4-field Technique Research Articles

AI segmentation as a quality improvement tool in radiotherapy planning for breast cancer

AI segmentation has been recently introduced in the local department for delineation of targets and organs-at-risk (OAR) for a wide range of tumour sites. For breast radiotherapy, AI segmentation can provide target delineation (breast and lymph nodes) and required OAR, and this has enabled a stepwise series of improvements to the local planning technique.Clinician feedback deemed 67 - 89 % of nodal target volumes required no edits or only minor edits, so AI breast and lymph nodes volumes were first used to guide tangent and supraclavicular field placement, instead of a bony-anatomy based technique.Next, evolution from anatomical field-placement to true inverse optimised planning was introduced using AI to create the required target volumes. For internal mammary node (IMN) treatments, the previous 3-field technique prohibited Deep Inspiration breath-hold (DIBH), due to the couch rotation used to match field edges. The roll-out of VMAT (volumetric-modulated arc therapy) with DIBH enabled by AI therefore resulted in a dose reduction to ipsi-lateral lung, and in mean heart dose compared to the old 3-field technique. Median time from CT scan to VMAT IMN plan approval reduced from 12 days (with manual contouring) to 7 days using reviewed and edited AI-generated volumes.Consistent, high-quality contours for 9 OAR and breast PTVs for all patients facilitates comparison with NHS-E scorecards as a benchmark for plan quality. Workflows have been simplified, with significant time-savings. DIBH radiotherapy is now available to more patients, further improving dose sparing for heart and lung.

Dosimetric comparison between intensity modulated radiotherapy and three-dimensional conformal radiotherapy in adjuvant setting after radical cystectomy in high-risk urothelial bladder cancer

Objective: To compare the 4-field 3D conformal radiotherapy technique (3DCRT) to the intensity-modulated radiotherapy (IMRT) 9-field technique for adjuvant radiotherapy post radical cystectomy in high-risk urothelial bladder cancer cases. Patients and Methods: A dosimetric analysis of 11 urothelial bladder cancer patients who underwent radical cystectomy was performed. These patients were presented to the radiotherapy department, National Cancer Institute, Cairo, between 2018 and 2020 with adjuvant radiotherapy using the IMRT technique. Two plans were designed for each patient, one using 9-field IMRT and the second using 4-field 3DCRT. The two techniques were compared, including the PTV, bowel bag, rectum, neobladder, and pelvic bone marrow. Results: Comparing different DVHs, the planning target volume (PTV) was adequately covered in both plans, while the 9-field IMRT technique delivered significantly lower doses to OARs (bowel, rectum, and pelvic bone marrow). Conclusion: The IMRT technique incredibly spared the OARs more than that obtained by the 3DCRT technique, while both techniques covered the PTV adequately. The IMRT technique, through sparing OARs, was expected to decrease early and late radiation side effects.

Comparison of intensity-modulated radiotherapy with the 5-field technique, helical tomotherapy and volumetric modulated arc therapy for localized prostate cancer.

The outcomes of three methods of intensity-modulated radiation therapy (IMRT) for localized prostate cancer were evaluated. Between 2010 and 2018, 308 D’Amico intermediate- or high-risk patients were treated with 2.2 Gy daily fractions to a total dose of 74.8 Gy in combination with hormonal therapy. Overall, 165 patients were treated with 5-field IMRT using a sliding window technique, 66 were then treated with helical tomotherapy and 77 were treated with volumetric modulated arc therapy (VMAT). The median age of patients was 71 years. The median follow-up period was 75 months. Five-year overall survival (OS) and biochemical or clinical failure-free survival (FFS) rates were 95.5 and 91.6% in the 5-field IMRT group, 95.1 and 90.3% in the tomotherapy group and 93.0 and 88.6% in the VMAT group, respectively, with no significant differences among the three groups. The 5-year cumulative incidence of late grade ≥2 genitourinary and gastrointestinal toxicities were 7.3 and 6.2%, respectively, for all patients. Late grade ≥2 gastrointestinal toxicities were less frequent in patients undergoing VMAT (0%) than in patients undergoing 5-field IMRT (7.3%) and those undergoing tomotherapy (11%) (P = 0.025), and this finding appeared to be correlated with the better rectal DVH parameters in patients undergoing VMAT. Other toxicities did not differ significantly among the three groups, although bladder dose-volume parameters were slightly worse in the tomotherapy group than in the other groups. Despite differences in the IMRT delivery methods, X-ray energies and daily registration methods, all modalities may be used as IMRT for localized prostate cancer.

