Prostate cancer radiation dose response: results of the M. D. Anderson phase III randomized trial

A comparison of dose-volume constraints derived using peak and longitudinal definitions of late rectal toxicity

BACKGROUND AND PURPOSE

Accurate reporting of complications following radiotherapy is an important part of the feedback loop to improve radiotherapy techniques. The definition of toxicity is normally regarded as the maximum or peak (P) grade of toxicity reported over the follow-up period. An alternative definition (integrated longitudinal toxicity (ILT)) is proposed which takes into account both the severity and the duration of the complication.

METHODS AND MATERIALS

In this work, both definitions of toxicity were used to derive dose-volume constraints for six specific endpoints of late rectal toxicity from a cohort of patients who received prostate radiotherapy in the MRC RT01 trial. The dose-volume constraints were derived using ROC analysis for 30, 40, 50, 60, 65 and 70 Gy.

RESULTS

Statistically significant dose-volume constraints were not derived for all dose levels tested for each endpoint and toxicity definition. However, where both definitions produced constraints, there was generally good agreement. Variation in the derived dose-volume constraints was observed to be larger between endpoints than between the two definitions of toxicity. For one endpoint (stool frequency (LENT/SOM)) statistically significant dose-volume constraints were only derived using ILT.

CONCLUSIONS

The longitudinal definition of toxicity (ILT) produced results consistent with those derived using peak toxicity and in some cases provided additional information which was not seen by analysing peak toxicity alone.

Validation of functional imaging with pathology for tumor delineation in the prostate

INTRODUCTION

A study was performed to validate magnetic resonance (MR) based prostate tumor delineations with pathology.

MATERIAL AND METHODS

Five patients with biopsy proven prostate cancer underwent a T2 weighted (T2w), diffusion weighted MRI (DW-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) scan before prostatectomy. Suspicious regions were delineated based on all available MR information. After prostatectomy whole-mount hematoxylin-eosin stained (H&E) sections were made. Tumor tissue was delineated on the H&E stained sections and compared with the MR based delineations. The registration accuracy between the MR images and H&E stained sections was estimated.

RESULTS

A tumor coverage of 44-89% was reached by the MR based tumor delineations. The application of a margin of approximately 5mm to the MR based tumor delineations yielded a tumor coverage of 85-100% in all patients. Errors created during the registration procedure were 2-3mm, which cannot completely explain the limited tumor coverage.

CONCLUSIONS

An accurate tissue processing and registration method was presented (registration error 2-3mm), which enables the validation of MR based tumor delineations with pathology. Reasonable tumor coverage of about 85% and larger was found when applying a margin of approximately 5 mm to the MR based tumor delineations.

Stereotactic body radiotherapy: a review

Stereotactic body radiotherapy (SBRT) combines the challenge of meeting the stringent dosimetric requirements of stereotactic radiosurgery with that of accounting for the physiological movement of tumour and normal tissue. Here we present an overview of the history and development of SBRT and discuss the radiobiological rationale upon which it is based. The published results of SBRT for lung, liver, pancreas, kidney, prostate and spinal lesions are reviewed and summarised. The current evidence base is appraised and important ongoing trials are identified.

Radiation dose escalation for localized prostate cancer: intensity-modulated radiotherapy versus permanent transperineal brachytherapy

BACKGROUND

In the current study, the effects of dose escalation for localized prostate cancer treatment with intensity-modulated radiotherapy (IMRT) or permanent transperineal brachytherapy (BRT) in comparison with conventional dose 3-dimensional conformal radiotherapy (3D-CRT) were evaluated.

METHODS

This study included 853 patients; 270 received conventional dose 3D-CRT, 314 received high-dose IMRT, 225 received BRT, and 44 received external beam radiotherapy (EBRT) + BRT boost. The median radiation doses were 68.4 grays (Gy) for 3D-CRT and 75.6 Gy for IMRT. BRT patients received a prescribed dose of 144 Gy with iodine-125 (I-125) or 120 Gy with palladium-103 (Pd-103), respectively. Patients treated with EBRT + BRT received 45 Gy of EBRT plus a boost of 110 Gy with I-125 or 90 Gy with Pd-103. Risk group categories were low risk (T1-T2 disease, prostate-specific antigen level <or=10 ng/mL, and a Gleason score <or=6), intermediate risk (increase in value of 1 of the factors), and high risk (increase in value of >or=2 factors).

RESULTS

With a median follow-up of 58 months, the 5-year biochemical control (bNED) rates were 74% for 3D-CRT, 87% for IMRT, 94% for BRT, and 94% for EBRT + BRT (P <.0001). For the intermediate-risk group, high-dose IMRT, BRT, or EBRT + BRT achieved significantly better bNED rates than 3D-CRT (P <.0001), whereas no improvement was noted for the low-risk group (P = .22). There was no increase in gastrointestinal (GI) toxicity from high-dose IMRT compared with conventional dose 3D-CRT, although there was more grade 2 genitourinary (GU) toxicity (toxicities were graded at the time of each follow-up visit using a modified Radiation Therapy Oncology Group [RTOG] scale). BRT caused more GU but less GI toxicity, whereas EBRT + BRT caused more late GU and GI toxicity than IMRT or 3D-CRT.

CONCLUSIONS

The data from the current study indicate that radiation dose escalation improved the bNED rate for the intermediate-risk group. IMRT caused less acute and late GU toxicity than BRT or EBRT + BRT.

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.

A prospective phase III randomized trial of hypofractionation versus conventional fractionation in patients with high-risk prostate cancer

PURPOSE

To compare the toxicity and efficacy of hypofractionated (62 Gy/20 fractions/5 weeks, 4 fractions per week) vs. conventional fractionation radiotherapy (80 Gy/40 fractions/8 weeks) in patients with high-risk prostate cancer.

METHODS AND MATERIALS

From January 2003 to December 2007, 168 patients were randomized to receive either hypofractionated or conventional fractionated schedules of three-dimensional conformal radiotherapy to the prostate and seminal vesicles. All patients received a 9-month course of total androgen deprivation (TAD), and radiotherapy started 2 months thereafter.

RESULTS

The median (range) follow-up was 32 (8-66) and 35 (7-64) months in the hypofractionation and conventional fractionation arms, respectively. No difference was found for late toxicity between the two treatment groups, with 3-year Grade 2 rates of 17% and 16% for gastrointestinal and 14% and 11% for genitourinary in the hypofractionation and conventional fractionation groups, respectively. The 3-year freedom from biochemical failure (FFBF) rates were 87% and 79% in the hypofractionation and conventional fractionation groups, respectively (p = 0.035). The 3-year FFBF rates in patients at a very high risk (i.e., pretreatment prostate-specific antigen (iPSA) >20 ng/mL, Gleason score >or=8, or T >or=2c), were 88% and 76% (p = 0.014) in the former and latter arm, respectively. The multivariate Cox analysis confirmed fractionation, iPSA, and Gleason score as significant prognostic factors.

CONCLUSIONS

Our findings suggest that late toxicity is equivalent between the two treatment groups and that the hypofractionated schedule used in this trial is superior to the conventional fractionation in terms of FFBF.

Anti-tumor effect of small interfering RNA targeting the androgen receptor in human androgen-independent prostate cancer cells

Early phase prostate cancer is usually androgen-dependent, with the androgen/androgen receptor (AR) signaling pathway playing a central role. At this stage, the cancer responds well to androgen ablation therapy, but prostate cancers eventually acquire androgen independence and more aggressive phenotypes. Several studies, however, have shown that the majority of tumors still express functional AR, which is often amplified and mutated. To determine if the AR is a plausible therapeutic target, we investigated the anti-tumor effect of small interfering RNAs targeting the AR (siAR) in the human prostate cancer cells, LNCaP and 22Rv1, which express mutated AR. In both types of cells, transfection of siAR suppressed mutated AR expression and significantly reduced cell growth. Furthermore, atelocollagen-mediated systemic siAR administration markedly inhibited the growth of 22Rv1 cells subcutaneously xenografted in castrated nude mice. These results suggest that the AR is still a key therapeutic target even in androgen-independent prostate cancer (AIPC). Silencing of AR expression in AIPC opens promising therapeutic perspectives.

Image guided dose escalated prostate radiotherapy: still room to improve

BACKGROUND

Prostate radiotherapy (RT) dose escalation has been reported to result in improved biochemical control at the cost of greater late toxicity. We report on the application of 79.8 Gy in 42 fractions of prostate image guided RT (IGRT). The primary objective was to assess 5-year biochemical control and potential prognostic factors by the Phoenix definition. Secondary endpoints included acute and late toxicity by the Radiotherapy Oncology Group (RTOG) scoring scales.

METHODS

From October/2001 and June/2003, 259 men were treated with at least 2-years follow-up. 59 patients had low, 163 intermediate and 37 high risk disease. 43 had adjuvant hormonal therapy (HT), mostly for high- or multiple risk factor intermediate-risk disease (n = 25). They received either 3-dimensional conformal RT (3DCRT, n = 226) or intensity modulated RT (IMRT) including daily on-line IGRT with intraprostatic fiducial markers.

RESULTS

Median follow-up was 67.8 months (range 24.4-84.7). There was no severe (grade 3-4) acute toxicity, and grade 2 acute gastrointestinal (GI) toxicity was unusual (10.1%). The 5-year incidence of grade 2-3 late GI and genitourinary (GU) toxicity was 13.7% and 12.1%, with corresponding grade 3 figures of 3.5% and 2.0% respectively. HT had an association with an increased risk of grade 2-3 late GI toxicity (11% v 21%, p = 0.018). Using the Phoenix definition for biochemical failure, the 5 year-bNED is 88.4%, 76.5% and 77.9% for low, intermediate and high risk patients respectively. On univariate analysis, T-category and Gleason grade correlated with Phoenix bNED (p = 0.006 and 0.039 respectively). Hormonal therapy was not a significant prognostic factor on uni- or multi-variate analysis. Men with positive prostate biopsies following RT had a lower chance of bNED at 5 years (34.4% v 64.3%; p = 0.147).

CONCLUSION

IGRT to 79.8 Gy results in favourable rates of late toxicity compared with published non-IGRT treated cohorts. Future avenues of investigation for toxicity reduction include IMRT, margin reduction, and dose modulation targeted to sites of disease burden. Further work is required to maximize efficacy beyond that achieved through radiation dose escalation alone.

Prostate positioning errors associated with two automatic registration based image guidance strategies

Daily image guidance for helical tomotherapy prostate patients is based on the registration of pretreatment megavoltage CT (MVCT) images and the original planning CT. The goal of registration, whether manual or automatic, is the overlap of the prostate; otherwise prostate misplacement may compromise the efficacy of treatment or lead to increased toxicity. A previous study demonstrated that without the aid of implanted fiducials, manual registration results in inaccurate prostate positioning. The objective of this work is to quantify prostate misplacement that results from automatic bone matching (BM) and image matching (IM) registration algorithms. 204 MVCT images from eight high‐risk tomotherapy prostate patients were incorporated into this retrospective study. BM and IM registration algorithms – based on maximization of mutual information of bony anatomy only and the entire image, respectively – were used to independently register MVCT images to their respective planning images. A correlation coefficient based algorithm that uses known planning CT contour information was used for automatic prostate localization in each MVCT image. Daily prostate misplacement was determined by repositioning as calculated from the BM and the IM algorithms. Mean (±SD) and maximum 3D prostate positioning errors were 3.7±2.1mm and 11.8 mm for bone matching, and 4.6±2.3mm and 11.5 mm for image matching. In terms of translational directions, IM would lead to prostate positioning error ≥3mm in any of the LR, AP or SI directions in 62% of treatment fractions. The corresponding value for BM is 51%. The values for positioning errors ≥5mm were 29% and 17% for IM and BM, respectively. This data suggests automatic daily image guidance for tomotherapy prostate patients should be based on bone matching instead of image matching.

