC genotypes, and 16.4, 13.3, and 10.3 months for RAD54L 157 CC, CT, and TT genotypes, respectively. A significantly reduced survival was associated with the variant alleles of XRCC2 R188H and XRCC3 A17893G in subgroup analysis. When the four genes were analyzed in combination, an increasing number of adverse alleles were associated with a significantly decreased survival. Subgroup analyses have shown that the genotype effect on survival was present among patients without metastatic disease or among patients who receive radiotherapy. These observations suggest that polymorphisms of genes involved in the repair of DNA double-strand breaks significantly affect the clinical outcome of patients with pancreatic cancer.

Mechanisms of cell sensitization to alpha radioimmunotherapy by doxorubicin or paclitaxel in multiple myeloma cell lines

PURPOSE

The purpose of this study was to analyze different mechanisms (cell cycle synchronization, DNA damage, and apoptosis) that might underlie potential synergy between chemotherapy (paclitaxel or doxorubicin) and radioimmunotherapy with alpha radionuclides.

EXPERIMENTAL DESIGN

Three multiple myeloma cell lines (LP1, RMI 8226, and U266) were treated with 213Bi-radiolabeled B-B4, a monoclonal antibody that recognizes syndecan-1 (CD138) 24 hours after paclitaxel (1 nmol/L) or doxorubicin (10 nmol/L) treatment. Cell survival was assessed using a clonogenic survival assay. Cell cycle modifications were assessed by propidium iodide staining and DNA strand breaks by the comet assay. Level of apoptosis was determined by Apo 2.7 staining.

RESULTS

Radiation enhancement ratio showed that paclitaxel and doxorubicin were synergistic with alpha radioimmunotherapy. After a 24-hour incubation, paclitaxel and doxorubicin arrested all cell lines in the G2-M phase of the cell cycle. Doxorubicin combined with alpha radioimmunotherapy increased tail DNA in the RPMI 8226 cell line but not the LP1 or U266 cell lines compared with doxorubicin alone or alpha radioimmunotherapy alone. Neither doxorubicin nor paclitaxel combined with alpha radioimmunotherapy increased the level of apoptosis induced by either drug alone or alpha radioimmunotherapy alone.

CONCLUSION

Both cell cycle arrest in the G2-M phase and an increase in DNA double-strand breaks could lead to radiosensitization of cells by doxorubicin or paclitaxel, but apoptosis would not be involved in radiosensitization mechanisms.

Effects of cisplatin and gamma-irradiation on cell survival, the induction of chromosomal aberrations and apoptosis in SW-1573 cells

PURPOSE

Cisplatin was found to radiosensitize SW-1573 cells by inhibition of PLDR. Therefore, it was investigated whether cisplatin combined with gamma-radiation leads to an increase in the number of chromosomal aberrations or apoptotic cells compared with radiation alone.

METHODS

Confluent cultures of the human lung carcinoma cell line SW-1573 were treated with 1 microM cisplatin for 1 h, 4 Gy gamma-radiation, or a combination of both. Cell survival was studied by the clonogenic assay. Aberrations were analysed by FISH in prematurely condensed chromosomes (PCC) and the induction of apoptosis by counting fragmented nuclei.

RESULTS

A radiosensitizing effect of cisplatin on cell survival was observed if time for PLDR was allowed. An increased number of chromosomal fragments were observed immediately after irradiation compared with 24 h after irradiation whereas color junctions are only formed 24 h after irradiation. No increase in chromosomal aberrations was found after combined treatment, but a significantly enhanced number of fragmented nuclei were observed when confluent cultures were replated after allowing PLDR.

CONCLUSION

The inhibition of PLDR by cisplatin in delayed plated SW-1573 cells did not increase chromosomal aberrations, but increased the induction of apoptosis.

Biweekly Paclitaxel and Gemcitabine for Patients with Advanced Urothelial Cancer Ineligible for Cisplatin-Based Regimen

BACKGROUND

To avoid cisplatin-related gastrointestinal, renal and other toxicity while maintaining efficacy in the palliative setting or second line chemotherapeutic regimen for cisplatin-resistant urothelial cancer, chemotherapeutic regimens have been investigated that do not include cisplatin. The current study was designed to evaluate efficacy, clinical feasibility and safety of gemcitabine and paclitaxel (GP) regimen in patients with metastatic urothelial cancer who were ineligible for standard cisplatin-based combination chemotherapy.