Outcomes of and treatment planning considerations for a hybrid technique delivering proton pencil-beam scanning radiation to women with metal-containing tissue expanders undergoing post-mastectomy radiation

BackgroundFollowing mastectomy, immediate breast reconstruction often involves the use of temporary tissue expanders (TEs). TEs contain metallic ports (MPs), which complicate proton pencil-beam scanning (PBS) planning. A technique was implemented for delivering PBS post-mastectomy radiation (PMRT) to patients with TEs and MPs. MethodsA protocol utilizing a hybrid single- and multi-field optimization (SFO, MFO) technique was developed. Plans were robustly optimized using a Monte Carlo algorithm. A CTV_eval structure including chest wall (CW) and regional nodal (RNI) targets and excluding the TE was evaluated. Organ at risk (OAR) dosimetry and acute toxicities were analyzed. ResultsTwenty-nine women were treated with this technique. A 2-field SFO technique was used superior and inferior to the MP, with a 3 or 4-field MFO technique used at the level of the MP. Virtual blocks were utilized so that beams did not travel through the MP. A port-to-CW distance of 1 cm was required. Patients underwent daily image-guidance to ensure the port remained within a 0.5 cm internal planning volume (ITV).Median RT dose to CTV_eval was 50.4 Gy (45.0–50.4). Median 95% CTV_eval coverage was 99.5% (95–100). Optically stimulated luminescent dosimeter (OSLD) readings were available for 8 patients and correlated to the dose measurements in the treatment planning system (TPS); median OSLD ratio was 0.99 (range, 0.93–1.02). ConclusionsDelivering PMRT with PBS for women with metal-containing TEs using a hybrid SFO/MFO technique is feasible, reproducible, and achieves excellent dose distributions. Specialized planning and image-guidance techniques are required to safely utilize this treatment in the clinic.

Intensity-Modulated Proton Therapy (IMPT) Treatment of Angiosarcoma of the Face and Scalp.

PurposeTo successfully plan and treat a patient with diffuse angiosarcoma involving the face and scalp with intensity-modulated proton therapy (IMPT) before surgical resection.Materials and MethodsA patient presented to the radiation oncology department for preoperative treatment of an angiosarcoma diffusely involving the face and scalp. A 4-field IMPT technique was used to create a homogeneous dose distribution to the entire target volume while sparing underlying critical structures from toxicity and low-dose spread. A custom Monte Carlo optimizer was necessary to achieve treatment goals. Biological dose was evaluated with a linear energy transfer–based biological enhancement model. Robustness criteria were evaluated per department standard. The patient was successfully planned and treated according to clinical goals.ResultsThe patient successfully completed the course of IMPT and was able to undergo surgical resection. Pathology indicated no presence of angiosarcoma.ConclusionIMPT using a custom Monte Carlo optimizer is a suitable radiation therapy treatment option for patients with diffuse angiosarcoma of the scalp and face.

Feasibility of Monte-Carlo algorithm in comparison with collapse-cone dose calculation algorithm of a commercial treatment planning system in the presence of high-density metallic implant: a dosimetric study

BackgroundThe number of people with implanted hip prosthesis has grown worldwide. For radiotherapy planning of patients with hip implants, few main challenges are encountered. The aim of the present study was to evaluate the feasibility of different planning algorithms in the presence of high-density metallic implant in the treatment of patients with carcinoma cervix.ResultsIt was found that D98% were 44.49 ± 0.11, 44.51 ± 0.13, 44.39 ± 0.22, and 44.45 ± 0.16 Gy for 4FMC6MV (4-field technique calculated with Monte-Carlo algorithm and 6 MV photon energy), 4FMC6MV_WP (4-field technique calculated with Monte-Carlo algorithm and 6 MV photon energy without prosthesis), 4FCC6MV (4-field technique calculated with collapse-cone-convolution algorithm and 6 MV photon energy), and 4FCC6MV_WP (4-field technique calculated with collapse-cone-convolution algorithm and 6 MV photon energy without prosthesis) respectively. Similarly, D2% were 49.40 ± 0.84, 49.05 ± 0.76, 48.97 ± 0.91, and 48.57 ± 0.85 Gray (Gy) for 4FMC6MV, 4FMC6MV_WP, 4FCC6MV, and 4FCC6MV_WP respectively. The present study has not suggested any major difference between the Monte-Carlo (MC) and collapse-cone-convolution (CCC) calculation algorithm in the presence of high-Z metallic implants. Volume of bowel receiving 15 Gy dose has shown a significant difference with prosthesis cases. This study investigates that hip prosthesis creates considerable changes in the treatment planning of cervical malignancies.ConclusionCCC algorithm is in good agreement with MC calculation algorithm in the presence of high-density metallic implants in terms of target coverage and avoidance organ sparing except few parameters.

