Investigation of the changes in the prostate,bladder, and rectal wall sizes during external beam radiotherapy

Aim and backgroundThe change in the prostate size for radiotherapy has not yet been elucidated. The coverage of radiation dose is affected by changes in the prostate size. We evaluated the changes in the prostate, rectum, and bladder wall sizes during IMRT of fraction 2 Gy/day using MRI.Materials and methodsTwenty-four patients with prostate cancer were enrolled in this study. MRI was performed at three time points. While the initial MRI was performed before the start of radiotherapy (RT), the second MRI was performed at 38 Gy (range: 36–40 Gy), which represented the halfway point of the RT course. The last MRI was performed on the day of completion of the RT course (76 Gy; range: 74–78 Gy). We estimated the prostate, rectum, and bladder wall sizes at three time points.ResultsWe observed no significant difference between the estimated sizes of the prostate during RT in all three phases. In addition, the volume of the rectal wall remained unchanged in all phases. However, the volume of the bladder wall significantly decreased from the initial to the last time points. Furthermore, the standard deviation (SD) obtained by subtracting the final size from the initial one was large (mean, 30.1; SD, 10.1).ConclusionsThe volume of the bladder wall decreased during IMRT. The range of subtraction of the volume of the bladder wall was extensive. Thus, the estimation of the bladder wall may be useful to reduce the inter-fraction variation.     

Stereotactic radiotherapy for bone oligometastases

About 60–90% of cancer patients are estimated to develop bone metastases, particularly in the spine.Bone scintigraphy, computed tomography (CT ) and magnetic resonance imaging (MRI ) are currently used to assess metastatic bone disease; positron emission tomography/computed tomography (PET-CT ) has become more widespread in clinical practice because of its high sensitivity and specificity with about 95% diagnostic accuracy. The most common and well-known radiotracer is 18F-fluorodeoxyglucose (¹⁸FDG); several other PET-radiotracers are currently under investigation for different solid tumors, such as ¹¹C or ¹⁸FDG-choline and prostate specific membrane antigen (PSMA)-PET/CT for prostate cancer. In treatment planning, standard and investigational imaging modalities should be registered with the planning CT so as to best define the bone target volume. For target volume delineation of spine metastases, the International Spine Radiosurgery Consortium (ISRC ) of North American experts provided consensus guidelines. Single fraction stereotactic radiotherapy (SRT ) doses ranged from 12 to 24 Gy; fractionated SRT administered 21–27 Gy in 3 fractions or 20–35 Gy in 5 fractions. After spine SRT, less than 5% of patients experienced grade ≥ 3 acute toxicity. Late toxicity included the extremely rare radiation-induced myelopathy and a 14% risk of de novo vertebral compression fractures.     

Local control of 1–5 fraction radiotherapy regimens for spinal metastases: an analysis of the impacts of biologically effective dose and primary histology

BackgroundThis analysis evaluates the impacts of biologically effective dose (BED) and histology on local control (LC) of spinal metastases treated with highly conformal radiotherapy to moderately-escalated doses.Materials and methodsPatients were treated at two institutions from 2010–2020. Treatments with less than 5 Gy per fraction or 8 Gy in 1 fraction were excluded. The dataset was divided into three RPA classes predictive of survival (1). The primary endpoint was LC.Results223 patients with 248 treatments met inclusion criteria. Patients had a median Karnofsky Performance Status (KPS ) of 80, and common histologies included breast (29.4%), non-small cell lung cancer (15.7%), and prostate (13.3%). A median 24 Gy was delivered in 3 fractions (BED: 38.4 Gy) to a median planning target volume (PTV) of 37.3 cc. 2-year LC was 75.7%, and 2-year OS was 42.1%. Increased BED was predictive of improved LC for primary prostate cancer (HR = 0.85, 95% CI: 0.74–0.99). Patients with favorable survival (RPA class 1) had improved LC with BED ≥ 40 Gy (p = 0.05), unlike the intermediate and poor survival groups. No grade 3–5 toxicities were reported.ConclusionsModerately-escalated treatments were efficacious and well-tolerated. BED ≥ 40 Gy may improve LC, particularly for prostate cancer and patients with favorable survival.     

