***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE A subset of head and neck cancers is associated with the human papillomavirus ( HPV ) . Viral infection is closely correlated with expression of p16(INK4A ) in these tumors . We evaluated  p16(INK4A )  as a prognostic marker of treatment response and survival in a well-defined and prospect ively collected cohort of patients treated solely with conventional radiotherapy in the Danish Head and Neck Cancer Group ( DAHANCA ) 5 trial . PATIENTS AND METHODS Immunohistochemical expression of p16(INK4A ) was analyzed in pretreatment paraffin-embedded tumor blocks from 156 patients treated with conventional primary radiotherapy alone .  The influence of p16(INK4A ) status on locoregional tumor control , disease-specific survival , and overall survival after radiotherapy  was evaluated . RESULTS p16(INK4A ) positivity was found in 35 tumors ( 22 % ) . Tumor-positivity for p16(INK4A ) was significantly correlated with improved locoregional tumor control ( 5-year actuarial values 58 % v 28 % ; P = .0005 ) , improved disease-specific survival ( 72 % v 34 % ; P = .0006 ) , and improved overall survival ( 62 % v 26 % ; P = .0003 ) . In multivariate analysis , p16(INK4A ) remained a strong independent prognostic factor for locoregional failure ( hazard ratio [ HR ] , 0.35 ; 95 % CI , 0.19 to 0.64 ) , disease-specific death ( HR , 0.36 ; 95 % CI , 0.20 to 0.64 ) , and overall death ( HR , 0.44 ; 95 % CI , 0.28 to 0.68 ) . CONCLUSION Expression of p16(INK4A ) has a major impact on treatment response and survival in patients with head and neck cancer treated with conventional radiotherapy The objective of this study was to develop a prospect ively applicable method for classifying comorbid conditions which might alter the risk of mortality for use in longitudinal studies . A weighted index that takes into account the number and the seriousness of comorbid disease was developed in a cohort of 559 medical patients . The 1-yr mortality rates for the different scores were : " 0 " , 12 % ( 181 ) ; " 1 - 2 " , 26 % ( 225 ) ; " 3 - 4 " , 52 % ( 71 ) ; and " greater than or equal to 5 " , 85 % ( 82 ) . The index was tested for its ability to predict risk of death from comorbid disease in the second cohort of 685 patients during a 10-yr follow-up . The percent of patients who died of comorbid disease for the different scores were : " 0 " , 8 % ( 588 ) ; " 1 " , 25 % ( 54 ) ; " 2 " , 48 % ( 25 ) ; " greater than or equal to 3 " , 59 % ( 18 ) . With each increased level of the comorbidity index , there were stepwise increases in the cumulative mortality attributable to comorbid disease ( log rank chi 2 = 165 ; p less than 0.0001 ) . In this longer follow-up , age was also a predictor of mortality ( p less than 0.001 ) . The new index performed similarly to a previous system devised by Kaplan and Feinstein . The method of classifying comorbidity provides a simple , readily applicable and valid method of estimating risk of death from comorbid disease for use in longitudinal studies . Further work in larger population s is still required to refine the approach because the number of patients with any given condition in this study was relatively small CONTEXT Patients with cancer often have other medical ailments , referred to as comorbidity . Comorbidity may impact treatment decision-making , prognosis , and quality of care assessment . OBJECTIVE To assess whether comorbidity information can provide important prognostic information in a hospital-based cancer registry . DESIGN , SETTING , AND PARTICIPANTS An observational prospect i ve cohort study using comorbidity data collected by trained hospital-based cancer registrars . Comorbidity was obtained through medical record review using the Adult Comorbidity Evaluation 27 , a vali date d chart-based comorbidity instrument . A total of 17,712 patients receiving care between January 1 , 1995 , and January 31 , 2001 , for the primary diagnosis of new cancer of the prostate , lung ( nonsmall cell ) , breast , digestive system , gynecological , urinary system , or head and neck were included . MAIN OUTCOME MEASURE Duration in months of overall survival . RESULTS A total of 19,268 patients were included in the study ; median duration of follow-up was 