Dosimetric Evaluation of Chest Wall Superficial Dose With or Without Bolus in Postmastectomy Radiotherapy

Chest wall bolus use has been standard practice in postmastectomy radiotherapy (PMRT) for patients without skin involvement, resulting in increased toxicity without strong data to show improved outcomes. Centers are moving away from use of bolus in PMRT, but the dosimetric effects have not been quantified. We aim to compare differences in dose between non-bolus and bolus plans to the superficial chest wall. We conducted a retrospective analysis on 30 patients treated with PMRT from December 2018 to June 2019 at our center. Patients received 4256 cGy in 16 fractions to chest wall and regional nodes using 4-field 3D conformal technique, 6 and/or 15 MV photons, and 0.5 cm bolus. The clinically planned datasets were used to generate non-bolus and bolus plans for each patient using the anisotropic analytical algorithm (AAA). The first 10 patients also had non-bolus and bolus plans generated using Acuros XB (AXB). Evaluation volumes were created by extracting surface layers from the clinical chest wall: 3 mm surface, 5 mm surface, and the layer between 3-5 mm depth. The 3 mm and 5 mm surface layers were chosen to match the most common definitions of skin in current breast studies, while the 3-5 mm layer represents the subcutaneous tissue immediately deep to the skin. Mean age, mean chest wall thickness, dermatitis grade level per CTCAE v5.0, and the mean V80%, V95%, and D2cc were reported for all plans. Mean patient age was 56 years (range 36 to 85 years). Mean chest wall thickness was 2.3 cm (1.1 to 6.5 cm). The most common beam energies were 6 and 15 MV photons (70%), followed by 15 MV alone (20%) and 6 MV alone (10%). Most had grade 1 (63%) and 2 (33%) dermatitis to the chest wall and axilla, with one patient developing grade 3 dermatitis. Mean V80%, V95%, and D2cc for the non-bolus and bolus plans were calculated using AAA (n = 30) and AXB (n = 10), as reported in the below table. While large differences exist in superficial layers, the 3-5 mm layer demonstrates consistent coverage for V80% with or without bolus. When AXB calculation is used, the differences are even more minimal in the 3-5 mm layer for both V80% and V95%. This result is expected based on AXB’s superior superficial dose modelling. Our findings support the reduced use of bolus for PMRT patients without risk factors for dermal or dermal-lymphatic involvement.Tabled 1Abstract 2770; Table3 mm surface5 mm surface3-5 mm layerD2cc (%)Non-BolusBolusNon-BolusBolusNon-BolusBolusNon-BolusBolusAAA V80% (%)38.497.662.397.796.498.1107107AAA V95% (%)4.788.322.390.049.594.7AXB V80% (%)60.099.676.999.799.9100109109AXB V95% (%)23.796.249.397.286.298.7 Open table in a new tab

Impact of Pelvic Intensity-modulated Radiotherapy (IMRT) on Lymph Node Coverage and Dose to Critical Organs, Compare to Three-Dimensional Conformal Radiation Therapy (3D-CRT), in Localized High-Risk Prostate Cancer

Men with high risk prostate cancer (HR-PrCa) are typically treated with combined androgen deprivation therapy and curative radiotherapy (RT) consisting of pelvic nodal and prostate/seminal vesicle (PrSV) irradiation followed by PrSV boost RT. 3D-CRT or IMRT are used for the treatment of pelvic nodes. A phase II randomized study examining the effect of RT technique on patient Quality of Life (QoL) was completed in our institution. Here, we report an early analysis of the dosimetric impact of 3D-CRT versus IMRT in patients participating in this study. A total of 105 men with HR-PrCa were randomized at 1:1 ratio to receive either pelvic 3D-CRT (standard 4-field conformal technique) or multi-beam IMRT, consisting of 4500cGy in 25 fractions to planning target volume (PTV) 1, followed by boost RT to PTV2 of 2496cGy in 13 fractions. The latter was delivered using a 7-field IMRT in all patients. Organs at risk (OAR) and clinical target volumes (CTV) were delineated on CT simulation images. The lymph node target included the common, internal, external iliac, obturator and pre-sacral lymph nodes in accordance with RTOG guidelines. CTV1 consisted of nodal CTV plus PrSV. CTV2 was minimized to PrSV. The PTV consisted of an expansion of 7 mm beyond CTV. For consistency, in comparison between the two techniques, IMRT fields were modified to results to similar superior border coverage as 3D-CRT, at the level of L5-S1. Bladder and rectum were contoured as solid organs. To take inter-fractional bowel motion into account, bowel was delineated as whole pelvic and abdominal cavity excluding bones, muscle, and other OAR. Pelvic RT with 3DCRT missed significant percentage of pelvic nodal volume. PTV1 D95% showed mean difference of -4.96, 95% CI (-6.41, -1.74); p = 0.0013 and D99% showed mean difference of -11.56, 95% CI (-14.96, -8.17); p< 0.00001 in favor of IMRT. There was significant difference in PTV1 heterogeneity index (D2%-D95%/D50%) (Mean diff = 0.22, 95%CI (0.14, 0.29); P<0.00001). IMRT decreased dose to OAR. Rectum V30 was 97% in 3DCRT compare to 93.41% in IMRT arm with absolute difference of 3.81% (95% CI (1.52, 6.11); P = 0.0014). Bladder V40 and V50 were significantly reduced (V40: 84 % vs 62% for 3DCRT vs IMRT, absolute difference of 22% (95%, CI (15.55, 28.2); P<0.0001); V50 absolute reduction of 18% with IMRT (95%, CI (11.53, 24.48); P<0.0001). Similarly, IMRT reduced total body/bone irradiation significantly. This randomized study of 3D-CRT versus pelvic IMRT is an appropriate setting to investigate the dosimetric impact of pelvic IMRT and help define its potential benefits on patient QoL. This early analysis suggests that utilization of IMRT for pelvic RT could offer dosimetric advantages by improve lymph node coverage and reducing RT dose to OAR. The results are in agreement with an improved bowel-related QoL observed in this study. On-going analysis examines correlations between dosimetric and patient QoL data.

