No abstract available

[en] Purpose: To study the radiation dose response as determined by biochemical relapse-free survival in patients with favorable localized prostate cancers, i.e., Stage T1-T2, biopsy Gleason score (bGS) ≤6, and pretreatment prostate-specific antigen (iPSA) ≤10 ng/mL. Methods and Materials: A total of 292 patients with favorable localized prostate cancer were treated with radiotherapy alone between 1986 and 1999. The median age was 69 years. Sixteen percent of cases (n=46) were African-American. The distribution by clinical T stage was as follows: T1/T2A, 243 (83%); and T2B/T2C, 49 (17%). The distribution by iPSA was as follows: ≤4 ng/mL, 49 (17%); and >4 ng/mL, 243 (83%). The mean iPSA level was 6.2 (median, 6.4). The distribution by bGS was as follows: ≤5 in 89 cases (30%) and 6 in 203 cases (70%). The median radiation dose was 70.0 Gy (range, 63.0-78.0 Gy). Doses of ≤70.0 Gy were delivered in 175 cases, 70.2-72.0 Gy in 24 cases, 74 Gy in 30 cases, and 78 Gy in 63 cases. For patients receiving <72 Gy, the median dose was 68 Gy, vs. 78 Gy for patients receiving ≥72 Gy. A conformal technique was used in 129 (44%) of cases. The median follow-up was 43 months (range, 3-153). Results: For the entire cohort, the projected 5- and 8-year biochemical relapse-free survival (bRFS) rates were both 81%. For patients receiving ≥72 Gy, the 5- and 8-year bRFS rates were both 95% vs. only 77% for patients receiving <72 Gy, p=0.010. For patients receiving 74 Gy, the 4-year bRFS rate was 94% vs. 96% for patients receiving 78 Gy, p 0.90. A multivariate analysis for factors affecting bRFS rates using Cox proportional hazards was performed for all cases using the following variables: age (continuous variable), race (black vs. white), iPSA (continuous variable), bGS (≤5 vs. 6), Stage (T1-2A vs. T2B-C), radiation dose (continuous variable), and radiation technique (conformal vs. standard). From the multivariate analysis, only iPSA (p=0.017, χ²=5.7), and radiation dose (p=0.021, χ²=5.3) were independent predictors of outcome. Age (p=0.94), race (p=0.89), stage (p=0.45), biopsy GS (p=0.40), and radiation technique (p=0.45) were not. Conclusion: There is a clear radiation dose response in patients with favorable localized prostate cancers (i.e., Stage T1-T2, biopsy Gleason score ≤6, and iPSA ≤10 ng/mL). At least 74 Gy should be delivered to the prostate and periprostatic tissues. With our cohort of patients, longer follow-up will be needed to assess the importance of doses exceeding 74 Gy

[en] To demonstrate the dosimetric advantages and disadvantages of standard anteroposterior-posteroanterior (S-AP/PA_A_A_A), inverse-planned AP/PA (IP-AP/PA) and volumetry-modulated arc (VMAT) radiotherapies in the treatment of children undergoing whole-lung irradiation. Each technique was evaluated by means of target coverage and normal tissue sparing, including data regarding low doses. A historical approach with and without tissue heterogeneity corrections is also demonstrated. Computed tomography (CT) scans of 10 children scanned from the neck to the reproductive organs were used. For each scan, 6 plans were created: (1) S-AP/PA_A_A_A using the anisotropic analytical algorithm (AAA), (2) IP-AP/PA, (3) VMAT, (4) S-AP/PA_N_O_N_E without heterogeneity corrections, (5) S-AP/PA_P_B using the Pencil-Beam algorithm and enforcing monitor units from technique 4, and (6) S-AP/PA_A_A_A_[_F_M_] using AAA and forcing fixed monitor units. The first 3 plans compare modern methods and were evaluated based on target coverage and normal tissue sparing. Body maximum and lower body doses (50% and 30%) were also analyzed. Plans 4 to 6 provide a historic view on the progression of heterogeneity algorithms and elucidate what was actually delivered in the past. Averages of each comparison parameter were calculated for all techniques. The S-AP/PA_A_A_A technique resulted in superior target coverage but had the highest maximum dose to every normal tissue structure. The IP-AP/PA technique provided the lowest dose to the esophagus, stomach, and lower body doses. VMAT excelled at body maximum dose and maximum doses to the heart, spine, and spleen, but resulted in the highest dose in the 30% body range. It was, however, superior to the S-AP/PA_A_A_A approach in the 50% range. Each approach has strengths and weaknesses thus associated. Techniques may be selected on a case-by-case basis and by physician preference of target coverage vs normal tissue sparing.

