The University of California, Irvine experience with tomotherapy using the Peacock system

Feasibility of helical tomotherapy for radical dose retreatment in pelvic area: A report of 4 cases

Aims and background

To retrospectively determine acute toxicity and local control in patients with recurrence after definitive radiotherapy for prostate, bladder and rectal carcinoma.

Methods

Between September 2009 and March 2010, 4 patients with a prior history of pelvic radiotherapy were treated with helical tomotherapy. The prior course of radiotherapy was given for prostate cancer in 2 patients, bladder carcinoma in 1 patient and rectal carcinoma in 1 patient. The median prescribed dose of the prior course of radiotherapy was 6320 cGy (range, 5000–7600), and the median elapsed time between the first and second course was 17 months (range, 4–73). The total prescribed dose for tomotherapy retreatment was 60 Gy in 3 patients and 50 Gy in 1 patient. Hormone therapy was administered to 2 patients before and during radiation. No patient underwent surgical resection.

Results

The cumulative mean dose to the rectum ranged from 3813 to 6058 cGy; cumulative rectal maximum dose to 1 cc ranged from 6475 to 8780 cGy. Regarding the bladder, the cumulative mean dose was between 4384 and 7612 cGy; cumulative maximum dose to 1 cc ranged from 7560 to 9790 cGy. All patients completed the re-irradiation course. Acute genitourinary toxicity (RTOG scale) was grade 0 in 3 patients and grade 1 in 1 patient; acute gastrointestinal toxicity was grade 0 in 3 patients and grade 1 in 1 patient. With a median follow-up of 9 months (range, 7–12), late toxicity was G0 in all patients. Three patients showed partial response with computed tomography or magnetic resonance imaging, and 1 had a PSA decrease.

Conclusions

Re-irradiation with helical tomotherapy was well tolerated, with low rates of acute and late toxicity. It can be therefore considered a useful tool to improve local control in patients previously treated with radiotherapy. However, a larger number of patients and a longer follow-up are required to assess retreatment safety.

Quality assurance of TomoDirect treatment plans using I'mRT MatriXX

Purpose:

To evaluate the performance of 2D-array I’mRT MatriXX for dose verification of TomoDirect treatment plans.

Methods:

In this study, a 2D-array ion chamber device – the I’mRT MatriXX and Multicube Phantom from IBA – was used for dose verification of different TomoDirect plans. Pre-treatment megavoltage computed tomography (MVCT) was performed on the phantom setup for position correction. After the irradiation of treatment plans on the I’mRT MatriXX and Multicube Phantom, the measured doses of coronal planes were compared with those from the planning calculations for verification. The results were evaluated by comparing the absolute dose difference in the high dose region as well as the gamma analysis of the 2D-dose distributions on the coronal plane. The comparison was then repeated with the measured dose corrected for angular dependence of the MatriXX.

Results:

When angular dependence is taken into account, the passing rate of gamma analysis is over 90% for all measurements using the MatriXX. If there is no angular dependence correction, the passing rate of gamma analysis worsens for treatment plans with dose contribution from the rear. The passing rate can be as low as 53.55% in extreme cases, i.e. where all doses in the treatment plan are delivered from the rear.

Conclusion:

It is important to correct the measured dose for angular dependence when verifying TomoDirect treatment plans using the MatriXX. If left uncorrected, a large dose discrepancy may be introduced to the verification results.

Volumetric modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer

INTRODUCTION

Volumetric modulated arc therapy (VMAT), a complex treatment strategy for intensity-modulated radiation therapy, may increase treatment efficiency and has recently been established clinically. This analysis compares VMAT against established IMRT and 3D-conformal radiation therapy (3D-CRT) delivery techniques.

METHODS

Based on CT datasets of 9 patients treated for prostate cancer step-and-shoot IMRT, serial tomotherapy (MIMiC), 3D-CRT and VMAT were compared with regard to plan quality and treatment efficiency. Two VMAT approaches (one rotation (VMAT1x) and one rotation plus a second 200 degrees rotation (VMAT2x)) were calculated for the plan comparison. Plan quality was assessed by calculating homogeneity and conformity index (HI and CI), dose to normal tissue (non-target) and D(95%) (dose encompassing 95% of the target volume). For plan efficiency evaluation, treatment time and number of monitor units (MU) were considered.