Anaplastic thyroid cancer: outcomes of trimodal therapy

BackroundThe purpose of this study is to assess the impact of trimodal therapy [surgery, chemotherapy and external beam radiotherapy (EBRT)] in patients with anaplastic thyroid cancer (ATC) treated with curative intent.Materials and methodsRetrospective review of patients with ATC treated at a tertiary referral centre between January 2009 and June 2020. Data were collected regarding demographics, histology, staging, treatment and outcomes.ResultsSeven patients (4 female) were identified. Median age was 58 years (range 52–83 years). All patients received EBRT with concurrent doxorubicin. Six patients received surgery followed by chemoradiotherapy (CRT), and one underwent neoadjuvant CRT followed by surgery. Median radiological tumour size was 50mm (range 40–90 mm). Six patients had gross extrathyroidal extension and three had N1b disease. Prescribed radiotherapy schedules were 46.4 Gy in 29 bidaily fractions (n = 2, treated 2010), 60 Gy in 30 daily fractions (n = 2), 66 Gy in 30 fractions (n = 2) and 70 Gy in 35 fractions (n = 1; patient received neoadjuvant CRT). CRT was discontinued early for two patients due to toxicities. At median follow up of 5.8 months, 42.9% (3/7) patients were alive and disease-free. Only one patient developed a local failure. Three patients died from distant metastases without locoregional recurrence.ConclusionsDespite poor prognosis of ATC, selected patients with operable tumours may achieve high locoregional control rates with trimodal therapy, with possibility of long-term survival in select cases.     

Time-Staged Gamma Knife Stereotactic Radiosurgery for Large Cerebral Arteriovenous Malformations: A Preliminary Report

ObjectiveWe retrospectively analyzed our experience with time-staged gamma knife stereotactic radiosurgery (GKS) in treating large arteriovenous malformation(AVM)s;≥ 10 cm³).MethodsForty-five patients who underwent time-staged GKS (2-stage, n = 37;3-stage,n = 8) between March 1998 and December 2011 were included. The mean volume treated was 20.42±6.29 cm³ (range, 10.20–38.50 cm³). Obliteration rates of AVMs and the associated complications after GKS were evaluated.ResultsMean AVM volume (and median marginal dose) at each GKS session in the 37 patients who underwent 2-stage GKS was 19.67±6.08 cm³ (13 Gy) at session 1 and 6.97±6.92 cm³ (17 Gy) at session 2. The median interval period was 39 months. After follow-up period of 37 months, the complete obliteration rate was 64.9%. The mean AVM volume (and median marginal dose) at each GKS session in the 8 patients who underwent 3-stage GKS was 23.90±6.50 cm³ (12.25 Gy), 19.43±7.46 cm³ (13.5 Gy), 7.48±6.86 cm³ (15.5 Gy) at session 1, 2, and 3, respectively. The median interval duration between each GKS session was 37.5 and 38 months, respectively. After a median follow-up period of 47.5 months, 5 patients (62.5%) achieved complete obliteration. Postradiosurgical hemorrhage developed in 5 patients (11.1%) including one case of major bleeding and 4 cases of minor bleeding. No patient suffered from clinically symptomatic radiation necrosis following radiation.ConclusionTime-staged GKS could be an effective and safe treatment option in the management of large AVMs.     

Pretreatment CT and PET radiomics predicting rectal cancer patients in response to neoadjuvant chemoradiotherapy

BackgroundThe purpose of this study was to characterize pre-treatment non-contrast computed tomography (CT) and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) based radiomics signatures predictive of pathological response and clinical outcomes in rectal cancer patients treated with neoadjuvant chemoradiotherapy (NACR T).Materials and methodsAn exploratory analysis was performed using pre-treatment non-contrast CT and PET imaging dataset. The association of tumor regression grade (TRG) and neoadjuvant rectal (NAR) score with pre-treatment CT and PET features was assessed using machine learning algorithms. Three separate predictive models were built for composite features from CT + PET.ResultsThe patterns of pathological response were TRG 0 (n = 13; 19.7%), 1 (n = 34; 51.5%), 2 (n = 16; 24.2%), and 3 (n = 3; 4.5%). There were 20 (30.3%) patients with low, 22 (33.3%) with intermediate and 24 (36.4%) with high NAR scores. Three separate predictive models were built for composite features from CT + PET and analyzed separately for clinical endpoints. Composite features with α = 0.2 resulted in the best predictive power using logistic regression. For pathological response prediction, the signature resulted in 88.1% accuracy in predicting TRG 0 vs. TRG 1–3; 91% accuracy in predicting TRG 0–1 vs. TRG 2–3. For the surrogate of DFS and OS, it resulted in 67.7% accuracy in predicting low vs. intermediate vs. high NAR scores.ConclusionThe pre-treatment composite radiomics signatures were highly predictive of pathological response in rectal cancer treated with NACR T. A larger cohort is warranted for further validation.     

