Reduced Dose Posterior to Prostate Correlates With Increased PSA Progression in Voxel-Based Analysis of 3 Randomized Phase 3 Trials

PURPOSE

Reducing margins during treatment planning to decrease dose to healthy organs surrounding the prostate can risk inadequate treatment of subclinical disease. This study aimed to investigate whether lack of dose to subclinical disease is associated with increased disease progression by using high-quality prostate radiation therapy clinical trial data to identify anatomically localized regions where dose variation is associated with prostate-specific antigen progression (PSAP).

METHODS AND MATERIALS

Planned dose distributions for 683 patients of the Trans-Tasman Radiation Oncology Group 03.04 Randomized Androgen Deprivation and Radiotherapy (RADAR) trial were deformably registered onto a single exemplar computed tomography data set. These were divided into high-risk and intermediate-risk subgroups for analysis. Three independent voxel-based statistical tests, using permutation testing, Cox regression modeling, and least absolute shrinkage selection operator feature selection, were applied to identify regions where dose variation was associated with PSAP. Results from the intermediate-risk RADAR subgroup were externally validated by registering dose distributions from the RT01 (n = 388) and Conventional or Hypofractionated High Dose Intensity Modulated Radiotherapy for Prostate Cancer Trial (CHHiP) (n = 253) trials onto the same exemplar and repeating the tests on each of these data sets.

RESULTS

Voxel-based Cox regression revealed regions where reduced dose was correlated with increased prostate-specific androgen progression. Reduced dose in regions associated with coverage at the posterior prostate, in the immediate periphery of the posterior prostate, and in regions corresponding to the posterior oblique beams or posterior lateral beam boundary, was associated with increased PSAP for RADAR and RT01 patients, but not for CHHiP patients. Reduced dose to the seminal vesicle region was also associated with increased PSAP for RADAR intermediate-risk patients.

CONCLUSIONS

Ensuring adequate dose coverage at the posterior prostate and immediately surrounding posterior region (including the seminal vesicles), where aggressive cancer spread may be occurring, may improve tumor control. It is recommended that particular care be taken when defining margins at the prostate posterior, acknowledging the trade-off between quality of life due to rectal dose and the preferences of clinicians and patients.

Phase 1 Trial of Stereotactic Body Radiation Therapy Neoadjuvant to Radical Prostatectomy for Patients With High-Risk Prostate Cancer

PURPOSE

This study aimed to evaluate the feasibility and safety of prostate stereotactic body radiation therapy (SBRT) neoadjuvant to radical prostatectomy (RP) in a phase 1 trial. The primary endpoint was treatment completion rate without severe acute surgical complications. Secondary endpoints included patient-reported quality of life and physician-reported toxicities.

METHODS AND MATERIALS

Patients with nonmetastatic high-risk or locally advanced prostate cancer received 24 Gy in 3 fractions to the prostate and seminal vesicles over 5 days, completed 2 weeks before RP. Patients with pN1 disease were treated after multidisciplinary discussion and shared decision making. Patient-reported quality of life (International Prostate Symptom Score and Expanded Prostate Cancer Index Composite 26-item version questionnaires) and physician-reported toxicity (Common Terminology Criteria for Adverse Events, version 4.03) were assessed before SBRT, immediately before surgery, and at 3-month intervals for 1 year.

RESULTS

Twelve patients were enrolled, and 11 completed treatment (1 patient had advanced disease on prostate-specific membrane antigen positron emission tomography after enrollment but before treatment). There were no significant surgical complications. After RP, 2 patients underwent additional radiation therapy to nodes with androgen suppression for pN1 disease. Median follow-up after completion of treatment was 20.1 months, with 9 of 11 patients having a follow-up period of >12 months. Two patients had biochemical recurrence (prostate-specific antigen ≥0.05) within the first 12 months, with an additional 2 patients found to have biochemical recurrence after the 12-month period. The highest Common Terminology Criteria for Adverse Events genitourinary grades were 0, 1, 2, and 3 (n = 1, 4, 4, and 2, respectively), and the highest gastrointestinal grades were 0, 1, and 2 (n = 9, 1, and 1, respectively). At 12 months, incontinence was the only grade ≥2 toxicity. One and 2 of 9 patients had grade 2 and 3 incontinence, respectively. On the Expanded Prostate Cancer Index Composite (26-item version), the mean/median changes in scores from baseline to 12 months were -32.8/-31.1 for urinary incontinence, -1.6/-6.2 for urinary irritative/obstructive, -2.1/0 for bowel, -34.4/-37.5 for sexual function, and -10.6/-2.5 for hormonal. The mean/median change in International Prostate Symptom Score from baseline to 12 months was 0.5/0.5.

CONCLUSIONS

RP after neoadjuvant SBRT appears to be feasible and safe at the dose tested. The severity of urinary incontinence may be higher than RP alone.

Moderately HRT vs. CRT for localized prostate cancer using image-guided VMAT with SIB: evaluation of acute and late toxicities

Purpose

This retrospective study aims at investigating the effects of moderately hypofractionated radiation therapy (HRT) on acute and late toxicities as well as on early biochemical control and therapeutic efficiency compared to conventional radiation therapy (CRT) in prostate cancer.

Patients and methods

We analyzed 55 HRT patients irradiated with the total dose of 60 Gy in 20 fractions delivered over 4 weeks. These patients were compared to a control group of 55 patients who received CRT with a total of <78 Gy in 37–39 fractions delivered over circa 8 weeks. External beam radiation therapy (EBRT) was conducted using daily image-guided (cone beam CT) volumetric modulated arc therapy (VMAT) and a simultaneously integrated boost (SIB) for both groups to protect the rectum. Acute toxicities were evaluated according to Common Terminology Criteria for Adverse Events (CTCAE) v5, whereas chronic toxicities were assessed in accordance with LENT-SOMA. Patient traits were compared by implementing t‑tests and Wilcoxon–Whitney tests for continuous variables, whereas discrete characteristics were evaluated by applying two-tailed Fisher’s exact tests. In addition, we calculated average treatment effects (ATE). Thereby, propensity score matching (PSM) based on nearest-neighbor matching considering age, comorbidities, and risk stratification as covariates was applied. The statistical analysis was conducted using Stata 14.2 (StataCorp LLC, TX, USA).

Results

As confirmed by the descriptive tests, the ATE revealed that the intensity and occurrence of urinary frequency (p = 0.034) and proctitis (p = 0.027) significantly decreased for the HRT group, whereas all other acute toxicities did not differ significantly between the HRT and CRT groups. For late toxicities, neither statistical tests nor ATE estimation showed significant differences. Also, no significant difference was found regarding the decrease in prostate specific antigen (PSA) after a median follow-up of 13 months (range 2–28 months), which indicates biochemical freedom from progression.

Conclusion

HRT offers several medical and economic advantages and should therefore be considered as a useful alternative to CRT.

[Stereotactic body radiation therapy with CyberKnife accelerator for low- and intermediate risk prostate cancer]

We report implementation of stereotactic body radiotherapy (SBRT) for the treatment of early, localized prostate cancer patients, and acute side effects caused by radiation therapy. Between February 2018 and July 2018, 36 prostate cancer patients were treated with SBRT. Treatments were performed with "CyberKnife M6" linear accelerator. In low-risk patients 8 Gy was delivered to the prostate in each fraction. For intermediate risk, 8 Gy to the prostate and 6.5 Gy to the seminal vesicles were delivered by each fraction with a simultaneous integrated boost technique. A total of 5 fractions (total dose 40 Gy) were given every second working days. Acute radiogenic genitourinary (GU) and gastrointestinal (GI) side effects were assessed using the Radiation Therapy Oncology Group (RTOG) score. The duration of radiotherapy was 1 week and 3 days. The frequency of acute radiogenic side effects was as follows: GU grade 0: 13.9%, grade I: 30.6%, grade II: 52.8%, grade III: 2.7%. GI grade 0: 55.5%, grade I: 30.6%, grade II: 13.9%, grade III: 0%. Grade IV-V side effects were not observed. SBRT appears to be a safe and well tolerated treatment in patients with early stage, localized prostate cancer.

Intensity-modulated radiotherapy for prostate cancer with seminal vesicle involvement (T3b): A multicentric retrospective analysis

OBJECTIVES

No study has reported clinical results of external-beam radiotherapy specifically for T3b prostate cancer. The possibility of escalating the dose to the involved seminal vesicles (ISV) while respecting the dose constraints in the organs at risk is thus so far not clearly demonstrated. The objective of the study was to analyze the dose distribution and the clinical outcome in a large series of patients who received IMRT for T3b prostate cancer.

MATERIALS AND METHODS

This retrospective analysis included all patients who received IMRT and androgen deprivation therapy for T3b prostate cancer, between 2008 and 2017, in six French institutions, with available MRI images and dosimetric data.

RESULTS

A total of 276 T3b patients were included. The median follow-up was 26 months. The median (range) prescribed doses (Gy) to the prostate and to the ISV were 77 (70-80) and 76 (46-80), respectively. The dose constraint recommendations were exceeded in less than 12% of patients for the rectum and the bladder. The 5-year risks of biochemical and clinical recurrences and cancer-specific death were 24.8%, 21.7%, and 10.3%, respectively. The 5-year risks of local, pelvic lymph node, and metastatic recurrences were 6.4%, 11.3%, and 15%, respectively. The number of involved lymph nodes (≤ 2 or ≥ 3) on MRI was the only significant prognostic factor in clinical recurrence (HR 9.86) and death (HR 2.78). Grade ≥ 2 acute and 5-year late toxicity rates were 13.2% and 12% for digestive toxicity, and 34% and 31.5% for urinary toxicity, respectively. The dose to the pelvic lymph node and the age were predictive of late digestive toxicity.

CONCLUSION

IMRT for T3b prostate cancer allows delivery of a curative dose in the ISV, with a moderate digestive toxicity but a higher urinary toxicity. Lymph node involvement increases the risk of recurrence and death.

Treatment-related toxicity in men who received Intensity-modulated versus 3D-conformal radiotherapy after radical prostatectomy: A national population-based study

BACKGROUND AND PURPOSE

In the post-prostatectomy setting the value of Intensity-modulated (IMRT) relative to 3D-conformal radiotherapy (3D-CRT) in reducing toxicity remains unclear. We compared genitourinary (GU) and gastrointestinal (GI) toxicity after post-prostatectomy IMRT or 3D-CRT.

