Amr Taha

PURPOSE: To compare volumetric-modulated arc therapy (VMAT) with 3D-conformal radiation therapy (3D-CRT) mediastinal irradiation for stage I-II supra-diaphragmatic Hodgkin's Lymphoma (HL).

PATIENTS AND METHODS: Eleven patients were planned for RT after 4-6 cycles of ABVD chemotherapy: conventional 3D-CRT (AP/PA) and VMAT plans were conformed to the same PTV. Objective was to choose the best PTV coverage plan with the least OAR dose. The 2 plans were compared for: PTV coverage, mean dose and V5,V20lung, mean dose and V30heart, V5, V10, V15breast (female patients), and the integral body dose.

RESULTS: Both techniques achieved adequate PTV coverage. Mean lung and heart dose was consistently lower in VMAT plans. The lung V20 dose was acceptable for VMAT, but exceeded the tolerance threshold in 6 cases with 3DCRT plans. A mean difference of 15.9% for both lungs V20 favored VMAT plans; average MLD difference was 2.3Gy less for VMAT plans. Similarly, lower maximum and mean heart doses with a 3.3Gy dose reduction and a 9.4% difference in V30 favored VMAT plans. Mean V5lung/female breast and integral dose were invariably higher in VMAT plans because of the low-dose spread.

CONCLUSIONS: VMAT is a valuable technique for treatment of large mediastinal HL. VMAT spares the lung and heart compared to 3DCRT using ISRT in select HL cases. VMAT allows dose escalation for post-chemotherapy residual disease with minimal dose to OARs. VMAT low radiation dose (V5) to the normal tissues, and the increased integral dose should be considered.

BACKGROUND: The pediatric diffuse intrinsic pontine glioma (DIPG) outcome remains dismal despite multiple therapeutic attempts.

PURPOSE: To compare the results of treatment of pediatric diffuse intrinsic pontine glioma (DIPG) using hypofractionated versus conventional radiotherapy.

PATIENTS AND METHODS: Seventy-one newly diagnosed DIPG children were randomized into hypofractionated (HF) (39Gy/13 fractions in 2.6weeks) and conventional (CF) arm (54Gy/30 fractions in 6weeks).

RESULTS: The median and one-year overall survival (OS) was 7.8months and 36.4±8.2% for the hypofractionated arm, and 9.5 and 26.2±7.4% for the conventional arm respectively. The 18-month OS difference was 2.2%. The OS hazard ratio (HR) was 1.14 (95% CI: 0.70-1.89) (p=0.59). The hypofractionated arm had a median and one-year progression-free survival (PFS) of 6.6months and 22.5±7.1%, compared to 7.3 and 17.9±7.1% for the conventional arm. The PFS HR was 1.10 (95% CI: 0.67-1.90) (p=0.71). The 18-month PFS difference was 1.1%. These differences exceed the non-inferiority margin. The immediate and delayed side effects were not different in the 2 arms.

CONCLUSIONS: Hypofractionated radiotherapy offers lesser burden on the patients, their families and the treating departments, with nearly comparable results to conventional fractionation, though not fulfilling the non-inferiority assumption.

BACKGROUND: The pediatric diffuse intrinsic pontine glioma (DIPG) outcome remains dismal despite multiple therapeutic attempts.

PURPOSE: To compare the results of treatment of pediatric diffuse intrinsic pontine glioma (DIPG) using hypofractionated versus conventional radiotherapy.

PATIENTS AND METHODS: Seventy-one newly diagnosed DIPG children were randomized into hypofractionated (HF) (39Gy/13 fractions in 2.6weeks) and conventional (CF) arm (54Gy/30 fractions in 6weeks).

RESULTS: The median and one-year overall survival (OS) was 7.8months and 36.4±8.2% for the hypofractionated arm, and 9.5 and 26.2±7.4% for the conventional arm respectively. The 18-month OS difference was 2.2%. The OS hazard ratio (HR) was 1.14 (95% CI: 0.70-1.89) (p=0.59). The hypofractionated arm had a median and one-year progression-free survival (PFS) of 6.6months and 22.5±7.1%, compared to 7.3 and 17.9±7.1% for the conventional arm. The PFS HR was 1.10 (95% CI: 0.67-1.90) (p=0.71). The 18-month PFS difference was 1.1%. These differences exceed the non-inferiority margin. The immediate and delayed side effects were not different in the 2 arms.