31 months . Of these patients , 1556 ( 8.0 % ) were excluded due to missing or unknown data . Severity of comorbidity strongly influenced survival in a dose-dependent fashion and the impact of comorbidity was independent of cancer stage . Compared with patients without comorbidity , the adjusted hazard ratio associated with mild comorbidity was 1.21 ( 95 % confidence interval [ CI ] , 1.13 - 1.30 ) , moderate comorbidity was 1.86 ( 95 % CI , 1.73 - 2.00 ) , and severe comorbidity was 2.56 ( 95 % CI , 2.35 - 2.81 ) . Adjusted Kaplan-Meier survival curves revealed that at any point in time the patients with more severe levels of comorbidity had worse survival ( partial chi2(3 ) due to comorbidity , 523.54 ; P<.001 ) . Model discrimination ranged from 0.71 for head and neck to 0.86 for prostate cancers . CONCLUSIONS Comorbidity is an important independent prognostic factor for patients with cancer . The inclusion of comorbidity in hospital-based cancer registries will increase the value and use of observational research BACKGROUND The best treatment for advanced head and neck cancer remains unclear . Proponents of various therapeutic regimens continue to debate this issue with inconclusive and frequently biased data and with carefully selected patients in controlled trials to support their approach . To assess the outcome of patients in a real-world situation , we review ed a prospect ively maintained data base of patients with head and neck cancer . METHODS We review ed data from 591 consecutive patients with stage III or IV squamous cell carcinoma treated at a university medical center from January 1 , 1992 , through December 31 , 2000 , and analyzed survival using the Kaplan-Meier method . RESULTS Overall survival was 48 % , 40 % , and 33 % at 2 , 3 , and 5 years , respectively . We found a significant death rate due to comorbid conditions . The primary tumor was treated surgically ( with or without postoperative radiation ) in 363 patients , with survival of 55 % , 46 % , and 38 % at 2 , 3 , and 5 years , respectively . The tumor was treated primarily with radiation therapy ( with or without neck dissection ) in 193 patients , with survival of 40 % , 33 % , and 27 % at 2 , 3 , and 5 years , respectively . Overall survival in the surgical group was better than in the radiation group ( P = .005 , log-rank chi 2 test ) . The radiation group was subcategorized into those who underwent radiation because the tumor was so advanced as to be unresectable ( n = 86 ) , because they were too unhealthy to undergo radical surgery ( n = 23 ) , and because they elected radiation therapy ( n = 84 ) . Survival in each of the radiation subgroups at 2 , 3 , and 5 years was 28 % , 20 % , and 14 % , respectively , in the unresectable group ; 34 % , 22 % , and 11 % , respectively , in the unhealthy group ; and 57 % , 53 % , and 46 % , respectively , in the elective group . Thus , survival in the elective radiation subgroup exceeded that of the surgical group , although not statistically . We analyzed data regarding T and N stages , age , race , surgical margin status , postoperative radiation therapy , chemotherapy , radiation dose , and tumor site . Multivariate analysis of the surgical group and elective radiation subgroup showed that N stage and age were the strongest predictors of survival and that the method of therapy was not significant . For oropharyngeal cancer , the patients in the elective radiation subgroup did as well as the surgical group . Many patients were noncompliant with portions of therapy , with a result ing reduction in survival . CONCLUSIONS The data demonstrate the value of analyzing a consecutive series of patients with advanced head and neck cancer . By including patients with comorbidities and those who are noncompliant , we determined a realistic expectation of patient outcomes . By including all patients , the data dramatically show the impact of age , comorbidity , and advanced stage on survival . The survival of patients who underwent elective radiation therapy in combination with neck dissection was similar to that of patients treated with primary tumor surgery . This was particularly true for oropharyngeal tumors . The site and stage-specific data are useful in counseling patients with advanced head and