Dosimetric And Clinical Study Of Simultaneous Integrated Boost Conformal Radiotherapy In Central Locally Advanced Non Small Cell Lung Cancer

Objective: To compare the dose distribution between conventionalfractionation radiotherapy (CFR) and simultaneous integrated boost conformalradiotherapy (SIB-CR) in central locally advanced non-small cell lung cancer(LANSCLC). To evaluate the feasibility of simultaneous integrated boostconformal radiotherapy in patients with central locally advanced non-smallcell lung cancer.Methods:1. Comparison of dosimetric distribution between SIB-CRplans and CFR plans: Ten patients with locally advanced non-small cell lungcancer were collected, immobilized by thermoplast and scanned from lowerneck to upper abdomen on the CT simulator. The tumor target and the organsat risk (OARs) were outlined. GTV is including the primary tumor andenlarged regional nodes, CTV was defined as the GTV plus a6-8mm, PTV asthe CTV plus8mm margin, and PTV1was GTV plus6mm. Two differentradiation treatment plans were designed for each patient: Conventionalfractionation radiotherapy (CFR): PTV was given6000cGy in30fractions andsimultaneous integrated boost conformal radiotherapy (SIB-CR): PTV wasgiven5040cGy in28fractions, and PTV1was given6440cGy in28fractionssimultaneously. The two plans were evaluated by dose distribution of thetargets and OARs such as lung, esophagus, spinal cord and heart.2. Clinicalobservation of SIB-CR in central LANSCLC: Thirty-three patients withLANSCLC were treated with SIB-CR planning between December2007andMay2011. Immobilized by thermoplast and scanned from lower neck to upperabdomen on the CT simulator. The tumor target and the organs at risk (OARs)were outlined. GTV is including the primary tumor and enlarged regionalnodes, CTV was defined as the GTV plus a6-8mm margin, PTV as the CTV plus8mm margin, and PTV1was GTV plus6mm. Simultaneous integratedboost conformal radiotherapy (SIB-CR) was used. The prescribed dose ofPTV was5040cGy/28fractions and GTV was given to6440cGy/28fractionssimultaneously. The total treatment time was about5.5weeks (1time a day,5fractions a week). The acute radiation toxicities such as radiation pneumonitis,radiation esophagitis and leukocytopenia were graded according to RTOGradiation scoring criteria every week from the start of treatment to threemonths after the end of treatment. The tumor response was evaluated at onemonth after the end of treatment. Survival was calculated from the start oftreatment until death or last follow-up day and analyzed using theKaplan-Meier method.Results:1. The GTVD90and GTVD95of SIB-CR plans were177.70±20.05cGy and175.70±13.59cGy respectively,higher than those ofCFR plans (P＜0.05). The mean lung dose, V8, V10, V13, V20, V30, V40andV50were lower in SIB-CR plan than those in CFR plan (P＜0.05).Comparing with the CFR plans, SIB-CR plans were lower in maximum doseof spinal cord, maximum dose, mean dose and V45of esophagus (P＜0.05).2.Clinical observation:(1) In clinical study, there were30male and3femalepatients. The median age was64years (range,49-77). There was1patientwith IIb disease,29patients with IIIa disease and3patients with IIIb disease.(2) Twenty-five patients received radiotherapy combined with chemotherapyand eight patients only received radiotherapy.(3) Tumor response: Thecomplete response (CR) was1patient, the partial response (PR)31patientsand the stable disease (SD)1patient. The overall tumor response (CR+PR)rate was96.97%(32/33).(4) The median follow-up time was13months(range,2-38). The1-,2-year survival rates were68.2%,43.0%respectively.The1-,2-year local control rates were95.8%,72.8%respectively. The1-,2-year survival rates of radiotherapy with chemotherapy were76.2%,52.2%respectively, while the1-,2-year survival rates of radiotherapy withoutchemotherapy were43.8%,14.6%respectively (P=0.024).(5) The acuteradiation pnemonitis and esophagitis rates were36.36%and33.33% respectively. No grade3or grade4radiation pneumonitis or esophagitis wasobserved. The leukocytopenia rate was39.39%, and there was1case of grade3.(6) Eighteen patients had therapy failure. The total failure rate was54.55%.Five patients developed locoregional failure alone and eleven patientsdeveloped distant metastasis alone. Two patients were locoregional and distantmetastasis concomitantly.Conclusion:1. SIB-CR planning conferred higher dose coverage fortumor target and lower dose for lung, spinal cord, esophagus and heart.2. TheSIB-CR technique for locally advanced non-small cell lung cancer wasfeasible and with a higher tumor response. The SIB-CR also could shorten thetotal radiotherapy duration in patients. Radiation toxicities can be welltolerated. The late toxicities and long-term survival need to be observed.