A role for COX2-derived PGE2 and PGE2-receptor subtypes in head and neck squamous carcinoma cell proliferation

The overexpression of cyclooxygenase (COX)-2 is a frequent event in squamous cell carcinomas of the head and neck (HNSCC), and non-steroidal anti-inflammatory drugs, which are potent inhibitors of COX-1 and COX-2, exert chemopreventive effects on HNSCC cancer development. COX-2 promotes the release of the pro-inflammatory mediator prostaglandin E2 (PGE2), which acts on its cell surface G protein-coupled receptors EP1, EP2, EP3, and EP4. Here, we investigated the role of PGE2 and its receptors in cellular proliferation in HNSCC. The expression of COX-2 and EP1-4 was examined in immortalized oral epithelial cells and in a representative panel of HNSCC cell lines, and based on these data EP1-EP3 and COX-2 expression were evaluated by immunohistochemistry in a large clinical sample collection using HNSCC tissue microarrays. The ability of selective COX-2 inhibition to block PGE2 secretion was measured by ELISA specific assays. The effects of PGE2 on cell proliferation were evaluated using PGE2, its stable analog, and EP2 and EP3-specific synthetic agonists. The results presented here show that HNSCC tumoral lesions and their derived cell lines constitutively express COX-2 and the EP1, EP2 and EP3 receptors for PGE2. HNSCC cells secrete PGE2, which can be suppressed by low concentrations of COX-2 selective inhibitors, without inhibiting cell proliferation. Exogenously added stable PGE2 and EP3-specific agonists induce DNA synthesis in all HNSCC cell lines tested. Overall, our study supports the emerging notion that PGE2 produced in the tumor microenvironment by the overexpression of COX-2 in tumoral and inflammatory cells may promote the growth of HNSCC cells in an autocrine and paracrine fashion by acting on PGE2 receptors that are widely expressed in most HNSCC cancer cells. In particular, our findings suggest that EP3 receptor may play a more prominent role in HNSCC cell growth promotion, thus providing a rationale for the future evaluation of this PGE2 receptor as a target for HNSCC prevention strategies.     

Human papillomavirus-associated head and neck squamous cell carcinoma: mounting evidence for an etiologic role for human papillomavirus in a subset of head and neck cancers

There is increasing molecular and epidemiologic evidence that human papillomavirus (HPV) is associated with a distinct subset of head and neck squamous cell carcinomas. The strength and consistency of HPV DNA presence in oropharyngeal cancers bolster the argument that this association is likely causal. HPV-positive tonsillar cancer in particular is emerging as a specific disease entity with distinct molecular, pathologic, and clinical characteristics. Recent data suggest that the incidence of tonsillar carcinoma in the United States is increasing, despite a decline in tobacco use, supporting the existence of other important risk factors such as HPV infection. Individuals with a history of an HPV-associated anogenital cancer and HIV-infected men are at increased risk for tonsillar carcinoma. This review focuses on the recent literature (since 1998) investigating the relationship between HPV and head and neck cancer development, using the current paradigm for causal inference in epidemiologic research attributed to Sir A. Bradford Hill. Data examining the association of HPV with pathogenesis of head and neck squamous cell carcinoma before 1999 were previously reviewed in this journal.     

Cyclooxygenase-2-derived prostaglandin E2 activates beta-catenin in human cholangiocarcinoma cells: evidence for inhibition of these signaling pathways by omega 3 polyunsaturated fatty acids