CONCLUSIONS: Hypofractionated radiotherapy offers lesser burden on the patients, their families and the treating departments, with nearly comparable results to conventional fractionation, though not fulfilling the non-inferiority assumption.

BACKGROUND AND PURPOSE: To quantify the organ motion relative to bone in different breathing states in pediatric neuroblastoma using cone beam CT (CBCT) for better definition of the planning margins during abdominal IMRT.

METHODS AND MATERIALS: Forty-two datasets of kV CBCT for 9 pediatric patients with abdominal neuroblastoma treated with IMRT were evaluated. Organs positions on planning CT scan were considered the reference position against which organs and target motions were evaluated. The position of the kidneys and the liver was assessed in all scans. The target movement was evaluated in four patients who were treated for gross residual disease.

RESULTS: The mean age of the patients was 4.1 ± 1.6 years. The range of target movement in the craniocaudal direction (CC) was 5mm. In the CC direction, the range of movement was 10mm for the right kidney, and 8mm for the left kidney. Similarly, the liver upper edge range of motion was 11 mm while the lower edge range of motion was 13 mm.

CONCLUSIONS: With the use of daily CBCT we may be able to reduce the PTV margin. If CBCT is not used daily, a wider margin is needed.

PURPOSE: To investigate the role of stereotactic radio surgery (SRS) and hypo-fractionated stereotactic radiotherapy (SRT) in treatment of benign intracranial meningioma.

PATIENTS AND METHODS: Between 2003 and 2010, 32 patients with a median age of 44 years (range 21-67 years) were treated with SRS (n=19), and hypo-fractionated SRT (n=13) for intracranial meningioma. Fourteen patients underwent SRS or SRT as their primary treatment, while 18 patients underwent post operative SRS or SRT (PORT). Cumulative progression free survival, overall cumulative survival, toxicity and symptomatology were evaluated.

RESULTS: The median follow up period was 39 months (range 6-72 months). The 5 year overall survival and progression free survival were 90 ± 5% and 94 ± 4% after SRT or SRS respectively. Symptoms were improved or stable in 94% of patients. Acute toxicity was mild, and was seen in 41% of patients. Clinically significant late morbidity or new cranial nerve palsies did not occur.

CONCLUSION: Stereotactic radio surgery (SRS) and hypo-fractionated stereotactic radiotherapy (SRT) are effective and safe treatment modality for local control of meningioma with low risk of significant late toxicity. In case of large tumor size and adjacent critical structures, hypo-fractionated SRT is highly recommended.

PURPOSE: To evaluate the potential for dose escalation with intensity-modulated radiotherapy (IMRT) in positron emission tomography-based radiotherapy planning for locally advanced non-small-cell lung cancer (LA-NSCLC).

METHODS AND MATERIALS: For 35 LA-NSCLC patients, three-dimensional conformal radiotherapy and IMRT plans were made to a prescription dose (PD) of 66 Gy in 2-Gy fractions. Dose escalation was performed toward the maximal PD using secondary endpoint constraints for the lung, spinal cord, and heart, with de-escalation according to defined esophageal tolerance. Dose calculation was performed using the Eclipse pencil beam algorithm, and all plans were recalculated using a collapsed cone algorithm. The normal tissue complication probabilities were calculated for the lung (Grade 2 pneumonitis) and esophagus (acute toxicity, grade 2 or greater, and late toxicity).

RESULTS: IMRT resulted in statistically significant decreases in the mean lung (p <.0001) and maximal spinal cord (p = .002 and 0005) doses, allowing an average increase in the PD of 8.6-14.2 Gy (p ≤.0001). This advantage was lost after de-escalation within the defined esophageal dose limits. The lung normal tissue complication probabilities were significantly lower for IMRT (p <.0001), even after dose escalation. For esophageal toxicity, IMRT significantly decreased the acute NTCP values at the low dose levels (p = .0009 and p <.0001). After maximal dose escalation, late esophageal tolerance became critical (p <.0001), especially when using IMRT, owing to the parallel increases in the esophageal dose and PD.

CONCLUSION: In LA-NSCLC, IMRT offers the potential to significantly escalate the PD, dependent on the lung and spinal cord tolerance. However, parallel increases in the esophageal dose abolished the advantage, even when using collapsed cone algorithms. This is important to consider in the context of concomitant chemoradiotherapy schedules using IMRT.