METHODS

Gemcitabine 2500 mg/m(2) and paclitaxel 150 mg/m(2) were administered intravenously every 2 weeks for 23 patients (17 males and 6 females) with advanced urothelial cancer who were ineligible for cisplatin-based chemotherapy; metastatic disease being resistant to cisplatin-based chemotherapy regimen in 14, heavy toxicity in prior cisplatin-based chemotherapy in three, poor ECOG performance in two and impaired renal function in four. Average age was 67 (53-77). Performance status was 0 in 18 patients, 1 in three patients and 2 in two patients.

RESULTS

The overall response rate was 30% (95% CI 15.6-50.8%). Of the 23 patients, no patient attained CR and 7 patients had PR. In the cisplatin-resistant group, the response rate was 14.2% (2/14; 95% CI 4.0-39.9%). In the remaining patients ineligible for cisplatin, the response rate was 55.5% (5/9; 95% CI 26.6-81.1%). The median duration of response was 4 months (range 3-8). The median duration of survival for all patients was 12.1 months (95% CI 8.6-15.5). Myelosuppression, predominantly neutropenia, was the most common serious toxicity and toxicity of Grade 3 or greater was observed in six patients (26%). Among non-hematological toxicity, neuralgia was the most commonly observed and occurred in nine patients (39%) although no patient had toxicity of Grade 3 or greater. Three patients had interstitial pneumonitis possibly attributed to gemcitabine. One patient developed severe bilateral disease after two cycles of the regimen, which was partially resolved with corticosteroid therapy.

CONCLUSION

GP regimen is effective in some patients with cisplatin-resistant urothelial cancer and promising as second line chemotherapy. GP regimen is more effective and well tolerated as first line chemotherapy in patients ineligible for cisplatin-based chemotherapy. Toxicity is generally mild but care must be taken for patients with risk of interstitial pneumonitis. A further larger scale study is required to confirm the efficacy of the GP regimen.

Phase I study of cisplatin and irinotecan combined with concurrent hyperfractionated accelerated thoracic radiotherapy for locally advanced non-small cell lung carcinoma

BACKGROUND

Irinotecan, when combined with cisplatin, is an effective treatment for advanced non-small cell lung cancer (NSCLC). This constitutes a rationale for conducting a phase I study of chemoradiotherapy including this combination for locally advanced NSCLC.

PATIENTS AND METHODS

Patients with locally advanced NSCLC and a performance status of 0 or 1 were eligible. The protocol consisted of escalating doses of irinotecan on days 1 and 15, and daily low-dose cisplatin (6 mg/m(2) daily for a total dose of 120 mg/m(2)) combined with concurrent hyperfractionated accelerated thoracic irradiation (1.5 Gy twice daily for a total dose of 60 Gy).

RESULTS

The maximum tolerable dose was 50 mg/m(2) of irinotecan, and the dose-limiting toxicity was esophagitis. Tumor response was observed in 50% of cases, and the median survival time of the 12 patients enrolled was 10.1 months, including two patients with 5-year disease-free survival. A pharmacokinetics study demonstrated an accumulation of total platinum, but not of free platinum, during the 26-day treatment period.

CONCLUSION

The recommended dose for phase II studies was determined.

Pancreatic cancer cell radiation survival and prenyltransferase inhibition: the role of K-Ras

Activating K-ras mutations are found in approximately 90% of pancreatic carcinomas and may contribute to the poor prognosis of these tumors. Because radiotherapy is frequently used in pancreatic cancer treatment, we assessed the contribution of oncogenic K-ras signaling to pancreatic cancer radiosensitivity. Seven human pancreatic carcinoma lines with activated K-ras and two cell lines with wild-type ras were used to examine clonogenic cell survival after Ras inhibition. Ras inhibition was accomplished by small interfering RNA (siRNA) knockdown of K-ras expression and by blocking Ras processing using a panel of prenyltransferase inhibitors of differing specificity for the two prenyltransferases that modify K-Ras. K-ras knockdown by siRNA or inhibition of prenyltransferase activity resulted in radiation sensitization in vitro and in vivo in tumors with oncogenic K-ras mutations. Inhibition of farnesyltransferase alone was sufficient to radiosensitize most K-ras mutant tumors, although K-Ras prenylation was not blocked. These results show that inhibition of activated K-Ras can promote radiation killing of pancreatic carcinoma in a superadditive manner. The finding that farnesyltransferase inhibition alone radiosensitizes tumors with K-ras mutations implies that a farnesyltransferase inhibitor-sensitive protein other than K-Ras may contribute to survival in the context of mutant K-ras. Farnesyltransferase inhibitors could therefore be of use as sensitizers for pancreatic carcinoma radiotherapy.