Cholangiocarcinoma is a highly malignant neoplasm of the biliary tree. It has a high rate of mortality, and currently, there is no effective chemoprevention and treatment. This study was designed to investigate the potential effect of omega 3 polyunsaturated fatty acids (omega 3-PUFA) on human cholangiocarcinoma cell growth and to determine their mechanisms of actions. Treatment of three human cholangiocarcinoma cells (CCLP1, HuCCT1, SG231) with two omega 3-PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for 12 to 72 h resulted in a dose- and time-dependent inhibition of cell growth; in contrast, arachidonic acid, a omega 6-PUFA, had no significant effect. The omega 3-PUFA effect is due to the induction of apoptosis, given that DHA induced the cleaved form of PARP, caspase-3, and caspase-9. DHA and EPA treatment caused dephosphorylation (and hence, the activation) of glycogen synthase kinase-3beta (GSK-3beta) with a decline of beta-catenin protein. Accordingly, DHA treatment also decreased the beta-catenin-mediated T cell factor/lymphoid enhancer factor (TCF/LEF) reporter activity, and inhibited the expression of c-Met, a beta-catenin-controlled downstream gene implicated in cholangiocarcinogenesis. The GSK-3beta inhibitor, SB216763, partially prevented DHA-induced reduction of beta-catenin protein and TCF/LEF reporter activity, and restored cell growth, suggesting the involvement of GSK-3beta dephosphorylation in omega 3-PUFA-induced beta-catenin degradation. In parallel, DHA treatment also induced the formation of the beta-catenin/Axin/GSK-3beta binding complex, further leading to beta-catenin degradation. Moreover, DHA inhibited the expression of cyclooxygenase-2 (COX-2) and enhanced the expression of 15-hydroxyprostaglandin dehydrogenase, a physiologic COX-2 antagonist, in human cholangiocarcinoma cells. These findings suggest that omega 3-PUFAs block cholangiocarcinoma cell growth at least in part through inhibition of Wnt/beta-catenin and COX-2 signaling pathways. Thus, utilization of omega 3-PUFAs may represent an effective and safe therapeutic approach for the chemoprevention and treatment of human cholangiocarcinoma.     

Modulation of CXCR3 ligand secretion by prostaglandin E2 and cyclooxygenase inhibitors in human breast cancer

Introduction

In murine breast cancer models, the two interferon-gamma (IFN-γ) inducible chemokines and CXC-chemokine receptor 3 (CXCR3) receptor ligands, monokine induced by γ-interferon (CXCL9) and interferon-γ-inducible protein-10 (CXCL10) impair tumor growth and metastasis formation through recruitment of natural killer (NK) cells and tumor-suppressive T lymphocytes. In human breast cancer, CXCL9 mRNA overexpression correlates with the number of tumor infiltrating lymphocytes and predicts response to different chemotherapeutic regimens. Raising the intratumoral CXCR3 ligand concentration is therefore a possible way to enhance immune intervention in breast cancer. Little is known, however, about expression levels and regulation of these chemokines in human breast cancer. Since the inhibition of cyclooxygenases (COX) has been shown to reduce tumor growth and incidence of metastases in a lymphocytic and IFN-γ dependent manner, we argued that COX isoenzymes are a pharmacologic target to increase intratumoral CXCR3 ligand concentration in human breast cancer.

Methods

CXCL9 was visualized in breast cancer specimens by immunohistochemistry, expression levels of CXCL9 and cyclooxygenases were determined by ELISA and western blotting, respectively. For regulation studies, Michigan Cancer Foundation-7 (MCF-7) and M.D. Anderson - Metastatic Breast 231 (MDA-MB 231) breast cancer cells were stimulated with IFN-γ with or without prostaglandin E₂ (PGE₂) or COX inhibitors (indomethacin, acetylsalicylic acid (ASA), celecoxib). CXCR3 ligand release from cells was measured by ELISA.

Results

Within the tumor microenvironment, cancer cells are the major source of CXCL9. PGE₂ impairs IFN-γ mediated CXCL9 and CXCL10 release from MCF-7 and MDA-MB 231 cells, and inhibition of endogenous cyclooxygenases by indomethacin or ASA correspondingly increases this secretion. Otherwise, high concentrations of the Cyclooxygenase-2 (COX-2) specific antagonist celecoxib have opposite effects and impair CXCL9 and CXCL10 release. In human breast cancer tissue specimens there is an inverse correlation between COX-2 overexpression and CXCL9 concentration, suggesting that the observed in vitro effects are of importance in vivo as well.

