Pelvic Intensity-modulated Radiotherapy Research Articles

Pelvic and Paraaortic Field IMRT With Weekly Concurrent Cisplatin for the Treatment of Locally Advanced Squamous Cell Carcinoma of the Uterine Cervix

Pelvic and Paraaortic Field IMRT With Weekly Concurrent Cisplatin for the Treatment of Locally Advanced Squamous Cell Carcinoma of the Uterine Cervix

Can Bone Marrow Dosimetric Parameters Predict for Myelotoxicity in Cervical Cancer Patients Treated With Concurrent Chemotherapy and Extended-Field Intensity-Modulated Pelvic Radiotherapy (EF-IMRT)?

Can Bone Marrow Dosimetric Parameters Predict for Myelotoxicity in Cervical Cancer Patients Treated With Concurrent Chemotherapy and Extended-Field Intensity-Modulated Pelvic Radiotherapy (EF-IMRT)?

Predictors of Hematologic Toxicity and Implications for Bone-Marrow Sparing Pelvic IMRT for Cervical Cancer

Predictors of Hematologic Toxicity and Implications for Bone-Marrow Sparing Pelvic IMRT for Cervical Cancer

Analysis of toxicity in patients with high risk prostate cancer treated with intensity-modulated pelvic radiation therapy and simultaneous integrated dose escalation to prostate area

Background and purpose To report the treatment-related morbidity in patients with prostate cancer treated with an optimized pelvic intensity-modulated radiation therapy (IMRT) and simultaneous integrated dose escalation to prostate/prostate bed. Materials and methods Between November 2003 and May 2006, 55 patients with localized prostate cancer and >15% risk of lymph node involvement were treated with pelvic IMRT and simultaneous dose escalation to prostate area. Twenty-four patients received a radical radiation therapy program, and the remaining thirty-one patients received a postoperative irradiation as adjuvant treatment or after biochemical or macroscopic local/regional relapse. After a customized immobilization all patients underwent contrast-enhanced CT. On the CT slices CTV1 and CTV2 were delineated. CTV 1 included the prostate and seminal vesicles or prostate bed. CTV 2 consisted of CTV 1 plus pelvic nodes. CTV 1 and CTV 2 were then expanded by 0.5 and 1 cm, respectively, to generate the planning target volumes. IMRT treatment plans were generated using commercial inverse planning software. Total doses of 66–80 Gy and 50–59 Gy in 33–40 fractions were prescribed to the prostate area and pelvis, respectively. The worst acute and late rectal, intestinal and GU toxicities during and after treatment were scored according to the EORTC/RTOG scales. Results The IMRT dose distribution provided excellent PTV coverage and satisfying sparing of all the organs at risk, with no patient experiencing >grade 2 acute or late toxicities. Patients without acute grade 2 intestinal, rectal, and GU toxicity were 91%, 71%, and 63%, respectively. After a median follow-up of 19 months (interquartile range of 9 to 28 months), late grade 2 toxicity was detected only for rectum, with an actuarial 2-year rate of freedom from G2 rectal bleeding of 92%. (CI 95% 0.83–0.99.) Conclusions Pelvic IMRT and simultaneous dose escalation to prostate area is a well-tolerated technique in patients with prostate cancer requiring treatment of pelvic lymph nodes, and seems to be associated with a lower frequency and severity of side effects when compared with conventional techniques reported in other series.

Chronic Genitourinary and Gastrointestinal Toxicity of Prostate Cancer Patients Undergoing Pelvic Radiotherapy With Intensity-Modulated Versus 4-Field Technique

To compare chronic GU and GI toxicity of pelvic radiotherapy delivered using intensity-modulated radiotherapy (IMRT) versus conventional 4-field technique. The records of consecutive prostate cancer patients receiving RT at a single institution with a minimum follow-up of 120 days were reviewed; 48 of these patients received a prostate boost preceded by pelvic radiotherapy (PRT), 14 with IMRT (IM-PRT), and 34 with 4-field (4F-PRT). Dosimetric endpoints for the bladder, rectum, composite, and target for the PRT plans were compared using the 2-tailed t test. Late RTOG GU and GI toxicity were compared using the chi test. Ordered logit regression analyses were performed using all major patient, disease, and treatment factors as covariates. IM-PRT demonstrated superior bladder and rectum dosimetric endpoints over 4F-PRT for the PRT portion of the treatment and for the composite treatment at the expense of higher target inhomogeneity in the PRT portion of the treatment plan. Late GU toxicity was significantly lower in the IM-PRT group (P < 0.001), whereas late GI toxicity was similar in both groups (P = 0.44). When considering a similar follow-up interval in both groups, however, the difference in GU toxicity only reached a trend (P = 0.10). The regression analyses showed that no factor, including IMRT, reached significance in predicting GU or GI toxicity. Use of pelvic IMRT for prostate cancer patients was not associated with reduction of late GI toxicity but was associated with a small reduction of late GU toxicity. This reduction of late GU toxicity warrants further exploration in consortium studies.

SU‐FF‐T‐452: Whole Pelvic IMRT Treatment for Post Operative Gynecological Malignancies, Sheba Experience

Background and Purpose: To evaluate the use of IMRT treatment for post operative gynecological malignancies for better organ at risk sparing to reduce treatment toxicity that will allow dose escalation. Creating guidelines for that treatment. Recognize treatment limits and problems in ITPS and QA for very large IMRT volumes and fields. Patients and Methods: five patients were selected with endometrial cancer treated postoperatively. Bladder, rectal wall, small and large bowel were delineated as organs at risk. A seven field IMRT plan prescription dose 50.4 Gy and compared with conformal 4 fields plan (DVH). QA performed with film dosimetry and ion chambers. Results: significant improvements were observed for irradiated volume of rectal wall and bladder. With IMRT the average irradiated volume of small and large bowel was reduced dramatically and the impact of IMRT was large for postoperative patients, in one patient treatment volume was very large (24833cc of normal tissue) the ITPS could calculate only if the calculation grid was 10mm spaced, that lead to a disagreement in QA and patient was treated 3D conformal. Conclusions: IMRT significantly reduced the absolute volume of rectal wall, bladder and bowel irradiated at the prescribed dose level in post operative gynecologic patients. Due to large treatment volumes we have to be aware of disagreements between calculations and dosimetry.

Design, development, and implementation of the Radiological Physics Center's pelvis and thorax anthropomorphic quality assurance phantoms

The Radiological Physics Center (RPC) developed two heterogeneous anthropomorphic quality assurance phantoms for use in verifying the accuracy of radiation delivery: one for intensity-modulated radiation therapy (IMRT) to the pelvis and the other for stereotactic body radiation therapy (SBRT) to the thorax. The purpose of this study was to describe the design and development of these two phantoms and to demonstrate the reproducibility of measurements generated with them. The phantoms were built to simulate actual patient anatomy. They are lightweight and water-fillable, and they contain imageable targets and organs at risk of radiation exposure that are of similar densities to their human counterparts. Dosimetry inserts accommodate radiochromic film for relative dosimetry and thermoluminesent dosimetry capsules for absolute dosimetry. As a part of the commissioning process, each phantom was imaged, treatment plans were developed, and radiation was delivered at least three times. Under these controlled irradiation conditions, the reproducibility of dose delivery to the target TLD in the pelvis and thorax phantoms was 3% and 0.5%, respectively. The reproducibility of radiation-field localization was less than 2.5 mm for both phantoms. Using these anthropomorphic phantoms, pelvic IMRT and thoracic SBRT radiation treatments can be verified with a high level of precision. These phantoms can be used to effectively credential institutions for participation in specific NCI-sponsored clinical trials.