Mismatch repair proficiency is not required for radioenhancement by gemcitabine

PURPOSE

Mismatch repair (MMR) proficiency has been reported to either increase or decrease radioenhancement by 24-h incubations with gemcitabine. This study aimed to establish the importance of MMR for radioenhancement by gemcitabine after short-exposure, high-dose treatment and long-exposure, low-dose treatment.

METHODS AND MATERIALS

Survival of MMR-deficient HCT116 and MMR-proficient HCT116 + 3 cells was analyzed by clonogenic assays. Mild, equitoxic gemcitabine treatments (4 h, 0.1 microM vs. 24 h, 6 nM) were combined with gamma-irradiation to determine the radioenhancement with or without recovery. Gemcitabine metabolism and cell-cycle effects were evaluated by high-performance liquid chromatography analysis and bivariate flow cytometry.

RESULTS

Radioenhancement after 4 h of 0.1 microM of gemcitabine was similar in both cell lines, but the radioenhancement after 24 h of 6 nM of gemcitabine was reduced in MMR-proficient cells. No significant differences between both cell lines were observed in the gemcitabine metabolism or cell-cycle effects after these treatments. Gemcitabine radioenhancement after recovery was also lower in MMR-proficient cells than in MMR-deficient cells.

CONCLUSION

Mismatch repair proficiency decreases radioenhancement by long incubations of gemcitabine but does not affect radioenhancement by short exposures to a clinically relevant gemcitabine dose. Our data suggest that MMR contributes to the recovery from gemcitabine treatment.

Etoposide sensitizes CT26 colorectal adenocarcinoma to radiation therapy in BALB/c mice

AIM: To investigate the combined effect of etoposide and radiation on CT26 colorectal adenocarcinoma implanted into BALB/c mice.

METHODS: We evaluated the radiosensitizing effect of etoposide on CT26 colorectal adenocarcinoma in a syngeneic animal model. BALB/c mice were subcutaneously implanted with CT26 cells and divided into four groups: control (intra-peritoneal saline2) group, etoposide (5 mg/kg intra-peritoneally2) group, radiation therapy (RT 5 Gy2 fractions) group, and combination therapy with etoposide (5 mg/kg intra-peritoneally 1 h before radiation) group.

RESULTS: Tumor growth was significantly inhibited by RT and combination therapy. The effect of combination therapy was better than that of RT. No significant changes were noted in body weight, plasma alanine aminotransferase, or creatinine in any group. The leukocyte count significantly but transiently decreased in the RT and combination therapy groups, but not in the etoposide and control groups. There was no skin change or hair loss in the RT and combination therapy groups.

CONCLUSION: Etoposide can sensitize CT26 colorectal adenocarcinoma in BALB/c mice to RT without significant toxicity.

Alteration of radiotherapy fractionation and concurrent chemotherapy: a new frontier in head and neck oncology?

Despite recent advances in multimodality management of patients with stage III-IV head and neck squamous cell carcinoma, the prognosis in these patients remains disappointing. In an attempt to improve treatment outcome, several teams recently investigated the role of altered fractionation radiotherapy in conjunction with systemic chemotherapy. The controlled trials that investigated this combined approach indicate that, although the magnitude of its effect was less marked for survival indices than for local-regional control, the addition of chemotherapy to altered fractionation regimens results in a clear improvement for these endpoints compared with hyperfractionated or accelerated regimens alone. The key challenge now is to optimize the synergism of these regimens in order to increase their therapeutic ratio in terms of both local-regional and systemic outcomes. This review is a critical appraisal of the real opportunities offered by the application of treatments aimed at increasing the dose intensity of radiotherapy delivered concurrently with cytotoxic drugs.

