Feasibility Of Intensity-modulated Radiotherapy Research Articles

IMRT as an Alternative Technique for Intracavitary Brachytherapy in Patients with Carcinoma of the Cervix: A Feasibility Study Using Unified Dosimetric Index.

Intracavitary brachytherapy (ICBT) plays an important role in the management of carcinoma of the cervix. This study attempts to find the feasibility of intensity-modulated radiation therapy (IMRT) as a boost for patients who are not suitable for ICBT in order to improve their disease-free and overall survival. Twenty patients with carcinoma of the cervix were included in this study. Nine fields of IMRT and ICBT plans were generated for PTVBoost. Various dosimetric indices like coverage, conformity, homogeneity, and gradient index were calculated, and the corresponding unified dosimetric index (UDI) values were generated. Plans were classified based on combined UDI, and the UDI values were compared with those of ICBT. In addition, rectum and bladder doses were compared. All the dosimetric indices were within acceptable limits except for the gradient index. The gradient index of the IMRT and ICBT plans were 8.77 ± 0.26 and 1.33 ± 0.06 respectively (p < 0.0001). The mean of combined UDI with standard deviation was 32.557 ± 8.940 and plan quality was calculated from these values. Rectum and bladder doses for ICBT were lesser than IMRT (p < 0.0001). ICBT is the gold standard for boost RT in carcinoma of the cervix patients. IMRT boost is feasible for patients who are unsuitable on medical grounds for brachytherapy.

Multi-institutional feasibility study of intensity-modulated radiotherapy with chemotherapy for locally advanced non-small cell lung cancer.

This multi-institutional clinical trial evaluated the feasibility of intensity-modulated radiotherapy (IMRT) for patients with locally advanced non-small cell lung cancer (NSCLC). The major inclusion criteria were clinical stage III NSCLC, age 20-74years, and Eastern Cooperative Oncology Group performance status 0-1. Patients were treated with either cisplatin + S-1 (CS; four cycles every 4weeks) or carboplatin + paclitaxel (CP; administered weekly with thoracic radiotherapy [RT], plus two consolidation cycles) concurrently with IMRT (60Gy in 30 fractions). The primary endpoint was a treatment completion rate, defined as at least two cycles of CS or five cycles of CP during IMRT and completing 60Gy IMRT within 56days after the start of treatment, assumed its 90% confidence interval exceeds 60%. RT quality assurance was mandatory for all the patients. Twenty-two patients were registered. One patient withdrew due to pulmonary infection before starting treatment. RT plans were reviewed and none was judged as a protocol violation. Grade 2 and 3 pneumonitis occurred in four (19%) and one (5%) patients, respectively. Seventeen patients met the primary endpoint, with a treatment completion rate of 77.3% (90% confidence interval [CI] 58.0%-90.6%). Four patients failed to complete chemotherapy due to chemotherapy-related adverse events, but 20 patients completed IMRT. There were no treatment-related deaths. The 2-year progression-free and overall survival rates were 31.8% (95% CI 17.3%-58.7%) and 77.3% (95% CI 61.6%-96.9%), respectively. The treatment completion rate did not meet the primary endpoint, but 20 of 22 patients completed IMRT.

Feasibility of intensity-modulated radiation therapy with concurrent chemotherapy in patients with Siewert type II and III adenocarcinoma of the esophagogastric junction before surgery