MATERIALS AND METHODS

A population-based study of all patients treated with post-prostatectomy 3D-CRT (n = 2422) and IMRT (n = 603) was conducted between January 1 2010 and December 31 2013 in the English National Health Service. We identified severe GI and GU toxicity using a validated coding-framework and compared IMRT and 3D-CRT using a competing-risks proportional hazards regression analysis.

RESULTS

There was no difference in GI toxicity between patients who received IMRT and 3D-CRT (3D-CRT: 5.8 events/100 person-years; IMRT: 5.5 events/100 person-years; adjusted HR: 0.85, 95%CI: 0.63-1.13; p = 0.26). The GU toxicity rate was lower with IMRT but this effect was not statistically significant (3D-CRT: 5.4 events/100 person-years; IMRT: 3.8 events/100 person-years; adjusted HR: 0.76, 95%CI: 0.55-1.03; p = 0.08).

CONCLUSIONS

The use of post-prostatectomy IMRT compared to 3D-CRT is not associated with a statistically significant reduction in rates of severe GU and GI toxicity, although there is some evidence that GU toxicity is lower with IMRT. We would caution against rapid transition to post-prostatectomy IMRT until further evidence is available supporting its superiority.

Arecoline cannot alter testicular dysfunction and pineal activation caused by noise in wistar rat

Millions of people consume betel nut for increased capacity to work and for stress reduction. The nut contains arecoline, which has multiple side effects on endocrine functions. Objective of the work is to investigate pineal-testicular responses to noise and after arecoline treatment in noise in rats. Noise exposure (100 dB, 6 h daily, 10 days) caused pineal stimulation ultrastructurally and at indoleamines level. Leydig cell dysfunction with fall of testosterone level and suppression of sex accessories were noticed. In contrast, pineal activity was inhibited and reproductive functions were stimulated after arecoline administration, confirmed from reversed changes to those of noise. Arecoline treatment in noise exposure showed same results as in noise both in pineal and in reproductive functions. It is concluded that noise causes testicular dysfunction probably by gonadotropin suppression induced by pineal melatonin in noise. Furthermore, arecoline cannot prevent it in noise in rats.

A modeling study of functional magnetic resonance imaging to individualize target definition of seminal vesicles for external beam radiotherapy

BACKGROUND

Pre-treatment magnetic resonance imaging (MRI) can give patient-specific evaluation of suspected pathologically involved volumes in the seminal vesicles (SV) in prostate cancer patients. By targeting this suspicious volume we hypothesize that radiotherapy is more efficient without introducing more toxicity. In this study we evaluate the concept of using MRI-defined target volumes in terms of tumor control probability (TCP) and rectal normal tissue complication probability (NTCP).

MATERIAL AND METHODS

Twenty-one high-risk prostate cancer patients were included. Pre-treatment CT images, T2 weighted (T2w) MRI and two multi-parametric MRI were acquired. Overlap between a suspicious volume in the SV observed on T2w images and a suspicious volume observed on either multi-parametric MRI was assumed to reflect a true malignant region (named 'MRI positive'). In addition the entire SV on the CT-scan was delineated. Three treatment plans of 2 Gy ×39 fractions were generated per patient: one covering the MRI positive volume in SV and prostate with margin of 11 mm to the MRI positive in the SV and two plans covering prostate and SV using 11 and 7 mm SV margin, respectively. All plans were prescribed the same PTV mean dose. Rectal NTCP grade ≥2 was evaluated with the Lyman-Kutcher-Burman model and TCP was estimated by a logistic model using the combined MRI positive volume in SV and prostate as region-of-interest.

RESULTS

Fourteen of twenty-one patients were classified as MRI positive, six of which had suspicious volumes in all three MRI modalities. On average TCP for the plan covering prostate and the MRI positive volume was 3% higher (up to 11%) than the two other plans which was statistically significant. The increased TCP was obtained without increasing rectal NTCP grade ≥2.

CONCLUSIONS

Using functional MRI for individualized target delineation in the SV may improve the treatment outcome in radiotherapy of prostate cancer without increasing the rectal toxicity.

Single Course IMRT Plan to Deliver 45 Gy to Seminal Vesicles and 81 Gy to Prostate in 45 Fractions

We treat prostate and seminal vesicles (SV) to 45 Gy in 25 fractions (course 1) and boost prostate to 81 Gy in 20 more fractions (course 2) with Intensity Modulated Radiation Therapy (IMRT). This two-course IMRT with 45 fractions delivered a non-uniform dose to SV and required two plans and two QA procedures. We used Linear Quadratic (LQ) model to develop a single course IMRT plan to treat SV to a uniform dose, which has the same biological effective dose (BED) as that of 45 Gy in 25 fractions and prostate to 81 Gy, in 45 fractions. Single course IMRT plans were compared with two-course IMRT plans, retrospectively for 14 patients. With two-course IMRT, prescription to prostate and SV was 45 Gy in 25 fractions and to prostate only was 36 Gy in 20 fractions, at 1.8 Gy/fraction. With 45-fraction single course IMRT plan, prescription to prostate was 81 Gy and to SV was 52 or 56 Gy for a α/β of 1 and 3, respectively. 52 Gy delivered in 45 fractions has the same BED of 72 Gy3 as that of delivering 45 Gy in 25 fractions, and is called Matched Effective Dose (MED). LQ model was used to calculate the BED and MED to SV for α/β values of 1–10. Comparison between two-course and single course IMRT plans was in terms of MUs, dose-max, and dose volume constraints (DVC). DVC were: 95% PTV to be covered by at least 95% of prescription dose; and 70, 50, and 30% of bladder and rectum should not receive more than 40, 60, and 70% of 81 Gy. SV Volumes ranged from 2.9–30 cc. With two-course IMRT plans, mean dose to SV was non-uniform and varied between patients by 48% (54 to 80 Gy). With single-course IMRT plan, mean dose to SV was more uniform and varied between patients by only 9.6% (58.2 to 63.8 Gy), to deliver MED of 56 Gy for α/β − 1. Single course IMRT plan MUs were slightly larger than those for two-course IMRT plans, but within the range seen for two-course plans (549–959 MUs, n=51). Dose max for single-course plans were similar to two-course plans. Doses to PTV, rectum and bladder with single course plans were as per DVC and comparable to two-course plans. Single course IMRT plan reduces IMRT planning and QA time to half.

Clinical and technical feasibility of ultra-boost irradiation in Dominant Intraprostatic Lesion by Tomotherapy: preliminary experience and revision of literature

BACKGROUND

The aim of this paper was to present our experience of dominant intraprostatic lesions (DIL) irradiation up to an EQD2 of 93,2 Gy with helical tomotherapy.

METHODS

Between March 2012 and December 2014, 15 staged II-III patients with intermediate-high risk prostate cancer were enrolled in our protocol of DIL dose escalation by Tomotherapy. All patients were submitted to a multiparametric MRI (including DCE and DWI series), in order to visualize DILs. Considering a mean α/β ratio of 3 for prostate cancer the prescribed doses were: 83.2 Gy in 32 fractions of 2.6 per fraction (EQD2=93.2 Gy) on the DILs, 75.2 Gy in 32 fractions of 2.35 Gy per fraction (EQD2=80.5 Gy) on the prostate gland and 67.2 Gy in 32 fraction of 2.1 (EQD2=68.5 Gy) on the seminal vesicles.

RESULTS

With a mean follow-up of 16 months (range 2-39), no overall severe acute toxicities >G3 were observed; one patient out of 15 (6.6%) had acute gastrointestinal (GI) toxicity equal to G2, while two cases (13.3%) had G2 acute genitourinary (GU) toxicity. No >G2 late toxicity was observed. At last follow-up, for all patients, the biochemical disease free survival was 100%.

CONCLUSIONS

The irradiation of the whole prostate and seminal vesicles up to an EQD2 of 80.5 Gy and of DILs up to 93.2 Gy was clinically feasible and safe, without acute severe toxicity. Although with a short follow-up, late toxicities are currently absent and no patient relapsed.

Evaluating organ delineation, dose calculation and daily localization in an open-MRI simulation workflow for prostate cancer patients

BACKGROUND

This study describes initial testing and evaluation of a vertical-field open Magnetic Resonance Imaging (MRI) scanner for the purpose of simulation in radiation therapy for prostate cancer. We have evaluated the clinical workflow of using open MRI as a sole modality for simulation and planning. Relevant results related to MRI alignment (vs. CT) reference dataset with Cone-Beam CT (CBCT) for daily localization are presented.

METHODS

Ten patients participated in an IRB approved study utilizing MRI along with CT simulation with the intent of evaluating the MRI-simulation process. Differences in prostate gland volume, seminal vesicles, and penile bulb were assessed with MRI and compared to CT. To evaluate dose calculation accuracy, bulk-density-assignments were mapped onto respective MRI datasets and treated IMRT plans were re-calculated. For image localization purposes, 400 CBCTs were re-evaluated with MRI as the reference dataset and daily shifts compared against CBCT-to-CT registration. Planning margins based on MRI/CBCT shifts were computed using the van Herk formalism.

RESULTS

Significant organ contour differences were noted between MRI and CT. Prostate volumes were on average 39.7% (p = 0.002) larger on CT than MRI. No significant difference was found in seminal vesicle volumes (p = 0.454). Penile bulb volumes were 61.1% higher on CT, without statistical significance (p = 0.074). MRI-based dose calculations with assigned bulk densities produced agreement within 1% with heterogeneity corrected CT calculations. The differences in shift positions for the cohort between CBCT-to-CT registration and CBCT-to-MRI registration are -0.15 ± 0.25 cm (anterior-posterior), 0.05 ± 0.19 cm (superior-inferior), and -0.01 ± 0.14 cm (left-right).

CONCLUSIONS

This study confirms the potential of using an open-field MRI scanner as primary imaging modality for prostate cancer treatment planning simulation, dose calculations and daily image localization.