RESULTS

For MIMiC/IMRT(MLC)/VMAT2x/VMAT1x/3D-CRT, mean CI was 1.5/1.23/1.45/1.51/1.46 and HI was 1.19/1.1/1.09/1.11/1.04. For a prescribed dose of 76 Gy, mean doses to organs-at-risk (OAR) were 50.69 Gy/53.99 Gy/60.29 Gy/61.59 Gy/66.33 Gy for the anterior half of the rectum and 31.85 Gy/34.89 Gy/38.75 Gy/38.57 Gy/55.43 Gy for the posterior rectum. Volumes of non-target normal tissue receiving > or =70% of prescribed dose (53 Gy) were 337 ml/284 ml/482 ml/505 ml/414 ml, for > or =50% (38 Gy) 869 ml/933 ml/1155 ml/1231 ml/1993 ml and for > or =30% (23 Gy) 2819 ml/3414 ml/3340 ml/3438 ml /3061 ml. D(95%) was 69.79 Gy/70.51 Gy/71,7 Gy/71.59 Gy/73.42 Gy. Mean treatment time was 12 min/6 min/3.7 min/1.8 min/2.5 min.

CONCLUSION

All approaches yield treatment plans of improved quality when compared to 3D-conformal treatments, with serial tomotherapy providing best OAR sparing and VMAT being the most efficient treatment option in our comparison. Plans which were calculated with 3D-CRT provided good target coverage but resulted in higher dose to the rectum.

Technological advances in radiation oncology for central nervous system tumors

Advances in computer software technology have led to enormous progress that has enabled increasing levels of complexity to be incorporated into radiotherapy treatment planning systems. Because of these changes, the delivery of radiotherapy evolved from therapy designed primarily on plain 2-dimensional X-ray images and hand calculations to therapy based on 3-dimensional images incorporating increasingly complex computer algorithms in the planning process. In addition, challenges in treatment planning and radiation delivery, such as problems with setup error and organ movement, have begun to be systematically addressed, ushering in an era of so-called 4-dimensional radiotherapy. This review article discusses how these advances have changed the way in which many common neoplasms of the central nervous system are being treated at present.

Standard fractionation intensity modulated radiation therapy (IMRT) of primary and recurrent glioblastoma multiforme

BACKGROUND

Intensity-modulated radiation therapy (IMRT) affords unparalleled capacity to deliver conformal radiation doses to tumors in the central nervous system. However, to date, there are few reported outcomes from using IMRT, either alone or as a boost technique, for standard fractionation radiotherapy for glioblastoma multiforme (GBM).

METHODS

Forty-two patients were treated with IMRT alone (72%) or as a boost (28%) after 3-dimensional conformal radiation therapy (3D-CRT). Thirty-three patients with primary disease and 9 patients with recurrent tumors were included. Thirty-four patients (81%) had surgery, with gross tumor resection in 13 patients (36%); 22 patients (53%) received chemo-radiotherapy. The median total radiation dose for all patients was 60 Gy with a range from 30.6 to 74 Gy. Standard fractions of 1.8 Gy/day to 2.0 Gy/day were utilized.

RESULTS

Median survival was 8.7 months, with 37 patients (88%) deceased at last contact. Nonparametric analysis showed no survival difference in IMRT-boost vs. IMRT-only groups.

CONCLUSION

While technically feasible, preliminary results suggest delivering standard radiation doses by IMRT did not improve survival outcomes in this series compared to historical controls. In light of this lack of a survival benefit and the costs associated with use of IMRT, future prospective trials are needed to evaluate non-survival endpoints such as quality of life and functional preservation. Short of such evidence, the use of IMRT for treatment of GBM needs to be carefully rationalized.

An arc-sequencing algorithm for intensity modulated arc therapy

Intensity modulated arc therapy (IMAT) is an intensity modulated radiation therapy delivery technique originally proposed as an alternative to tomotherapy. IMAT uses a series of overlapping arcs to deliver optimized intensity patterns from each beam direction. The full potential of IMAT has gone largely unrealized due in part to a lack of robust and commercially available inverse planning tools. To address this, we have implemented an IMAT arc-sequencing algorithm that translates optimized intensity maps into deliverable IMAT plans. The sequencing algorithm uses simulated annealing to simultaneously optimize the aperture shapes and weights throughout each arc. The sequencer enforces the delivery constraints while minimizing the discrepancies between the optimized and sequenced intensity maps. The performance of the algorithm has been tested for ten patient cases (3 prostate, 3 brain, 2 head-and-neck, 1 lung, and 1 pancreas). Seven coplanar IMAT plans were created using an average of 4.6 arcs and 685 monitor units. Additionally, three noncoplanar plans were created using an average of 16 arcs and 498 monitor units. The results demonstrate that the arc sequencer can provide efficient and highly conformal IMAT plans. An average sequencing time of approximately 20 min was observed.

Intensity-modulated radiation therapy for the treatment of pediatric cancer patients

Intensity-modulated radiation therapy (IMRT) is a novel form of radiotherapy, which has the potential to reduce the amount of radiation unintentionally delivered to normal tissues while maintaining a high radiation dose to the tumor in comparison with standard radiation techniques. In adults, this technology has been implemented in a number of tumor sites, but in children it has been little used. This article will review the current studies in which IMRT has been used in children. It will also discuss possible future applications for IMRT, and anticipated problems with its use.

Intensity-Modulated Radiation Therapy for Prostate Cancer

Prostate cancer is among the most common solid malignancies. A number of treatment alternatives exist for localized prostate cancer, including observation, prostatectomy, brachytherapy, and external-beam radiation therapy (EBRT). External-beam radiation therapy has changed dramatically during the past several years. Older techniques paved the way for 3-dimensional conformal radiation therapy (CRT), which in turn facilitated the introduction of intensity-modulated radiation therapy (IMRT). The prostate has served as a model disease site for the implementation of IMRT. As indicated by a growing body of experience, IMRT for prostate cancer represents a major technologic and clinical advance for radiation therapy. In this article, a review is provided of the evolution of EBRT leading to IMRT, the unique features making the prostate an ideal disease site for employing IMRT, the details of the clinical implementation of prostate IMRT and supporting technologic advancements, and the currently reported clinical outcomes of IMRT in prostate cancer. In addition, future directions of prostate IMRT, both technologic and clinical, are discussed.

Intensity-modulated radiation therapy for the spine at the University of California, Irvine

Radiation treatment of malignant diseases of the spine poses unique challenges to the radiation oncology treatment team. Intensity-modulated radiation therapy (IMRT) offers the capability of delivering high doses to targets near the spine while respecting spinal cord tolerance. At the University of California, Irvine, 8 patients received a total of 10 courses to the spine for a variety of primary and metastatic malignant conditions. This paper discusses anatomical considerations, spinal cord radiation myelopathy, and treatment planning issues as it relates to the treatment of spinal cord lesions. Between October 1997 and August 2001, a total of 8 patients received 10 courses of IMRT for primary or metastatic disease of the spine. Cancers treated included metastatic lung, renal, adrenocortical cancers, and primary sarcomas and giant cell tumor. Five cases had 6 courses given for re-irradiation of symptomatic disease and 3 cases had 4 courses of IMRT as primary management of their spinal lesions. Although 3 courses were given postoperatively, these were for grossly residual disease. For the re-irradiation patients, the mean follow-up interval was 4 months. The local control was estimated at 14%. Of the patients treated with primary intent, the mean follow-up was 9 months and the local control rate 75%. No patients developed spinal cord complications.

Intensity-modulated radiation therapy in the treatment of children

Intensity-modulated radiation therapy (IMRT) is a relatively new method of conformal radiotherapy delivery that is rapidly being incorporated in clinical practice. Of all patients treated with conformal techniques, children are the most likely to benefit as normal, developing structures can be minimized in the radiation field. The advantages of IMRT, including increased conformality and possible dose escalation, are discussed in this review. Possible disadvantages of IMRT in children are also discussed, such as lack of dose homogeneity in the target volume, increased dose to nontarget tissues, reliability of treatment setup, increased anesthesia time in younger children, and prolonged treatment planning. The issue of increased risk of second malignancy in this very young population is important, as many of these children will be long-term survivors with current multimodality therapy.