Objective To analyze the feasibility of intensity-modulated radiation therapy (IMRT) with concurrent chemotherapy in patients with locally advanced Siewert type Ⅱ and Ⅲ adenocarcinoma of the esophagogastric junction (AEG). Methods A prospective study was performed on 45 patients with locally advanced Siewert type Ⅱ and Ⅲ AEG. These patients received two cycles of XELOX chemotherapy and concurrent IMRT to the involved field (45 Gy/25 f, 5 f/week) for 6 to 8 weeks before surgical resection. The patients ingested 800 to 1000 ml water to distend the stomach before computed tomography (CT) scan. The gross tumor volume of the primary tumor (GTV-t) was delineated on the CT image with a stomach wall thickness of>5 mm. GTV-t was expanded by a 2.0 cm margin along the esophagus, a 1.5-2.0 cm margin along the stomach, and a 0.8 cm margin axially outward to generate the clinical target volume of the primary tumor (CTV-t). GTV-lymph node (GTV-nd) was delineated based on CT/magnetic resonance imaging scan. CTV-nd only included GTV-nd and the involved lymph nodes. Planning target volume was generated by expanding the CTV by 0.8 to 1.0 cm. The feasibility of target volume delineation was explored by analyzing postoperative pathological examination results and radiotherapy toxicities. Results All the 45 patients completed preoperative concurrent chemoradiotherapy and surgery, with two cycles of chemotherapy in 39 patients and one cycle in 6 patients. The rates of R0 resection and pathological complete response (pCR) were 95.6%(43/45) and 22.2%(10/45), respectively. There were 10(22.2%), 17(37.8%), 15(33.3%), and 3(6.7%) patients with tumor regression grades 0, 1, 2, 3, respectively. The rate of lymph node metastasis was 37.8%(17/45), and the lymph node ratio was 4.33%(46/1062). The postoperative pathological examination showed that T and N downstaging after surgery was observed in 24 and 26 patients, respectively; the proportions of patients with T3-T4 tumors and positive lymph nodes after surgery declined by 51.1%(P=0.000) and 42.2%(P=0.000), respectively. The overall incidence of radiation esophagitis/gastritis was 44.4%(20/45), and the incidence rates of grade 1, 2, and 3 radiation esophagitis/gastritis were 18%, 22%, and 4%, respectively. The incidence of acute radiation pneumonitis was 6.7%(3/45), all in grades 1 and 2. There was one perioperative treatment-related death. Conclusions Two cycles of XELOX chemotherapy combined with concurrent 45 Gy radiotherapy before surgery in patients with locally advanced Siewert type Ⅱ and Ⅲ AEG can achieve a relatively high pCR rate, effectively reduce the lymph node metastasis rate, achieve downstaging, and increase R0 resection rate. This regimen has many good advantages, including low incidence of acute toxicities, good tolerability, and acceptable rate of perioperative treatment-related deaths. The target volume delineation involving metastatic lymph nodes is feasible. Key words: Esophagogastric junction adenocarcinoma/radiotherapy; Esophagogastric junction adenocarcinoma/chemotherapy; Involved-field irradiation, feasibility

High dose (54 Gy) Pre-operative Tomotherapy for Retroperitoneal Liposarcoma: Results of a Phase 2 Multicenter Study

To evaluate efficacy and feasibility of intensity-modulated radiotherapy (IMRT) with tomotherapy followed by surgery, especially concerning the high-level of radiotherapy (RT) prescribed dose (54 Gy/30 fractions/6 weeks). Helical tomotherapy was used for pre-operative RT. Inclusion criteria were operable, biopsy-proven, retroperitoneal liposarcomas. Clinical Target Volume (CTV) and mains organs at risk (contralateral kidney, bowel bag) were systematically discussed with the surgeon. Prescribed dose was 54 Gy at the median of PTV) Main dosimetric constraints concerned contralateral kidney (Dmax ≤ 12 Gy mean dose ≤ 8 Gy) and bowel bag (V45 Gy ≤ 33% and V30 Gy ≤ 50%). Surgery was planned 4 to 8 weeks after RT. Toxicity was graded according to CTCAE V3.0. Overall survival (OS) was estimated using Kaplan-Meier method. Due to competing risks, we estimated the cumulative incidence of loco-regional relapse; 95% confidence intervals are reported [95% CI]. From 04/2009 to 09/2013, 48 patients were included. Mean age: 62 years (y) (36 to 82). All but 1 patient were OMS ≤ 2. Histological types were 20 well differentiated (WDLS) and 28 dedifferentiated liposarcomas. Mean CTV was 2954 cc (920-4989). Treatment: All patients but1completed the radiosurgical schedule. Monobloc exerese was always achieved. Surgical margins were R0 (16; 34%), R1 (28; 60%), R2 (2; 4%) or missing (1; 2%). Twenty-nine patients underwent bowel resection, including large bowel (28/29), small bowel (4/29) and duodenum (1/29). Oncological outcomes: Median follow-up was 4.7years. Cumulative incidence of loco-regional relapse at3 and 5 years was 17% [8%; 29%] and 31% [16%; 47%], respectively. Estimates were 5% and 35% for dedifferentiated liposarcoma and 26% and 26% for well differentiated liposarcoma. OS at 3 and 5 years was 81% [66%; 89%]) and 78% ([63%; 88%] respectively. Toxicity within the first 6 months was higher than expected: mean weight loss during RT was 5.4 kg (about 8% of mean body weight) and 8.9 kg at the first visit after surgery. At 2 months, grade 3 toxicities included duodenal stenosis (1/46), intestinal fistula (1/46) and enterocolitis (1/46) and grade 4 toxicity included GI fistula (1/46). At 6 months and 1 year, no further severe toxicities were observed. Five cases of second cancers were reported: 1 myeloid leukemia, 2 pancreatic, and 2 breast carcinomas. This trial highlights the feasibility of preoperative 54 Gy RT. Although efficacy data (local control and OS) are encouraging, high incidence rates of acute toxicities and second cancers should be considered. Preoperative RT for WDLS remains questionable. Results from ongoing EORTC phase III Strass trial may provide further level of evidence for this approach.