Effects of acute gamma radiation on the reproductive ability of the earthworm Eisenia fetida

Earthworms are the most suitable biological indicators of radioactive pollution because they are the parts of nutritional webs, and are present in relatively high numbers. Four months old Eisenia fetida were exposed to different doses of gamma radiation, namely 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 & 60 Gy to study the effects of radiation on different reproductive parameters. The number of cocoons laid and the hatchlings emerged were recorded for all the selected doses. There was no reduction in cocoon production, however; decreasing size and weight of the cocoons was observed from the samples exposed to 20 Gy and above doses. Significant reductions in the hatchlings were recorded in earthworms exposed to 10 Gy and above doses. The dose response curves for a percentage reduction in hatchlings were constructed. Exposure to radiation dose of 1 and 2 Gy did not show any reduction, however, there was ≈10%, ≈50% and ≈90% decrease in the hatchlings in samples exposed to 3, 15 and 45, 50, 55 and 60 Gy doses respectively. Delayed hatchability was also reported at al exposure level. Histology of irradiated earthworms revealed that the structural damage in the seminal vesicles was prominent at the exposed dose of 3 Gy onwards with complete degeneration on exposure to 60 Gy of gamma radiation.

Adding intensity-modulated radiotherapy to the pelvis does not worsen the adverse effect profiles compared to limited field radiotherapy in men with prostate cancer at 12-month follow-up

To compare adverse effects and toxicity in men with high-risk or locally advanced prostate cancer when adding intensity-modulated radiotherapy (IMRT) technique to the pelvis.

PATIENTS AND METHODS

In this prospective follow-up study 180 patients treated with conformal radiotherapy (RAD) to the prostate and vesiculae seminales (boost volumes; PV) and long-term androgen deprivation therapy (LADT), were compared to 90 patients managed by LADT, RAD to the PV and additionally pelvic IMRT. Adverse effects were self-reported at baseline, at 3- and 12-month follow-up. At each time point, the patients rated a questionnaire covering urinary, bowel, and sexual function and bother, quality of life, fatigue, and mental distress.

RESULTS

At 3-month follow-up urinary and bowel functions were significantly decreased among IMRT compared to RAD. At 12-month follow-up both groups showed the same reductions within the urinary, bowel and sexual domains. RAD patients had more mental distress than IMRT patients. The scores on quality of life, fatigue and mental distress hardly influenced function or bother within the urinary, bowel or sexual domains.

CONCLUSIONS

Men treated for high-risk or locally advanced prostate cancer with a combination of LADT, RAD and IMRT including PV and pelvic structures had considerably more acute side effects at 3 months than men treated with LADT and RAD to the PV only. However, at 12-month follow-up, the observed genitourinary and gastrointestinal function and bother were similar in both groups.

Preliminary toxicity analysis of 3-dimensional conformal radiation therapy versus intensity modulated radiation therapy on the high-dose arm of the Radiation Therapy Oncology Group 0126 prostate cancer trial

PURPOSE

To give a preliminary report of clinical and treatment factors associated with toxicity in men receiving high-dose radiation therapy (RT) on a phase 3 dose-escalation trial.

METHODS AND MATERIALS

The trial was initiated with 3-dimensional conformal RT (3D-CRT) and amended after 1 year to allow intensity modulated RT (IMRT). Patients treated with 3D-CRT received 55.8 Gy to a planning target volume that included the prostate and seminal vesicles, then 23.4 Gy to prostate only. The IMRT patients were treated to the prostate and proximal seminal vesicles to 79.2 Gy. Common Toxicity Criteria, version 2.0, and Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer late morbidity scores were used for acute and late effects.

RESULTS

Of 763 patients randomized to the 79.2-Gy arm of Radiation Therapy Oncology Group 0126 protocol, 748 were eligible and evaluable: 491 and 257 were treated with 3D-CRT and IMRT, respectively. For both bladder and rectum, the volumes receiving 65, 70, and 75 Gy were significantly lower with IMRT (all P<.0001). For grade (G) 2+ acute gastrointestinal/genitourinary (GI/GU) toxicity, both univariate and multivariate analyses showed a statistically significant decrease in G2+ acute collective GI/GU toxicity for IMRT. There were no significant differences with 3D-CRT or IMRT for acute or late G2+ or 3+ GU toxicities. Univariate analysis showed a statistically significant decrease in late G2+ GI toxicity for IMRT (P=.039). On multivariate analysis, IMRT showed a 26% reduction in G2+ late GI toxicity (P=.099). Acute G2+ toxicity was associated with late G3+ toxicity (P=.005). With dose-volume histogram data in the multivariate analysis, RT modality was not significant, whereas white race (P=.001) and rectal V70 ≥15% were associated with G2+ rectal toxicity (P=.034).

CONCLUSIONS

Intensity modulated RT is associated with a significant reduction in acute G2+ GI/GU toxicity. There is a trend for a clinically meaningful reduction in late G2+ GI toxicity with IMRT. The occurrence of acute GI toxicity and large (>15%) volumes of rectum >70 Gy are associated with late rectal toxicity.

[Effect of radio-ecological conditions in the ChNPP exclusion zone on morphofunctional state and responsiveness of organs and tissues of laboratory animals]

The state of hematopoietic, reproductive and endocrine systems of the organisms of male rats and their offspring in generations (F0-F1-F2) was studied, and the sensitivity of an organism to the action of carcinogen (Af mice) after a stay in the ChNPP exclusion zone was analyzed. It was ascertained that the most significant changes of the morphofunctional state of the animals were observed in the II generation (F2), which remained for a long period under the conditions of radioactive contamination. We have revealed an increased number of leukocytes, neutrophils, lymphocytes, and, especially, monocytes as against while the decrease in the number of erythrocytes and haemoglobin content; the decrease of thyroid function and cortical layer of the adrenals as opposed to while the increase in the relative weight of testes and their epididymides and the decrease in the number of spermatocytes and spermatozoa in the testis tissue. The exposure of Af mice in the exclusion zone increases the processes of mutagenesis and carcinogenesis, and changes the organism response to standardized action of chemical carcinogen. The increase in the exposure time of animals intensifies metabolic processes in a cell and increases their sensitivity to the action of xenobiotics.

Acute toxicity in high-risk prostate cancer patients treated with androgen suppression and hypofractionated intensity-modulated radiotherapy

PURPOSE

To report acute toxicity resulting from radiotherapy (RT) dose escalation and hypofractionation using intensity-modulated RT (IMRT) treatment combined with androgen suppression in high-risk prostate cancer patients.

METHODS AND MATERIALS

Sixty patients with a histological diagnosis of high-risk prostatic adenocarcinoma (having either a clinical Stage of > or =T3a or an initial prostate-specific antigen [PSA] level of > or =20 ng/ml or a Gleason score of 8 to 10 or a combination of a PSA concentration of >15 ng/ml and a Gleason score of 7) were enrolled. RT prescription was 68 Gy in 25 fractions (2.72 Gy/fraction) over 5 weeks to the prostate and proximal seminal vesicles. The pelvic lymph nodes and distal seminal vesicles concurrently received 45 Gy in 25 fractions. The patients were treated with helical TomoTherapy-based IMRT and underwent daily megavoltage CT image-guided verification prior to each treatment. Acute toxicity scores were recorded weekly during RT and at 3 months post-RT, using Radiation Therapy Oncology Group acute toxicity scales.

RESULTS

All patients completed RT and follow up for 3 months. The maximum acute toxicity scores were as follows: 21 (35%) patients had Grade 2 gastrointestinal (GI) toxicity; 4 (6.67%) patients had Grade 3 genitourinary (GU) toxicity; and 30 (33.33%) patients had Grade 2 GU toxicity. These toxicity scores were reduced after RT; there were only 8 (13.6%) patients with Grade 1 GI toxicity, 11 (18.97%) with Grade 1 GU toxicity, and 5 (8.62%) with Grade 2 GU toxicity at 3 months follow up. Only the V60 to the rectum correlated with the GI toxicity.

CONCLUSION

Dose escalation using a hypofractionated schedule to the prostate with concurrent pelvic lymph node RT and long-term androgen suppression therapy is well tolerated acutely. Longer follow up for outcome and late toxicity is required.

Comparison of dose contribution to normal pelvic tissues among conventional, conformal and intensity-modulated radiotherapy techniques in prostate cancer

High-energy external radiotherapy has become one of the most common treatment in localized prostate cancer. We compared the difference of dose distribution, mainly at the 5-30 Gy dose level, in the irradiated pelvic volume among three modalities of radiotherapy for patients with prostate cancer: conventional, conformal and intensity-modulated radiotherapy (IMRT). We selected six patients with prostate cancer treated by conformal radiotherapy at the doses of 46 Gy to PTVN (prostate and seminal vesicles), and 70 Gy to PTV-T (prostate). The conventional technique": an 8-field arrangement was used; the conformal technique 4 fields with a boost through 6 fields. For IMRT, a five-beam arrangement was used. Dose-volume histograms (DVH) were analyzed and compared among the three techniques. The IMRT technique significantly increased the pelvic volume covered by the isodose surfaces below 15 Gy as compared with the conventional and conformal techniques. The mean absolute increase for the pelvic volume included between 5-30 Gy for the IMRT technique, was about 2 900 ml as compared with the conventional technique. However, IMRT significantly reduced the irradiated volume of the rectum in the dose range of 5 to 40 Gy, also significantly reduced the irradiated volume of bladder and femoral heads, and obtained a similar or improved isodose distribution in the PTVs. In addition, the use of IMRT slightly increased the relative dose delivered to the body volume outside the pelvis, as estimated by the use of specific software. A long-term follow-up will be needed to evaluate potential late treatment complications related to the use of IMRT and the low or moderate irradiation dose level obtained in the pelvis and in the whole body.

Intensity modulated neutron radiotherapy for the treatment of adenocarcinoma of the prostate

PURPOSE

This study investigates the enhanced conformality of neutron dose distributions obtainable through the application of intensity modulated neutron radiotherapy (IMNRT) to the treatment of prostate adenocarcinoma.

