Pooja Jain

Inter-fraction motion and dosimetric consequences during breast intensity-modulated radiotherapy (IMRT)

BACKGROUND AND PURPOSE Intensity-modulated radiotherapy (IMRT) can improve dose homogeneity within the breast planned target volume (PTV), but may be more susceptible to patient/organ motion than standard tangential radiotherapy (RT). We used daily cone-beam CT (CBCT) imaging to assess inter-fraction motion during breast IMRT and its subsequent impact on IMRT and standard RT dose homogeneity. MATERIALS AND METHODS Ten breast cancer patients selected for IMRT were studied. CBCT images were acquired immediately after daily treatment. Automatic image co-registration was used to determine patient positioning variations. Daily PTV contours were used to calculate PTV variations and daily delivered IMRT and theoretically planned tangential RT dose. RESULTS Group systematic (and random) setup errors detected by CBCT were 5.7 (3.9)mm laterally, 2.8 (3.5)mm vertically and 2.3 (3.2)mm longitudinally. Rotations >2 degrees in any axis occurred on 53/106 (50%) occasions. Daily PTV volume varied up to 23%. IMRT dose homogeneity was superior at planning and throughout the treatment compared with standard RT (1.8% vs. 15.8% PTV received >105% planned mean dose), despite increased motion sensitivity. CONCLUSIONS CBCT revealed inadequacies of current patient positioning and verification procedures during breast RT and confirmed improved dose homogeneity using IMRT for the patients studied.

Quantifying motion for pancreatic radiotherapy margin calculation.

BACKGROUND AND PURPOSE Pancreatic radiotherapy (RT) is limited by uncertain target motion. We quantified 3D patient/organ motion during pancreatic RT and calculated required treatment margins. MATERIALS AND METHODS Cone-beam computed tomography (CBCT) and orthogonal fluoroscopy images were acquired post-RT delivery from 13 patients with locally advanced pancreatic cancer. Bony setup errors were calculated from CBCT. Inter- and intra-fraction fiducial (clip/seed/stent) motion was determined from CBCT projections and orthogonal fluoroscopy. RESULTS Using an off-line CBCT correction protocol, systematic (random) setup errors were 2.4 (3.2), 2.0 (1.7) and 3.2 (3.6)mm laterally (left-right), vertically (anterior-posterior) and longitudinally (cranio-caudal), respectively. Fiducial motion varied substantially. Random inter-fractional changes in mean fiducial position were 2.0, 1.6 and 2.6mm; 95% of intra-fractional peak-to-peak fiducial motion was up to 6.7, 10.1 and 20.6mm, respectively. Calculated clinical to planning target volume (CTV-PTV) margins were 1.4 cm laterally, 1.4 cm vertically and 3.0 cm longitudinally for 3D conformal RT, reduced to 0.9, 1.0 and 1.8 cm, respectively, if using 4D planning and online setup correction. CONCLUSIONS Commonly used CTV-PTV margins may inadequately account for target motion during pancreatic RT. Our results indicate better immobilisation, individualised allowance for respiratory motion, online setup error correction and 4D planning would improve targeting.

An analysis of breast motion using high-frequency, dense surface points captured by an optical sensor during radiotherapy treatment delivery

Patient motion is an important factor affecting the quality of external beam radiotherapy in breast patients. We analyse the motion of a dense set of surface points on breast patients throughout their treatment schedule to assess the magnitude and stability of motion, in particular, with respect to breast volume. We use an optical sensor to measure the surface motion of 13 breast cancer patients. Patients were divided into two cohorts dependent upon breast volume. Measurements were made during radiotherapy treatment beam delivery for an average of 12 fractions per patient (total 158 datasets). The motion of each surface point is parameterized in terms of its period, amplitude and relative phase. Inter-comparison of the motion parameters across treatment schedules and between patients is made through the creation of corresponding regions on the breast surfaces. The motion period is spatially uniform and is similar in both patient groups (mean 4 s), with the small volume cohort exhibiting greater inter-fraction period variability. The mean motion amplitude is also similar in both groups with a range between 2 mm and 4 mm and an inter-fraction variability generally less than 1 mm. There is a phase lag of up to 0.4 s across the breast, led by the sternum. Breast patient motion is reasonably stable between and during treatment fractions, with the large volume cohort exhibiting greater repeatability than the small volume one.

Efficacy and Tolerability of Limited Field Radiotherapy with Concurrent Capecitabine in Locally Advanced Pancreatic Cancer

AIMS Patients with locally advanced pancreatic cancer (LAPC) are most commonly managed with chemotherapy or concurrent chemoradiotherapy (CRT), which may or may not include non-involved regional lymph nodes in the clinical target volume. We present our results of CRT for LAPC using capecitabine and delivering radiotherapy to a limited radiation field that excluded non-involved regional lymph nodes from the clinical target volume. MATERIALS AND METHODS Thirty patients were studied. Patients received 50.4 Gy external beam radiotherapy in 28 fractions, delivered to a planning target volume expanded from the primary tumour and involved nodes only. Capecitabine (500-600 mg/m2) was given twice daily continuously during radiotherapy. Toxicity and efficacy data were prospectively collected. RESULTS Nausea, vomiting and tumour pain were the most common grade 2 toxicities. One patient developed grade 3 nausea. The median time to progression was 8.8 months, with 20% remaining progression free at 1 year. The median overall survival was 9.7 months with a 1 year survival of 30%. Of 21 patients with imaged progression, 13 (62%) progressed systemically, three (14%) had local progression, two (10%) had locoregional progression and three (14%) progressed with both local/locoregional and systemic disease. CONCLUSION CRT using capecitabine and limited field radiotherapy is a well-tolerated, relatively efficacious treatment for LAPC. The low toxicity and low regional progression rates support the use of limited field radiotherapy, allowing evaluation of this regimen with other anti-cancer agents.

Efficacy and toxicity of limited field concurrent chemoradiotherapy (CRT) with capecitabine for locally advanced pancreatic cancer (LAPC)

15586 Background: Treatment outcome in LAPC remains poor. As treatment-related toxicity limits CRT dose-intensification, we evaluated the efficacy/toxicity of capecitabine based CRT in LAPC patients using limited field irradiation, excluding elective nodal areas. Methods: 25 consecutive LAPC patients eligible for CRT were treated at a single institute. Capecitabine was administered at 500–600 mg/m2/b.i.d continuously (including weekends) from day one to completion of radiotherapy (RT). RT was delivered conformally to a dose of 50.4Gy in 28 fractions over 5.5 weeks. The gross tumour volume consisting of the pancreatic tumour and any involved peri-pancreatic nodes was isometrically expanded by 0.5 cm to generate the clinical target volume (CTV). The planning target volume (PTV) comprised the CTV plus a 1cm margin AP/LR and a 1.5 - 2 cm margin SI. Patients were reviewed weekly to monitor weight and collect toxicity data. Time to disease progression and survival were calculated from diagnosis. Results: Median...