Conclusions

Suppressing endogenous PGE₂ synthesis by cyclooxygenase inhibition increases CXCL9 and CXCL10 release from breast cancer cells and is therefore a pharmacologic candidate to enhance intratumoral immune infiltration. Yet, to this end the unselective COX inhibitors ASA and indomethacin seem preferable to celecoxib that at higher concentrations reduces CXCR3 ligand release most probably due to COX independent mechanisms.     

A possible role for human papillomaviruses in head and neck cancer

Human papillomaviruses (HPVs) cause benign tumors in the respiratory tract. Mounting evidence suggests that they also play a role in the etiology of a subset of head and neck cancers. Carcinomas in patients with a history of recurrent respiratory papillomatosis clearly are caused by persisting HPV interacting with one or more carcinogenic agents. Verrucous carcinomas of the oral cavity, tonsillar and tongue carcinomas are strongly linked with HPVs, based on molecular epidemiologic data. Tonsillar cancers have been shown to express HPV RNA, presumed necessary to induce and maintain a carcinoma, supporting a viral etiology. This paper reviews the molecular and cellular basis for considering HPVs as causttive agents of cancer, and reviews the literature that considers the possible role of HPVs in head and neck cancer.     

The prostaglandin E2 receptor EP2 is required for cyclooxygenase 2-mediated mammary hyperplasia

Expression of cyclooxygenase 2 (COX-2) in breast cancer correlates with poor prognosis, and COX-2 enzyme inhibitors reduce breast cancer incidence in humans. We recently showed that COX-2 overexpression in the mammary gland of transgenic mice induced mammary cancer. Because prostaglandin E2 (PGE2) is the major eicosanoid and because the EP2 subtype of the PGE2 receptor is highly expressed in the mammary tumors, we tested if this G protein-coupled receptor is required for tumorigenesis. We crossed the MMTV-COX-2 transgenic mice with Ep2-/- mice and studied tumor development in bigenic mice. Lack of EP2 receptor strongly suppressed COX-2-induced effects such as precocious development of the mammary gland in virgins and the development of mammary hyperplasia in multiparous female mice. Interestingly, the expression of amphiregulin, a potent mammary epithelial cell growth factor was down regulated in mammary glands of Ep2-/- mice. Total cyclic AMP (cAMP) levels were reduced in Ep2-/- mammary glands suggesting that PGE2 signaling via the EP2 receptor activates the Gs/cAMP/protein kinase A pathway. In mammary tumor cell lines, expression of the EP2 receptor followed by treatment with CAY10399, an EP2-specific agonist, strongly induced amphiregulin mRNA levels in a protein kinase A-dependent manner. These data suggest that PGE2 signaling via the EP2 receptor in mammary epithelial cells regulate mammary gland hyperplasia by the cAMP-dependent induction of amphiregulin. Inhibition of the EP2 pathway in the mammary gland may be a novel approach in the prevention and/or treatment of mammary cancer.     

