***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: Background Increasing clinical data supports a low α/β ratio for prostate adenocarcinoma , potentially lower than that of surrounding normal tissues . A hypofractionated , weekly radiation therapy ( RT ) schedule should result in improved tumour control , reduced acute toxicity , and similar or decreased late effects . We report the toxicity profile of such treatment . Material s and Methods We conducted a multi-institution phase I/II trial of three-dimensional conformal radiation therapy ( 3D-CRT )  for favourable-risk prostate cancer ( T1a-T2a , Gleason ≤ 6 and PSA < 10 ng/ml ) .  RT consisted of 45 Gy in nine 5 Gy fractions , once weekly . Primary end-points were feasibility and late gastrointestinal ( GI ) toxicity ( RTOG scale ) , while secondary end-points included acute GI toxicity , acute and late genitourinary ( GU ) toxicity , biochemical control , and survival . Results Between 2006 and 2008 , 80 patients were treated . No treatment interruptions occurred . The median follow-up is 33 months ( range : 20 - 51 ) . Maximal grade 1 , 2 , and 3 acute ( < 3 months ) GU toxicity was 29 % , 31 % and 5 % respectively ( no grade 4 ) . Acute GI grade 1 toxicity was reported in 30 % while grade 2 occurred in 14 % ( no grade 3 or 4 ) . Crude late grade ≥ 3 toxicity rates at 31 months were 2 % for both GU and GI toxicity . Cumulative late grade ≥ 3 GI toxicity at 3 years was 11 % . Two patients  had PSA failure according to the Phoenix definition . The three-year actuarial biochemical control rate is 97 % . Conclusions Weekly RT with 45 Gy in 9 fractions is feasible and results in comparable toxicity . Long term tumour control and survival remain to be assessed PURPOSE To compare the toxicity and efficacy of hypofractionated ( 62 Gy/20 fractions/5 weeks , 4 fractions per week ) vs. conventional fractionation radiotherapy ( 80 Gy/40 fractions/8 weeks ) in patients with high-risk prostate cancer . METHODS AND MATERIAL S From January 2003 to December 2007 , 168 patients were r and omized to receive either hypofractionated or conventional fractionated schedules of three-dimensional conformal radiotherapy to the prostate and seminal vesicles . All patients received a 9-month course of total and rogen deprivation ( TAD ) , and radiotherapy started 2 months thereafter . RESULTS The median ( range ) follow-up was 32 ( 8 - 66 ) and 35 ( 7 - 64 ) months in the hypofractionation and conventional fractionation arms , respectively . No difference was found for late toxicity between the two treatment groups , with 3-year Grade 2 rates of 17 % and 16 % for gastrointestinal and 14 % and 11 % for genitourinary in the hypofractionation and conventional fractionation groups , respectively . The 3-year freedom from biochemical failure ( FFBF ) rates were 87 % and 79 % in the hypofractionation and conventional fractionation groups , respectively ( p = 0.035 ) . The 3-year FFBF rates in patients at a very high risk ( i.e. , pretreatment prostate-specific antigen ( iPSA ) > 20 ng/mL , Gleason score > or=8 , or T > or=2c ) , were 88 % and 76 % ( p = 0.014 ) in the former and latter arm , respectively . The multivariate Cox analysis confirmed fractionation , iPSA , and Gleason score as significant prognostic factors . CONCLUSIONS Our findings suggest that late toxicity is equivalent between the two treatment groups and that the hypofractionated schedule used in this trial is superior to the conventional fractionation in terms of FFBF Hypofractionated  radiation therapy for prostate cancer has become of increasing interest with the recognition of a potential improvement in therapeutic ratio with treatments delivered in larger-sized fractions . In addition , the associated reduction in fraction number produces attractive cost and patient convenience advantages as well . A still limited but growing number of hypofractionation trials have reported acceptable short-term levels of toxicity and biochemical control , but most have insufficient follow-up to ensure the long-term safety and efficacy of this approach . This situation will improve as many currently active trials mature , particularly several high-value r and omized trials . In contrast , extreme hypofractionation , with schedules delivering only on the