Outcomes of and Treatment Planning Considerations for A Novel Technique Delivering Proton Pencil-Beam Scanning Radiation to Women With Metal-Containing Tissue Expanders Undergoing Post-Mastectomy Radiation

Breast reconstructive tissue expanders (TEs) contain metallic ports (MCPs) comprised of high “Z” materials. This presents a challenge for proton pencil-beam scanning (PBS) planning given potential dose attenuation and concern for port movement. We hypothesize that a novel technique utilizing hybrid single- and multi-field optimizations (SFO, MFO) for delivering post-mastectomy radiation (PMRT) using proton PBS for patients with TEs and MCPs will be robust and uphold the dosimetric benefits of proton therapy. A protocol utilizing a hybrid SFO/MFO technique was prospectively developed. Plans were robustly optimized using a Monte Carlo algorithm. A CTV_eval structure including chest wall (CW) and regional nodal (RNI) targets and excluding boost plans and the TE metallic components plus a 1 cm margin was evaluated for target coverage, robustness, and dose homogeneity. Thirteen women with TEs completed PMRT between 2/12/19 and 1/2/20. Median age was 46 years (range, 37-60), 67% were white. Median body-mass index (BMI) was 24 (range, 19-36). 75% of patients had left-sided disease. A 2 or 3-field SFO technique was used superior and inferior to the MCP, while a 3 or 4-field MFO technique was used at the level of the MCP. At the level of the MCP, beams were blocked to deliver dose anterior/posterior and lateral to the port without going through it. A port-to-CW distance of 1cm was required to deliver dose posteriorly. Anterior, anterior oblique, and lateral beam angles were utilized. Anterior beams were given with a couch kick to enter under the breast and deliver dose behind the expander. Patients underwent daily image-guidance to ensure the port remained within a 5mm planning volume (PRV). The median total RT dose to CTV_eval was 50.4Gy (45.0-50.4) delivered in 1.8Gy/fraction; 5 (38%) of plans utilized a boost. Median ipsilateral lung V20 was 20% (2.0-29); median average heart dose was 1.7Gy (0.5-3.5). Median 100% CTV_eval coverage was 95% (90-95) with a median homogeneity index of 4.2(1.9-18). OSLD readings anterior to the port were performed on 5 patients and correlated to the dose measurements in the TPS. When evaluating plan robustness, median worst-case 95% CTV_eval coverage was 95% (90-97%). There was one ≥ G2 acute toxicity of G4 skin necrosis in a patient with very thin tissue flaps which did not occur immediately anterior to the port but required expander removal. At a median follow up of 3.0 months, 2 patients had successful permanent reconstructions after RT completion. Delivering PMRT with PBS for women with metal-containing TEs using a novel hybrid SFO/MFO technique is feasible, robust, achieves excellent dose distributions to targets and OARs, and did not lead to unexpected toxicities. Additional dosimetric, physics and set up techniques are required to safely deploy this treatment in the clinic. This is the largest series to date describing the delivery of PMRT to women with MCPs, and suggests that MCPs may not preclude treatment with PBS.