Clinical Outcome in Posthysterectomy Cervical Cancer Patients Treated With Concurrent Cisplatin and Intensity-Modulated Pelvic Radiotherapy: Comparison With Conventional Radiotherapy

To assess local control and acute and chronic toxicity with intensity-modulated radiation therapy (IMRT) as adjuvant treatment of cervical cancer. Between April 2002 and February 2006, 68 patients at high risk of cervical cancer after hysterectomy were treated with adjuvant pelvic radiotherapy and concurrent chemotherapy. Adjuvant chemotherapy consisted of cisplatin (50 mg/m(2)) for six cycles every week. Thirty-three patients received adjuvant radiotherapy by IMRT. Before the IMRT series was initiated, 35 other patients underwent conventional four-field radiotherapy (Box-RT). The two groups did not differ significantly in respect of clinicopathologic and treatment factors. IMRT provided compatible local tumor control compared with Box-RT. The actuarial 1-year locoregional control for patients in the IMRT and Box-RT groups was 93% and 94%, respectively. IMRT was well tolerated, with significant reduction in acute gastrointestinal (GI) and genitourinary (GU) toxicities compared with the Box-RT group (GI 36 vs. 80%, p = 0.00012; GU 30 vs. 60%, p = 0.022). Furthermore, the IMRT group had lower rates of chronic GI and GU toxicities than the Box-RT patients (GI 6 vs. 34%, p = 0.002; GU 9 vs. 23%, p = 0.231). Our results suggest that IMRT significantly improved the tolerance to adjuvant chemoradiotherapy with compatible locoregional control compared with conventional Box-RT. However, longer follow-up and more patients are needed to confirm the benefits of IMRT.

The role and strategy of IMRT in radiotherapy of pelvic tumors: Dose escalation and critical organ sparing in prostate cancer

To investigate the intensity-modulated radiotherapy (IMRT) strategy in dose escalation of prostate and pelvic lymph nodes. Plan dosimetric data of 10 prostate cancer patients were compared with two-dimensional (2D) or IMRT techniques for pelvis (two-dimensional whole pelvic radiation therapy [2D-WPRT] or IM-WPRT) to receive 50 Gy or 54 Gy and additional prostate boost by three-dimensional conformal radiation therapy or IMRT (3D-PBRT or IM-PBRT) techniques up to 72 Gy or 78 Gy. Dose-volume histograms (DVHs), normal tissue complication probabilities (NTCP) of critical organ, and conformity of target volume in various combinations were calculated. In DVH analysis, the plans with IM-WPRT (54 Gy) and additional boost up to 78 Gy had lower rectal and bladder volume percentage at 50 Gy and 60 Gy, compared with those with 2D-WPRT (50 Gy) and additional boost up to 72 Gy or 78 Gy. Those with IM-WPRT (54 Gy) also had better small bowel sparing at 30 Gy and 50 Gy, compared with those with 2D-WPRT (50 Gy). In NTCP, those with IM-WPRT and total dose of 78 Gy achieved lower complication rates in rectum and small bowel, compared with those of 2D-WPRT with total dose of 72 Gy. In conformity, those with IM-WPRT had better conformity compared with those with 2D-WPRT with significance (p < 0.005). No significant difference in DVHs, NTCP, or conformity was found between IM-PBRT and 3D-PBRT after IM-WPRT. Initial pelvic IMRT is the most important strategy in dose escalation and critical organ sparing. IM-WPRT is recommended for patients requiring WPRT. There is not much benefit for critical organ sparing by IMRT after 2D-WPRT.