order of 5 fractions , is truly in its infancy for prostate cancer , with extremely limited tolerance and efficacy information currently available . Several uncertainties in the radiobiology of hypofractionation mitigate for an organized , cautious investigational approach . The fractionation response ( alpha/beta ratio ) of prostate cancers and , for that matter , late-responding normal tissues , has yet to be rigorously defined . Additionally , the linear-quadratic ( LQ ) model used in the design of hypofractionation schedules is subject to its own uncertainties , particularly with respect to the upper limit of fraction sizes for which it remains valid . Contemporary dose-escalated radiation therapy is already highly effective , making it imperative that ongoing and future studies of hypofractionation be performed in carefully design ed , r and omized clinical trials . Clinical validation permitting , the adaptation of hypofractionation as a st and ard of care could profoundly influence future management of localized prostate cancer PURPOSE To determine if escalated radiation dose using hypofractionation significantly reduces biochemical and /or clinical disease failure ( BCDF ) in men treated primarily for prostate cancer . PATIENTS AND METHODS Between June 2002 and May 2006 , men with favorable- to high-risk prostate cancer were r and omly allocated to receive 76 Gy in 38 fractions at 2.0 Gy per fraction ( conventional fractionation intensity-modulated radiation therapy [ CIMRT ] ) versus 70.2 Gy in 26 fractions at 2.7 Gy per fraction ( hypofractionated IMRT [ HIMRT ] ) ; the latter was estimated to be equivalent to 84.4 Gy in 2.0 Gy fractions . High-risk patients received long-term and rogen deprivation therapy ( ADT ) , and some intermediate-risk patients received short-term ADT . The primary end point was the cumulative incidence of BCDF . Secondarily , toxicity was assessed . RESULTS There were 303 assessable patients with a median follow-up of 68.4 months . No significant differences were seen between the treatment arms in terms of the distribution of patients by clinicopathologic or treatment-related ( ADT use and length ) factors . The 5-year rates of BCDF were 21.4 % ( 95 % CI , 14.8 % to 28.7 % ) for CIMRT and 23.3 % ( 95 % CI , 16.4 % to 31.0 % ) for HIMRT ( P = .745 ) . There were no statistically significant differences in late toxicity between the arms ; however , in subgroup analysis , patients with compromised urinary function before enrollment had significantly worse urinary function after HIMRT . CONCLUSION The hypofractionation regimen did not result in a significant reduction in BCDF ; however , it is delivered in 2.5 fewer weeks . Men with compromised urinary function before treatment may not be ideal c and i date s for this approach PURPOSE Hypofractionated radiotherapy has an intrinsically different normal tissue and tumor radiobiology . The results of a prospect i ve trial of stereotactic body radiotherapy ( SBRT ) for prostate cancer with long-term patient-reported toxicity and tumor control rates are presented . METHODS AND MATERIAL S From 2003 through 2009 , 67 patients with clinical ly localized low-risk prostate cancer were enrolled . Treatment consisted of 36.25 Gy in 5 fractions using SBRT with the CyberKnife as the delivery technology . No patient received hormone therapy . Patient self-reported bladder and rectal toxicities were grade d on the Radiation Therapy Oncology Group scale ( RTOG ) . RESULTS Median follow-up was 2.7 years . There were no grade 4 toxicities . Radiation Therapy Oncology Group Grade 3 , 2 , and 1 bladder toxicities were seen in 3 % ( 2 patients ) , 5 % ( 3 patients ) , and 23 % ( 13 patients ) respectively . Dysuria exacerbated by urologic instrumentation accounted for both patients with Grade 3 toxicity . Urinary incontinence , complete obstruction , or persistent hematuria was not observed . Rectal Grade 3 , 2 , and 1 toxicities were seen in 0 , 2 % ( 1 patient ) , and 12.5 % ( 7 patients ) , respectively . Persistent rectal bleeding was not observed . Low- grade toxicities were substantially less frequent with QOD vs. QD dose regimen ( p = 0.001 for gastrointestinal and p = 0.007 for genitourinary ) . There were two prostate-specific antigen ( PSA ) , biopsy-proven failures