RapidArc radiotherapy planning for prostate cancer: Single-arc and double-arc techniques vs. intensity-modulated radiotherapy

RapidArc is a novel technique using arc radiotherapy aiming to achieve intensity-modulated radiotherapy (IMRT)-quality radiotherapy plans with shorter treatment time. This study compared the dosimetric quality and treatment efficiency of single-arc (SA) vs. double-arc (DA) and IMRT in the treatment of prostate cancer. Fourteen patients were included in the analysis. The planning target volume (PTV), which contained the prostate gland and proximal seminal vesicles, received 76 Gy in 38 fractions. Seven-field IMRT, SA, and DA plans were generated for each patient. Dosimetric quality in terms of the minimum PTV dose, PTV hotspot, inhomogeneity, and conformity index; and sparing of rectum, bladder, and femoral heads as measured by V70, V-40, and V20 (% of volume receiving >70 Gy, 40 Gy, and 20 Gy, respectively), treatment efficiency as assessed by monitor units (MU) and treatment time were compared. All plan objectives were met satisfactorily by all techniques. DA achieved the best dosimetric quality with the highest minimum PTV dose, lowest hotspot, and the best homogeneity and conformity. It was also more efficient than IMRT. SA achieved the highest treatment efficiency with the lowest MU and shortest treatment time. The mean treatment time for a 2-Gy fraction was 4.80 min, 2.78 min, and 1.30 min for IMRT, DA, and SA, respectively. However, SA also resulted in the highest rectal dose. DA could improve target volume coverage and reduce treatment time and MU while maintaining equivalent normal tissue sparing when compared with IMRT. SA achieved the greatest treatment efficiency but with the highest rectal dose, which was nonetheless within tolerable limits. For busy units with high patient throughput, SA could be an acceptable option. © 2012 American Association of Medical Dosimetrists.link_to_subscribed_fulltex

Evolution of treatment for nasopharyngeal cancer--success and setback in the intensity-modulated radiotherapy era

Background and purpose: To assess the therapeutic gains and setbacks as we evolved from the 2-dimensional radiotherapy (2DRT) to conformal 3-dimensional (3DRT) and to intensity-modulated (IMRT) era. MATERIALS AND METHODS: 1593 consecutive patients from 1994 to 2010 were retrospectively analyzed. Evolving changes in the different era included advances in staging investigation, radiotherapy technique, dose escalation, and use of chemotherapy. RESULTS: The 3DRT era achieved significant improvement in local failure-free rate (L-FFR), disease-specific survival (DSS) and overall survival (OS). Neurological damage and bone/soft tissue necrosis were significantly reduced. However, the improvement in distant failure-free rate (D-FFR) was insignificant, and more hearing impairment occurred due to chemotherapy. Significantly higher D-FFR was achieved in the IMRT era, but L-FFR did not show further improvement. 5-Year DSS increased from 78% in the 2DRT, to 81% in the 3DRT, and 85% in the IMRT era, while the corresponding neurological toxicity rate decreased from 7.4% to 3.5% and 1.8%. CONCLUSIONS: Significant improvement in survival and reduction of serious toxicity was achieved as we evolved from 2DRT to 3DRT and IMRT era; the therapeutic ratio for all T-categories improved with more conformal techniques. Improvements in tumor control were attributed not only to advances in RT technique, but also to better imaging and increasing use of potent chemotherapy. However, it should also be noted that hearing impairment significantly increased due to chemotherapy, L-FFR reached a plateau in the 3DRT era, and it is worrisome that the result for T4 remained unsatisfactory. Besides exploring for more potent chemotherapy and innovative methods, the guideline on dose constraint should be re-visited to optimize the therapeutic ratio.link_to_OA_fulltex

Fitting of Biological Parameters for Tumor Control Probability of Nasopharyngeal Carcinoma

Tumor Control Probability (TCP) is useful for plan evaluation, but there is little data on the values of biological parameters α and σ for Nasopharyngeal Carcinoma (NPC). This study aims to estimate these parameters based on the observed tumor control of 351 patients with NPC

The strength/weakness of the AJCC/UICC staging system (7th edition) for nasopharyngeal cancer and suggestions for future improvement

Background and purpose: To evaluate the current AJCC/UICC staging system (7th edition) for nasopharyngeal carcinoma and to explore for future improvement. Materials and methods: A total of 985 patients, initially staged with preceding 5-6th edition, were retrospectively re-staged with the 7th edition. All were assessed by magnetic resonance imaging, and all 945 non-disseminated patients were irradiated with conformal/intensity-modulated technique. Results: Staging factors by both the 5-6th edition and the 7th edition were strongly significance for important endpoints (p < 0.001). Down-staging of the previous T2a to T1 and, stages IIA to I in the 7th edition was appropriate. However, the impacts on overall stage distribution and prognostication were minimal. Further down-staging of the current T2 to T1, N2 to N1, stages II to I, and merging of N3a and N3b, stages IVA and IVB were suggested. With the 7th edition, the 5-year disease-specific survival (DSS) was 100% for stage I, 95% for II, 90% for III, 67% for IVA, 68% for IVB and 18% for IVC. The corresponding DSS for the proposed stages I, II, III and IV were 95%, 86%, 67% and 18%, respectively. Conclusions: The changes introduced in the 7th edition were appropriate, but the magnitude of improvement was minimal. With improving results by modern management, further simplification of the staging system is suggested. The proposed system could lead to more accurate prognostication, further validation is warranted. © 2012 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex