Ngot-Swan Chong

Total Marrow Irradiation with Helical Tomotherapy for Bone Marrow Transplantation of Multiple Myeloma: First Experience in Asia

Three Asian patients with plasma cell myeloma stage IIIa with IgG predominant were selected for autologous hematopoietic cell transplantation (HSCT). Total marrow irradiation (TMI) tomotherapy planned with melphalan 140 mg/m2 as a preconditioning regimen of HSCT. Two image sets of computed tomography (CT) were scanned with 2.5 mm and 5 mm for the upper and lower part of the plan, respectively. The junction was determined and marked at 15 cm above knee on both thighs for upper and lower part of the plan. The clinical target volume (CTV) included the entire skeletal system. The planning target volume (PTV) was generated with with 0.8 cm for CTVextremities and with 0.5 cm margin for all other bones of CTV. A total dose of 800 cGy (200 cGy/fraction) was delivered to the PTV. Update to presentation, all of three patients post transplant without evidence of active disease were noted. During TMI treatment, one with grade 1 vomiting, two with grade 1 nausea, one with grade 1 mucositis, and three with grade 1 anorexia were noted. Toxicity of treatment was scored according to the Common Terminology Criteria for Adverse Events v3.0 (CTCAE v3.0). The average for upper part versus lower part of PTVBone marrow of CI and H-index were 1.5 and 1.4 versus 1.2 and 1.2, respectively. The dose reduction of TMI tomotherapy to various OARs of head, chest, and abdomen relative to TBI varied from 31% to 74%, 21% to 51%, and 46% to 63%, respectively. The maximum average value of registration for upper torso versus lower extremities in different translation directions were 5.1 mm versus 4.1 mm for pretreatment and 1.5 mm versus 0.7 mm for post-treatment, respectively. The average treatment time for the upper versus lower part in beam-on time, setup time, and MVCT registration time took roughly 49.9, 23.3, and 11.7 min versus 11.5, 10.0, and 7.3 min, respectively. The margin of PTV could be less than 1 cm under good fixation and close position confirmation with MVCT. Antiemetics should be prescribed in the whole course of TMI for emesis prevention. TMI technique replaced TBI technique with 8 Gy as conditioning regiment for multiple myeloma could be acceptable for the Asian and the outcomes were feasible for the Asian.

Comparison of coplanar and noncoplanar intensity-modulated radiation therapy and helical tomotherapy for hepatocellular carcinoma

BackgroundTo compare the differences in dose-volume data among coplanar intensity modulated radiotherapy (IMRT), noncoplanar IMRT, and helical tomotherapy (HT) among patients with hepatocellular carcinoma (HCC) and portal vein thrombosis (PVT).MethodsNine patients with unresectable HCC and PVT underwent step and shoot coplanar IMRT with intent to deliver 46 - 54 Gy to the tumor and portal vein. The volume of liver received 30Gy was set to keep less than 30% of whole normal liver (V30 < 30%). The mean dose to at least one side of kidney was kept below 23 Gy, and 50 Gy as for stomach. The maximum dose was kept below 47 Gy for spinal cord. Several parameters including mean hepatic dose, percent volume of normal liver with radiation dose at X Gy (Vx), uniformity index, conformal index, and doses to organs at risk were evaluated from the dose-volume histogram.ResultsHT provided better uniformity for the planning-target volume dose coverage than both IMRT techniques. The noncoplanar IMRT technique reduces the V10 to normal liver with a statistically significant level as compared to HT. The constraints for the liver in the V30 for coplanar IMRT vs. noncoplanar IMRT vs. HT could be reconsidered as 21% vs. 17% vs. 17%, respectively. When delivering 50 Gy and 60-66 Gy to the tumor bed, the constraints of mean dose to the normal liver could be less than 20 Gy and 25 Gy, respectively.ConclusionNoncoplanar IMRT and HT are potential techniques of radiation therapy for HCC patients with PVT. Constraints for the liver in IMRT and HT could be stricter than for 3DCRT.

Should helical tomotherapy replace brachytherapy for cervical cancer? Case report

BackgroundStereotactic body radiation therapy (SBRT) administered via a helical tomotherapy (HT) system is an effective modality for treating lung cancer and metastatic liver tumors. Whether SBRT delivered via HT is a feasible alternative to brachytherapy in treatment of locally advanced cervical cancer in patients with unusual anatomic configurations of the uterus has never been studied.Case PresentationA 46-year-old woman presented with an 8-month history of abnormal vaginal bleeding. Biopsy revealed squamous cell carcinoma of the cervix. Magnetic resonance imaging (MRI) showed a cervical tumor with direct invasion of the right parametrium, bilateral hydronephrosis, and multiple uterine myomas. International Federation of Gynecology and Obstetrics (FIGO) stage IIIB cervical cancer was diagnosed. Concurrent chemoradiation therapy (CCRT) followed by SBRT delivered via HT was administered instead of brachytherapy because of the presence of multiple uterine myomas with bleeding tendency. Total abdominal hysterectomy was performed after 6 weeks of treatment because of the presence of multiple uterine myomas. Neither pelvic MRI nor results of histopathologic examination at X-month follow-up showed evidence of tumor recurrence. Only grade 1 nausea and vomiting during treatment were noted. Lower gastrointestinal bleeding was noted at 14-month follow-up. No fistula formation and no evidence of haematological, gastrointestinal or genitourinary toxicities were noted on the most recent follow-up.ConclusionsCCRT followed by SBRT appears to be an effective and safe modality for treatment of cervical cancer. Larger-scale studies are warranted.