2277: Acute Toxicity Assessment of a Single Institution Series of Prostate Cancer Patients Treated With Pelvic Intensity Modulated Radiation Therapy With Synchronous Integrated Boost to the Prostate or Prostate Bed

We investigated the feasibility of delivering elective pelvic nodal RT combined with a hypofractionated RT regimen to the primary site by employing IMRT with a synchronous integrated boost (SIB) for patients with intermediate to high-risk prostate cancer. We analyzed acute toxicity of SIB IMRT in patients treated either primarily for prostate cancer or with post-operative or salvage RT following prostatectomy. For primary treatment, the prostate planning target volume (PTVprostate) was the prostate plus a 5 mm posterior margin and 1 cm margin in other directions; the nodal PTV (PTVnodes) included the internal, external, and lower common iliac vessels plus a 1 cm circumferential margin. SIB IMRT plans were designed to deliver 70 Gy to the PTVprostate in 28 fractions (2.5 Gy/fraction) while simultaneously delivering 50.4 Gy to the PTVnodes. Post-operative or salvage SIB IMRT included a dose of 64 Gy in 32 fractions to the PTVpost-op, here defined as the prostate bed plus a 1 cm margin, while simultaneously delivering 54.4 Gy to the PTVnodes. The NCIC CTCAE v3.0 was employed to score toxicity. Twenty-seven patients (18 definitive, 5 adjuvant, 4 salvage) were treated between early 2004 and late 2005. The median age at the beginning of treatment was 63 years (range 53–77). Twenty-two out of 27 patients received androgen suppression as a component of treatment, including all patients in the primary RT cohort. Twenty-six out of 27 patients received treatment as prescribed, with 1 patient discontinuing radiation one fraction prior to completion due to a medical problem unrelated to his treatment. Median follow-up of all patients was 9 months (3–19 months). The incidence of any acute grade 1 or 2 event was 96%. The most common acute event was urinary frequency/urgency, which occurred in 81% of patients (67% grade 1, 14% grade 2). Acute diarrhea occurred in 56% of patients (37% grade 1, 15% grade 2, 4% grade 3). The incidence of any grade 3 or higher acute toxicity was 4% (1/27); that patient experienced severe diarrhea while on treatment, but was found to have clostridium difficile colitis, and his symptoms improved rapidly on antibiotics. Pelvic IMRT with synchronous integrated boost to the prostate/prostate bed for high-risk prostate cancer, either given in the primary or post-operative/salvage setting, was acutely well tolerated in our series of patients. Additional follow-up is necessary to ensure that no unexpected late toxicity occurs. SIB IMRT to the pelvis combines elective nodal RT and hypofractionation to the primary and warrants further study in a clinical trial setting.

2154: A Comparison of Supine Intensity-Modulated Radiotherapy Treatment With Prone 3D Conformal Radiotherapy for Rectal Cancer: Preliminary Results of Dosimetric Analysis

Patients with locally advanced rectal cancer are routinely treated with combined chemoradiation as part of their overall treatment plan. This carries the possibility of significant GI toxicity, leading to the desire to decrease radiation dose to normal organs. Classically, patients have been treated in the prone position with conventional 3D techniques, though patient reproducibility in the prone position is uncertain and there remains a large volume of organ exposure to radiation. This study evaluates the feasibility of pelvic intensity-modulated radiotherapy (IMRT) in the supine position compared to 3D conformal radiotherapy (3DCRT) in the prone position for rectal cancer.

Intensity-modulated radiotherapy improves lymph node coverage and dose to critical structures compared with three-dimensional conformal radiation therapy in clinically localized prostate cancer