METHODS AND MATERIALS

An in-house algorithm was used to optimize individual segments for IMNRT generated using an organ-at-risk (OAR) avoidance approach. A number of beam orientation schemes were investigated in an attempt to approach an optimum solution. The IMNRT plans were created retrospectively for 5 patients previously treated for prostate adenocarcinoma using fast neutron therapy (FNT), and a comparison of these plans is presented. Dose distributions and dose-volume histograms (DVHs) were analyzed and plans were evaluated based on percentage volumes of rectum and bladder receiving 95%, 80%, and 50% (V(95), V(80), V(50)) of the prescription dose, and on V(60) for both the femoral heads and GM(muscle) group.

RESULTS

Plans were normalized such that the IMNRT DVHs for prostate and seminal vesicles were nearly identical to those for conventional FNT plans. Use of IMNRT provided reductions in rectum V(95) and V(80) of 10% (2-27%) and 13% (5-28%), respectively, and reductions in bladder V(95) and V(80) of 12% (3-26%) and 4% (7-10%), respectively. The average decrease in V(60) for the femoral heads was 4.5% (1-18%), with no significant change in V(60) for the GM(muscle) group.

CONCLUSIONS

This study provides the first analysis of the application of intensity modulation to neutron radiotherapy. The IMNRT technique provides a substantial reduction in normal tissue dose in the treatment of prostate cancer. This reduction should result in a significant clinical advantage for this and other treatment sites.

Influence of rectum delineation (rectal volume vs. rectal wall) on IMRT treatment planning of the prostate

PURPOSE

To evaluate the delineation of either the rectal volume (RV) or the rectal wall (RW) in intensity-modulated radiotherapy (IMRT) for prostate cancer: influence on dose distribution to the targets and organs at risk (OARs) was investigated.

MATERIAL AND METHODS

For ten patients with localized prostate cancer IMRT treatment plans were generated with the RV, wall including the filling, and the RW without the lumen as OAR (plan-RV and plan-RW), respectively. Two different IMRT treatment- planning systems (TPS) were utilized. The influence on target coverage and sparing of OARs was investigated.

RESULTS

No influence was seen on target coverage and sparing of the bladder and femoral heads. Doses to the RV were significantly reduced in plan-RV for all evaluated dose levels: maximum 26% and 17%, respectively, in both TPS. The dose distribution to the RW was not significantly different between plan-RV and plan-RW.

CONCLUSION

The different delineation of the OAR rectum significantly affected the inverse IMRT treatment-planning process. The use of the RV as OAR resulted in improved dose distributions to the RV. Therefore, it is suggested using the RV as OAR in IMRT treatment planning of the prostate.

[Image-guided radiotherapy for prostate cancer]

Intensity modulated radiotherapy (IMRT) has improved the capability to apply geometrically individualised high radiotherapy doses to the prostate bed, prostate and seminal vesicles. A high risk of geometrical miss with conformal methods, however, has been documented for mobile targets such as the prostate. Modern, non-invasive localisation techniques are therefore mandatory to further optimise conformal radiotherapy for prostate cancer. This review summarises technological advances related to "image-guided radiotherapy" (IGRT) which will further improve target positioning in prostate cancer radiotherapy.

New implant technique for separation of the seminal vesicle and rectal mucosa for high-dose-rate prostate brachytherapy

PURPOSE

For safer treatment of seminal vesicles (SVs), we initiated a new technique using an anchor applicator for high-dose-rate interstitial brachytherapy (HDR-ISBT) of prostate cancer.

METHODS AND MATERIALS

Between January 2004 and March 2005, 23 intermediate- to high-risk patients were treated with HDR-ISBT as monotherapy. Transrectal ultrasonography guided implantation of the treatment applicator in and around the prostate gland and proximal SV. We used an "anchor" applicator to prevent posterior displacement of the SV. After insertion of the anchor applicator, the actual treatment applicator was implanted at the best position for optimal SV coverage. SV coverage was analyzed using a dose-volume histogram.

RESULTS

Implantation of the applicator on the posterior side of the SV was successful for 43 of 46 SVs (93%). The median percentage of the SVs receiving the prescribed dose was 41% (range 11-86%). Only one case of acute Grade 2 toxicity (3%) was seen.

CONCLUSIONS

Our anchor applicator technique for HDR-ISBT can separate the SV from the rectum. This is the first report of dose-volume histogram analysis of the SV for HDR-ISBT.

When should the seminal vesicles be included in the target volume in prostate radiotherapy?

External beam radiotherapy to the prostate and seminal vesicles as a radical treatment for prostate cancer can result in a significant dose being delivered to the rectum. This can be reduced if the target volume includes the prostate only. Using a Medline search, published studies are reviewed to show that the risk of seminal vesicle involvement can be accurately predicted using readily available pre-treatment parameters. We recommend when to exclude the seminal vesicles from a target volume, and the proportion of seminal vesicles that should be included in a target volume in higher risk patients.

Increased Risk of Biochemical and Clinical Failure for Prostate Patients with a Large Rectum at Radiotherapy Planning: Results from the Dutch Trial of 68 GY Versus 78 Gy

PURPOSE

To investigate whether a large rectum filling visible on the planning CT scan was associated with a decrease in freedom from any failure (FFF) and freedom from clinical failure (FFCF) for prostate cancer patients.

METHODS AND MATERIALS

Patients from the Dutch trial (78 Gy vs. 68 Gy) with available acute toxicity data were analyzed (n = 549). A 10-mm margin was applied for the first 68 Gy and 0-5 mm for the 10-Gy boost. The dose in the seminal vesicles (SVs) was prescribed within four treatment groups according to the estimated risk of SV involvement. Two potential risk factors (RFs) for a geometric miss were defined: (1) an anorectal volume > or = 90 cm(3) and > or = 25% of treatment-time diarrhea (RF1); and (2) the mean cross-sectional area of the anorectum (RF2). We tested whether these were significant predictors for FFF and FFCF within each treatment group.

RESULTS

Significant results were observed only for patients with a risk of SV involvement > 25% (dose of 68-78 Gy to the SVs, n = 349). We found a decrease in FFF (p = 0.001) and FFCF (p = 0.01) for the 87 patients with RF1 (for RF2, p = 0.02 and p = 0.01, respectively). The estimated decrease in the FFCF rate at 5 years was 15%.

CONCLUSION

Tumor control was significantly decreased in patients with a risk of SV involvement > 25% and at risk of geometric miss. Current image guidance techniques offer several solutions to geometrically optimize the treatment. Additional research is needed to evaluate whether geometric misses can be prevented using these techniques.

Treatment results of adjuvant radiotherapy and salvage radiotherapy after radical prostatectomy for prostate cancer

BACKGROUND

The indications for and the efficacy of radiation therapy after radical operation for patients with prostate cancer are not clear. We analyzed the treatment results of adjuvant radiotherapy and salvage radiotherapy after radical prostatectomy.

METHODS

Between September 1997 and November 2004, 57 patients received adjuvant radiotherapy or salvage radiotherapy after radical prostatectomy. Fifteen patients received radiation therapy because of positive margins and/or extracapsular invasion in surgical specimens (adjuvant group). Forty-two patients received radiation therapy because of rising prostate-specific antigen (PSA) during follow-up (salvage group). Radiation therapy was delivered to the fossa of the prostate +/- seminal vesicles by a three-dimensional (3-D) conformal technique to a total dose of 60-66 Gy (median, 60 Gy). Biochemical control was defined as the maintenance of a PSA level of less than 0.2 ng/ml.

RESULTS

The median follow-up period after radiation therapy was 33 months (range, 12-98 months). Three-year biochemical control rates were 87% for the adjuvant group and 61% for the salvage group. For patients in the salvage group treated without hormone therapy, the preradiation PSA value was the most significant factor for the biochemical control rate. The 3-year biochemical control rate was 93% in patients whose preradiation PSA was 0.5 ng/ml or less and 29% in patients whose preradiation PSA was more than 0.5 ng/ml. No severe adverse effects (equal to or more than grade 3) were seen in treated patients.

CONCLUSION

Radiation therapy after radical prostatectomy seemed to be effective for adjuvant therapy and for salvage therapy in patients with a preradiation PSA of 0.5 ng/ml or less. Also, radiation to the fossa of the prostate +/- seminal vesicles, to a total dose of 60-66 Gy, using a three-dimensional (3-D) conformal technique, seemed to be safe.

[Three-dimensional conformal radiation therapy for prostate cancer in Hamamatsu Medical Center]

We retrospectively evaluated acute and late radiation morbidity and short-term PSA relapse-free survival of 53 patients with localized prostate cancer who received three dimensional radiation therapy (3D-CRT) that targeted prostate and seminal vesicles in Hamamatsu Medical Center from 1999.10 to 2005.4. The total dose was increased from 70 to 74 Gy in increments of 2.0 Gy. We divided these patients into two groups who received 70-72 Gy or 74 Gy. Then we analyzed whether there were differences between those two groups in acute radiation morbidity. We also analyzed late radiation morbidity in the 70(-)-72 Gy group. Acute radiation morbidity and late morbidity were described according to the RTOG acute radiation morbidity scoring criteria 1995 and RTOG/EORTC late radiation morbidity scoring scheme 1995, respectively. No acute grade 3 or 4 toxicity and no late grade 4 toxicity was observed. Late grade 3 rectal bleeding was observed in only one patient who received 70 Gy. Acute toxicity was well tolerated and did not correlate with total dose.

Dose distribution in 3-dimensional conformal radiotherapy for prostate cancer: Comparison of two treatment techniques (six coplanar fields and two dynamic arcs)

PURPOSE

To compare dose distribution for two techniques of 3-dimensional conformal radiotherapy (RT): 6-field technique (6F) and 2-dynamic arc therapy (2DA).

METHODS AND MATERIALS

Thirty nonmetastatic prostate cancer patients were included. In each patient, two treatment plans were prepared: with six coplanar fields (45 degrees , 90 degrees , 135 degrees , 225 degrees , 270 degrees , 315 degrees ) and with two dynamic lateral 100 degrees -wide arcs (40-140 degrees , 220-320 degrees ). Dose-volume histograms (DVHs) were computed and mean area under curve (AUC) values were calculated for the DVHs of Planning Target Volume (PTV), rectum, urinary bladder and femoral heads. Doses given to 30% of rectum (DR(30)), to 60% of rectum (DR(60)), to 50% of bladder (DB(50)), to 50% of femoral head (DF(50)) and to 95% of PTV (DPTV(95)) were reported as a percentage of the total dose.

