Simplifying intensity-modulated radiotherapy plans with fewer beam angles for the treatment of oropharyngeal carcinoma.

The first aim of the present study was to investigate the feasibility of using fewer beam angles to improve delivery efficiency for the treatment of oropharyngeal cancer (OPC) with inverse-planned intensity-modulated radiation therapy (IP-IMRT). A secondary aim was to evaluate whether the simplified IP-IMRT plans could reduce the indirect radiation dose. The treatment plans for 5 consecutive OPC patients previously treated with a forward-planned IMRT (FP-IMRT) technique were selected as benchmarks for this study. The initial treatment goal for these patients was to deliver 70 Gy to > or = 95% of the planning gross tumor volume (PTV-70) and 59.4 Gy to > or = 95% of the planning clinical tumor volume (PTV-59.4) simultaneously. Each case was re-planned using IP-IMRT with multiple beam-angle arrangements, including four complex IP-IMRT plans using 7 or more beam angles, and one simple IMRT plan using 5 beam angles. The complex IP-IMRT plans and simple IP-IMRT plans were compared to each other and to the FPIMRT plans by analyzing the dose coverage of the target volumes, the plan homogeneity, the dose-volume histograms of critical structures, and the treatment delivery parameters including delivery time and the total number of monitor units (MUs). When comparing the plans, we found no significant difference between the complex IP-IMRT, simple IP-IMRT, and FP-IMRT plans for tumor target coverage (PTV-70: p = 0.56; PTV-59.4: p = 0.20). The plan homogeneity, measured by the mean percentage isodose, did not significantly differ between the IP-IMRT and FP-IMRT plans (p = 0.08), although we observed a trend toward greater inhomogeneity of dose in the simple IP-IMRT plans. All IP-IMRT plans either met or exceeded the quality of the FP-IMRT plans in terms of dose to adjacent critical structures, including the parotids, spinal cord, and brainstem. As compared with the complex IP-IMRT plans, the simple IP-IMRT plans significantly reduced the mean treatment time (maximum probability for four pairwise comparisons: p = 0.0003). In conclusion, our study demonstrates that, as compared with complex IP-IMRT, simple IP-IMRT can significantly improve treatment delivery efficiency while maintaining similar target coverage and sparing of critical structures. However, the improved efficiency does not significantly reduce the total number of MUs nor the indirect radiation dose

Simplifying intensity-modulated radiotherapy plans with fewer beam angles for the treatment of oropharyngeal carcinoma.

The first aim of the present study was to investigate the feasibility of using fewer beam angles to improve delivery efficiency for the treatment of oropharyngeal cancer (OPC) with inverse-planned intensity-modulated radiation therapy (IP-IMRT). A secondary aim was to evaluate whether the simplified IP-IMRT plans could reduce the indirect radiation dose. The treatment plans for 5 consecutive OPC patients previously treated with a forward-planned IMRT (FP-IMRT) technique were selected as benchmarks for this study. The initial treatment goal for these patients was to deliver 70 Gy to > or = 95% of the planning gross tumor volume (PTV-70) and 59.4 Gy to > or = 95% of the planning clinical tumor volume (PTV-59.4) simultaneously. Each case was re-planned using IP-IMRT with multiple beam-angle arrangements, including four complex IP-IMRT plans using 7 or more beam angles, and one simple IMRT plan using 5 beam angles. The complex IP-IMRT plans and simple IP-IMRT plans were compared to each other and to the FPIMRT plans by analyzing the dose coverage of the target volumes, the plan homogeneity, the dose-volume histograms of critical structures, and the treatment delivery parameters including delivery time and the total number of monitor units (MUs). When comparing the plans, we found no significant difference between the complex IP-IMRT, simple IP-IMRT, and FP-IMRT plans for tumor target coverage (PTV-70: p = 0.56; PTV-59.4: p = 0.20). The plan homogeneity, measured by the mean percentage isodose, did not significantly differ between the IP-IMRT and FP-IMRT plans (p = 0.08), although we observed a trend toward greater inhomogeneity of dose in the simple IP-IMRT plans. All IP-IMRT plans either met or exceeded the quality of the FP-IMRT plans in terms of dose to adjacent critical structures, including the parotids, spinal cord, and brainstem. As compared with the complex IP-IMRT plans, the simple IP-IMRT plans significantly reduced the mean treatment time (maximum probability for four pairwise comparisons: p = 0.0003). In conclusion, our study demonstrates that, as compared with complex IP-IMRT, simple IP-IMRT can significantly improve treatment delivery efficiency while maintaining similar target coverage and sparing of critical structures. However, the improved efficiency does not significantly reduce the total number of MUs nor the indirect radiation dose