Efficacy and Feasibility of Intensity-Modulated Radiation Therapy for Prostate Cancer in Renal Transplant Recipients

BackgroundIn transplant patients with localized prostate cancer, irradiation is not proposed as often as it is in healthy adults because of the post-radiation risks, such as ureteral stenosis and gastrointestinal toxicity as the result of fragile tissue. The objective of the study was to analyze the efficacy and feasibility of intensity-modulated radiation therapy (IMRT) for prostate cancer in renal transplant recipients (RTRs). MethodsBetween May 2005 and December 2014, all patients who had undergone IMRT for clinically localized prostate cancer at our institution were retrospectively identified (n = 365). Of these patients, 2 had a history of renal transplantation. We reviewed all available clinical data. One patient had a functioning graft and the other had restarted hemodialysis 7 years after the transplantation. ResultsThe mean time from renal transplantation to prostate cancer diagnosis was 11 years. The mean follow-up after irradiation was 43 months. The 2 patients remain free of prostate-specific antigen progression. There was no severe acute and chronic genitourinary and gastrointestinal toxicity. Renal function of the patient with a functioning graft as measured by serum creatinine was stable during and after the irradiation. ConclusionsIMRT is feasible and acceptable as a minimally invasive treatment in the carefully selected RTRs with localized prostate cancer. This treatment should be considered a good option for RTRs with localized prostate cancer.

Does intensity-modulated radiotherapy reduce the risk of pelvic insufficiency fractures in gynaecological cancers?

AbstractBackgroundIncreasingly we are using a combination of surgery, chemotherapy and radiotherapy for treatment of gynaecological malignancies. Most studies in literature are concentrated on the concept of survival. There is minimal data examining the impact of these treatments on quality of life. Survival being a surrogate marker is an arbitrary end point and is of arguable significance if quality of life is not maintained. Long-term side effects of radiotherapy are debilitating and severely affect quality of life. Pelvic insufficiency fractures (PIF) are a known long-term side effect of radiotherapy. Intensity-modulated radiotherapy (IMRT) is being routinely used in the treatment of prostate and head and neck cancer. We postulated that use of IMRT in gynaecological cancers reduces the incidence of PIF.Patients and methodsWe retrospectively reviewed 10 cases of PIF treated on standard treatment. We recalculated dose volume histograms based on IMRT protocols for patients with PIF.ResultsWe found that none of the patients received any radiation at the fracture site and the total radiation received to the sacrum was lower compared with the standard treatment protocols.ConclusionsWe conclude that the feasibility of IMRT in gynaecological cancers should be further evaluated and might be an useful tool in reducing the number of PIF.