Cellular response to chemotherapy and radiation in cervical cancer

Effect of irradiation alone and irradiation after 5-fluorouracil (5-FU), paclitaxel, or cisplatin (CDDP) was investigated in human cervical cell lines (CaSki, ME180, SiHa, and C33A). High-risk human papillomavirus (HPV) (+) CaSki and SiHa cells were the most resistant to CDDP, 5-FU, and radiation treatments. Radiation and CDDP and 5-FU resulted in decreased survival of HPV 16 and 18 (+) cells, whereas addition of paclitaxel to radiation treatments decreased killing. Enhanced killing of ME180 cells containing HPV39 sequences was demonstrated with chemoradiotherapy with all agents. HPV(-) C33A was more sensitive to radiation than the other cell lines, and the addition of chemotherapeutic agents did not result in significant change in cytotoxicity. Expression of survivin was inversely proportional to cell sensitivity to CDDP, 5-FU, and radiation. Constitutive AKT levels are the lowest in cell lines that are the most resistant to CDDP, 5-FU, and radiation. These data provide correlation of response to combined therapeutic modalities with HPV status of cervical cancer and expression of survivin and AKT.

Gemcitabine twice weekly as a radiosensitiser for the treatment of brain metastases in patients with carcinoma: a phase I study

Conventional treatment for brain metastases (BM) is whole-brain radiotherapy (WBRT). Efficacy is poor. It might be increased by a potent radiosensitiser such as gemcitabine which is believed to cross the disrupted blood–brain barrier. Primary objective of this study was to determine the maximum tolerated dose (MTD) of twice weekly gemcitabine given concurrently with WBRT. Patients with BM from carcinoma were included. The dose of WBRT was 30 Gys (10 daily fractions). Gemcitabine was given 2–4 h prior to WBRT on days 1 and 8 for the first cohort of patients and then on days 1, 4, 8 and 11. Starting dose was 25 mg m⁻², escalated by 12.5 mg m⁻² increments. At least three patients were included per level. Dose limiting toxicity (DLT) was defined as grade 4 haematological or grade ⩾3 nonhaematological toxicity. A total of 25 patients were included; 74% had a PS 1 (ECOG). In all, 23 had non-small-cell lung cancer, six colorectal, four breast, two renal cell and one oesophageal carcinoma. A total of 92% had concurrent extracranial disease. Six had single BM, 13 had two or three BM and six multiple. Up to 50 mg m⁻² (level 4) no DLT was observed. At 62.5 mg m⁻², one out of six patients developed DLT (thrombocytopenia-bleeding). The next dose level (75 mg m⁻²) was abandoned after grade 4 bone marrow toxicity (fatal neutropenic sepsis) was seen in one out of two patients. So that the dose of 50 mg m⁻² will be taken forward for further study.

A novel fusion suicide gene yeast CDglyTK plays a role in radio-gene therapy of nasopharyngeal carcinoma

To investigate a novel suicide gene for nasopharyngeal carcinoma (NPC) therapy, the yCDglyTK gene was constructed by fusing yeast cytosine deaminase (CD) and herpes simplex type 1 thymidine kinase. The expression of the yCDglyTK gene was detected by RT-PCR and Western blotting, and its bioactivity was demonstrated by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. An animal study was carried out in which BALB/C nude mice bearing yCDglyTK gene-modified tumors were treated with prodrugs and radiation. Our results revealed that the yCDglyTK gene could be expressed in CNE-2 cells in vitro. In MTT analysis, at the transfection rate of 10%, 66% cells were killed. The synergistic effect of CD and TK showed 91% of yCDglyTK-transfected cells were killed with the treatment of 5-fluorocytosine (5-FC) alone, 60% killed with ganciclovir (GCV) alone, and 75% killed with 5-FC and GCV together. In vivo, the tumor volume in all of the four prodrugs and/or radiation-treated groups were significantly different from that in the PBS-controlled group (P<.01); also yCDglyTK+prodrug+radiation group was different from the other three groups (P<.05). Our findings suggested there was a synergistic antitumor effect when combining suicide gene therapy and radiation, and yCDglyTK has potent antitumor efficacy and may be a candidate suicide gene for cancer therapy.