neck cancer regarding treatment choices BACKGROUND In head and neck cancer , the locoregional failure of patients with positive margins , vascular or perineural invasion , and extracapsular spread is high and results in poor survival . OBJECTIVE To assess the effect of adjuvant chemoradiotherapy in improving treatment outcomes among older patients with head and neck cancer . METHODS Forty patients undergoing radical surgery ( median age , 73.5 years [ range , 70 - 78 years ] ) were enrolled ( 35 men and 5 women ; Eastern Cooperative Oncology Group performance status , grade 0 - 2 ) . Disease sites included the oral cavity ( 10 patients ) , oropharynx ( 12 patients ) , hypopharynx ( 8 patients ) , and larynx ( 10 patients ) ; pathological TNM classifications included T1 N2 ( 8 patients ) , T2 N1 - 2 ( 12 patients ) , T3 N0 - 2 ( 8 patients ) , and T4 N0 - 2 ( 12 patients ) , with the following poor prognostic factors : positive margins ( 6 patients ) , vascular invasion ( 14 patients ) , neural invasion ( 16 patients ) , and extracapsular spread ( 26 patients ) . All patients were treated with carboplatin ( 30 mg/m2 on days 1 - 5 of weeks 1 , 3 , and 5 ) concomitant with radiotherapy ( 54.0 Gy to all risk volumes plus 10.0 Gy to high-risk volumes ; 5 daily fractions of 1.8 Gy each per week ) . RESULTS No grade 4 toxicity was observed . Grade 3 toxicity included mucositis ( 10 patients ) , neutropenia ( 6 patients ) , dermatitis ( 2 patients ) , and thrombocytopenia ( 1 patient ) . The radiotherapy dose administered was 52.0 Gy to all risk volumes plus 10.0 Gy to high-risk volumes . Thirty-two patients ( 80 % ) received 3 cycles , 6 ( 15 % ) received 2 cycles , and 2 ( 5 % ) received 1 cycle . Three-year survival was as follows : disease-free survival , 58 % ; overall survival , 64 % ; and local control , 79 % . CONCLUSIONS Adjuvant chemoradiotherapy may be successful in fit older patients . The results of adjuvant chemoradiotherapy were better than those observed in a comparable group treated with radiotherapy alone and were similar to those observed in a younger group with the same poor prognostic factors treated with adjuvant carboplatin plus radiotherapy The elderly are often treated less aggressively in an attempt to preserve their quality of life with regards to toxicity . However , there are few data regarding the acute and late toxicity of radiotherapy ( RT ) in elderly patients . From February 1980 to March 1995 , 1589 patients with head and neck cancers who enrolled in EORTC trials received RT and were available for analysis on RT toxicity . Patients over 65 years of age were in excess of 20 % . Data regarding age and acute objective mucosal reactions were available for 1307 patients and 1288 had toxicity > or = grade 1 . Age and acute functional mucosal reactions were registered for 838 patients and 824 patients had toxicity > or = grade 1 . Bodyweight alteration during treatment was available in 1252 patients ; it increased in 153 patients and decreased in 1099 patients . Late toxicities were examined only if they occurred before an eventual tumour failure in order to avoid confusion between effects of first- and second-line treatments . 749 patients were available for analysis of which 646 had late toxicity grade > or = 1 . Survival and toxicity were examined in different age ranges from 50 to 75 years and over . There was no significant difference in survival between each age group . A trend test was performed to assess any correlation between age and the acute occurring toxicity . There was no significant difference in acute objective mucosal reactions ( P = 0.1 ) and in weight loss > 10 % ( P = 0.441 ) . In contrast , older patients had more severe ( grade 3 and 4 ) functional acute toxicity ( P < 0.001 ) than younger patients . We evaluated the probability of late toxicity 
    Output:
    
The prevalence of comorbidity increased with age and the presence of comorbidity influenced treatment and treatment selection .
Furthermore , comorbidity was associated with lower socio economic status and increased the risk of early retirement after treatment .
Increasing comorbidity-score was associated with increased risk of death .
Comorbidity is important in HNSCC and significantly impacts on overall survival .