Evidence for a clonal origin of head and neck tumors

According to the inactive-X hypothesis only one of the two genes at X-linked loci is active in somatic cells of females. Thus, in women heterozygous for the A and B genes at the X-linked glucose-6-phosphate dehydrogenase (G-6-PD) locus, single cells or clones of cells show either type A or type B enzyme. Similarly, pure tumors with a clonal origin arising in G-6-PD heterozygotes exhibit only type A or B enzyme, while those with multiple cell origin may show both A and B enzymes. The G-6-PD types of normal and neoplastic tissue were determined in 28 patients with tumors of the head and neck who were heterozygous at the G-6-PD locus. Normal tissues contained two enzyme types. Only one tumor from the 11 patients with anaplastic carcinoma of the nasopharynx was pure enough (i. e., with a relatively small number of non-tumor cells) to allow firm conclusions. This tumor had a single enzyme phenotype and this is compatible with a clonal origin. Single enzyme phenotypes were also found in the two benign tumors and in single cases of plasmacytoma, melanoma, neuroblastoma and reticulum-cell sarcoma. The data from three cases of carcinoma of the palate and from single cases of carcinoma of an ectopic salivary gland and the thyroid gland respectively are also compatible with a clonal origin. Only one relatively pure tumor had a double enzyme phenotype, but even in this case, the evidence for a multiple cell origin is not convincing. Thus, the data in this and other studies suggest that at least one step in the development of most human neoplasms occurs in a single cell, i. e., the mature tumors have a clonal origin.     

Gene expression changes during repopulation in a head and neck cancer xenograft

Background/purposeTo investigate temporal changes in global gene expression and pathways involved in the response to irradiation during phases of growth inhibition, recovery and repopulation in a human head and neck squamous cell cancer (HNSCC) xenograft.Methods and materialsLow passage head and neck squamous cancer cells (UT-14-SCC) were injected into the flanks of female nu/nu mice to generate xenografts. After tumors reached a size of 500 mm³, they were treated with either sham RT or 15 Gy in one fraction. At different time points, days 0, 3, and 10 for controls and days 4, 7, 12, and 21 after irradiation, the tumors were harvested for global gene expression analysis and pathway analysis.ResultsThe tumors showed growth inhibition through days 4–7 and began the transition to regrowth around the day 12 time point. When comparing the pooled controls to each day of treatment, there were 22, 119, 125, and 25 differentially expressed genes on days 4, 7, 12, and 21 respectively using a p ⩽ 0.01 and a 2-fold cut-off. Gene Ontology (GO), gene set enrichment analysis (GSEA) and sub-network enrichment analysis (SNEA) identified different biological processes, cell process pathways and expression targets to be active on each time point after irradiation. An important observation was that the molecular events on day 12 which represented the transition from growth inhibition to regrowth identified interferon and cytokine related genes and signaling pathways as the most prominent.ConclusionThe findings in this study compliment research which has identified components of interferon-related signaling pathways to be involved in radioresistance. Further work will be required to understand the significance of these genes in both radioresistance and treatment response leading to new therapeutic strategies and prognostic tools.     

Isolation of a peptide for targeted drug delivery into human head and neck solid tumors

Lack of tumor specificity remains a major problem with chemotherapies in that side effects prevent the delivery of dosages of drugs that are required to eliminate tumors. In this report, we describe the isolation of a 12-mer peptide (HN-1), with approximately 1% of the mass of typical antibodies, that meets several criteria for targeted drug delivery into a solid tumor. First, internalization of HN-1 by human head and neck squamous cell cancer (HNSCC) cells suggests that HN-1 is capable of translocating drugs across cell membranes. Second, HN-1 appears to be HNSCC-specific, given its reduced uptake by nonmalignant human oral keratinocytes and other types of human cells, its preferential binding to primary HNSCC, and its localization to HNSCC-derived xenografts. Third, the presence of HN-1 within HNSCC xenografts suggests that it is capable of penetrating tumor tissues. Our results establish the utility of tumor-specific peptides for targeted drug delivery into solid tumors.     