Differential role of RB in response to UV and IR damage

The retinoblastoma tumor suppressor (RB) is functionally inactivated in the majority of cancers and is a critical mediator of DNA damage checkpoints. Despite the critical importance of RB function in tumor suppression, the coordinate impact of RB loss on the response to environmental and therapeutic sources of damage has remained largely unexplored. Here, we utilized a conditional knockout system to ablate RB in adult fibroblasts. This model system enabled us to investigate the temporal role of RB loss on cell cycle checkpoints and DNA damage repair following ultraviolet (UV) and ionizing radiation (IR) damage. We demonstrate that RB loss compromises rapid cell cycle arrest following UV and IR exposure in adult primary cells. Detailed kinetic analysis of the checkpoint response revealed that disruption of the checkpoint is concomitant with RB target gene deregulation, and is not simply a manifestation of chronic RB loss. RB loss had a differential effect upon repair of the major DNA lesions induced by IR and UV. Whereas RB did not affect resolution of DNA double-strand breaks, RB-deficient cells exhibited accelerated repair of pyrimidine pyrimidone photoproducts (6-4 PP). In parallel, this repair was coupled with enhanced expression of specific factors and the behavior of proliferating cell nuclear antigen (PCNA) recruitment to replication and repair foci. Thus, RB loss and target gene deregulation hastens the repair of specific lesions distinct from its ubiquitous role in checkpoint abrogation.

Relevance and irrelevance of DNA damage response to radiotherapy

Ionizing radiation (IR) has been used to treat human malignancies since the early part of the 20th century. To date, most of the advances in radiotherapy have focused on optimization of treatment delivery schedules and technologic improvements in the physical targeting of dose. By comparison, many of the discoveries regarding the molecular basis of DNA damage and repair have not yet been translated to clinical practice. This article offers some perspectives regarding modulators of radiation effects and the challenges faced as we approach newer molecular targets. Our goal is to frame the issues that contribute to the apparent disconnect between laboratory discoveries and improvements in clinically relevant therapeutics.

Use of radiation and a slow-release cisplatin formulation for treatment of canine nasal tumors

The purpose of this study was to evaluate the combined use of radiation and a slow-release cisplatin chemotherapy formulation for treatment of malignant nasal tumors in dogs. In this retrospective analysis, 51 dogs were evaluated with respect to treatment toxicity, tumor type, stage of disease, cribriform plate involvement, and overall survival. In general, treatment was well tolerated. Mean and median survival as assessed by the Kaplan-Meier product limit method was 570 and 474 days, respectively. No other factors, including tumor type, stage of disease, or cribriform plate invasion had a significant impact on survival. In conclusion, a combination of slow release cisplatin chemotherapy and radiation for the treatment of canine nasal tumors is well tolerated. Results of this analysis warrant further study to elucidate possible other beneficial radiation potentiating drugs and dosing schedules.

Enhancement of Radiation Effect by Aphanamixis polystachya in Mice Transplanted with Ehrlich Ascites Carcinoma

The effect of radiation on tumor tissue can be optimized by adding radiosensitizing agents, in order to achieve a greater degree of tumor damage than expected from the use of either treatment alone. The ethanolic extract of Aphanamixis polystachya (APE) was tested in Swiss albino mice transplanted with Ehrlich ascites carcinoma (EAC) and exposed to various doses of gamma-radiation. EAC mice received 0, 10, 25, 50, 75, 100, 150 or 200 mg/kg body wt APE before exposure to 6 Gy gamma-radiation followed by once daily administration for another 8 consecutive days post-irradiation. The optimum radiosensitizing dose was found to be 50 mg/kg APE that was further tested in EAC mice exposed to 0, 1, 2, 4, 6 or 8 Gy hemi body gamma-radiation. The best effect of APE and radiation was observed for 6 Gy gamma-radiation. The splitting of 50 mg into two equal fractions of 25 mg and administering the split dose with a gap of 8 h on 1, 3, 5, 7 or 9 d of tumor inoculation resulted in an increased survival even when the drug was administered at late stages (day 5) of tumor development. The APE treatment before irradiation elevated lipid peroxidation followed by a reduction in the glutathione contents. Treatment of tumor bearing mice with APE before irradiation further reduced the activities of various antioxidant enzymes like glutathione peroxidase, glutathione-s-transferase, superoxide dismutase and catalase at different post last drug administration (PLDA) times.