with negative metastatic workup . Median PSA at follow-up was 0.5 ± 0.72 ng/mL. The 4-year Kaplan-Meier PSA relapse-free survival was 94 % ( 95 % confidence interval , 85%-102 % ) . CONCLUSION Significant late bladder and rectal toxicities from SBRT for prostate cancer are infrequent . PSA relapse-free survival compares favorably with other definitive treatments . The current evidence supports consideration of stereotactic body radiotherapy among the therapeutic options for localized prostate cancer OBJECTIVE To report late toxicity outcomes from a r and omized trial comparing conventional and hypofractionated prostate radiation therapy and to identify dosimetric and clinical parameters associated with late toxicity after hypofractionated treatment . METHODS AND MATERIAL S Men with localized prostate cancer were enrolled in a trial that r and omized men to either conventionally fractionated intensity modulated radiation therapy ( CIMRT , 75.6 Gy in 1.8-Gy fractions ) or to dose-escalated hypofractionated IMRT ( HIMRT , 72 Gy in 2.4-Gy fractions ) . Late ( ≥90 days after completion of radiation therapy ) genitourinary ( GU ) and gastrointestinal ( GI ) toxicity were prospect ively evaluated and scored according to modified Radiation Therapy Oncology Group criteria . RESULTS 101 men received CIMRT and 102 men received HIMRT . The median age was 68 , and the median follow-up time was 6.0 years . Twenty-eight percent had low-risk , 71 % had intermediate-risk , and 1 % had high-risk disease . There was no difference in late GU toxicity in men treated with CIMRT and HIMRT . The actuarial 5-year grade ≥2 GU toxicity was 16.5 % after CIMRT and 15.8 % after HIMRT ( P=.97 ) . There was a nonsignificant numeric increase in late GI toxicity in men treated with HIMRT compared with men treated with CIMRT . The actuarial 5-year grade ≥2 GI toxicity was 5.1 % after CIMRT and 10.0 % after HIMRT ( P=.11 ) . In men receiving HIMRT , the proportion of rectum receiving 36.9 Gy , 46.2 Gy , 64.6 Gy , and 73.9 Gy was associated with the development of late GI toxicity ( P<.05 ) . The 5-year actuarial grade ≥2 GI toxicity was 27.3 % in men with R64.6Gy ≥ 20 % but only 6.0 % in men with R64.6Gy < 20 % ( P=.016 ) . CONCLUSIONS Dose-escalated IMRT using a moderate hypofractionation regimen ( 72 Gy in 2.4-Gy fractions ) can be delivered safely with limited grade 2 or 3 late toxicity . Minimizing the proportion of rectum that receives moderate and high dose decreases the risk of late rectal toxicity after this hypofractionation regimen OBJECTIVE To evaluate the accuracy , utility , and cost effectiveness of a new electromagnetic patient positioning and continuous , real-time monitoring system , which uses permanently implanted resonant transponders in the target ( Calypso 4D Localization System and Beacon transponders , Seattle , WA ) to continuously monitor tumor location and movement during external beam radiation therapy of the prostate . MATERIAL S AND METHODS This clinical trial studied 43 patients at 5 sites . All patients were implanted with 3 transponders each .  In 41 patients , the system was used for initial alignment at each therapy session . Thirty-five patients had continuous monitoring during their radiation treatment . Over 1,000 alignment comparisons were made to a commercially available kV X-ray positioning system ( BrainLAB ExacTrac , Munich , Germany ) . Using decision analysis and Markov processes , the outcomes of patients were simulated over a 5-year period and measured in terms of costs from a payer 's perspective and quality -adjusted life years ( QALYs ) . RESULTS All patients had satisfactory transponder implantations for monitoring purpose s. In over 75 % of the treatment sessions , the correction to conventional positioning ( laser and tattoos ) directed by an electromagnetic patient positioning and monitoring system was greater than 5 mm . Ninety-seven percent ( 34/35 ) of the patients who underwent continuous monitoring had target motion that exceeded preset limits at some point 
    Output:
    
PATIENT SUMMARY Hypofractionation for prostate cancer delivers relatively high doses of radiation per treatment .
Prospect i ve studies support the safety of moderate hypofractionation , while extreme fractionation may have greater toxicity .