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BackgroundTo establish the feasibility of the dosimetric compliance criteria of the RTOG 1308 trial through testing against Intensity Modulation Radiation Therapy (IMRT) and Passive Scattering Proton Therapy (PSPT) plans.MethodsTwenty-six lung IMRT and 26 proton PSPT plans were included in the study. Dose Volume Histograms (DVHs) for targets and normal structures were analyzed. The quality of IMRT plans was assessed using a knowledge-based engineering tool.ResultsMost of the RTOG 1308 dosimetric criteria were achieved. The deviation unacceptable rates were less than 10 % for most criteria; however, a deviation unacceptable rate of more than 20 % was computed for the planning target volume minimum dose compliance criterion. Dose parameters for the target volume were very close for the IMRT and PSPT plans. However, the PSPT plans led to lower dose values for normal structures. The dose parameters in which PSPT plans resulted in lower values than IMRT plans were: lung V5Gy (%) (34.4 in PSPT and 47.2 in IMRT); maximum spinal cord dose (31.7 Gy in PSPT and 43.5 Gy in IMRT); heart V5Gy (%) (19 in PSPT and 47 in IMRT); heart V30Gy (%) (11 in PSPT and 19 in IMRT); heart V45Gy (%) (7.8 in PSPT and 12.1 in IMRT); heart V50% (Gy) (7.1 in PSPT and 9.8 in IMRT) and mean heart dose (7.7 Gy in PSPT and 14.9 Gy in IMRT).ConclusionsThe revised RTOG 1308 dosimetric compliance criteria are feasible and achievable.

Purpose To analyze the toxicity and patterns of failure of proton therapy given in ablative doses for medically inoperable early-stage non-small cell lung cancer (NSCLC). Methods and Materials Eighteen patients with medically inoperable T1N0M0 (central location) or T2-3N0M0 (any location) NSCLC were treated with proton therapy at 87.5 Gy (relative biological effectiveness, RBE) at 2.5 Gy/fraction in this phase I/II study. All patients underwent treatment simulation with 4-dimensional (4D) computed tomography (CT); internal gross tumor volumes (iGTVs) were delineated on maximal intensity projection (MIP) images and modified by visual verification of the target volume in 10 breathing phases. The iGTV with MIP density was used to design compensators and apertures to account for tumor motion. Therapy consisted of passively scattered protons. All patients underwent repeat 4D CT simulations during treatment to assess the need for adaptive replanning. Results At a median follow-up time of 16.3 months (range, 4.8–36.3 months), no patient had experienced grade 4 or 5 toxicity. The most common adverse effect was dermatitis (grade 2, 67%; grade 3, 17%), followed by grade 2 fatigue (44%), grade 2 pneumonitis (11%), grade 2 esophagitis (6%), and grade 2 chest wall pain (6%). Rates of local control were 88.9%, regional lymph node failure 11.1%, and distant metastasis 27.8%. Twelve patients (67%) were still alive at the last follow-up; five had died of metastatic disease and one of preexisting cardiac disease. Conclusions Proton therapy to ablative doses is well tolerated and produces promising local control rates for medically inoperable early-stage NSCLC.

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We have measured the double-to-single photoionization ratio of beryllium ͑1s 2 2s 2 ͒ between 28 and 40 eV and determined the relative single-and double-photoionization cross sections. In this energy region only simultaneous but not sequential emission of both 2s electrons can take place. We also compare our data with recent theoretical calculations and find good agreement with our data. The previously found scaling law for the double-to-single photoionization ratio is confirmed with high accuracy.