High failure rate in spinal ependymomas with long-term follow-up1

Data on spinal ependymomas are sparse, and prognostic factors remain controversial. The primary aim of this study is to review a historical cohort, with large patient numbers and long follow-up, and provide estimates of time to progression (TTP) and survival after progression. As a secondary aim, we assess the effects of potential prognostic variables. Thirty-seven patients with spinal cord ependymomas received postoperative radiation therapy from 1955 to 2001. The influences of radiation dose, extent of resection, Karnofsky performance score, tumor location, and multifocality were assessed in univariate analyses by using the Cox proportional hazards model. The median follow-up for patients who did not fail was 121 months (range, 8–312 months). Kaplan-Meier estimates of 5-, 10-, and 15-year percentage progression free are 75% ± 7.4%, 50% ± 9.1%, and 46% ± 9.3%, respectively. Median TTP, for those who recurred, is 68 months (range, 2–324 months), with 12 of 21 failures occurring after five years. Of the prognostic factors examined, only greater extent of resection significantly correlated with longer TTP (P = 0.02). Local relapse rates for spinal ependymomas are higher than previously cited, with a large proportion of failures occurring more than five years after diagnosis. Extensive surgical resection correlates with longer time to recurrence, and we thus recommend maximal excision while avoiding surgical morbidity. The overall high rate of recurrence leads us to recommend radiation to doses of 45 to 54 Gy for all patients who do not have gross total resections, and long, close follow-up

The role of up-front radiation therapy for incompletely resected pediatric WHO grade II low-grade gliomas1

The purpose of this study was to assess the impact of early radiation therapy and extent of surgical resection on progression-free survival (PFS) and overall survival (OS) in children with WHO grade II low-grade gliomas (LGGs). We conducted a historical cohort study of 90 patients, ages 21 or younger, diagnosed with WHO grade II LGGs between 1970 and 1995. Median follow-up for surviving patients was 9.4 years (range, 0.5–22.6 years). Tests for variables correlating with OS and PFS were conducted by using log-rank tests and Cox proportional hazards models. Eleven patients underwent gross total resections (GTRs), 43 had subtotal resections, and 34 underwent biopsy only at diagnosis. Two patients underwent biopsy at time of recurrence. Of the 90 patients, 52 received radiation as part of their initial therapy following diagnosis (early-RT group). The overall five-year PFS and OS rates ± SE were 56% ± 5% and 90% ± 3%, respectively. Ten-year PFS and OS rates were 42% ± 6% and 81% ± 5%, respectively. For patients older than three years and without GTRs, administration of early radiation did not appear to influence PFS or OS (P = 0.98 and P = 0.40, respectively; log-rank test). This was confirmed by multivariate analyses (P = 0.95 and P = 0.33 for PFS and OS, respectively). Of the 11 patients with GTRs, disease progressed in only two, and all were alive with no evidence of disease at last follow-up. Patients who underwent GTRs had significantly longer PFS (P = 0.02), but did not have significantly improved OS. Excellent long-term survival rates were achieved for children with WHO grade II LGGs. We were unable to demonstrate a benefit for administering radiation as part of initial treatment. An outcome benefit was seen with greater extent of resection