The feasibility of choosing intensity-modulated radiotherapy to treat 3 -5 brain metastases from nonsmall cell lung cancer

Objective This study evaluates the feasibility of intensity-modulated radiation therapy (IMRT) to treat patients with 1 -5 brain metastases from non-small cell lung cancer (NSCLC).Methods 30 IMRT patients with brain metastases for NSCLC studied retrospectively.Whole brain radiotherapy plus three-dimensional conformal radiotherapy (WBRT + 3DCRT) and WBRT plus stereotactic radiotherapy ( WBRT + SRT) plans were generated.Planning target volume ( PTV ) and organs at risk dose were measured and compared by dose volume histogram.Differences were analyzed in the three techniques by Wilcoxon Z -test.Results D99％ of the shoulder ( D99％-D90％ ) from IMRT were higher than from WBRT +3DCRT and WBRT+SRT in all cases.From D15％ of slope (D90％-D10％) to D5％ of tail (D10％ -D1％ ),IMRT were lower than WBRT + 3DCRT and WBRT + SRT ( Z =- 4.72,P =0.000 and Z =- 4.72,P =0.000).D10％ and D5％ of IMRT were (35.1 ±1.42) Gy and (37.7 ±2.91) Gy,WBRT +3DCRT were (36.5±2.86) Gy and ( 39.1 ± 3.56) Gy ;WBRT + SRT were (36.2 ± 2.57) Gy and ( 38.7 ± 3.67) Gy.IMRT vs WBRT+ 3DCRT and WBRT + SRT were significant ( Z=-3.18,-3.18,P=0.001,0.001 and Z=- 4.11,- 3.02,P =0.000,0.002) in 13 patients with 3 - 5 brain metastases.The total mean monitor units were 14756.3,9614.8 and 9043.2 for IMRT,WBRT +3DCRT and WBRT + SRT plans,respectively,with a 38.7％ reduction from IMRT to WBRT + SRT (Z =-4.78,-4.78,P =0.000,0.000).The brain doses around metastases were similar in the three techniques with 1 -2 metastases,but IMRT was the best with 3 -5 metastases.Conclusions IMRT can advance brain metastases dose and improve the planning target minimum dose and spare the dose around brain metastases.Only IMRT is the best choice for just sparing the dose around brain metastases among 3 -5 brain metastases. Key words: Lung neoplasms metastasis,brain/radiothcrapy; Radiotherapy,intensity-modulated Radiotherapy,whole brain; Radiotherapy,three-dimensional conformal; Radiotherapy,stereotactic; Dose volume histogram

Feasibility of intensity-modulated radiation therapy (IMRT) with PET-defined simultaneous integrated boost (SIB) for distal rectal adenocarcinoma (DRA).

550 Background: PET/CT guided preoperative IMRT is being used with increasing frequency in standard practice but reports of methods, efficacy, and toxicity are limited. We report the AGH experience from 2007-2010 of IMRT with SIB for DRA. Methods: 22 pts with stage IB–IV DRA (8 with anal canal involvement) were treated with preoperative concurrent IMRT with SIB, 5FU-based chemotherapy. 15 received weekly oxaliplatin. All had PET/CT simulation. The planned target volume included PET-avid primary tumor and LNs with median margins of 3mm (range, 0–13), in a median of 24 fx (range, 20–28), a median dose of 2.25 Gy/fx (range, 1.9–2.4 Gy) to a median total dose of 53.3 Gy (range, 50.6–57.2 Gy). Clinical target volume included non PET-avid 1st echelon LNs with a median dose of 2.0 Gy/fx (range, 1.6–2.3 Gy) to a total median dose of 47 Gy (range, 40.7–54.04 Gy). Median follow-up was 18 mos (range, 4–35). Late toxicities were scored using CTCAE v. 3.0. Results: 17 of 22 patients (TNM stages IB (3), IIA (3), IIB (1), IIIA (2), IIIB (7), IV (1)) were treated curatively. The remaining 5 pts were treated palliatively. The median length of time from completion of radiation to surgery was 81 days (range, 48–398). 5 pts did not have surgery due to advanced metastatic disease (3), death (1) or biopsy proven complete response (CR) (1). R0 resection was accomplished in 15 of 17 surgical pts including 13/14 curative and 2/3 palliative cases. R1 resection occurred in 2 pts; 1 with stage IIIB and 1 with stage IV. No pts had R2 resection. 6 pts (5 with T2 lesions and 1 with a T4 lesion) had a pathologic CR. 2 of 3 non-surgical pts with metastatic disease had LRF at 5 and 11 mos. 9/22 pts had no late toxicity, 9/22 ≤ grade 2 and 4/22 had grade 3 late toxicity. No patients with T2 tumors had grade 3 late toxicity, and this appeared to be related to lower GTV. Kaplan-Meier freedom from grade 3late toxicity was 85% at 18 mos. Conclusions: IMRT with SIB is an accurate targeting technique in pts with DRA that showed a pathologic CR in 100% of T2 lesions. Advanced T stage and larger GTV were possible risk factors for grade 3 late toxicity. [Table: see text] No significant financial relationships to disclose.