Dosimetric comparison between different radiotherapy protocols for prostate cancer using Geant4 Monte Carlo simulation

We aimed to evaluate absorbed doses received by organs at risk (OARs) following prostate treatment with external beam radiotherapy (EBRT), using different techniques (3D-CRT and box), number of fields (4 and 6 fields) and photon energies (6 and 10 MV). The MIRD5 adult male anthropomorphic phantom in GEANT4 package was used. However, the prostate, rectum and both femoral heads were not available, hence, were created within the phantom. A dose of 75 Gy was prescribed to the prostate, in all simulated treatments. Field size of 6.4 × 5.9 cm2 was used in all techniques. For 3D-CRT technique, beams with similar shape to the prostate were used, while for box technique, square-shaped beams were used. Absorbed doses to OARs (rectum, urinary bladder and both femoral heads) were then evaluated. The 3D-CRT technique resulted in lower dose to OARs compared to box technique. Also, the findings show an inverse relationship between number of fields and the OARs doses. There was no dose difference between the OARs with different beam energies. In conclusion, the 6-field 3D-CRT technique with 6 MV photon beam is an ideal treatment option for prostate cancer.

Dosimetric Effect Resulting From the Collimator Angle, the Isocenter Move, and the Gantry Angle Errors

Introduction: Dose distribution can be affected by diverse parameters, such as beam orientations, and collimator angles. These parameters should respect and maintain the international recommended levels during the realization of the quality assurance protocols of linear accelerators. This study aimed at evaluating the dosimetric effects on treatment quality considering the mechanical error fluctuations in the recommended range. Material and Methods: This study included ten patients with head and neck cancer. All of them were treated using three-dimensional conformal radiotherapy with the simple 3-field classic technique. Initially, an optimized treatment plan was computed for each patient. Afterward, similar calculations were executed by varying isocenter position, gantry and collimator angles. Eventually, dosimetric evaluations based on dose-volume histograms were studied and analyzed by Wilcoxon signed rank test for each plan. Results: The analysis of the dose-volume histograms of tumor volumes and organs at risk, as well as the dosimetry calculation, revealed that the small errors of 0.5° in gantry and collimator angles have minimal effects on dose distribution. However, the variation in isocenter coordinating up to 1 mm may influence the patients’ treatment quality, particularly in the spinal cord and the brainstem, in which Wilcoxon's test showed significant effects in all plans. Conclusion: According to the results, the quality of the treatment plans is almost insensitive to the errors of the gantry and the collimator angles of the order 0.5° though it is relatively sensitive to isocenter errors (1 mm). These should be reduced in order to avoid overdose when applying the conventional 3-field technique.

Fear of cancer recurrence trajectory during radiation treatment and follow-up into survivorship of patients with breast cancer

BackgroundFear of cancer recurrence (FCR) has been shown to be higher in patients treated with external beam radiotherapy (RT) compared to those untreated. However, little is known about the dynamics of patient’s FCR during and after RT. The aim of this study was to examine FCR levels in a longitudinal panel design with breast cancer patients receiving RT.MethodsConsecutive newly-diagnosed breast cancer patients (n = 94) attending a single cancer centre were invited to complete a 7-item FCR scale (FCR7) that was collected weekly by paper instrument and at a follow-up phone call 6–8 weeks after completion of RT. Descriptive statistics, and Latent Growth Curve Modelling (LGCM) were utilised to analyse the data.ResultsWomen who were younger, single/separated, had chemotherapy, had extra boost radiation treatment, taking Herceptin and treated by 4-field technique reported higher recurrence fear at baseline. There was strong evidence of substantial variation in the trajectory of FCR (z = − 3.54, p < .0001). The average trajectory of FCR over RT was negative (unstandardized estimate = − 0.59) and associated with FCR follow-up level (standardised estimate = 0.36, z = 3.05, p < .002), independent of baseline recurrence fears.ConclusionPatients vary in their trajectory of recurrence fears over RT which predicts FCR approximately 2 months following treatment. Review appointments by therapy radiographers presents an opportunity to intervene in FCR trajectories.Trial registrationClinicalTrials.gov: NCT02599506. Prospectively registered on 11th March 2015.

Dosimetric comparison of anterior posterior-posterior anterior 2-field three-dimensional conformal radiotherapy, 4-field three-dimensional conformal radiotherapy and "forward" plan intensity modulated radiotherapy techniques in female lymphoma patients irradiated to neck and mediastinum.