[en] Purpose: To study the impact of biochemical failure on overall survival rates during the first 10 years after definitive radiotherapy for localized prostate cancer. Methods and Materials: The analysis was performed on 936 cases treated at a single institution between 1986 and 1998 with definitive radiotherapy. The median age of treatment was 69 years (range: 46-86 years). Pretreatment PSA levels (iPSA) and biopsy Gleason scores (bGS) were available for all cases. The clinical stage was T1/T2A in 63%, T2B/C in 27%, and T3 in 10%. The median iPSA level was 9.6 ng/mL (range: 0.4-692.9 ng/mL). The iPSA was ≤10 in 53% and >10 in 47%. The bGS was ≤6 in 59% and ≥7 in 41%. Androgen deprivation (AD) was administered in 181 cases (19%) for a median duration of 6 months (range: 1-6 months). All 181 cases received AD neoadjuvantly, i.e., before and/or during the radiotherapy. No AD was delivered after the completion of radiation. The median radiation dose was 70 Gy (range: 60-78 Gy). The radiotherapy technique was conformal in 376 (40%) cases. The American Society of Therapeutic Radiology and Oncology definition of biochemical failure (bF) was used; 316 cases (34%) had failed biochemically, and 620 (66%) had not. The end point was overall survival (OS). Time to death was determined from the time of definitive radiotherapy. The median PSA follow-up was 58 months. The median follow-up times for bF vs. no-bF cases were 77 and 49 months, respectively. A multivariate analysis of factors affecting OS using the proportional hazards model was performed for all cases using the following variables: age (>65 vs. ≤65 years), race (African-American vs. Caucasian), clinical T stage (T1-2A vs. T2B-C vs. T3), bGS (≤6 vs. 7 vs. ≥8), iPSA (continuous variable), use of AD (yes vs. no), year of therapy (continuous variable), radiation dose (continuous variable), radiation technique (conformal vs. standard), and biochemical failure (yes vs. no). Results: The 5-year OS rate for the entire group was 89% (95% CI [confidence interval]: 86-91%). The 5-year OS rates for bF vs. no-bF patients were 89% (95% CI: 86-93%) and 89% (95% CI: 86-92%), respectively. The 10-year OS rate for the entire group was 68% (95% CI: 61-75%). The 10-year OS rates for bF vs. no-bF patients were 65% (95% CI: 56-74%) and 77% (95% CI: 69-84%), respectively. The difference between bF and no bF was not significant in predicting overall survival in univariate analysis (log-rank test, p=0.68). On multivariate analysis, bGS (p<0.001), T stage (p=0.003), radiation dose (p=0.017), year of therapy (p=0.031), and age (p=0.020) were independent predictors of death. iPSA levels (p=0.33), race (p=0.80), radiation technique (p=0.16), and use of AD (p=0.09) were not predictive of OS. Biochemical failure (p=0.052) showed only a trend for independently predicting overall survival on multivariate analysis. Conclusion: Biochemical failure after definitive radiotherapy for localized prostate cancer is not associated with increased mortality within the first 10 years after initial therapy, although a trend toward worse outcome was observed at 10 years. Longer follow-up from initial therapy is needed to fully understand the impact of biochemical failure on overall survival. With longer follow-up, significant differences might be observed at 15 or 20 years after therapy

No abstract available

[en] In the current molecular-targeted cancer treatment era, many new agents are being developed so that optimizing therapy with a combination of radiation and drugs is complex. The use of emerging laboratory technologies to further biological understanding of drug-radiation mechanisms of action will enhance the efficiency of the progression from preclinical studies to clinical trials. In 2017, the National Cancer Institute (NCI) solicited proposals through PAR 16-111 to conduct preclinical research combining targeted anticancer agents in the Cancer Therapy Evaluation Program's portfolio with chemoradiation.