High-precision radiotherapy for craniospinal irradiation: evaluation of three-dimensional conformal radiotherapy, intensity-modulated radiation therapy and helical TomoTherapy

This study aimed to establish the feasibility of intensity-modulated radiation therapy (IMRT) in craniospinal irradiation (CSI) using conventional linear accelerator (IMRT_LA) and compare it dosimetrically with helical TomoTherapy (IMRT_Tomo) and three-dimensional conformal radiotherapy (3DCRT). CT datasets of four previously treated patients with medulloblastoma were used to generate 3DCRT, IMRT_LA and IMRT_Tomo plans. A CSI dose of 35 Gy was prescribed to the planning target volume (PTV). IMRT_LA plans for tall patients were generated using an intensity feathering technique. All plans were compared dosimetrically using standardised parameters. The mean volume of each PTV receiving at least 95% of the prescribed dose (V(95%)) was >98% for all plans. All plans resulted in a comparable dose homogeneity index (DHI) for PTV_brain. For PTV_spine, IMRT_Tomo achieved the highest mean DHI of 0.96, compared with 0.91 for IMRT_LA and 0.84 for 3DCRT. The best dose conformity index was achieved by IMRT_Tomo for PTV_brain (0.96) and IMRT_LA for PTV_spine (0.83). The IMRT_Tomo plan was superior in terms of reduction of the maximum, mean and integral doses to almost all organs at risk (OARs). It also reduced the volume of each OAR irradiated to various dose levels, except for the lowest dose volume. The beam-on time was significantly longer in IMRT_Tomo. In conclusion, IMRT_Tomo for CSI is technically easier and potentially dosimetrically favourable compared with IMRT_LA and 3DCRT. IMRT for CSI can also be realised on a conventional linear accelerator even for spinal lengths exceeding maximum allowable field sizes. The longer beam-on time in IMRT_Tomo raises concerns about intrafraction motion and whole-body integral doses.

Intensity-Modulated Radiation Therapy With or Without Chemotherapy for Nasopharyngeal Carcinoma: Radiation Therapy Oncology Group Phase II Trial 0225

To investigate the feasibility of intensity-modulated radiation therapy (IMRT) with or without chemotherapy, and to assess toxicities, failure patterns, and survivals in patients with nasopharyngeal carcinoma (NPC). Radiation consisted of 70 Gy given to the planning target volumes of primary tumor plus any N+ disease and 59.4 Gy given to subclinical disease, delivered over 33 treatment days. Patients with stage T2b or greater or with N+ disease also received concurrent cisplatin (100 mg/m(2)) on days 1, 22, and 43 followed by adjuvant cisplatin (80 mg/m(2)) on day 1; fluorouracil (1,000 mg/m(2)/d) on days 1 through 4 administered every 4 weeks for three cycles. Tumor, clinical status, and acute/late toxicities were assessed. The primary objective was to test the transportability of IMRT to a multi-institutional setting. Between February 2003 and November 2005, 68 patients with stages I through IVB NPC (of which 93.8% were WHO types 2 and 3) were enrolled. Prescribed IMRT (target delineation) was given to 83.8%, whereas 64.9% received chemotherapy per protocol. The estimated 2-year local progression-free (PF), regional PF, locoregional PF, and distant metastasis-free rates were 92.6%, 90.8%, 89.3%, and 84.7%, respectively. The estimated 2-year PF and overall survivals were 72.7% and 80.2%, respectively. Acute grade 4 mucositis occurred in 4.4%, and the worst late grade 3 toxicities were as follows: esophagus, 4.7%; mucous membranes, 3.1%; and xerostomia, 3.1%. The rate of grade 2 xerostomia at 1 year from start of IMRT was 13.5%. Only two patients complained of grade 3 xerostomia, and none had grade 4 xerostomia. It was feasible to transport IMRT with or without chemotherapy in the treatment of NPC to a multi-institutional setting with 90% LRPF rate reproducing excellent reports from single institutions. Minimal grade 3 and lack of grade 4 xerostomia were encouraging.