The aim of this study was to quantify gains in lymph node coverage and critical structure dose reduction for whole-pelvis (WP) and extended-field (EF) radiotherapy in prostate cancer using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3DCRT) for the first treatment phase of 45 Gy in the concurrent treatment of lymph nodes and prostate. From January to August 2005, 35 patients with localized prostate cancer were treated with pelvic IMRT; 7 had nodes defined up to L5-S1 (Group 1), and 28 had nodes defined above L5-S1 (Group 2). Each patient had 2 plans retrospectively generated: 1 WP 3DCRT plan using bony landmarks, and 1 EF 3DCRT plan to cover the vascular defined volumes. Dose-volume histograms for the lymph nodes, rectum, bladder, small bowel, and penile bulb were compared by group. For Group 1, WP 3DCRT missed 25% of pelvic nodes with the prescribed dose 45 Gy and missed 18% with the 95% prescribed dose 42.75 Gy, whereas WP IMRT achieved V(45 Gy) = 98% and V(42.75 Gy) = 100%. Compared with WP 3DCRT, IMRT reduced bladder V(45 Gy) by 78%, rectum V(45 Gy) by 48%, and small bowel V(45 Gy) by 232 cm3. EF 3DCRT achieved 95% coverage of nodes for all patients at high cost to critical structures. For Group 2, IMRT decreased bladder V(45 Gy) by 90%, rectum V(45 Gy) by 54% and small bowel V(45 Gy) by 455 cm3 compared with EF 3DCRT. In this study WP 3DCRT missed a significant percentage of pelvic nodes. Although EF 3DCRT achieved 95% pelvic nodal coverage, it increased critical structure doses. IMRT improved pelvic nodal coverage while decreasing dose to bladder, rectum, small bowel, and penile bulb. For patients with extended node involvement, IMRT especially decreases small bowel dose.

Intensity-modulated versus conventional pelvic radiotherapy for prostate cancer: Analysis of acute toxicity: Jani AB, Su A, Milano MT, Department of Radiation and Cellular Oncology, University of Chicago Hospitals, Chicago, IL

To provide a single-institution analysis of the influence of pelvic intensity-modulated radiotherapy (RT) on acute genitourinary (GU) and gastrointestinal (GI) toxicity. The records of 610 consecutive patients with prostate cancer receiving RT were reviewed. Of these 610 patients, 49 had received a prostate boost preceded by pelvic RT (PRT), 15 intensity-modulated PRT (IM-PRT), and 34 four-field PRT (4F-PRT). The dosimetric endpoints for the bladder, rectum, and target for the PRT plans were compared using the paired t test; similar dosimetric analyses were done for the composite plans. Acute GU and GI toxicity were compared using the chi-square test. Ordered logit regression analyses were performed using all major treatment factors as covariates. The bladder and rectum dosimetric endpoints were improved for IM-PRT compared with 4F-PRT for the PRT portion of the treatment plan (P = 0.06 and P = 0.03, respectively) and for the composite treatment plan (P = 0.04 and P = 0.01, respectively), at the expense of greater target inhomogeneity in the PRT portion of the treatment plan (P < 0.01). GU toxicity was significantly lower in the IM-PRT group (P < 0.001), and GI toxicity was similar in both groups (P = 0.637). The regression analyses showed that intensity-modulated RT for the pelvic portion of treatment was the only factor significantly predicting for GU toxicity (P = 0.05); no major treatment factor reached significance in predicting GI toxicity. Compared with 4F-PRT, the use of IM-PRT improved dosimetric outcomes, was not associated with a reduction in acute GI toxicity, and was associated with a reduction in acute GU toxicity in the treatment of prostate cancer.

Dosimetric predictors of acute hematologic toxicity in cervical cancer patients treated with concurrent cisplatin and intensity-modulated pelvic radiotherapy

To identify dosimetric parameters associated with acute hematologic toxicity (HT) and chemotherapy delivery in cervical cancer patients undergoing concurrent chemotherapy and intensity-modulated pelvic radiotherapy. We analyzed 37 cervical cancer patients receiving concurrent cisplatin (40 mg/m(2)/wk) and intensity-modulated pelvic radiotherapy. Pelvic bone marrow (BM) was contoured for each patient and divided into three subsites: lumbosacral spine, ilium, and lower pelvis. The volume of each region receiving 10, 20, 30, and > or =40 Gy (V(10), V(20), V(30), and V(40), respectively) was calculated. HT was graded according to the Radiation Therapy Oncology Group system. Multivariate regression models were used to test associations between dosimetric parameters and HT and chemotherapy delivery. Increased pelvic BM V(10) (BM-V(10)) was associated with an increased Grade 2 or worse leukopenia and neutropenia (odds ratio [OR], 2.09; 95% confidence interval [CI], 1.24-3.53; p = 0.006; and OR, 1.41; 95% CI, 1.02-1.94; p = 0.037, respectively). Patients with BM-V(10) > or =90% had higher rates of Grade 2 or worse leukopenia and neutropenia than did patients with BM-V(10) <90% (11.1% vs. 73.7%, p < 0.01; and 5.6% vs. 31.6%, p = 0.09) and were more likely to have chemotherapy held on univariate (16.7% vs. 47.4%, p = 0.08) and multivariate (OR, 32.2; 95% CI, 1.67-622; p = 0.02) analysis. No associations between HT and V(30) and V(40) were observed. Dosimetric parameters involving the lumbosacral spine and lower pelvis had stronger associations with HT than did those involving the ilium. The volume of pelvic BM receiving low-dose radiation is associated with HT and chemotherapy delivery in cervical cancer patients undergoing concurrent chemoradiotherapy.

TH‐D‐224C‐02: The State of Radiotherapy Physics Through The Eyes of a Quality Auditor

Purpose: To assess the radiotherapy programs of institutions participating in NCI sponsored clinical trials and assist them to implement remedial actions. Materials and Methods: The Radiological Physics Center (RPC) has developed an extensive Quality Assurance (QA) program over the past 38 years. This program includes on‐site dosimetry reviews where measurements on therapy machines are made, records are reviewed and personnel are interviewed. The program's remote audit tools include mailed dosimeters (TLD) to verify output calibration, comparison of dosimetry data with RPC “standard” data, evaluation of benchmarkd and patient calculations to verify the treatment planning algorithms, review of institution's QA procedures and records, and use of anthropomorphic phantoms to verify tumor dose delivery. The RPC assists institutions in finding the origins of discrepancies, and in resolving them. Results: The percent of institutions receiving dosimetry recommendations has been level at 70% for the past 5 years. The most frequent recommendations were for maintenance of an appropriate QA program, beam calibration, depth dose and wedge factors. Since TG‐51 was published, the number of reference calibrations meeting the RPC's ±3% criterion has decreased. The TLD program shows that only ∼3% of the beams are outside our ±5%/±5mm criteria, but these discrepancies are distributed over nearly 15% of the institutions. There continues to be a 33% percent first time failure rate for the IMRT H&amp;N anthropomorphic phantom. The other anthropomorphic phantoms, i.e. pelvic IMRT, lung stereotactic and liver stereotactic, have higher pass rates. Conclusion: Numerous dosimetry errors continue to exist and the RPC's QA program plays an important role in identifying and helping institutions resolve these errors to improve not only the quality of clinical trial patients' treatments, but also all patients treated at the participating institution.This work was supported by PHS grants CA10953 and CA081647 awarded by NCI.

A quantitative study of IMRT delivery effects in commercial planning systems for the case of oesophagus and prostate tumours

This study focuses on understanding the impact of intensity-modulated radiotherapy (IMRT) delivery effects when applied to plans generated by commercial treatment-planning systems such as Pinnacle (ADAC Laboratories Inc.) and CadPlan/Helios (Varian Medical Systems). These commercial planning systems have had several version upgrades (with improvements in the optimization algorithm), but the IMRT delivery effects have not been incorporated into the optimization process. IMRT delivery effects include head-scatter fluence from IMRT fields, transmission through leaves and the effect of the rounded shape of the leaf ends. They are usually accounted for after optimization when leaf sequencing the "optimal" fluence profiles, to derive the delivered fluence profile. The study was divided into two main parts: (a) analysing the dose distribution within the planning-target volume (PTV), produced by each of the commercial treatment-planning systems, after the delivered fluence had been renormalized to deliver the correct dose to the PTV; and (b) studying the impact of the IMRT delivery technique on the surrounding critical organs such as the spinal cord, lungs, rectum, bladder etc. The study was performed for tumours of (i) the oesophagus and (ii) the prostate and pelvic nodes. An oesophagus case was planned with the Pinnacle planning system for IMRT delivery, via multiple-static fields (MSF) and compensators, using the Elekta SL25 with a multileaf collimator (MLC) component. A prostate and pelvic nodes IMRT plan was performed with the Cadplan/Helios system for a dynamic delivery (DMLC) using the Varian 120-leaf Millennium MLC. In these commercial planning systems, since IMRT delivery effects are not included into the optimization process, fluence renormalization is required such that the median delivered PTV dose equals the initial prescribed PTV dose. In preparing the optimum fluence profile for delivery, the PTV dose has been "smeared" by the IMRT delivery techniques. In the case of the oesophagus, the critical organ, spinal cord, received a greater dose than initially planned, due to the delivery effects. The increase in the spinal cord dose is of the order of 2-3 Gy. In the case of the prostate and pelvic nodes, the IMRT delivery effects led to an increase of approximately 2 Gy in the dose delivered to the secondary PTV, the pelvic nodes. In addition to this, the small bowel, rectum and bladder received an increased dose of the order of 2-3 Gy to 50% of their total volume. IMRT delivery techniques strongly influence the delivered dose distributions for the oesophagus and prostate/pelvic nodes tumour sites and these effects are not yet accounted for in the Pinnacle and the CadPlan/Helios planning systems. Currently, they must be taken into account during the optimization stage by altering the dose limits accepted during optimization so that the final (sequenced) dose is within the constraints.

Combination of prone position and intensity-modulated radiation therapy (IMRT) reduces small bowel doses in radiation therapy for gynecologic malignancies

ObjectiveTo evaluate if the combination of both prone position on a belly board and intensity-modulated radiotherapy (IMRT) further reduces the radiation dose to small bowel in pelvic RT for gynecologic malignancies.MethodsConformal pelvic RT plans were computed in 13 patients with gynecologic malignancies who had pre-existing planning computed tomography (CT) scans in both the supine position and prone position on a belly board. There were 10 cervical cancer and 3 endometrial cancer patients. A limited arc technique (180° arc length) and an extended arc technique (340° arc length) were used in IMRT plans. Normal tissue regions of interest (ROI) included small bowel, large bowel and bladder. Dose and volume for normal tissue structures were traced and compared between supine and prone plans using the paired t-test.ResultsFor the limited arc technique, prone position using a belly board device improved small bowel sparing. Analysis of the results showed a 12∼26 Gy reduction of volume of small bowel irradiation compared to the supine position. With the extended arc technique, there was no obvious radiation reduction in the prone position. Large bowel and bladder dose showed no significant differences between prone and supine position with either technique.ConclusionProne positioning on a belly board decreases the small bowel dose in gynecologic pelvic IMRT, and the magnitude of improvement depended on the limited arc IMRT technique used.

Intensity-modulated versus conventional pelvic radiotherapy for prostate cancer: Analysis of acute toxicity

Objectives To provide a single-institution analysis of the influence of pelvic intensity-modulated radiotherapy (RT) on acute genitourinary (GU) and gastrointestinal (GI) toxicity. Methods The records of 610 consecutive patients with prostate cancer receiving RT were reviewed. Of these 610 patients, 49 had received a prostate boost preceded by pelvic RT (PRT), 15 intensity-modulated PRT (IM-PRT), and 34 four-field PRT (4F-PRT). The dosimetric endpoints for the bladder, rectum, and target for the PRT plans were compared using the paired t test; similar dosimetric analyses were done for the composite plans. Acute GU and GI toxicity were compared using the chi-square test. Ordered logit regression analyses were performed using all major treatment factors as covariates. Results The bladder and rectum dosimetric endpoints were improved for IM-PRT compared with 4F-PRT for the PRT portion of the treatment plan ( P = 0.06 and P = 0.03, respectively) and for the composite treatment plan ( P = 0.04 and P = 0.01, respectively), at the expense of greater target inhomogeneity in the PRT portion of the treatment plan ( P <0.01). GU toxicity was significantly lower in the IM-PRT group ( P <0.001), and GI toxicity was similar in both groups ( P = 0.637). The regression analyses showed that intensity-modulated RT for the pelvic portion of treatment was the only factor significantly predicting for GU toxicity ( P = 0.05); no major treatment factor reached significance in predicting GI toxicity. Conclusions Compared with 4F-PRT, the use of IM-PRT improved dosimetric outcomes, was not associated with a reduction in acute GI toxicity, and was associated with a reduction in acute GU toxicity in the treatment of prostate cancer.