The evolving role of surgery in the management of head and neck tumors

PURPOSE OF REVIEW: This paper reviews recent surgical contributions to the multidisciplinary approach to head and neck cancer treatment as well as published data on pertinent questions in the field. RECENT FINDINGS: The role of surgery in the strategy of organ preservation via chemoradiation, including treatments of complications and locoregional recurrences, such as when N1-N3 necks should be operated on and the role of CT and positron emission tomography (PET) scanning. Also covered are the role of sentinel lymph node biopsy for the detection of occult micrometastases in the N0 neck and the value of fluorodeoxyglucose PET scanning combined with the former. Transoral laser surgery for tumors of the larynx or of the hypopharynx is discussed, as is a new technique of reconstruction involving the anterolateral thigh free flap. Also included are quality of swallowing after resections and reconstruction of the oral cavity and orpharyngeal tumors. SUMMARY: Surgery must define its role in the multidisciplinary treatment of advanced cancers, which currently often favors (chemo)radiotherapy protocols. Organ sparing by transoral laser surgery for laryngeal and hypopharyngeal cancer has established itself within our armamentarium and its exact role will be further refined. Larger and well-executed studies on sentinel lymph node biopsy in the clinically negative neck are needed before this procedure can be implemented in our routines. The latest addition, the anterolateral thigh flap, to further decrease patients' morbidity is unlikely to completely replace the currently favored radial forearm flap in soft tissue replacement of the head and neck. Outcome analysis, including swallowing, is a major step that surgeons should further investigate.     

Microsomal prostaglandin E synthase-1 is overexpressed in head and neck squamous cell carcinoma.

Elevated levels of prostaglandin E(2) (PGE(2)) occur in head and neck squamous cell carcinoma (HNSCC) and have been associated with a poor prognosis. Recently, an inducible microsomal prostaglandin E synthase-1 (mPGES) was identified. This enzyme converts the cyclooxygenase product prostaglandin H(2) (PGH(2)) to PGE(2). Given the apparent significance of PGE(2) in carcinogenesis, it is important to elucidate the mechanisms that account for increased amounts of PGE(2) in HNSCC. By immunoblot analysis, mPGES was overexpressed in 11 of 14 (79%) cases of HNSCC compared with adjacent normal tissue. Immunohistochemistry localized mPGES expression to neoplastic epithelial cells. Cell culture was used to determine whether cellular transformation was associated with increased amounts of mPGES. Levels of mPGES protein and mRNA were markedly elevated in HNSCC cell lines (1483 and Ca9-22) versus a nontumorigenic oral epithelial cell line (MSK-Leuk1). Interestingly, treatment of MSK-Leuk1 cells with PGE(2) caused both dose- and time-dependent stimulation of cell growth. Each of the four known receptors for PGE(2) (E-prostanoid receptor subtypes 1-4) was detected in head and neck squamous mucosa. Taken together, these results suggest that overexpression of mPGES contributes to the increased levels of PGE(2) found in HNSCC. Additional studies will be needed to determine whether this enzyme is a bona fide target for anticancer therapy.     

Ototoxicity after radiotherapy for head and neck tumors

PURPOSE: To investigate the incidence of radiation-induced ototoxicity according to the total dose delivered to specific parts of the auditory system, fractionation, and chemotherapy. METHODS AND MATERIALS: Records of 325 patients treated for primary extracranial head and neck tumors with curative intent who received radiotherapy between 1964 and 2000 (median follow-up, 5.4 years) were retrospectively reviewed. Reconstructions of the treatment plans were generated to estimate the doses received by components of the auditory system. RESULTS: Radiotherapy-induced morbidity developed in 41.8% of patients (external ear, 33.2%; middle ear, 28.6%; and inner ear, 26.8%). Univariate/multivariate analyses indicate that total dose received by parts of the auditory system seem to be significant, though fractionation and chemoradiation may contribute to the incidence of ototoxicities. Sensorineural hearing loss (SNHL) was observed in 49 patients (15.1%). Univariate and multivariate analyses indicated that age (p = 0.0177 and p = 0.005) and dose to cochlea (p < 0.0001 and p < 0.0001) were significant, and chemoradiation (p = 0.0281 and p = 0.006) may increase the incidence of SNHL. Five-year and 10-year actuarial risk of clinically overt SNHL increased to 37% (p > 0.0001) above doses of 60.5 Gy compared to 3% at doses below 60.5 Gy. For patients treated with adjuvant chemotherapy, clinically overt SNHL increased to 30% compared to 18% in the no-chemotherapy group at 10 years (p = 0.0281). CONCLUSION: Radiotherapy toxicity was observed in all parts of the auditory system with median doses for incidence varying between 60 Gy to 66 Gy. Total dose to organ seems to be a significant factor though fractionation and chemo-radiation may contribute to ototoxicities.     