Toxicity risk of non-target organs at risk receiving low-dose radiation: case report

AbsatractThe spine is the most common site for bone metastases. Radiation therapy is a common treatment for palliation of pain and for prevention or treatment of spinal cord compression. Helical tomotherapy (HT), a new image-guided intensity modulated radiotherapy (IMRT), delivers highly conformal dose distributions and provides an impressive ability to spare adjacent organs at risk, thus increasing the local control of spinal column metastases and decreasing the potential risk of critical organs under treatment. However, there are a lot of non-target organs at risk (OARs) occupied by low dose with underestimate in this modern rotational IMRT treatment. Herein, we report a case of a pathologic compression fracture of the T9 vertebra in a 55-year-old patient with cholangiocarcinoma. The patient underwent HT at a dose of 30 Gy/10 fractions delivered to T8-T10 for symptom relief. Two weeks after the radiotherapy had been completed, the first course of chemotherapy comprising gemcitabine, fluorouracil, and leucovorin was administered. After two weeks of chemotherapy, however, the patient developed progressive dyspnea. A computed tomography scan of the chest revealed an interstitial pattern with traction bronchiectasis, diffuse ground-glass opacities, and cystic change with fibrosis. Acute radiation pneumonitis was diagnosed. Oncologists should be alert to the potential risk of radiation toxicities caused by low dose off-targets and abscopal effects even with highly conformal radiotherapy.

SU‐E‐T‐480: Classic Kaposi's Sarcoma at Lower‐Extremity Irradiation with Helical Tomotherapy

Purpose: To spare parts of the lymphatic drainage, muscle and skeleton of the lower extremities, a treatment technique using a helical tomotherapy (HT) for Classic Kaposis sarcoma (KS) was developed and the analysis of surface doses around the lesion was performed. Methods: To achieve a homogenous dose distribution over the surface of the lower extremity, the gaps between the toes of the foot of a patient were packed by a thermal plastic material (poly‐flex II). For more effective immobilization and precise localization, the poly‐flex II‐covering foot mold was enclosed by the water‐ equivalent wax shaped into a brick and marked the localization (wax‐mold). A treatment planningCT of the patient with the custom‐made wax‐poly‐flex II brick was taken. CTV was contoured around the lesion surface with at least 0.5 cm depth. The PTV was created by expanding an isotropic 0.5 cm margin from CTV. A core structure spaced with 0.5 cm from PTV was contoured and assigned as a constraint to achieve steep dose gradient at shallow region. A prescribed dose (Dp) of 37.5 Gy in 15 fractions with a field width of 2.5 cm and a pitch of 0.287 were used for Tomotherapy Hi Art Planning system. MVCT image registration was performed before daily treatment. The surface doses around the lesions were measured by EBT2 films. Results: The 95% of Dp was received by at least 95% of PTV, and the maximum dose was less than 110% of Dp. The dose distribution in the central core fell off steeply with the mean dose of 50% of Dp. The measured doses were 94 to 99% of Dp. Conclusions: Combined with the image‐guided HT and wax‐mold device, an adequate doses to the skin can be achieved and the doses to the normal structures can be reduced significantly for KS at lower‐extremity irradiation.

Total Marrow Irradiation with Helical Tomotherapy: A Case Report

A 53-year-old Asian woman with plasma cell myloma with IgG/kappa stage IIIa post chemotherapy was selected for autologous hematopoietic cell transplantation (HCT). Total marrow irradiation (TMI) tomotherapy was planned as a preconditioning regimen of HCT. A total dose of 800 cGy (200 cGy/ fraction) was delivered to the bone marrow. More than 10 months post transplant without evidence of active disease for the patient was noted. Except for Grade 1 nausea and vomiting there were no significantly adverse effects during TMI. The preconditioning regimen for the bone marrow transplant with helical tomotherapy targeting the bone marrow of the whole body is potentially less toxic and as efficacious in the patient. Antiemetics should be prescribed for the whole course of TMI for emesis prevention.

SU‐FF‐T‐342: Evaluation of Superficial Dose for Helical Tomotherapy with GAFCHROMIC® EBT Film

Purpose: To measure the surface dose using EBT films for helical tomotherapy. Materials and methods: A cylindrical solid water phantom was scanned on a Siemens Somatom CT scanner with 3mm slice thickness. Four types of tomotherapy plans were studied: 1. The PTV touching the surface, planned and treated with different thicknesses of bolus (0,3,5,8 and 10mm), 2. Same as first, but treated without the bolus, 3. The PTV extended by 5mm outside the surface, planned and treated with and without a 10mm bolus, and 4. The PTV withdrawn from the surface by 3mm to 5mm, planned and treated without bolus. For each case, a plan was created to deliver 2Gy to 95% of the PTV per fraction. Gafchromic EBT films were used to measure the surface and the target doses. We also measured the surface doses of five clinical patients to verify the phantom study results. Results: For type 1 cases, when planned and treated without the bolus, the surface dose was about 65% of the prescribed dose; when different thicknesses of bolus were used, the surface doses were slightly higher than the prescribed dose. For type 2 cases, the surface dose decreased by about 40% to 45% of the prescribed dose, whereas the dose to the rest of PTV only increased by less than 3%. For type 3 cases, the surface doses were similar to the other cases with and without the bolus. For type 4 cases, the surface dose decreased by about 40% relative to the prescribed dose. Conclusion: When the PTV touches the surface, using bolus to ensure sufficient dose coverage of the tumor volume is recommended. Conversely, when the target volume is withdrawn from the surface, adequate tumor coverage can be achieved without bolus while reducing the surface dose by about 40% to 45%.