| Part one: Dosimetric analysis of preoperative simultaneous integrated boostintensity-modulated radiotherapy for rectal cancerObjective: To explore the feasibility of simultaneous integrated boostintensity-modulated radiotherapy (SIB-IMRT) for preoperative radiotherapy in locallyadvanced rectal cancer (LARC) by comparing dosimetric differences betweenSIB-IMRT56.25Gyand IMRT50Gyin terms of target coverage and doses of organs at risk(OARs).Methods:10LARC patients treated with preoperative chemo-radiotherapy wereenrolled in this study.7-field SIB-IMRT56.25Gyand7-field IMRT50Gyplans were madefor each patient. The prescribed doses were56.25Gy in25fractions to pGTV，50Gy in25fractions to PTV in the SIB-IMRT56.25Gygroups. In the IMRT50Gygroup, PTV wasdelivered50Gy in25fractions. The dose distributions of target volumes, in terms ofconformity index(CI) and homogeneity index(HI), and doses of OARs were analyzedusing the dose-volume histogram(DVH)．Results: All SIB-IMRT56.25Gyplans met the needs of the prescribed doses andorgan at risk dose constraints．No significant difference in the CI for PTV50Gywas notedbetween the two groups. The Dmedianand D98%of the PTV were higher in theSIB-IMRT56.25Gygroup than in the IMRT50Gygroup (p＜0.05). Compared to IMRT50Gy,the addition of a simultaneous integrated boost in SIB-IMRT56.25Gyresulted insignificant increases in mean dose and V40to the bladder and significant increases ofV30and V40to femoral heads (p＜0.05for all points). There were no significantdifferences in dose to small bowel or pelvic bone marrow between the two sets of plans.Conclusions: Preoperative SIB-IMRT56.25Gyfor LARC is feasible dosimetricallywith respect to organ at risk dose constraints, and can be used in preoperative radiotherapy for LARC. Part two: Phase II trial of preoperative simultaneous integrated boostintensity-modulated radiotherapy with oral capecitabine in locally advanced rectalcancerObjective: A prospective clinical trial was conducted to evaluate the feasibility,safety, and short-term efficacy of preoperative capecitabine and simultaneous integratedboost (SIB) intensity-modulated radiotherapy (IMRT) in patients with locally advancedrectal cancer.Methods: Between August2012and July2013, totally20patients with resectablestage II or III rectal cancer received capecitabine (825mg/m2PO BID,5d/w×5weeks) and SIB-IMRT delivering56.25Gy (2.25Gy/fraction) to the gross tumor whilesimultaneously delivering50Gy (2.0Gy/fraction) to the regional lymph nodes andareas at risk for harboring microscopic disease. Total mesorectal excision was scheduled4to8weeks after the completion of chemoradiation. The primary endpoints includedpathological complete response rate (ypCR), tumor downstaging, toxicity andpostoperative complications. The secondary endpoint included rate of sphincter-sparingsurgery.Results: All20patients completed chemoradiation with strict compliance to theprotocol schedule; two patients did not undergo surgical resection. Of the18patientsevaluable for pathologic response, the ypCR rate was22.2%. Downstaging of theprimary tumor and lymph nodes was observed in11(61.1%) and9(81.8%) patients,respectively. There was no Grade3to4acute toxicity reported. Grade1/2toxicitiesincluded leucopenia, thrombocytopenia and diarrhea. Two patients (11.1%) developedpostoperative complications, which consisted of1patient who had rectovaginal fistulaeand1patient who had adhesion-related small-bowel obstruction. Of the16patients whohad tumors within5cm of the anal verge,10(62.5%) patients underwent sphincter-sparing procedures.Conclusions: According to our preliminary results, preoperative chemoradiationwith capecitabine and SIB-IMRT was safe and well tolerated for patients with locallyadvanced rectal cancer, the short term outcomes were promising. |
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