Dosimetric comparison of three different techniques in female lymphoma patients who had radiotherapy (RT) to the neck and mediastinum. Retrospective clinical study. Computerized tomography-simulator images of eight patients were obtained retrospectively. Using 6 MV-X photon energy, RT plans were formed with three different techniques (anterior posterior-posterior anterior 2-field three-dimensional conformal RT [AP-PA 2-field 3D-CRT], 4-field 3D-CRT and "forward" plan intensity modulated RT [FPIMRT]). Comparisons were in terms of homogeneity index (HI), conformity index (CI), and inhomogeneity coefficient for planning target volume (PTV); mean lung dose, V5Gy, V10Gy, V20Gy, V30Gy for lung; Dmean, V7.5Gy, V15Gy, V25Gy for heart; Dmean, V3.5Gy, V10Gy, V20Gy for breast; Dmax for spine; Dmean, V10Gy, V18Gy, V25Gy, V30Gy for thyroid. Since nonparametric tests had to be used due to the study population being < 30, Friedman and Wilcoxon signed-rank tests were implemented in trilateral and bilateral comparison of techniques, respectively. For statistical significance, P value was required to be <0.05. When FPIMRT was compared with AP-PA and 4-field techniques with respect to, HI (AP-PA/FPIMRT P: 0.017; 4-field/FPIMRT P: 0.03) and CI (AP-PA/FPIMRT P: 0.018; 4-field/FPIMRT P: 0.042), FPIMRT was more advantageous. In addition, FPIMRT was found more useful in terms of Dmax (AP-PA/FPIMRT P: 0.012; 4-Field/FPIMRT P: 0.012) for spinal cord and Dmean (AP-PA/FPIMRT P: 0.012; 4-field/FPIMRT P: 0.012) for thyroid. FPIMRT was superior in terms of PTV homogeneity and conformity. However, it was observed that for normal tissues, FPIMRT was advantageous only for spinal cord and thyroid; but it was not the most advantageous technique for some of the dose-volume parameters of the breast, lung, and heart.

Clinical results of accelerated hypofractionated radiotherapy for central-type small lung tumours.

We evaluated the efficacy and toxicity of accelerated hypofractionated radiotherapy (ahypof-rt) for central-type small lung tumours. Between November 2006 and January 2015, 40 patients with central-type small lung tumours underwent ahypof-rt delivered using 10 MV X-rays and a coplanar 3-field technique. The number of fractions ranged from 24 to 28, with a fraction size of 2.5-3 Gy. A total dose of 69-75 Gy to the isocentre of the planning target volume was administered to each patient. Cumulative survival and local control rates were calculated using the Kaplan-Meier method. The 27 men and 13 women enrolled in the study had a median age of 79 years (range: 60-87 years). The tumour stage was T1a in 9 patients, T1b in 17 patients, and T2a in 14 patients, with a median size of 26.5 cm (range: 11-49 cm). The median follow-up period was 23 months. A complete response was achieved in 3 patients (7.5%), and a partial response, in 17 patients (42.5%). The overall 2-year and 3-year local control rates were 87.3% and 81.8% respectively; the 2-year and 3-year overall survival rates were 78.9% and 66.7% respectively. Grade 3 pneumonitis occurred in 3 patients; no other severe adverse events (≥grade 3) were observed in any patient. Accelerated hypofractionated radiotherapy using a fraction size of 2.5-3 Gy was highly safe and can be a more effective treatment option than conventional radiotherapy for patients with central-type small lung tumours.

Elective breast radiotherapy including level I and II lymph nodes: A planning study with the humeral head as planning risk volume

BackgroundThe aim of this study was to assess the dose to the humeral head planning risk volume with the currently used high tangential fields (HTF) and compare different planning techniques for breast radiotherapy including axillary level I and II lymph nodes (PTVn) while sparing the humeral head.MethodsTen patients with left-sided breast cancer were enrolled in a planning study with 16 fractions of 2.66 Gy. Four planning techniques were compared: HTF, HTF with sparing of the humeral head, 6-field IMRT with sparing of the humeral head and VMAT with sparing of the humeral head. The humeral head + 10 mm was spared by restricting V40Gy < 1 cc.ResultsThe dose to the humeral head was too high with HTF (V40Gy on average 20.7 cc). When sparing the humeral head in HTF, PTVn V90% decreased significantly from 97.9% to 89.4%. 6-field IMRT and VMAT had a PTVn V90% of 98.2% and 99.5% respectively. However, dose to the lungs, heart and especially the contralateral breast increased with VMAT.ConclusionsThe humeral head is rarely spared when using HTF. When sparing the humeral head, the 6-field IMRT technique leads to adequate PTV coverage while not increasing the dose to the OARs.