AIM: To compare the accuracy of radiotherapy set-up using an electronic portal imaging device (EPID) versus megavoltage cone beam computed tomography (MV-CBCT) in paediatric patients.

MATERIALS AND METHODS: In total, 204 pairs of EPID and MV-CBCT were carried out for 72 patients in the first 3 treatment days and weekly thereafter.

RESULTS: For the whole group, the mean systematic EPID set-up errors were 1.8 (±1.7), 1.6 (±1.3), 1.4 (±1.5) mm and 2.3 (±1.7), 1.6 (±1.3), 2.4 (±1.6) mm for MV-CBCT in the longitudinal, lateral and vertical directions, respectively, whereas the mean EPID random errors were 2.0 (±1.7), 1.4 (±1.5), 1.2 (±1.6) and 1.9 (±1.5), 1.5 (±1.3), 2.1 (±1.7) mm for MV-CBCT in the longitudinal, lateral and vertical directions, respectively. For systematic errors of head and neck patients, there was a statistically significant difference in the lateral and vertical directions (P=0.027, 0.003), whereas in the non-head and neck patients there was a statistically significant difference in the lateral direction only (P=0.031). In head and neck patients, the mean random errors were significantly different in the vertical and lateral directions, whereas in non-head and neck patients, they were significantly different in the vertical direction only. The larger values alternate between the two modalities. The systematic and random errors (detected by EPID and MV-CBCT) were significantly correlated in almost all direction in all tumour sites.

CONCLUSIONS: The comparison between set-up error in EPID and MV-CBCT was not in favour of any of the two modalities. However, the two modalities were strongly correlated but fairly agreed and the differences between the shifts reported were small and hardly influenced the recommended planning target volume margin.

With the advancement in endoscopic surgery, radiation treatment planning and execution, as well as the use of new chemotherapeutic regimens, bladder conservation has evolved into a competing alternative to radical cystectomy. Trimodality treatment has the great advantage of preserving a normally functioning urinary bladder. Despite the absence of direct randomized trials comparing both modalities, trimodality treatment comprising maximal transuretheral resection of bladder tumors followed by different regimens of combined radiochemotherapy achieved comparable results to radical cystectomy in many trials. Those who did not achieve complete remission after induction radiochemotherapy were salvaged by radical cystectomy. Improving the radiotherapeutic window is a challenging issue. In radiotherapy for bladder cancer, uncertainties include set-up errors, patient movement, internal organ movement and volume changes due to bladder filling (both inter- and intrafraction). The advancement in treatment verification procedures in modern radiotherapy and the use of fiducial markers reduces set-up errors, while adaptive radiotherapy could decrease the unnecessary irradiation of normal tissues by tracking bladder volume changes. In addition, new radiotherapeutic techniques, such as intensity-modulated radiotherapy and volume-modulated radiotherapy, permit dose escalation to the target without increasing the dose to the surrounding normal tissues.

BACKGROUND AND PURPOSE: In this study on PDR treatment planning of utero-vaginal carcinoma, we analysed the dosimetry of traditional X-ray based plans as it presents on MR images. The potential gain of MRI-based dose optimisation was assessed.

PATIENTS AND METHODS: Sixteen patients boosted with PDR brachytherapy after external beam therapy were included. The clinical X-ray based plans were projected on MR images. The GTV, HR-CTV and IR-CTV were retrospectively contoured, as well as the bladder, rectum and sigmoid colon. The dose in the critical organs and target coverage was investigated. In a second phase, the plans were manually optimised using the MR information. The objectives were to lower the dose in the critical organs (or= 85 Gy(alphabeta10).

RESULTS: In the X-ray based plans, D(2cc) in bladder and sigmoid colon exceeded the tolerance doses in 10/16 and 7/16 patients, respectively. Coverage of the IR-CTV with the 60 Gy(alphabeta10) was acceptable. D90 of the HR-CTV was below 85 Gy(alphabeta10) in 13 out of 16 patients. After optimisation, the dose constraints in the OAR were not exceeded anymore in any patient. The average D(2cc) dose reduction was 7+/-6 Gy(alphabeta3) in the bladder and 7+/-4 Gy(alphabeta3) in the sigmoid colon for those patients in which the dose constraint was initially exceeded. In addition, an average dose increase of 3 Gy(alphabeta10) was accomplished in the HR-CTV.

CONCLUSIONS: MRI-based dose optimisation can play an important role to reduce the dose delivered to the critical organs and to improve target coverage.