A prospective observational study to analyse the influence of bladder and rectal volume changes on prostate radiotherapy using IMRT

AimTo analyse the interfractional bladder and rectal volume changes and the influence on prostate position.BackgroundInterfractional displacement of prostate due to variation in bladder and rectal volume is usual. It is only rational to study the bladder and rectal volume changes and their effects on prostate position during intensity modulated radiotherapy of prostate cancer.Materials and MethodsA prospective study was conducted on twenty patients with localized prostate cancer during the first phase of radiotherapy, where 50 gray in 25 fractions was delivered by the IMRT technique with daily cone beam computed tomography Bladder and rectum volumes were delineated on CBCT images and their volumes were noted. Prostate position was noted on each set of CBCT images with respect to specific reference points defined on the ileum and coccyx, and daily prostate displacement was noted.ResultsMean setup errors in vertical, longitudinal and lateral directions were noted as 1.49, 0.498 and 0.17 cm, respectively. Mean change in bladder and rectal volumes in daily CBCT images with respect to that on the first day CT images was noted as 101.94 and 10.22, respectively. Mean lateral and vertical displacement in prostate position was noted as 0.53 and 0.49 cm respectively. No considerable changes in dosimetric parameters were observed because of bladder and rectal volume changes.ConclusionsDaily CBCT should be done for accurate treatment delivery by the IMRT technique for prostate radiotherapy as prostate shifts physiologically with changes in rectal and bladder volumes.     

Feasibility and safety of definite volumetric modulated arc therapy with simultaneous integrated boost to the dominant intraprostatic lesion in patients with unfavorable intermediate to high-risk prostate cancer

BackgroundThe most common site of recurrence of prostate cancer after definite radiation therapy is the dominant intraprostatic lesion (DIL). This study aimed to investigate the feasibility and safety of definite volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) to the DIL in patients with unfavorable intermediate to high-risk prostate cancer.Materials and methodsIn this prospective uncontrolled clinical trial, patients were delivered VMAT at a dose of 87.75 Gy in 39 fractions or 70 Gy in 20 fractions to the DIL in combination with androgen deprivation therapy. Genitourinary (GU) and rectal toxicity, International Prostate Symptom Score (IPSS) and IPSS quality of life (IPSS-QOL) score were collected.ResultsForty-five patients with a median follow-up of 20 months were analyzed. The cumulative incidence of acute grade ≥ 2 GU and rectal toxicity was 33.1% and 9.5%, respectively. Regarding late toxicity, the cumulative incidence of grade ≥ 2 GU and rectal toxicity was 12.6% and 2.8%, respectively. During treatment, the mean increase of IPSS was +7.4 ± 4.2 and the mean increase of IPSS-QOL was +1.7 ± 1.3. However, both IPSS and IPSS-QOL scores returned to their baseline levels by 3-months post-treatment. No significant correlation between baseline characteristics and grade ≥ 2 GU or rectal toxicity was found.ConclusionFocal SIB to the DIL of ≥ 90 Gy EQD2 in unfavorable intermediate to high-risk prostate cancer patients resulted in tolerable toxicity profiles. The mean IPSS and IPSS-QOL scores both worsened during treatment; however, both scores returned to baseline level by 3 months after treatment.     

Definitive,intensity modulated tomotherapy with a simultaneous integrated boost for prostate cancer patients – Long term data on toxicity and biochemical control

AimTo report long-term data regarding biochemical control and late toxicity of simultaneous integrated boost intensity modulated radiotherapy (SIB-IMRT) with tomotherapy in patients with localized prostate cancer.BackgroundDose escalation improves cancer control after curative intended radiation therapy (RT) to patients with localized prostate cancer, without increasing toxicity, if IMRT is used.Materials and methodsIn this retrospective analysis, we evaluated long-term toxicity and biochemical control of the first 40 patients with intermediate risk prostate cancer receiving SIB-IMRT. Primary target volume (PTV) 1 including the prostate and proximal third of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. PTV 2 containing the prostate with smaller safety margins was treated as SIB to a total dose of 76 Gy with 2.17 Gy per fraction. Toxicity was evaluated using an adapted CTCAE-Score (Version 3).ResultsMedian follow-up of living patients was 66 (20–78) months. No late genitourinary toxicity higher than grade 2 has been reported. Grade 2 genitourinary toxicity rates decreased from 58% at the end of the treatment to 10% at 60 months. Late gastrointestinal (GI) toxicity was also moderate, though the prescribed PTV Dose of 76 Gy was accepted at the anterior rectal wall. 74% of patients reported any GI toxicity during follow up and no toxicity rates higher than grade 2 were observed. Grade 2 side effects were reported by 13% of the patients at 60 months. 5-year freedom from biochemical failure was 95% at our last follow up.ConclusionSIB-IMRT using daily MV-CT guidance showed excellent long-term biochemical control and low toxicity rates.     