Is There a Role for Pelvic Irradiation in Localized Prostate Adenocarcinoma? Update of the Long-Term Survival Results of the GETUG-01 Randomized Study

To report the long-term results of the French Genitourinary Study Group (GETUG)-01 study in terms of event-free survival (EFS) and overall survival (OS) and assess the potential interaction between hormonotherapy and pelvic nodes irradiation. Between December 1998 and June 2004, 446 patients with T1b-T3, N0pNx, M0 prostate carcinoma were randomly assigned to either pelvic nodes and prostate or prostate-only radiation therapy. Patients were stratified into 2 groups: "low risk" (T1-T2 and Gleason score 6 and prostate-specific antigen <3× the upper normal limit of the laboratory) (92 patients) versus "high risk" (T3 or Gleason score >6 or prostate-specific antigen >3× the upper normal limit of the laboratory). Short-term 6-month neoadjuvant and concomitant hormonal therapy was allowed only for high-risk patients. Radiation therapy was delivered with a 3-dimensional conformal technique, using a 4-field technique for the pelvic volume (46Gy). The total dose recommended to the prostate moved from 66Gy to 70Gy during the course of the study. Criteria for EFS included biologic prostate-specific antigen recurrences and/or a local or metastatic progression. With a median follow-up of 11.4years, the 10-year OS and EFS were similar in the 2 treatment arms. A higher but nonsignificant EFS was observed in the low-risk subgroup in favor of pelvic nodes radiation therapy (77.2% vs 62.5%; P=.18). A post hoc subgroup analysis showed a significant benefit of pelvic irradiation when the risk of lymph node involvement was <15% (Roach formula). This benefit seemed to be limited to patients who did not receive hormonal therapy. Pelvic nodes irradiation did not statistically improve EFS or OS in the whole population but may be beneficial in selected low- and intermediate-risk prostate cancer patients treated with exclusive radiation therapy.

Outcome of radiotherapy for pituitary adenomas

AimThe aim of this study was to analyze the outcome and toxicities and its correlation to patient related and treatment related factors. BackgroundPituitary adenomas are treated by radiation therapy (RT) as one of the modalities along with surgery and medical therapy. RT to pituitary adenomas is a challenge due to adjacent dose limiting structures such as optic apparatus and hypothalamus. Materials and methodsBetween January 2004 and December 2010, 94 patients treated for pituitary adenoma with RT who had hospital records of a minimum follow-up of 1 year were included in the analysis. Tests of correlation were done with regards to treatment factors. ResultsMale preponderance was noted in our patient population. Nonfunctioning and functioning tumors were equal in number in this series. Hypopituitarism was associated in 58.5% of patients prior to RT. Radiological tumor progression was seen in one patient (1/94) who had a nonfunctioning tumor. Among functioning tumors, biochemical remission was seen in 93.6% of patients at a median follow-up of 6 years. ConclusionsVisual complication was seen in 5.3% of patients and worsening or new onset hypopituitarism was seen in 6.4%. Conventional 3-field technique was associated with significantly more visual complication compared to Stereotactic Radiation Therapy (SRT) technique. Doses ≤50.4Gy showed a trend of reduced rate of visual and endocrine complications with no compromise in efficacy.

Clinical validation and benchmarking of knowledge-based IMRT and VMAT treatment planning in pelvic anatomy

PurposeThe aim of this work was to determine whether a commercial knowledge-based treatment planning (KBP) module can efficiently produce IMRT and VMAT plans in the pelvic region (prostate & cervical cancer), and to assess sensitivity of plan quality to training data and model parameters. MethodsInitial benchmarking of KBP was performed using prostate cancer cases. Structures and dose distributions from 40 patients previously treated using a 5-field IMRT technique were used for model training. Two types of model were created: one excluded statistical outliers (as identified by RapidPlan guidelines) and the other had no exclusions. A separate model for cervix uteri cancer cases was subsequently developed using 37 clinical patients treated for cervical cancer using RapidArc™ VMAT, with no exclusions. The resulting models were then used to generate plans for ten patients from each patient group who had not been included in the modelling process. Comparisons of generated RapidPlans with the corresponding clinical plans were carried out to indicate the required modifications to the models. Model parameters were then iteratively adjusted until plan quality converged with that obtained by experienced planners without KBP. ResultsInitial automated model generation settings led to poor conformity, coverage and efficiency compared to clinical plans. Therefore a number of changes to the initial KBP models were required. Before model optimisation, it was found that the PTV coverage was slightly reduced in the superior and inferior directions for RapidPlan compared with clinical plans and therefore PTV parameters were adjusted to improve coverage. OAR doses were similar for both RapidPlan and clinical plans (p>0.05). Excluding outliers had little effect on plan quality (p≫0.05). Manually fixing key optimisation objectives enabled production of clinically acceptable treatment plans without further planner intervention for 9 of 10 prostate test patients and all 10 cervix test patients. ConclusionsThe Varian RapidPlan™ system was able to produce IMRT & VMAT treatment plans in the pelvis, in a single optimisation, that had comparable sparing and comparable or better conformity than the original clinically acceptable plans. The system allows for better consistency and efficiency in the treatment planning process and has therefore been adopted clinically within our institute with over 100 patients treated.

