Robust Treatment Planning in Intrafraction Motion Using TomoDirect™ Intensity-modulated Radiotherapy for Breast Cancer.

BACKGROUND/AIM: To evaluate the robustness of radiotherapy treatment planning optimization for respiratory-moving breast cancer using fixed-angle beams planning TomoDirect™ intensity-modulated radiotherapy (IMRT). MATERIALS AND METHODS: A minimax optimisation algorithm was applied to 10 breast cancer patients. Two sets of treatment plans with or without robust techniques were prepared considering anterior-posterior and head-tail movements due to respiration. Parameters were compared between treatment plans: 95% planned target volume (PTV) dose, conformal index and homogeneity index (HI), and organs at risk (OAR) parameters including the lung volume receiving 20 Gy or more (V20) and 5 Gy (V5). RESULTS: Robust planning significantly improved parameters of 95% PTV dose and HI, without deteriorating V20 or V5 in the anterior-posterior movement, while it slightly improved 95% PTV and slightly deteriorated V20 in the head-tail movement. CONCLUSION: Robust treatment planning improves coverage of targets moving because of respiration in the treatment of breast cancer using TomoDirect; however, normal lung doses should be cautiously evaluated on a case-by-case basis.

Long-term outcome of proton beam radiosurgery for arteriovenous malformations larger than 30 mm in diameter.

The effectiveness of proton beam (PB) radiosurgery for large lesions is greater than for other treatment modalities. At our institute, PB radiosurgery is used to treat arteriovenous malformations (AVMs). We report the outcome of PB radiosurgery for AVMs over a period of 15 years, focusing on the efficacy of PB radiosurgery combined with embolization for AVMs ≥30 mm in diameter. We retrospectively analyzed 11 patients with AVMs ≥30 mm in diameter who were treated with PB radiosurgery between June 1990 and September 2005 at the Proton Medical Research Center of the University of Tsukuba. The mean irradiation dose was 25.3 gray-equivalent, and the mean duration of clinical follow up was 134.2 months (median 138 months). Pre-radiosurgical embolization was performed in all cases. Complete obliteration was achieved in 9 of the 11 patients. One patient experienced post-radiosurgical hemorrhage, and 1 patient experienced radiation-related aggravation of clinical symptoms due to radiation necrosis. Eight patients had excellent outcomes. The multimodal therapy approach of combining pre-radiosurgical embolization and PB radiosurgery for AVMs yielded a favorable outcome for AVMs ≥30 mm in diameter. Thus, PB radiosurgery is a viable treatment option for AVMs ≥30 mm in diameter.

Current practices and future directions of therapeutic strategy in glioblastoma: survival benefit and indication of BNCT.

Since 1998, we are performing clinical studies on treatment of GBM using conventional fractionated photon radiation therapy (CRT), proton beam therapy (PBT) or boron neutron capture therapy (BNCT). We investigated whether these radiation modalities improves the survival of patients with GBM. Sixty-eight cases of newly diagnosed GBM have been treated in our institution. After surgery, radiation therapy was performed using CRT with a dose of 60.0-61.2 Gy (n=36), hyperfractionated PBT concomitant with fractionated photon irradiation with a total dose of 96.6 Gy (n=17), or a single fraction of BNCT (n=15). In PBT, the surrounding volume of 2 cm from main tumor mass and the volume of perifocal edema were irradiated at dose of 75.6 and 60 Gy, respectively. The median OS time of the case series of BNCT for GBM has been reported as 13-20.7 M. In this study, the median OS and median time to MR change (TTM) for all patients were 25.7 and 11.9 M, respectively. The 1- and 2-year survival rates were 85.7% and 45.5%, respectively. On the other hand, in the patients who underwent CRT and ACNU-based chemotherapy, OS and 2-year survival rate were 14.2M and 17.9%, respectively. In the patients who underwent high-dose PBT, OS and 2-year survival rate were 21.3M and 38.5%, respectively. The present small case series of selected patients showed survival benefit after BNCT. The comparison using previously reported prognostic factor-based classifications suggest that outcome of BNCT in terms of survival appeared to have non-inferiority compared to the standard therapy. With respect to the case series as a high-dose radiation trial, the outcome (OS: 9.5-25 M) of previously reported may still be comparable to that of BNCT. Randomized trials of comparably selected patients are required to demonstrate conclusively that prolonged survival is a result of this tumor-selective radiotherapy.