Initial experience using intensity-modulated radiotherapy for recurrent nasopharyngeal carcinoma

PurposeTo report our initial experience on the feasibility, toxicity, and tumor control using intensity-modulated radiotherapy (IMRT) for retreatment of recurrent nasopharyngeal carcinoma (NPC). Methods and materialsA total of 49 patients with locoregional recurrent carcinoma in the nasopharynx were treated with IMRT between January 2001 and February 2002 at the Sun Yat-Sen University Cancer Center, Guangzhou, China. The average time to the nasopharyngeal recurrence was 30.2 months after initial conventional RT. The median isocenter dose to the nasopharynx was 70 Gy (range 60.9–78.0) for the initial conventional RT. All patients were restaged at the time of recurrence according to the 1992 Fuzhou, China staging system on NPC. The number of patients with Stage I, II, III and IV disease was 4, 9, 10, and 26, respectively. T1, T2, T3, and T4 disease was found in 4, 9, 11, and 25 patients, respectively. N0, N1, N2, and N3 disease was found in 46, 2, 0, and 1 patient, respectively. Invasion of the nasal cavity, maxillary sinus, ethmoid sinus, sphenoid sinus, and cavernous sinus and erosion of the base of the skull was found in 8, 1, 3, 8, 15, and 20 patients, respectively. The gross tumor volume (GTV) was contoured according to the International Commission on Radiation Units and Measurements (ICRU) Report 62 guidelines. The critical structures were contoured, and the doses to critical structures were constrained according to ICRU 50 guidelines. The GTV in the nasopharynx and positive lymph nodes in the neck received a prescription dose of 68–70 Gy and 60 Gy, respectively. All patients received full-course IMRT. Three patients who had positive lymph nodes were treated with five to six courses of chemotherapy (cisplatin + 5-fluorouracil) after IMRT. ResultsThe treatment plans showed that the percentage of GTV receiving 95% of the prescribed dose (V95-GTV) was 98.5%, and the dose encompassing 95% of GTV (D95-GTV) was 68.1 Gy in the nasopharynx. The mean dose to the GTV was 71.4 Gy. The average doses of the surrounding critical structures were much lower than the tolerable thresholds. At a median follow-up of 9 months (range 3–13), the locoregional control rate was 100%. Three cases (6.1%) of locoregional residual disease were seen at the completion of IMRT, but had achieved a complete response at follow-up. Three patients developed metastases at a distant site: two in the bone and one in the liver and lung at 13 months follow-up. Acute toxicity (skin, mucosa, and xerostomia) was acceptable according to the Radiation Therapy Oncology Group criteria. Tumor necrosis was seen toward the end of IMRT in 14 patients (28.6%). ConclusionThe improvement in tumor target coverage and significant sparing of adjacent critical structures allow the feasibility of IMRT as a retreatment option for recurrent NPC after initial conventional RT. This is the first large series using IMRT to reirradiate local recurrent NPC after initial RT failed. The treatment-related toxicity profile was acceptable. The initial tumor response/local control was also very encouraging. In contrast to primary NPC, recurrent NPC reirradiated with high-dose IMRT led to the shedding of tumor necrotic tissue toward the end of RT. More patients and longer term follow-up are warranted to evaluate late toxicity and treatment outcome.

Initial experience of using intensity modulated radiation therapy (IMRT) for recurrent nasopharyngeal carcinoma

Purpose/Objective: To report initial experience using intensity modulated radiation therapy (IMRT)(feasibility, toxicity and tumor control) for re-treatment recurrent nasopharyngeal carcinoma. Materials/Methods: 49 patients (KPS≥80) with local-regional recurrence in nasopharynx were treated with IMRT from Jan. 2001 to Feb. 2002 at Cancer Center, Zhongshan University, Guangzhou, China. The average time for local-regional in recurrence nasopharynx was 30.16 months after initial conventional radiotherapy. The isocenter dose on nasopharynx had medean dose 70Gy (60.88-78Gy) in 49 patients initial conventional radiotherapy. The number of patients with stage II, III and IV disease were 4, 9, 10 and 26 respectively. T1, T2, T3 and T4 disease were 4, 9, 11 and 25 cases respectively. N0, N1 and N3 disease were 46, 2 and 1 cases respectively. Of them, the invasion of nasal cavity, maxillary sinus, ethmoid sinus, sphenoid sinus, cavernous sinus and the erosion of base skull were found in 8, 1, 3, 8, 15 and 20 cases respectively. The GTV were contoured according to ICRU 62 guideline. Two CTV (CTV1 and CTV2) were set-up for the subclinical disease in nasopharynx. The CTV1 was defined 0.5-1cm away from the border of GTV. The CTV2 was defined 1-1.5cm away from the border of CTV1. The critical structures were contoured and the doses to critical structures were constrined according to ICRU 50 guideline. The inverse planning IMRT were created with CORVUS 3.0 planning system (Peacock,NOMOS) and treated with segmental tomotherapy techniques (MIMiC).The gantry rotation arc was 105 to 255 degree and beamlet changed every 5 degree. The GTV in nasopharynx and the lymph nodes in the neck received prescription dose of 68-70Gy and 60Gy respectively. All patients received full course IMRT. Three patients who had positive the lymph nodes were treated with 5-6 courses of chemotherapy(Cisplatin + 5-FU) after IMRT. Results: The plans showed that the dose of PTV covering GTV D95 in nasopharynx was 68.09Gy, and the volume of GTV V95 was 98.46%. The mean dose of GTV, CTV1 and CTV2 were delivered by IMRT in 49 patients (Table 1). At a median follow-up of 7 months (range 1 to 13 months), the local-regional progression-free survival was 100%. 3 cases (6.1%) of local-regional residual diseases were seen in 49 patients by the end of IMRT. 14 patients (28.6%) were complicated by radio-necrosis of varying degree in the nasopharynx. Three patients have developed metastases at a distant site: 2 in the bone, 1 in the liver and lung at 13 months follow-up. Acute toxicity in 49 patients was evaluated according to the RTOG radiation morbidity scoring criteria by the end of IMRT treatment. 19, 19 and 1 patients had grade 0, 1 and 2 skin toxicity respectively. Grade 0, 1, 2 and 3 toxicity in oral mucosa were 16, 10, 21 and 2 patients respectively. 26, 18 and 5 patients had grade 1, 2 and 3 xerostomia respectively. Conclusions: The improvement in tumor target coverage and significant sparing of adjacent critical structures allow the feasibility of IMRT as a re-treatment option for recurrent NPC after initial radiotherapy. However, high dose IMRT for re-treatment can result in radio-necrosis of nasopharynx. We recommend that the prescription dose of GTV to be decreased and concurrent chemotherapy to be used in this setting. Tabled 1Critical StructuresMean Dose (Gy)Mean Volume (cc)Brain Stem28.5123.04Spinal Cord20.195.44Optical Chiasm21.560.87Pituitary32.590.21Len(L)3.910.20(R)4.100.20Optical Nerves(L)19.560.60(R)19.200.62Temporal Lobes(L)20.9840.46(R)22.1439.22Parotids(L)20.9710.98(R)18.4414.24T-M Joints(L)27.891.77(R)28.841.85Mandible bone(L)20.1936.30(R)19.7135.79 Open table in a new tab