Thermoluminescence dosimetry of the dose received by scrotum and testes in radiotherapy of rectal cancer,compared to the point doses calculated by 3D-planning software

PurposeRadiation received by the testes in the course of radiotherapy for rectal cancer may cause oligospermia and azospermia. We sought to determine the dose to the scrotum and testes with thermoluminescence dosimetry (TLD), and compare it to the dose calculated by 3D planning software.MethodsThe TLDs were fixed to the scrotum in six points anteriorly and posteriorly in two fractions of radiotherapy. All patients received a 50–50.4 Gy total dose in prone position with 3D-planning. The average dose of TLD measurements was compared to the average of 6 relevant point doses calculated by the planning software.ResultsThe mean scrotal dose of radiation in 33 patients as measured by TLD was 3.77 Gy (7.5% of the total prescribed dose), and the mean of point doses calculated by the planning software was 4.11 Gy (8.1% of the total dose), with no significant difference. A significant relationship was seen between the position of the inferior edge of the fields and the mean scrotal dose (P = .04). Also body mass index (BMI) was inversely related with the scrotal dose (P = .049).ConclusionWe found a dose of about 4 Gy received by the scrotum and testes from a total prescribed dose of 50 Gy in the radiotherapy of rectal carcinoma patients, with TLD measurements confirming testicular dose estimations by the planning software. This dose could be significantly harmful for spermatogenesis. Thus careful attention to the testicular dose in radiotherapy of rectal cancer for men desiring continued fertility is a necessity.     

Survival outcomes for patients with nasopharyngeal carcinoma in non–endemic region in the UK treated with intensity modulated based radiotherapy 65 Gy in 30 fractions ± weekly cisplatin chemotherapy

BackgroundNasopharyngeal carcinoma (NPC) is rare in the UK. The aim of the current study was to investigate survival outcomes for patients with NPC treated with (chemo)radiotherapy using 65 Gy in 30 fractions in a non-endemic region.Materials and methodsAll consecutive 62 patients with histology proven non-metastatic nasopharyngeal carcinoma diagnosed between January 2009 to June 2019 were included in this retrospective analysis.ResultsMedian age was 59 years (range:19–81). The majority of patients had stage III disease (66.1%). Induction chemotherapy was given in 21% of patients and 82.3% of patients received concomitant systemic therapy. All patients were treated with 65 Gy in 30 fractions. There was disease recurrence in 17.4% patients. The 5-year disease-free, disease-specific and overall survival were 81.9%, 79.2% and 76.4%, respectively. On univariate analysis, disease recurrence was associated with N-stage (p = 0.047) and overall stage group (p = 0.023).ConclusionTo the best of authors’ knowledge, this is the first report of the use of 65 Gy in 30 fractions of radiotherapy ± weekly cisplatin chemotherapy in NPC in a real-world setting. Our results are comparable to that from other non-endemic regions of the world using different dose fractionation of (chemo)radiotherapy. Future randomised control trials are warranted to compare various dose fractionations in these settings.     

Stereotactic radiotherapy for spinal hemangioblastoma – disease control and volume analysis in long-term follow up