No abstract available

[en] Cranial reirradiation is clinically appropriate in some cases but cumulative radiation dose to critical normal structures remains a practical concern. The authors developed a simple technique in 3D conformal proton craniospinal irradiation (CSI) to block organs at risk (OAR) while minimizing underdosing of adjacent target brain tissue. Two clinical cases illustrate the use of proton therapy to provide salvage CSI when a previously irradiated OAR required sparing from additional radiation dose. The prior radiation plan was coregistered to the treatment planning CT to create a planning organ at risk volume (PRV) around the OAR. Right and left lateral cranial whole brain proton apertures were created with a small block over the PRV. Then right and left lateral “inverse apertures” were generated, creating an aperture opening in the shape of the area previously blocked and blocking the area previously open. The inverse aperture opening was made one millimeter smaller than the original block to minimize the risk of dose overlap. The inverse apertures were used to irradiate the target volume lateral to the PRV, selecting a proton beam range to abut the 50% isodose line against either lateral edge of the PRV. Together, the 4 cranial proton fields created a region of complete dose avoidance around the OAR. Comparative photon treatment plans were generated with opposed lateral X-ray fields with custom blocks and coplanar intensity modulated radiation therapy optimized to avoid the PRV. Cumulative dose volume histograms were evaluated. Treatment plans were developed and successfully implemented to provide sparing of previously irradiated critical normal structures while treating target brain lateral to these structures. The absence of dose overlapping during irradiation through the inverse apertures was confirmed by film. Compared to the lateral X-ray and IMRT treatment plans, the proton CSI technique improved coverage of target brain tissue while providing the least additional radiation dose to the previously irradiated OAR. Proton craniospinal irradiation can be adapted to provide complete sparing of previously irradiated OARs. This technique may extend the option of reirradiation to patients otherwise deemed ineligible for further radiotherapy due to prior dose to critical normal structures

[en] Purpose: To investigate the moving gap region dosimetry in proton beam cranio-spinal irradiation (CSI) to provide optimal dose uniformity across the treatment volume. Material and methods: Proton beams of ranges 11.6 cm and 16 cm are used for the spine and the brain fields, respectively. Beam profiles for a 30 cm snout are first matched at the 50% level (hot match) on the computer. Feathering is simulated by shifting the dose profiles by a known distance two successive times to simulate a 2 x feathering scheme. The process is repeated for 2 mm and 4 mm gaps. Similar procedures are used to determine the dose profiles in the moving gap for a series of gap widths, 0-10 mm, and feathering step sizes, 4-10 mm, for a Varian iX 6MV beam. The proton and photon dose profiles in the moving gap region are compared. Results: The dose profiles in the moving gap exhibit valleys and peaks in both proton and photon beam CSI. The dose in the moving gap for protons is around 100% or higher for 0 mm gap, for both 5 and 10 mm feathering step sizes. When the field gap is comparable or larger than the penumbra, dose minima as low as 66% is obtained. The dosimetric characteristics for 6 MV photon beams can be made similar to those of the protons by appropriately combining gap width and feathering step size. Conclusion: The dose in the moving gap region is determined by the lateral penumbras, the width of the gap and the feathering step size. The dose decreases with increasing gap width or decreasing feathering step size. The dosimetric characteristics are similar for photon and proton beams. However, proton CSI has virtually no exit dose and is beneficial for pediatric patients, whereas with photon beams the whole lung and abdomen receive non-negligible exit dose

[en] The increase in relative biological effectiveness (RBE) of proton beams at the distal edge of the spread out Bragg peak (SOBP) is a well-known phenomenon that is difficult to quantify accurately in vivo. For purposes of treatment planning, disallowing the distal SOBP to fall within vulnerable tissues hampers sparing to the extent possible with proton beam therapy (PBT). We propose the distal RBE uncertainty may be straightforwardly mitigated with a technique we call “range modulation”. With range modulation, the distal falloff is smeared, reducing both the dose and average RBE over the terminal few millimeters of the SOBP. One patient plan was selected to serve as an example for direct comparison of image-guided radiotherapy plans using non-range modulation PBT (NRMPBT), and range-modulation PBT (RMPBT). An additional plan using RMPBT was created to represent a re-treatment scenario (RMPBTrt) using a vertex beam. Planning statistics regarding dose, volume of the planning targets, and color images of the plans are shown. The three plans generated for this patient reveal that in all cases dosimetric and device manufacturing advantages are able to be achieved using RMPBT. Organ at risk (OAR) doses to critical structures such as the cochleae, optic apparatus, hypothalamus, and temporal lobes can be selectively spared using this method. Concerns about the location of the RBE that did significantly impact beam selection and treatment planning no longer have the same impact on the process, allowing these structures to be spared dose and subsequent associated issues. This present study has illustrated that RMPBT can improve OAR sparing while giving equivalent coverage to target volumes relative to traditional PBT methods while avoiding the increased RBE at the end of the beam. It has proven easy to design and implement and robust in our planning process. The method underscores the need to optimize treatment plans in PBT for both traditional energy dose in gray (Gy) and biologic dose (RBE)