Increased expression of pro-inflammatory cytokines as a cause of lung toxicity after combined treatment with gemcitabine and thoracic irradiation

BACKGROUND AND PURPOSE

Preclinical evidence suggesting gemcitabine potentiates the anti-tumor effects of irradiation has resulted in clinical trials to evaluate the treatment efficacy of gemcitabine and concurrent thoracic irradiation in non-small-cell lung cancer (NSCLC). Although these studies demonstrated favorable tumor response, this combined treatment modality was accompanied by severe treatment-related toxicities predominantly of the lung. In an attempt to elucidate the determinants of lung toxicity for gemcitabine, we analyzed the expression of the pro-inflammatory cytokines TNF-alpha, IL-1alpha and IL-6 in the lung tissue of mice treated with gemcitabine and concurrent thoracic irradiation.

MATERIALS AND METHODS

Four study groups were defined: C57BL/6J mice that received neither irradiation nor gemcitabine (NT-group), those that received gemcitabine (120 mg/kg intraperitoneal, i.p.) but no irradiation (GEM-group), those that underwent thoracic irradiation (12 Gy) without gemcitabine (XRT-group), and those that received both gemcitabine (120 mg/kg i.p., 2 h before irradiation) and thoracic irradiation (GEM/XRT-group). The mice were sacrificed at 1 h, 1 and 3 days, 1, 2 and 4 weeks post-treatment (p.t.). The mRNA expression of TNF-alpha, IL-1alpha and IL-6 in the lung tissue was quantified by competitive RT-PCR. The cellular origin of the cytokine expression was identified by immunohistochemistry. The cytokine expression was correlated with histopathological alterations.

RESULTS

The TNF-alpha, IL-1alpha and IL-6 expression in the lung tissue of the GEM/XRT mice was clearly higher at all assessment time points compared to the NT mice (statistically significant at 1 h, 1 and 3 days, 1, 2 and 4 weeks p.t.), XRT mice (statistically significant at 1 week p.t.) or GEM mice (statistically significant at 1 h, 1 and 2 weeks p.t.). Maximal treatment-induced cytokine expression in the lung tissue of the GEM/XRT mice occurred already at 1 week p.t. (TNF-alpha: 30.9 +/- 5.3/IL-1alpha: 28.3 +/- 5.0/IL-6: 4.9 +/- 0.1 times basal level), and coincides with pathohistologically discernable interstitial pneumonitis. The elevated levels of TNF-alpha and IL-1alpha have been found to correlate with immunohistochemical staining of the bronchiolar epithelium and predominantly of inflammatory cells.

CONCLUSIONS

Our data provide evidence that the increased expression of pro-inflammatory cytokines and the induction of a cytokine-triggered inflammatory response may be a determinant of the observed elevated lung toxicity after concurrent treatment with gemcitabine and thoracic irradiation.

Unexpected toxicity following use of gemcitabine as a radiosensitizer in head and neck carcinomas: a veterinary radiation therapy oncology group pilot study

Gemcitabine (2',2'-difluorodeoxycytidine) was given intravenously twice weekly to 10 cats with oral squamous cell carcinoma and 15 dogs with nasal carcinoma undergoing radiotherapy as a radiosensitizing agent. The average total radiation dose was 50 Gy for dogs and 54 Gy for cats given Monday-Friday (planned dose of 54 and 57 Gy, respectively). Dogs received an average of five doses of gemcitabine beginning at 50 mg/m2, and cats received an average of five doses of gemcitabine beginning at 25 mg/m2. Twelve of 15 dogs and five of 10 cats required chemotherapy dose reduction or postponement because of hematologic or normal tissue toxicity. The results herein do not support the use of gemcitabine at the studied dose and schedule, as significant hematologic and local tissue toxicity was observed in the studied patients. Pharmacokinetic data are necessary to best define the efficacy and optimal dose and schedule of gemcitabine in combination with traditional radiotherapy.