BackgroundThis retrospective analysis evaluated the long-term outcome of spinal stereotactic body radiotherapy (SBRT) treatment for hemangioblastomas.Materials and methodsBetween 2010 and 2018, 5 patients with 18 Von-Hippel Lindau-related pial-based spinal hemangioblastomas were treated with fractionated SBRT. After precisely registering images of all relevant datasets, we delineated the gross tumor volume, spinal cord (including intramedullary cysts and/or syrinxes), and past radiotherapy regions. A sequential optimization algorithm was used for dose determinations, and patients received 25–26 Gy in five fractions or 24 Gy in three fractions. On-line image guidance, based on spinal bone structures, and two orthogonal radiographs were provided. The actuarial nidus control, surgery-free survival, cyst/syrinx changes, and progression-free survival were calculated with the Kaplan-Meier method. Toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events v5.0.ResultsThe median follow-up was 5 years after SBRT. Patients displayed one nidus progression, one need of neurosurgery, and two cyst/syrinx progressions directly connected to symptom worsening. No SBRT-related complications or acute adverse radiation-related events occurred. However, one asymptomatic radiological sign of myelopathy occurred two years after SBRT. All tumors regressed; the one-year equivalent tumor volume reduction was 0.2 mL and the median volume significantly decreased by 28% (p = 0.012). Tumor volume reductions were not correlated with the mean (p = 0.19) or maximum (p = 0.16) dose.ConclusionsSBRT for pial-based spinal hemangioblastomas was an effective, safe, viable alternative to neurosurgery in asymptomatic patients. Escalating doses above the conventional dose-volume limits of spinal cord tolerance showed no additional benefit.     

Stereotactic radiotherapy for adrenal oligometastases

Approximately 50% of melanomas, 30–40% of lung and breast cancers and 10–20% of renal and gastrointestinal tumors metastasize to the adrenal gland.Metastatic adrenal involvement is diagnosed by computed tomography (CT ) with contrast medium, ultrasound (which does not explore the left adrenal gland well), magnetic resonance imaging (MRI) with contrast medium and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸FDGPET-CT ) which also evaluates lesion uptake. The simulation CT should be performed with contrast medium; an oral bolus of contrast medium is useful, given adrenal gland proximity to the duodenum. The simulation CT may be merged with PET-CT images with ¹⁸FDG in order to evaluate uptaking areas. In contouring, the radiologically visible and/or uptaking lesion provides the gross tumor volume (GTV ). Appropriate techniques are needed to overcome target motion. Single fraction stereotactic radiotherapy (SRT ) with median doses of 16–23 Gy is rarely used. More common are doses of 25–48 Gy in 3–10 fractions although 3 or 5 fractions are preferred. Local control at 1 and 2 years ranges from 44 to 100% and from 27 to 100%, respectively. The local control rate is as high as 90%, remaining stable during follow-up when BED_10Gy is equal to or greater than 100 Gy. SRT-related toxicity is mild, consisting mainly of gastrointestinal disorders, local pain and fatigue. Adrenal insufficiency is rare.     

A dosemetric and radiobiological impact of VMAT and 3DCRT on lumbosacral plexuses,an underestimated organ at risk in cervical cancer patients

BackgroundThe purpose of this study was to evaluate dosimetric and radiobiological difference between volumetric modulated arc therapy (VMAT) and 3-dimensional conformal radiotherapy (3DCRT) in organ at risk (OAR) lumbosacral plexus (LSP) in cervical cancer patients.Materials and methods30 patients of cervical cancer who were treated using 3DCRT or VMAT along with chemotherapy followed by brachytherapy were enrolled. LSP was delineated retrospectively. Dosimetric and radiobiological difference was evaluated. Patients were followed for radiation induced lumbosacral plexopathy (RILSP).ResultsMedian follow-up was 12 months (3–16 months). 53.3% of patients were treated by 3DCRT and 46.7% by VMAT. The mean (±SD) LSP volume: 119.03 ± 15 cm³. The mean volume percentages (%) of the LSP: V5, V10, V20, V30, V40, V50, V55, and V60 were 100%, 99.8%, 99.2%, 94.3%, 84.03%, 59.7%, 0%, 0%, respectively. All patients received doses to the LSP in excess of 50 Gy, one patient received 55 Gy. A statistically significant difference was observed in the median value of V20, V30, V40, V50, D50, P2, P4, P7, P8, P9, and P10 across two different techniques of radiotherapy — VMAT and 3DCRT. None of the patients presented with RILSP. NTCP value was less in VMAT plans compared to 3DCRT, which is also statistically significant.ConclusionRILSP is a rare and often refractory complication of pelvic radiotherapy. Advance radiotherapy technique with proper OAR delineation and constraint can prevent the occurrence of RILSP. VMAT has potential benefits for the probability of dose reduction in LSP. Further studies are required focusing on dose distribution in LSP–OAR and radiotherapy modality.     