Radiation techniques for head and neck tumors.

PURPOSE: A technique that combines some advantages of conforming techniques for advanced oro- and hypopharyngeal carcinomas is proposed. The aim is to increase the dose homogeneity in the target volume relative to lateral opposed fields. METHODS AND MATERIALS: This publication compares conforming radiation techniques based on standard equipment, standard linear accelerator setup and commercially available planning software with lateral opposed fields. More advanced conformal techniques reported in the literature are taken into account in a semi-quantitative manner. Our standard method uses an arc rotation, sparing the spinal cord. In contrast to earlier methods of this type, the resulting dose deficit in the vicinity of the spine is compensated by static lateral wedged fields. Dose distributions for 25 consecutive patients were planned. RESULTS: The conforming techniques were found to produce more homogeneous dose distributions than lateral opposed fields. In the planning target volume (PTV) (mean: 940 cm(3)) a standard deviation of dose of 4.6% was achieved. Ninety-five percent of the PTV were enclosed by the 90% isodose. The maximal spinal cord dose was limited to 45 Gy. The dose distributions of these techniques could compete with literature data on advanced techniques (the published dose-volume histogram (DVHs) of PTVs were evaluated).At the linear accelerator time for realization took 14 min on average. The planning time is 1-4 h (mean: less than 2 h). CONCLUSION: A rotational technique applicable with standard equipment is presented. Dose coverage of target volumes is improved, while the spinal cord is spared.     

Population-based evidence of increased survival in human papillomavirus-related head and neck cancer

BackgroundEvidence from clinical, population-based and molecular studies has shown that human papillomavirus (HPV) infection can be a causal risk factor for a subset of head and neck squamous cell carcinomas (HNSCC). It is proposed that HPV-associated oropharyngeal cancer is a new disease entity that requires treatment and prevention strategies distinct from present recommendations.MethodsIn our population-based study we estimated incidence and survival trends in 8270 patients with HPV-related HNSCC (HPV⁺HNSCC) and HPV-unrelated HNSCC (HPV^–HNSCC) in Norway over the past three decades.ResultsIn the period 1981–1995, patients with HPV⁺HNSCC had poorer survival than HPV^–HNSCC (adjusted hazard ratio (HR) 1.3, 95% confidence interval (CI): 1.14–1.44). By 1996–2007, survival had increased in both groups, but the increase was significantly greater among HPV⁺HNSCC patients (HR 0.57, 95% CI: 0.48–0.67). During the same period, incidence also increased, but only for HPV⁺HNSCCs. From 1981–1995 to 1996–2007, median age at diagnosis for HPV⁺HNSCC decreased from 63.2 to 59.8 years, while for HPV^–HNSCC median age at diagnosis of 66.6 years remained unchanged.ConclusionsWe demonstrate a population level improvement in survival among patients with oropharyngeal squamous cell cancers commonly related to infection with HPV. In contrast, patients with HNSCC not related to HPV only showed a modest improvement in survival in the period 1981–2007. A concomitant increase in incidence and survival was observed for HPV-related cancers only. This trend cannot be explained by changes in treatment, cancer registration nor screening, but is most likely due to an increased prevalence of HPV-positive tumours.     