RESULTS

Mean DR(30) and DR(60) for 6F and 2DA were 75.8%, 51.5% and 72.2%, 37.2%, respectively. Mean DB(50) for 6F and 2DA were 68% and 64.2%, respectively. Mean right DF(50) for 6F and 2DA were 35.4% and 45.5%, respectively. Mean DPTV(95) for 6F and 2DA were 99% and 99.2%, respectively. Mean AUCs of DVHs of rectum and urinary bladder were significantly higher for 6F (this was more evident for small PTV and in the intermediate dose range). Mean AUC of DVHs of PTV and femoral heads were significantly higher for 2DA.

CONCLUSIONS

Both 6F and 2DA offer good dose distribution for PTV. 2DA allows for significantly better sparing of rectum and urinary bladder with slightly worse femoral head dose distribution. Further study is warranted in order to establish the clinical relevance of these differences.

Permanent prostate brachytherapy: is supplemental external-beam radiation therapy necessary?

Permanent prostate brachytherapy with or without supplemental therapies is a highly effective treatment for clinically localized prostate cancer, with biochemical outcomes and morbidity profiles comparing favorably with competing local modalities. However, the absence of prospective randomized brachytherapy trials evaluating the role of supplemental external-beam radiation therapy (XRT) has precluded the development of evidence-based treatment algorithms for the appropriate inclusion of such treatment. Some groups advocate supplemental XRT for all patients, but the usefulness of this technology remains largely unproven and has been questioned by recent reports of favorable biochemical outcomes following brachytherapy used alone in patients at higher risk. Given that brachytherapy can be used at high intraprostatic doses and can obtain generous periprostatic treatment margins, the use of supplemental XRT may be relegated to patients with a high risk of seminal vesicle and/or pelvic lymph node involvement. Although morbidity following brachytherapy has been acceptable, supplemental XRT has shown an adverse impact on long-term quality of life. The completion of ongoing prospective randomized trials will help define the role of XRT as a supplement to permanent prostate brachytherapy.

Comparison of treatment volumes and techniques in prostate cancer radiation therapy

OBJECTIVE

To compare dose-volume histograms (DVHs) for 3 target volumes (group 1, prostate + seminal vesicles + pelvic lymph nodes; group 2, prostate + seminal vesicles; group 3, prostate only) to determine the difference in dose to normal structures (rectum, bladder, and femoral heads) while controlling for target dose using 3-dimensional conformal radiation therapy (3DCRT) versus intensity modulated radiation therapy (IMRT).

METHODS

Ten patients with localized prostate cancer were randomly selected. 3DCRT and IMRT planning were done to deliver 75.6 Gy to the prostate, 50.4 Gy to the pelvic nodes, and 55.8 Gy to the seminal vesicles at a standard fractionation of 1.8 Gy. An additional plan delivering 75.6 Gy to the seminal vesicles using IMRT was run. DVHs were compared for 3DCRT and IMRT.

RESULTS

In all 3 groups, the percent rectum receiving > or =70 Gy, > or =60 Gy, and > or =40 Gy was significantly less for IMRT than for 3DCRT. Increasing target volumes, as necessary for pelvic nodal irradiation, overall did not result in higher rectal doses for IMRT. With 3DCRT, however, larger target volumes did increase the amount of rectum irradiated. Similar results were obtained for the femoral heads whereas results for the bladder were mixed.

CONCLUSION

When compared with 3DCRT, IMRT delivered equivalent or higher doses to the target volume with greater sparing of critical organs. Because dose-volume parameters have been shown to relate to toxicity, IMRT would appear to be the favored technique for prostate cancer radiation, particularly with regard to nodal treatment.

The Impact of Varying Volumes in Rectal Balloons on Rectal Dose Sparing in Conformal Radiation Therapy of Prostate Cancer

BACKGROUND AND PURPOSE

The use of a rectal balloon leads to a protection of the posterior rectal wall in irradiation of prostate cancer. The purpose of this analysis was to quantitatively assess the optimal volume in rectal balloons concerning rectal dose sparing in different clinical target volumes (CTVs) in prostate cancer irradiation.

PATIENTS AND METHODS

14 patients with localized prostate cancer undergoing external beam radiotherapy were investigated. The prostate, the entire and the proximal seminal vesicles were delineated as CTV. Treatment plans without a rectal balloon and with a rectal balloon inflated with 40 ml (six patients) or 60 ml air (eight patients) were generated for each CTV and compared concerning rectal dose volume histograms.

RESULTS

The use of a rectal balloon filled with 40 ml air led to no significant advantage in radiation exposure of the rectal wall in all CTVs. The use of a rectal balloon filled with 60 ml air resulted in a significant decrease of the exposed rectal wall volume in all CTVs with a reduced estimated risk for chronic toxicity in case of inclusion of the proximal or entire seminal vesicles into the CTV.

CONCLUSION

The use of a rectal balloon filled with 60 ml air led to a significantly decreased proportion of the irradiated rectal wall for all CTVs. This volume filled in rectal balloons is therefore recommended for use. In case of irradiation of the prostate without the seminal vesicles, the use of a rectal balloon should be considered carefully concerning the patients' imaginable discomfort using a rectal balloon and a questionable advantage concerning the estimated risk for chronic toxicity.

The sensitivity of dose distributions for organ motion and set-up uncertainties in prostate IMRT

BACKGROUND AND PURPOSE

To determine the effect of organ motion and set-up uncertainties on IMRT dose distributions for prostate.

METHODS

For five patients, IMRT techniques were designed to irradiate the CTV (prostate plus seminal vesicles). Technique I delivered 78 Gy to PTV1 (CTV+10 mm margin). Technique II delivered 68 Gy to PTV1, and a 10 Gy boost to PTV2 (CTV+an anisotropic margin of 0 to 5 mm). Technique III delivered 68 Gy to PTV1 and simultaneously 78 Gy to PTV2. Uncertainties were simulated using population statistics of organ motion and set-up accuracy. The average TCP (TCPpop) of the CTV and average NTCP (NTCPpop) of the rectal wall were calculated.

RESULTS

The planning TCP was a good predictor for TCPpop for Techniques I and II. Technique III was sensitive for geometrical uncertainties, reducing TCPpop by 0.8 to 2.4% compared to planning. NTCPpop was reduced for Technique III by a factor 2.6 compared to Technique I. For all plans, the planning NTCP was strongly correlated with NTCPpop.

CONCLUSIONS

Dose distributions created with Techniques I and II are insensitive for geometrical uncertainties, while Technique III resulted in a reduction of TCPpop. This reduction can be compensated by a small dose escalation, while still resulting in an NTCPpop of the rectal wall that is lower or comparable to Technique I.

Australia-wide comparison of intensity modulated radiation therapy prostate plans*

The aim of this study was to investigate the ability of Australian centres to produce high-dose intensity modulated radiation therapy (IMRT) prostate plans, and to compare the planning parameters and resultant dose distributions. Five Australian radiation therapy departments were invited to participate. Each centre received an identical 5 mm-slice CT data set complete with contours of the prostate, seminal vesicles, rectum, bladder, femoral heads and body outline. The planning team was asked to produce the best plan possible, using published Memorial Sloan-Kettering Cancer Centre prescription and dose constraints. Three centres submitted plans for evaluation. All plans covered the planning target volume adequately; however, only one plan met all the critical organ dose constraints. Although the planning parameters, beam arrangements and planning systems were different for each centre, the resulting plans were similar. In Australia, IMRT for prostate cancer is in the early stages of implementation, with routine use limited to a few centres.

Contemporary survival results and the role of radiation therapy in patients with node negative seminal vesicle invasion following radical prostatectomy

PURPOSE

Seminal vesicle invasion (SVI) in a radical prostatectomy (RRP) specimen is associated with a guarded prognosis. We evaluated patients with SVI treated in the pre-prostate specific antigen (PSA) (1983 to 1991) and PSA (1992 to 2003) eras.

MATERIALS AND METHODS

Of patients with prostate cancer treated with RRP from January 1983 through March 2002, 220 with SVI were evaluated, including 67 in the pre-PSA era and 153 in the PSA era. Postoperative PSA greater than 0.2 ng/ml was considered biochemical evidence of cancer progression. Survival rates were compared using Kaplan-Meier estimates to calculate progression-free, cancer specific and all cause survival. Multivariate Cox proportional hazard models were used to correlate variables with disease progression.

RESULTS

The incidence of SVI in the PSA era was lower than in the pre-PSA era (6.0% vs 10.2%, p = 0.001). To date 124 patients (56%) have had evidence of cancer progression. The 4 and 7-year progression-free, cancer specific and all cause survival rates were significantly higher in men with SVI in the PSA era (p = 0.02). PSA at diagnosis, cancerous surgical margins and higher Gleason score were significantly associated with progression. Neither adjuvant nor salvage radiotherapy appeared to confer a significant progression-free survival benefit.

CONCLUSIONS

The incidence of SVI has decreased in the PSA era. Progression-free, cancer specific and all cause survival rates following RRP in patients with SVI have improved in the PSA era. This may reflect earlier detection in this pathological tumor stage and more favorable prognostic factors associated with PSA screening. Adjuvant radiotherapy does not appear to confer any therapeutic benefit. Salvage radiotherapy can lead to durable PSA regressions in a small percent of men, although no long-term survival advantage can be proved.

Impact of setup uncertainty in the dosimetry of prostate and surrounding tissues in prostate cancer patients treated with Peacock/IMRT

The purpose of this paper was to assess the effect of setup uncertainty on dosimetry of prostate, seminal vesicles, bladder, rectum, and colon in prostate cancer patients treated with Peacock intensity-modulated radiation therapy (IMRT). Ten patients underwent computed tomography (CT) scans using the "prostate box" for external, and an "endorectal balloon" for target immobilization devices, and treatment plans were generated (T1). A maximum of +/-5-mm setup error was chosen to model dosimetric effects. Isodose lines from the T1 treatment plan were then superimposed on each patient's CT anatomy shifted by 5 mm toward the cephalad and caudal direction, generating 2 more dosimetric plans (H1 and H2, respectively). Average mean doses ranged from 74.5 to 74.92 Gy for prostate and 73.65 to 74.94 Gy for seminal vesicles. Average percent target volume below 70 Gy increased significantly for seminal vesicles, from 0.53% to 6.26%, but minimally for prostate, from 2.08% to 4.4%. Dose statistics adhered to prescription limits for normal tissues. Setup uncertainty had minimum impact on target dose escalation and normal tissue dosing. The impact of target dose inhomogeneity is currently evaluated in clinical studies.

The impact of a delay in initiating radiation therapy on prostate-specific antigen outcome for patients with clinically localized prostate carcinoma

BACKGROUND

To determine whether a delay in initiating external beam radiation therapy (RT) following diagnosis could impact prostate-specific antigen (PSA) outcome for patients with localized prostate cancer, 460 patients, who received 3D conformal RT to a median dose of 70.4 Gy for clinically localized prostate cancer between 1992 and 2001, were studied.

METHODS

The primary endpoint was PSA failure (American Society for Therapeutic Radiology and Oncology definition). Estimates of PSA control were made using the Kaplan-Meier method. Delay was defined as the time between diagnosis and the start of RT. Risk groups were defined based on known predictors of PSA outcome, namely, baseline PSA level, clinical T-category, Gleason score, and percentage of biopsy cores positive for tumor. Cox multivariate regression analysis was used to determine the ability of treatment delay to predict time to PSA failure after adjusting for the other known predictors.

RESULTS

Treatment delay independently predicted time to PSA failure following diagnosis for high-risk (Adjusted Hazard Ratio = 1.08 per month; P = 0.029) but not low-risk patients (P = 0.31). Patients with high-risk disease (n = 240) had 5-year estimates of PSA failure-free survival of 55% versus 39% (Plog-rank = 0.014) for those with delay < 2.5 months versus > or = 2.5 months respectively. The median delay was 2.5 months.

CONCLUSIONS

Treatment delay adversely affected PSA outcome for high-risk patients but not for low-risk patients following RT.

Comparison between manual and automatic segment generation in step-and-shoot IMRT of prostate cancer

PURPOSE

To compare two methods to generate treatment plans for intensity-modulated radiotherapy (IMRT) of prostate cancer, delivered in a step-and-shoot mode. The first method uses fluence optimization (inverse planning) followed by conversion of the fluence weight map into a limited number of segments. In the second method, segments are manually assigned using a class solution (forward planning), followed by computer optimization of the segment weights.

METHODS

Treatment plans for IMRT, utilizing a simultaneous integrated boost, were created. Plans comprise a five-field technique to deliver 78 Gy to the prostate plus seminal vesicles. Five patients were evaluated. Optimization objectives of both planning approaches concerned dose coverage of the target volumes and the dose distribution in the rectal wall. The two methods were evaluated by comparing dose distributions, the complexity of the resulting plan and the time expenditure to generate and to deliver the plan.

RESULTS

For both planning approaches 99% of the target volumes received 95% of the prescribed dose, which complies with our planning objectives. Inverse planning resulted in more conformal dose distributions than forward planning (conformity index: 1.37 versus 1.51). Inverse planning reduced the dose to the rectal wall compared to a manually designed plan, albeit to a small extent. The theoretical probability of severe rectal proctitis and/or stenosis was reduced on average by 1.9% with inverse planning. Maximal sparing of the rectal wall was achieved with inverse planning for a patient whose target volume was partly wrapped around the rectum. The number of segments generated with inverse planning ranged between 33 and 52, and between 9 and 13 segments for manually created segments.

CONCLUSION

Dose coverage of the planning target volumes is adequate for both approaches of planning. Inverse planning results in slightly better dose distributions with respect to the rectal wall compared to manual planning, at the cost of an increase of the number of segments by a factor of 3.

Rectal dose sparing with a balloon catheter and ultrasound localization in conformal radiation therapy for prostate cancer

BACKGROUND AND PURPOSE

To compare the rectal wall and bladder volume in the high dose region with or without the use of a balloon catheter with both three-dimensional (3D)-conformal and intensity modulated radiation therapy (CRT, IMRT) approaches in the treatment of prostate cancer.

MATERIAL AND METHODS

Five patients with a wide range of prostate volumes and treated with primary external beam radiation therapy for localized prostate cancer were selected for analysis. Pinnacle treatment plans were generated utilizing a 3D conformal six-field design and an IMRT seven coplanar-field plan with a novel, three-step optimization and with ultrasound localization. Separate plans were devised with a rectal balloon deflated or air inflated with and without inclusion of the seminal vesicles (SV) in the target volume. The prescription dose was 76Gy in 38 fractions of 2Gy each. Cumulative dose-volume histograms (DVHs) were analyzed for the planning target volume (PTV), rectal wall, and bladder with an inflated (60cc air) or deflated balloon with and without SV included. The volumes of rectal wall and bladder above 60, 65, and 70Gy with each treatment approach were evaluated.

RESULTS

Daily balloon placement was well-tolerated with good patient positional reproducibility. Inflation of the rectal balloon in all cases resulted in a significant decrease in the absolute volume of rectal wall receiving greater than 60, 65, or 70Gy. The rectal sparing ratio (RSR), consisting of a structure's high dose volume with the catheter inflated, divided by the volume with the catheter deflated, was calculated for each patient with and without seminal vesicle inclusion for 3D-CRT and IMRT. For 3D-CRT, RSRs with SV included were 0.59, 0.59, and 0.56 and with SV excluded were 0.60, 0.58, and 0.54 at doses of greater than 60, 65, and 70Gy, respectively. Similarly, for IMRT, the mean RSRs were 0.59, 0.59, and 0.63 including SV and 0.71, 0.66, and 0.67 excluding SV at these same dose levels, respectively. Averaged over all conditions, inflation of the rectal balloon resulted in a significant reduction in rectal volume receiving > or =65Gy to a mean ratio of 0.61 (P=0.01) or, in other words, a mean fractional high dose rectal sparing of 39%. There was a slight overall increase to 1.13 in the relative volume of bladder receiving at least 65Gy; however, this was not significant (P=0.6). Use of an endorectal balloon with a non-image-guided 3D-CRT plan produced about as much rectal dose sparing as a highly conformal, image-guided IMRT approach without a balloon. However, inclusion of a balloon with IMRT produced further rectal sparing still.

CONCLUSION

These results indicate that use of a rectal balloon with a 3D-CRT plan incorporating typical treatment margins will produce significant high dose rectal sparing that is comparable to that achieved by a highly conformal IMRT with ultrasound localization. Further sparing is achieved with the inclusion of a balloon catheter in an IMRT plan. Thus, in addition to a previously reported advantage of prostate immobilization, the use of a rectal displacement balloon during daily treatment results in high dose rectal wall sparing during both modestly and highly conformal radiotherapy. Such sparing could assist in controlling and limiting rectal toxicity during increasingly aggressive dose escalation.

[Effects of prolonged low-intensity irradiation on organ weight of the male rat reproductive system]

The effects of prolonged irradiation at accumulated doses from 0.5 to 6.0 Gy (dose rate 3.03 cGy/day) on reproductive organs' weight (testes, epididymises, seminal vesicles, prostate) of male rats starting from the early ontogenetic period were studied. On the first day after the irradiation with 1.0 Gy dose a significant loss of the weight in testes and epididymises was revealed. This leaded to the marked atrophy of the organs with the increase of the radiation dose. Long-term restoration of the weight of testes and epididimyses was registered. It was not completed during three months after radiation exposure at 2.0 Gy and higher doses for epididimyses and 4.0-6.0 Gy for testes. The respective changes in the seminal vesicles and prostate weight were less pronounced and had more complicated character. However in the distant period (30-90 days of postreatment) after exposure to 2.0 Gy these parameters were noticeably decreased.

[Conformal radiotherapy in prostate cancer: for whom and how?]

External radiotherapy is one of the modalities used to cure localized prostate carcinoma. Most of localized prostate carcinomas, specially those of the intermediate prognostic group, may benefit from escalated dose above 70 Gy at least as regard biochemical and clinical relapse free survival. 3D-CRT allows a reduction of the dose received by organs at risk and an increase of prostate dose over 70 Gy. It is on the way to become a standard. Intensity modulated radiation therapy increases dose homogeneity and reduces rectal dose. These methods necessitate rigorous procedures in reproducibility, delineation of volumes, dosimetry, daily treatment. They need also technological and human means. It is clear that localized prostate cancer is a good example for evaluation of these new radiotherapy modalities.

Intensity-modulated radiotherapy for a prostate patient with a metal prosthesis

When treating prostate patients having a metallic prosthesis with radiation, a 3D conformal radiotherapy (3DCRT) treatment plan is commonly created using only those fields that avoid the prosthesis in the beam's-eye view (BEV). With a limited number of portals, the resulting plan may compromise the dose sparing of the rectum and bladder. In this work, we investigate the feasibility of using intensity-modulated radiotherapy (IMRT) to treat prostate patients having a metallic prosthesis. Three patients, each with a single metallic prosthesis, who were previously treated at the University of Chicago Medical Center for prostate cancer, were selected for this study. Clinical target volumes (CTV = prostate + seminal vesicles), bladder, and rectum volumes were identified on CT slices. Planning target volumes (PTV) were generated in 3D by a 1-cm expansion of the CTVs. For these comparative studies, treatment plans were generated from CT data using 3DCRT and IMRT treatment planning systems. The IMRT plans used 9 equally-spaced 6-MV coplanar fields, with each field avoiding the prosthesis. The 3DCRT plans used 5 coplanar 18-MV fields, with each field avoiding the prosthesis. A 1-cm margin around the PTV was used for the blocks. Each of the 9-field IMRT plans spared the bladder and rectum better than the corresponding 3DCRT plan. In the IMRT, plans, a bladder volume receiving 80% or greater dose decreased by 20-77 cc, and a volume rectal volume receiving 80% or greater dose decreased by 24-40 cc. One negative feature of the IMRT plans was the homogeneity across the target, which ranged from 95% to 115%.

Improvement in dose escalation using the process of adaptive radiotherapy combined with three-dimensional conformal or intensity-modulated beams for prostate cancer

PURPOSE

Advances in technology allow the creation of complex treatment plans with tightly conforming doses. However, variations in positioning of the organ/patient with respect to treatment beams necessitate the use of an appreciable margin, potentially limiting dose escalation in many patients. To (1) reduce this margin and (2) test the hypothesis that the achievable level of dose escalation is patient dependent, a patient-specific, confidence-limited planning target volume (cl-PTV) was constructed using an adaptive radiotherapy (ART) process for prostate cancer treatment developed in-house. The potential dose escalation achievable with this ART process is quantified for both conformal radiotherapy (CRT) delivery and intensity-modulated radiotherapy (IMRT) delivery.

MATERIAL AND METHODS

Patients with organ confined prostate cancer were entered prospectively into an ART process developed in-house. This ART process has been designed to improve accuracy and precision of dose delivery, consequently enhancing dose escalation. In this process, a cl-PTV is constructed for each patient in the second week of treatment based upon on-line portal and CT images acquired during the first week of treatment. The treatment prescription dose, defined as the minimum dose to the cl-PTV, is selected based on predefined dose-volume constraints for rectum/bladder and derived from the pretreatment planning CT image. In addition, the treatment modality (CRT or IMRT) is determined based on the level of dose escalation achievable and the risk of inaccurate targeting. The potential for both dose escalation and the application of IMRT was evaluated by comparing the prescription doses delivered using the ART process, with the cl-PTV, to those in the traditional treatment process, with a conventional generic PTV. In addition, the distributions of potential geometric target underdosing and normal tissue overdosing were also calculated to evaluate the quality of the conventional treatment plans.

RESULTS

One hundred and fifty patients have been treated with the ART process. When compared to the treatment dose delivered with the conventional treatment process (generic PTV), an average 5% (2.5--10%) more dose could be delivered using the ART process with CRT, and 7.5% (2.5--15%) more dose could be delivered with IMRT. Of the 150 patients, 70% were treated to a minimum cl-PTV dose > or = 77.4 Gy (81.3 Gy ICRU isocenter dose). Dosimetric analysis revealed that 81 Gy to the cl-PTV (or 86.7 Gy ICRU) could be prescribed to at least 50% of patients if IMRT was applied using the ART process. In contrast, IMRT did not yield an obvious dose escalation gain if patients were treated using the generic PTV. Our results also demonstrate that the cl-PTV is significantly smaller than the conventional generic PTV for most patients, with a mean volume reduction of 24% (range, 5--43%).

CONCLUSION

These results support our hypothesis that the achievable level of dose escalation using ART is patient dependent. By using the ART process to develop a cl-PTV, one can (1) optimize the dose level, (2) increase the applicability of IMRT, and (3) improve the quality of dose delivery. The ART process provides the foundation to identify a suitable option (CRT or IMRT) for the delivery of a safe treatment and dose escalation. It is now our standard of practice for prostate cancer treatment.

Simultaneous irradiation for prostate cancer: intermediate results with modern techniques

PURPOSE

In this study of men with early stage prostate cancer we evaluated treatment outcome after modern simultaneous irradiation, comprising transperineal implantation followed by external beam radiation. Disease-free survival rates were calculated according to an undetectable prostate specific antigen (PSA) nadir.

MATERIALS AND METHODS

From 1992 to 1996, 689 men with clinical stage T1-T2, N0, Nx prostate cancer were treated with ultrasound guided transperineal 125iodine seed implantation followed 3 weeks later by external beam radiation. Disease-free status was defined as the achievement and maintenance of a PSA nadir of 0.2 ng./ml. or less. Median followup was 4 years (range 3 to 7). None of these men received neoadjuvant or adjuvant hormonal therapy.

RESULTS

Overall 5-year disease-free survival was 88%. The 5-year rate according to PSA 4.0 ng./ml. or less, 4.1 to 10.0, 10.1 to 20.0 and greater than 20.0 was 94%, 93%, 75% and 69%, respectively. Multivariate analysis revealed that pretreatment PSA was the strongest indicator of subsequent disease-free status in regard to Gleason score or clinical stage.

CONCLUSIONS

Intermediate treatment outcome analysis of modern simultaneous radiation supports the principles of radiation dose intensification for intracapsular disease plus the treatment of potential microscopic capsular penetration.

Potency preservation after three-dimensional conformal radiotherapy for prostate cancer: preliminary results

We sought to assess potency preservation after three-dimensional conformal radiotherapy (3D-CRT) in prostate cancer patients eligible for radical prostatectomy, conventional radiotherapy, 3D-CRT, or transperineal prostate implantation. Patients with more advanced disease are commonly treated with hormonal therapy, which can cause impotence, and were consequently excluded from the analysis. Between December 1991 and June 1998, 198 prostate cancer patients were treated with 3D-CRT at the University of California, Davis Medical Center. Fifty-two of these patients had a pretreatment prostate-specific antigen (PSA) level of 10.0 ng/ml or less, a Gleason score of 6 or less, and a 1997 AJCC clinical stage T1bN0M0 to T2bN0M0. One patient was not evaluable. None of the 51 evaluable patients had diabetes mellitus. In 40 patients, the prostate gland only was irradiated to a total dose of 66 to 79.2 Gy by using daily 1.8-Gy fractions. In 11 patients, the prostate and seminal vesicles were treated to 44 to 55.8 Gy. Lymph nodes were not included in the clinical target volume. The median age was 68 years, and the median length of follow-up was 15 months. Potency in this study is defined as an erection sufficient for vaginal penetration. Kaplan-Meier analysis was used to describe potency as a function of time after 3D-CRT. Of the 51 evaluable patients, 35 (69%) were potent, 15 were impotent, and 1 was sexually inactive before 3D-CRT. Kaplan-Meier estimates of the potency preservation rates 1, 2, and 3 years after 3D-CRT are 100%, 83%, and 63%, respectively. On multivariate analysis, age, total radiation dose, and a history of transurethral resection of the prostate did not significantly affect potency preservation rates. Three (43%) of 7 patients who became impotent after 3D-CRT and used sildenafil were subsequently able to achieve erections sufficient for vaginal penetration. The preliminary results reported herein suggest that approximately two thirds of prostate cancer patients will retain their potency 3 years after 3D-CRT. Further follow-up is necessary to assess long-term potency after 3D-CRT. Sildenafil should be considered in patients who develop radiation-induced impotence.

An evaluation of three-field coplanar plans for conformal radiotherapy of prostate cancer

BACKGROUND AND PURPOSE

A series of coplanar three-field configurations for two different clinical treatment volumes, prostate only (PO) and prostate plus seminal vesicles (PSV) were studied to determine the optimal three-field plan arrangement for prostate radiotherapy.

MATERIALS AND METHODS

A variety of conformal three-field 6 MV plans prescribed to both 64 and 74 Gy were created for PO and PSV volumes in each of ten patients. For description, the orientation of each sequential beam was named in a clockwise fashion. Plans included series with arrangements of 0 degrees, 60-150 degrees, 210-300 degrees; 0 degrees, 90 degrees, 225-255 degrees; 90 degrees, 210-240 degrees, 300-330 degrees and a four-field (4F) box plan for comparison. Six-hundred and eighty plans were compared using the rectal volume irradiated to greater than 50% (V(50)), 80% (V(80)), and 90% (V(90)) of the prescribed dose, normal tissue complications (NTCP) for rectum, bladder, and femoral heads (FH), and tumour control probabilities (TCP). FH tolerance was set at 52 Gy to 10% volume.

RESULTS

In comparing the 34 different three-field configurations for each of the PO and PSV groups, the greatest rectal sparing was achieved by a three-field plan with gantry angles of 0 degrees, 90 degrees, 270 degrees (PO: rectal V(80)=22.8+/-5.5% (1S.D.), V(90)=18.4+/-5.7%, and PSV: rectal V(80)=41.9+/-5.8%, V(90)=35.5+/-5.9%). This also improved on the 4F-box plan (PO: rectal V(80)=26.0+/-5.8%, V(90)=21.4+/-5.2%, P<0.001; and PSV: rectal V(80)=47.3+/-5.5%, V(90)=41.6+/-5.1%, P<0.001). The worst rectal sparing was seen with the 0 degrees, 120 degrees, 240 degrees plan (PO: rectal V(80)=35.2+/-8.0%, V(90)=30.3+/-7.1%, P<0.001; and PSV: rectal V(80)=65.7+/-9.0%, V(90)=58.8+/-8.8%, P<0.001). In the PO group, the increase in predicted rectal NTCP with dose escalation from 64 to 74 Gy was 3.3% using the 0 degrees, 90 degrees, 270 degrees plan, 4.7% with the 4F-box plan, and 6.9% with the 0 degrees, 120 degrees, 240 degrees plan. In the PSV group, dose escalation increased the predicted rectal NTCP by 7.9, 10.1 and 15.7% for the 0 degrees, 90 degrees, 270 degrees plan, 4F-box plan, and 0 degrees, 120 degrees, 240 degrees plan, respectively.

CONCLUSIONS

For both PO and PSV volumes, the three-field plan which afforded the greatest rectal sparing with acceptable bladder and femoral head doses was the 0 degrees, 90 degrees, 270 degrees plan. This plan also improved on the 4F-box. The increase in predicted rectal NTCP when escalating dose from 64 to 74 Gy was smaller using this plan compared to either the three-field 0 degrees, 120 degrees, 240 degrees plan or the 4F-box plan.

Feasibility study combining low dose rate (192)Ir brachytherapy and external beam radiotherapy aiming at delivering 80-85 Gy to prostatic adenocarcinoma

BACKGROUND

Increasing the radiation dose to prostatic adenocarcinoma has provided higher local control rates. A total of 80 Gy seem necessary to achieve this goal but patient set-up and prostate motion remain difficult problems to solve in conformal radiotherapy. Brachytherapy which overcomes these points could be an alternative way to external beam boost fields. We wanted to transpose the irradiation models largely used in cervix cancer treatment combining external beam radiotherapy and low dose rate brachytherapy.

MATERIALS AND METHODS

In 71 patients with 19.5 and 13 ng/ml mean and median PSA levels, respectively, a dose escalation from 74 to 85 Gy was performed in four groups.

RESULTS

Shifting from intraoperative placement of sources vectors (Group I) to positioning under ultrasound controls (groups II-IV), improving the implantation shape and optimizing radiation delivery to urethral bed have reduced the total dose to rectal wall under 65 Gy and to urethra under 100 Gy. Rectal/prostate dose ratio was lowered from 0.7 (Groups I-II) to 0.58 (Groups III-IV) while avoiding problems resulting from pelvic bone arch interference, prostate volume or seminal vesicles location. The mean and median follow-up periods are 28 and 18 months. In Groups III and IV 85% of patients without hormonotherapy treated with 80-85 Gy normalized PSA under 1 ng/ml within 6 months. No severe late effect has been noted for patients implanted under echographic control.

CONCLUSIONS

The method described allows to deliver 85 Gy. Longer follow-up is however needed but the levels of dose delivered are not expected to induce prohibitive side effects.

Conformal irradiation of concave-shaped PTVs in the treatment of prostate cancer by simple 1D intensity-modulated beams

BACKGROUND

In the case of concave-shaped PTVs including prostate (P) and seminal vesicles (SV), intensity-modulated radiation therapy (IMRT) should improve the therapeutic ratio of the treatment of prostate cancer.

PURPOSE

Comparing IMRT by simple 1D modulations with conventional 3D conformal therapy (i.e. non-IMRT) in the treatment of concave-shaped PTVs including P+SV.

MATERIALS AND METHODS

For five patients having a concave-shaped PTV (P+SV) previously treated at our Institute with conformal radiotherapy, conventional 3- and 4-fields conformal plans were compared with IMRT plans in terms of biological indices. IMRT plans were generated by using five equi-spaced beams with a partial shielding of the rectum obtainable with our single-absorber modulation technique (Fiorino C, Lev A, Fusca M, Cattaneo GM, Rudello F, Calandrino R. Dynamic beam modulation by using a single dynamic absorber. Phys. Med. Biol. 1995;40:221-240). The modulation was one-dimensional and the shape of the beams was at single minimum in correspondence with the 'core' of the rectum; the beam intensity in the minimum was set equal to 20 or 40% of the open beam intensity. All plans were simulated on the CADPLAN TPS using a pencil-beam based algorithm (with 18 MV X-rays). Tumour control probability (TCP) and normal tissue complication probabilities (NTCPs) (for rectum, bladder and femoral head) were calculated for all situations when varying the isocentre dose from 60 to 90 Gy. Dose distributions were corrected taking dose fractionation into account through the linear-quadratic model; for the TCP/NTCP estimations the Webb-Nahum and the Lyman-Kutcher models were respectively applied. Three different scores were considered: (a) increase of TCP while keeping rectum NTCP equal to 5% (TCP(5%)); (b) increase of the uncomplicated tumour control probability (P+); (c) increase of the biological-based scoring function (S+), developed by Mohan et al. (Mohan R, Mageras GS, Baldwin B, Clinically relevant optimization of 3D conformal treatments. Med. Phys. 1992;19:933-944). The impact of the uncertainty in the knowledge of the parameters of the biological models was investigated for TCP(5%).

RESULTS

(a) The average gain in TCP(5%) when considering IMRT against non-IMRT conformal plans was 7.3% (range 5.0-13.5%); (b) the average increase of P+ was 3.4% (range: 1. 0-8.5%); and (c) the average increase of S+ was 5.4% (range 2.9-12. 4%). The largest gain was found for one patient (patient 5) showing a significantly larger overlapping between PTV and rectum.

CONCLUSIONS

Simple 1D-IMRT may clearly improve the therapeutic ratio in the treatment of concave-shaped PTVs including P and SV. In the range of clinically suitable values, the impact of the uncertainty of the parameters n and sigma(alpha) does not significantly alter the main results concerning the gain in TCP(5%). The reported gain in terms of P+ and S+ should be considered with great caution because of the intrinsic uncertainties of the model's parameters and, for bladder, because the 'true' DVH (considering variations of the shape and dimension due to variable filling) may be very different from the DVH calculated on a single CT scan. Further investigations should consider inversely-optimised 1D and 2D-IMRT plan in order to compare them in terms of cost-benefit.

Optimization of coplanar six-field techniques for conformal radiotherapy of the prostate

PURPOSE

To determine the optimal coplanar treatment technique for six-field conformal radiotherapy of prostate only (PO) or prostate plus seminal vesicles (PSV).

METHODS AND MATERIALS

A series of 6-MV six-field coplanar treatment plans were created for PO and PSV volumes in 10 patients prescribed to both 64 and 74 Gy. All plans consisted of laterally-symmetric anterior oblique, lateral, and posterior oblique fields. The posterior oblique fields were varied through 20-45 degrees relative to the lateral fields, and for each of these angles, the anterior oblique fields were varied through 25-65 degrees relative to lateral. The plans were compared by means of rectal volumes irradiated to 80% or more of the prescribed dose (V80); normal tissue complication probability (NTCP) for rectum, bladder, and femoral heads; and tumor control probability (TCP). Femoral head tolerance was designated as 52 Gy to no more than 10% volume.

RESULTS

For the PO group, anterior oblique fields at 50 degrees from lateral and posterior oblique fields at 25 degrees from lateral produced the lowest V80, together with femoral head doses which were appropriate for most patients (V80 = 24.4+/-5.3% [1 SD]). Compared to a commonly-used six-field (reference) plan with both anterior and posterior oblique fields at 35 degrees from lateral (V80 = 26.3+/-5.9%), this represented an improvement (p = 0.001). For the PSV group, the optimal anterior and posterior oblique fields were at 65 degrees and 30 degrees from lateral, respectively (V80 = 47.5+/-6.3%). Relative to the reference plan (V80 = 49.4+/-5.6%), this was a marginal improvement (p = 0.07).

CONCLUSION

The optimized six-field plans provide increased rectal sparing at both standard and escalated doses. Moreover, the gain in TCP resulting from dose escalation can be achieved with a smaller increase in rectal NTCP using the optimized six-field plans.

Does prostate brachytherapy treat the seminal vesicles? A dose-volume histogram analysis of seminal vesicles in patients undergoing combined PD-103 prostate implantation and external beam irradiation

PURPOSE

Combined brachytherapy of the prostate and external beam irradiation (EBRT) of the prostate and seminal vesicles (SV) is becoming a popular treatment for high-risk prostate cancer. Dose-volume histogram (DVH) analysis of the SV in patients undergoing this treatment was performed to determine the dose distribution to the SV and the adequacy of this treatment in patients with potential SV involvement.

METHODS AND MATERIALS

Twenty-five consecutive patients were treated with a Pd-103 implant of the prostate alone and 45 Gy of EBRT to the prostate and SV. Attempts were not made to implant the SV but seeds were routinely placed at the junction of the prostate and SV. All patients underwent CT-based postimplant dosimetric analysis 1 month after implantation. As part of this analysis, DVH were generated for the prostate and total SV volume (SVT). In addition, the SV was divided into 6-mm-thick volumes identified as SV1, SV2, SV3, SV4, and SV5 starting from the junction of the prostate and SV and extending distally. DVH were also generated for these structures. Delivered dose was defined as the D90 (dose delivered to 90% of the organ on DVH).

RESULTS

The median volumes in cc of the prostate, SVT, SV1, SV2, SV3, SV4, and SV5 were 34.33, 9.75, 2.7, 3.48, 2.92, 3.18, and 1.96 respectively. The SVT contained from 0-9 seeds (median 2). There was little dose delivered to the SVT and SV volumes from the implanted prostate. The median D90 values for the prostate, SVT, SV1, SV2, SV3, SV4, and SV5 were 8615 cGy, 675 cGy, 3100 cGy, 1329 cGy, 553 cGy, 246 cGy, and 67 cGy, respectively. The dose delivered to the prostate covered small percentages of SV. The percents of SV volumes covered by the prostate D90 were 11, 35, 3.3, 0, 0, and 0 for SVT, SV1, SV2, SV3, SV4, and SV5, respectively.

CONCLUSIONS

DVH analysis of the SV reveals that dose generated from an implanted prostate contributes little to the SV. Those patients at high risk for SV involvement may be undertreated with combined EBRT to prophylactic doses and prostate implantation.

Intra- and inter-observer variability in contouring prostate and seminal vesicles: implications for conformal treatment planning

BACKGROUND AND PURPOSE

Accurate contouring of the clinical target volume (CTV) is a fundamental prerequisite for successful conformal radiotherapy of prostate cancer. The purpose of this study was to investigate intra- and inter-observer variability in contouring prostate (P) and seminal vesicles (SV) and its impact on conformal treatment planning in our working conditions.

MATERIALS AND METHODS

Inter-observer variability was investigated by asking five well-trained radiotherapists of contouring on CT images the P and the SV of six supine-positioned patients previously treated with conformal techniques. Short-term intra-observer variability was assessed by asking the radiotherapists to contour the P and SV of one patient for a second time, just after the first contouring. The differences among the inserted volumes were considered for both intra- and inter-observer variability. Regarding intra-observer variability, the differences between the two inserted contours were estimated by taking the relative differences in correspondence to the CT slices on BEV plots (antero-posterior and left-right beams). Concerning inter-observer variability, the distances between the internal and external envelopes of the inserted contours (named projected diagnostic uncertainties or PDUs) and the distances from the mean inserted contours (named mean contour distances or MCDs) were measured from BEV plots (i.e. parallel to the CT slices).

RESULTS

Intra-observer variability was relatively small (the average percentage variation of the volume was approximately 5%; SD of the differences measured on BEV plots within 1.8 mm). Concerning inter-observer variability, the percentage SD of the inserted volumes ranged from 10 to 18%. Differences equal to 1 cm in the cranio-caudal extension of P + SV were found in four out of six patients. The largest inter-observer variability was found when considering the anterior margin in the left-right beam of P top (MCD = 7.1 mm, 1 SD). Relatively high values for MCDs were also found for P bottom, for the posterior and lateral margins of P top (2.6 and 3.1 mm, respectively, I SD) and for the anterior margin of SV (2.8 mm, 1 SD). Relatively small values were found for P central (from 1.4 to 2.0 mm, 1 SD) and the posterior margin of SV (1.5 mm, 1 SD).

CONCLUSIONS

The application of larger margins taking inter-observer variability into account should be taken into consideration for the anterior and the lateral margins of SV and P top and for the lateral margin of P. The impact of short-term intra-observer variability does not seem to be relevant.