Protection of organs at risk during neoadjuvant chemoradiotherapy for gastric cancer based on a comparison between conformal and intensity-modulated radiation therapy.

The aim of the present study was to compare the techniques of dynamic intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) in patients with gastric cancer. Implementation of the IMRT technique does not significantly affect the minimum and maximum dose levels in the planning target volume (PTV), but more effectively protects the critical organs. The study group consisted of 25 patients. The results of the analysis of the conformity index (CI) and the homogeneity index (HI) showed that the doses in the PTV regions were at a comparable level. The CI for the PTV was 0.95 for the 2-field technique, 0.95 for the 3-field technique, 0.96 for the 4-field technique and 0.94 for the IMRT technique. The CIs for these techniques for the clinical target volume (CTV) were 0.96, 0.96, 0.97 and 0.96, respectively, and the CIs for the gross tumor volume (GTV) were 0.99, 0.99, 0.99 and 0.98, respectively. The HI values for the PTV were 1.12 for the 2-field technique, 1.12 for the 3-field technique, 1.09 for the 4-field technique and 1.09 for the IMRT technique, and the HI values for the CTV were 1.12, 1.12, 1.09 and 1.08 for the same techniques, respectively. The HI values for the GTV were 1.09, 1.09, 1.07 and 1.06, respectively, which indicated significantly superior performance in the regions of healthy tissue. Statistical study was based on Friedman's rank analysis of variance to determine the level of reliability of the tested groups of variables (P<0.001). The present study demonstrated that the IMRT technique in the pre-operative radiotherapy of gastric cancer patients results in superior treatment tolerance and reduces the risk of damage to healthy tissue that is in close proximity to the irradiated area.

Abstract P3-12-06: Active breathing control in the management of left-sided breast cancer with irradiation: A dosimetric analysis of cardiac and lung dose

Abstract Purpose: Deep inspiratory breath hold (DIBH) is a technique that has been increasingly utilized over the past several years for the purpose of reducing the radiation dose received by the heart and ipsilateral lung during radiotherapy (RT) for breast cancer. The purpose of this study was to provide a comparative analysis of cardiac and lung dose in patients treated with and without moderate DIBH with an active breathing control (ABC) device during RT for left-sided breast cancer at a community radiation oncology center. Methods: From June 2013 to December 2014, 83 patients with stages 0-III left-sided breast cancer were treated with RT. Of these, 45 patients underwent CT simulation with an ABC device and the remaining 38 patients underwent standard free-breathing CT simulation for RT planning. Twenty-eight patients in the ABC cohort were treated with standard tangent fields and 18 were treated with locoregional RT. The non-ABC cohort included 26 patients treated with standard tangents and 12 treated with locoregional RT. A 4- or 5-field technique was utilized in all locally advanced patients to allow for coverage of the supraclavicular fossa and internal mammary lymph nodes with inclusion of low axillary coverage based on individual risk factors. All patients were treated with 3D-conformal techniques utilizing multi-leaf collimators to block the heart. Comparisons were made between mean heart dose, heart V5, mean lung dose, and lung V5 with and without the use of ABC. Kruskal-Wallis tests were used to determine significance between groups with α for significance set at p ≤0.05. Results: On combined analysis, the use of DIBH with ABC resulted in a reduction in heart V5 (1.5 versus 5.4%; p=0.018). Mean heart dose, mean lung dose, and lung V5 were not significantly improved with the use of ABC. On subgroup analysis, patients treated with locoregional RT had reduced mean heart dose (161 cGy versus 309 cGy; p=0.014) and heart V5 (2.3% versus 14.8%; p&amp;lt;0.001) compared to patients treated with a standard free-breathing technique. Conclusions: The use of ABC provided a significant reduction in heart V5 in all patients with left-sided breast cancer and in mean heart dose and heart V5 in patients treated with locoregional RT. This retrospective, single-institution analysis demonstrates the feasibility of implementing moderate DIBH with ABC technology in the treatment of left-sided breast cancer in a community radiation oncology center. Citation Format: Gogineni ES, Kehrer JD, Jones GC, Premo C, Stinson S. Active breathing control in the management of left-sided breast cancer with irradiation: A dosimetric analysis of cardiac and lung dose. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-06.