Pelvic nodal dose escalation with prostate hypofractionation using conformal avoidance defined (H-CAD) intensity modulated radiation therapy

The management of prostate cancer patients with a significant risk of pelvic lymph node involvement is controversial. Both whole pelvis radiotherapy and dose escalation to the prostate have been linked to improved outcome in such patients, but it is unclear whether conventional whole pelvis doses of only 45–50 Gy are optimal for ultimate nodal control. The purpose of this study is to examine the dosimetric and clinical feasibility of combining prostate dose escalation via hypofractionation with conformal avoidance-based IMRT (H-CAD) dose escalation to the pelvic lymph nodes. One conformal avoidance and one conventional plan were generated for each of eight patients. Conformal avoidance-based IMRT plans were generated that specifically excluded bowel, rectum, and bladder. The prostate and lower seminal vesicles (PTV 70) were planned to receive 70 Gy in 2.5 Gy/fraction while the pelvic lymph nodes (PTV 56) were to concurrently receive 56 Gy in 2 Gy/fraction. The volume of small bowel receiving ≥45 Gy was restricted to 300 ml or less. These conformal avoidance plans were delivered using helical tomotherapy or LINAC-based IMRT with daily imaging localization. All patients received neoadjuvant and concurrent androgen deprivation with a planned total of two years. The conventional, sequential plans created for comparison purposes for all patients consisted of a conventional 4-field pelvic box prescribed to 50.4 Gy (1.8 Gy/fraction) followed by an IMRT boost to the prostate of 25.2 Gy (1.8 Gy/fraction) yielding a final prostate dose of 75.6 Gy. For all plans, the prescription dose was to cover the target structure. Equivalent uniform dose (EUD) analyses were performed on all targets and dose-volume histograms (DVH) were displayed in terms of both physical and normalized total dose (NTD), i.e. dose in 2 Gy fraction equivalents. H-CAD IMRT plans were created for and delivered to all eight patients. Analysis of the H-CAD plans demonstrates prescription dose coverage of >95% of both the PTV 70 (prostate) and PTV 56 (nodes). The EUDs for PTV 70 and PTV 56 were greater than prescription dose for all eight plans. Analysis of bio-effective DVHs demonstrated similar amounts of small bowel receiving ≥45 Gy for H-CAD and sequential plans, in spite of the significantly higher dose to which H-CAD treated the pelvic nodes. The treatment was well tolerated in the eight treated patients in that no grade 2 or higher acute gastrointestinal toxicities were seen. Prostate hypofractionation with concurrent conformal avoidance-based pelvic IMRT for high risk prostate cancer represents an efficient and promising method for achieving dose escalation both of pelvic lymph nodes and the prostate with modest acute toxicity. Unlike a vascular-guided targeting approach, conformal avoidance has the potential advantage of also encompassing at-risk nodes that are not contained within major nodal chains. A phase II trial to more thoroughly examine this treatment approach is currently underway.

Pelvic Intensity Modulated Radiation Therapy for High Risk Prostate Cancer

Pelvic Intensity Modulated Radiation Therapy for High Risk Prostate Cancer