Role of cell cycle in mediating sensitivity to radiotherapy

Multiple pathways are involved in maintaining the genetic integrity of a cell after its exposure to ionizing radiation. Although repair mechanisms such as homologous recombination and nonhomologous end-joining are important mammalian responses to double-strand DNA damage, cell cycle regulation is perhaps the most important determinant of ionizing radiation sensitivity. A common cellular response to DNA-damaging agents is the activation of cell cycle checkpoints. The DNA damage induced by ionizing radiation initiates signals that can ultimately activate either temporary checkpoints that permit time for genetic repair or irreversible growth arrest that results in cell death (necrosis or apoptosis). Such checkpoint activation constitutes an integrated response that involves sensor (RAD, BRCA, NBS1), transducer (ATM, CHK), and effector (p53, p21, CDK) genes. One of the key proteins in the checkpoint pathways is the tumor suppressor gene p53, which coordinates DNA repair with cell cycle progression and apoptosis. Specifically, in addition to other mediators of the checkpoint response (CHK kinases, p21), p53 mediates the two major DNA damage-dependent cellular checkpoints, one at the G(1)-S transition and the other at the G(2)-M transition, although the influence on the former process is more direct and significant. The cell cycle phase also determines a cell's relative radiosensitivity, with cells being most radiosensitive in the G(2)-M phase, less sensitive in the G(1) phase, and least sensitive during the latter part of the S phase. This understanding has, therefore, led to the realization that one way in which chemotherapy and fractionated radiotherapy may work better is by partial synchronization of cells in the most radiosensitive phase of the cell cycle. We describe how cell cycle and DNA damage checkpoint control relates to exposure to ionizing radiation.

Dysphagia following chemoradiation for locally advanced head and neck cancer

BACKGROUND

To assess the prevalence, severity and morbidity of dysphagia following concurrent chemoradiation for head and neck cancer.

PATIENTS AND METHODS

Patients who underwent chemotherapy and radiation for head and neck malignancies were evaluated for their ability to resume oral feeding following treatment. Modified barium swallow (MBS) studies were performed if the patients complained of dysphagia or if there was clinical suspicion of aspiration. The severity of dysphagia was graded on a scale of 1-7. If significant abnormalities were found, swallowing studies were repeated until resolution of dysphagia.

RESULTS

Between March 1999 and May 2002, 55 patients with locally advanced head and neck cancer underwent concurrent chemotherapy and radiation. Aspiration pneumonia was observed in eight patients, three during treatment and five following treatment. Five patients died from pneumonia. Two patients developed respiratory failure requiring intubation as a complication of pneumonia. At a median follow-up of 17 months (range 6-48 months), 25 patients (45%) developed severe dysphagia requiring prolonged tube feedings for more than 3 months (22 patients) or repeated dilatations (three patients). Among 33 patients who underwent MBS following treatment, 12 patients (36%) had silent aspiration (grade 6-7 dysphagia). Thirteen patients (39%) developed grade 4-5 dysphagia which required prolonged enteral nutritional support to supplement their oral intake. Most patients had severe weight loss (0-21 kg) during treatment, likely due in part to mucositis in the orodigestive tube.

CONCLUSIONS

Dysphagia is a common, debilitating and potentially life-threatening sequela of concurrent chemoradiation for head and neck malignancy. Physicians should be aware that the clinical manifestations of aspiration may be unreliable and insidious, because of the depressed cough reflex. Modified and traditional barium swallows should be performed following treatment to assess the safety of oral feeding and the structural integrity of the pharynx and esophagus. Patients with severe dysphagia may benefit from rehabilitation. Tube feeding should be continued for those with aspiration.

Cisplatin enhances the cytotoxicity of fast neutrons in a murine lymphoma cell line

The utilization of high linear energy transfer (LET) radiations, such as fast neutrons or carbon ions (hadrontherapy), offers promising perspectives in radiotherapy. While it is well known that by combining radiotherapy and chemotherapy, important therapeutic advantages can be obtained to cure cancer, there have been, so far, very few investigations on the effects of treatments combining an irradiation with high-LET particles and cancer drugs. The present study was therefore undertaken to examine the effects of exposure to 65 MeV fast neutrons combined with cisplatin in a murine T cell lymphoma (RDM4) in vitro. The cells were irradiated at doses ranging from 2 to 8 Gy without or with addition of cisplatin shortly before the irradiation, at concentrations between 0.3 and 12.5 µM. These treatments were applied concomitantly. Proliferation and apoptosis were assessed at different time intervals thereafter. The combination of irradiation with cisplatin was found to be more cytotoxic than either treatment alone. Furthermore, the cytotoxicity induced by this cotreatment resulted not only from apoptosis but also from other forms of cell death.Key words: apoptosis, cancer cells, fast neutrons, cisplatin.