Garcinol sensitizes human head and neck carcinoma to cisplatin in a xenograft mouse model despite downregulation of proliferative biomarkers

Platinum compounds such as cisplatin and carboplatin are frequently used as the first-line chemotherapy for the treatment of the head and neck squamous cell carcinoma (HNSCC). In the present study, we investigated whether garcinol, a polyisoprenylated benzophenone can chemosensitize HNSCC to cisplatin. We found that garcinol inhibited the viability of a panel of diverse HNSCC cell lines, enhanced the apoptotic effect of cisplatin, suppressed constitutive as well as cisplatin-induced NF-κB activation, and downregulated the expression of various oncogenic gene products (cyclin D1, Bcl-2, survivin and VEGF). In vivo study showed that administration of garcinol alone (0.5 mg/kg body weight, i.p. five times/week) significantly suppressed the growth of the tumor, and this effect was further increased by cisplatin. Both the markers of proliferation index (Ki-67) and microvessel density (CD31) were downregulated in tumor tissues by the combination of cisplatin and garcinol. The pharmacokinetic results of garcinol indicated that good systemic exposure was achievable after i.p. administration of garcinol at 0.5 mg/kg and 2 mg/kg with mean peak concentration (Cmax) of 1825.4 and 6635.7 nM in the mouse serum, respectively. Overall, our results suggest that garcinol can indeed potentiate the effects of cisplatin by negative regulation of various inflammatory and proliferative biomarkers.     

Lack of evidence for a role of chemotherapy in the routine management of locally advanced head and neck cancer

Numerous single-arm studies have shown that chemotherapy may produce a high rate of response and rapid shrinkage of tumor when used before radiation and/or surgery in patients with squamous-cell carcinoma of the head and neck. Despite this high rate of tumor response, randomized controlled trials do not indicate any consistent improvement in survival for patients receiving chemotherapy as compared with patients receiving local treatment alone. This population of patients often has poor performance status, and chemotherapy invariable adds some toxicity. Also, studies in animals suggest that some types of chemotherapy given before local radiation or surgery might increase the probability of distant metastases. Apart from pilot studies of feasibility, all future trials of chemotherapy should involve a randomized comparison with a group of patients receiving radiation and/or surgery alone. At present, chemotherapy has no place in the routine management of primary head and neck cancer.     

Optimization of uncomplicated control for head and neck tumors

Almost 200 patients have been treated for head and neck tumors at two different dose levels. Based on the clinically observed probabilities for tumor control and fatal normal tissue complications at the two dose levels, the dose giving maximum uncomplicated control has retrospectively been calculated and compared with the clinical data. A Poisson statistical model for control and complications has been used including a correlation parameter, delta, to describe the fraction of patients where control and complications are statistically independent. The clinically observed probability of uncomplicated tumor control, P+, is consistent with only a small fraction of the patients treated being statistically independent (delta = 0.2 or 20%). Customarily, 100% of the patients are assumed to be statistically independent with regard to tumor control and normal tissue complications. More precisely, the clinical data are consistent, with almost 20% of the patients being significantly more sensitive to radiation since they gain local tumor control but simultaneously suffer fatal complications. An even larger fraction of the patients (almost 30%) seemed to be more resistant to radiation, showing neither serious treatment complications nor control of the local tumor growth. It is suggested that if these patient groups could be identified by a predictive assay for the radiation sensitivity of their normal tissues and preferably also for their tumors, the uncomplicated tumor control could be increased by about 20%. This figure is based on the actuarial survival of the patients and has been corrected for the inevitable uncertainty in dose delivery. It is also pointed out that about 20% of the patients can never be saved by a predictive assay because of the considerable statistical variance associated with the Poisson process and the eradication of the last clonogenic tumor cell. Finally, note that the possible existence of radiation sensitive and resistant patient groups is consistent with known genetic deficiencies such as ataxia telangiectasia for the sensitive patients and the existence of repair efficient head and neck tumors that are unusually efficient in repairing double strand breaks. If such sensitive and resistant patient groups do exist, it should be sufficient to perform a predictive assay on normal tissues alone avoiding the often impossible task of sampling the most radiation resistant tumor cell line.