Incidence of radiation-induced hypothyroidism following head and neck irradiation: a single-center analysis

BackgroundThe purpose of this study was to investigate the incidence of primary hypothyroidism (HT), as well as any correlation between dosimetric parameters and thyroid dysfunctions after neck radiotherapy (RT) in head and neck cancer (HNC) patients.Materials and methodsThis study retrospectively reviewed HNC patients who finished neck RT for at least 12 months and who had available back-up treatment information. Eligible patients further received a single thyroid function test (TFT). Dosimetric parameters of the thyroid glands were retrospectively evaluated in order to detect any correlation between dose-volume parameters and primary HT.ResultsWe reviewed 1,102 HNC patients. Accordingly, 64 patients were deemed eligible and were included in this study. The median time interval between RT completion and TFT was 21 months (interquartile range, 14–34 months), while 26 patients (40.6%) were diagnosed with HT. The thyroid volume spared from a dose of 50 Gy (VS50_Gy) was found to be statistically significant and considered an associated factor for developing HT (p = 0.047). Furthermore, there was an observable trend indicating a reduction in the risk of HT when VS50_Gy was more than 5 cm³ (p = 0.052).ConclusionIn our study, VS50_Gy was determined to be a significant predictive parameter of radiation-induced HT.     

Phase I dose escalation trial of stereotactic radiotherapy prior to robotic prostatectomy in high risk prostate cancer

BackgroundThe aim of the study was to investigate the safety of combining preoperative stereotactic body radiotherapy (SBRT) with robotic radical prostatectomy (RP) for high risk prostate cancer (HRCaP). Many patients with HRCaP will require adjuvant or salvage radiotherapy after RP. The addition of preoperative SBRT before RP may spare patients from subsequent prolonged courses of RT.Materials and methodsEligible patients had NCC N HRCaP and received a total of 25 Gy or 30 Gy in five daily fractions of SBRT to the prostate and seminal vesicles followed by robotic RP with pelvic lymphadenectomy 31–45 days later. The primary endpoint was prevalence of acute genitourinary (GU) and gastrointestinal (GI) toxicity. Secondary endpoints were patient-reported quality of life (QOL) and biochemical recurrence (BcR).ResultsThree patients received preoperative SBRT to 25 Gy and four received 30 Gy. Median follow-up was 18 months. Highest toxicity was grade 2 and 3 in six (85.7%) and one (14.3%) patients, respectively. All patients developed grade 2 erectile dysfunction and 4 of 7 (57%) developed grade 2 urinary incontinence (UI) within a month after surgery. One patient developed acute grade 3 UI, but there was no grade ≥ 4 toxicity. One patient experienced acute grade 2 hemorrhoidal bleeding. On QOL, acute GU complaints were common and peaked within 3 months. Bowel symptoms were mild. Two patients with pN+ experienced BcR.ConclusionsPreoperative SBRT before robotic RP in HRCaP is feasible and safe. The severity of acute GU toxicity with preoperative SBRT may be worse than RP alone, while bowel toxicity was mild.     

Long-term follow-up results of endorectal balloon-assisted helical tomotherapy for localized prostate cancer patients in the high-risk group of gastrointestinal adverse events

BackgroundEndorectal balloon (ERB) has been shown to reduce rectal radiation dose and late gastrointestinal toxicities in patients with prostate cancer. However, the usefulness of ERBs for patients with prostate cancer whose rectal shape or size is suboptimal has not been investigated. The purpose of this study was to present the long-term follow-up results of ERB-assisted helical tomotherapy for localized prostate cancer patients whose initial radiation treatment planning (RTP) was unacceptable due to suboptimal rectal shape or size.Materials and methodsOf 541 consecutive patients with localized prostate cancer, 10 were included in this study whose RTPs without ERBs did not meet dose constraints due to: 1) Intestinal intrusion, 2) Small rectum; or 3) Unstable rectal shape. We re-planned using ERBs and delivered 76 Gy in 38 fractions, and evaluated the long-term usefulness and safety of ERB-assisted helical tomotherapy.ResultsAt a median follow-up of 109 months, there were no local recurrences of prostate cancer. The overall, cause-specific, and progression-free survivals at 10 years were 90.0%, 100%, and 83%, respectively. Adverse events of grade 3 or higher were not observed during or after ERB-assisted helical tomotherapy.ConclusionsWhen intestinal intrusion, a small rectum, or an unstable rectal shape is an obstacle for administering helical tomotherapy, ERBs might be the solution.     

Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment

AimTo assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction.BackgroundImplementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution.Materials and methodsSeventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed.ResultsIn 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively.ConclusionSufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.