PACS number: 87.19.xj, 87.57.nj

Focal salvage guided by T2-weighted and dynamic contrast-enhanced magnetic resonance imaging for prostate cancer recurrences

PURPOSE

Salvage treatment of the entire prostate for local recurrent cancer after primary radiotherapy is associated with high toxicity rates. Our goal was to show that, using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for the visualization of a recurrence, focal salvage treatment can be performed, with, potentially, a reduction in toxicity.

METHODS AND MATERIALS

We performed MRI, including a DCE sequence, in 7 patients with biopsy-proven locally recurrent prostate cancer. The specific regions of interest suspect for containing tumor were delineated using DCE and T(2)-weighted MRI scans. Subsequently, focal salvage high-dose-rate brachytherapy plans were created to illustrate the principle of focal salvage. Total salvage treatment plans were also created for comparison.

RESULTS

The transfer constant (K(trans)) values from the DCE were 0.33-0.67 min(-1) for areas suspect for tumor and 0.07-0.25 min(-1) for normal tissue. In 4 cases, a focal salvage plan could be generated; 93-100% of the gross tumor volume was covered with the prescribed dose, with relative sparing of the bladder, rectum, and urethra. In the total salvage plans, 24-53% of the gross tumor volume was covered, and the organs at risk received high doses. In 3 cases, a focal salvage plan could not be created because of multifocal tumor, seminal vesicle extension, or capsular extension.

CONCLUSION

Focal salvage treatment plans can be created in patients with local recurrent prostate cancer after radiotherapy. DCE-MRI supports the localization of the target area. This could lead to less toxicity in patients with local recurrent prostate cancer.

Protective effects of selenomethionine against ionizing radiation under the modulation of p53 tumor suppressor

Ionizing radiation (IR) therapy has been widely employed in the treatment of cancer. However, certain issues, including toxicity, have been raised in conjunction with IR therapy for cancer. Recently, selenomethionine (SeMet) as an antioxidant has been the subject of a great deal of attention for its chemopreventive effects. In this study, we found that DNA repair activity has been enhanced in response to SeMet against IR. In addition, our data showed that p53 functional activity was significantly reduced against IR in the cells expressing a mutant form of redox factor 1 (Ref-1) contrast with Ref-1 wild-type cells treated with SeMet, suggesting that p53 activation under the modulation of Ref-1 might play an important role in IR-treated cells in the presence of SeMet. Furthermore, IR-induced micronuclei numbers were also reduced after treatment with SeMet, strongly implicating protection by SeMet in genomic stability against IR-induced genotoxicity. From this study, we suggest that the p53-mediated protective mechanism of SeMet might provide clues for reducing side effects of IR therapy.

Excellent results from high dose rate brachytherapy and external beam for prostate cancer are not improved by androgen deprivation

PURPOSE

Prostate cancer patients treated with high dose rate brachytherapy and external beam radiation therapy were stratified by risk group for analysis to determine whether androgen deprivation therapy (ADT) affected outcome.

METHODS

From 1991 through 1998, 411 patients were treated with 4 fractions of 5.5 to 6.0 Gy high dose rate brachytherapy and a total of 36.0 to 39.6 Gy external beam radiation therapy (dose escalation over time). The dataset was prospective. Administration of ADT was not randomized, but it was the primary study variable. During this period, ADT was administered across all risk groups for various indications. It did not necessarily reflect advanced disease or large prostate size. There were 200 patients in the "ADT Group" (20% low, 48% intermediate, and 32% high risk) and 211 in the "No ADT Group" (33% low, 44% intermediate, 23% high risk). The median follow-up was 6.4 years. Cases were grouped according to low, intermediate, and high risk groups to reduce the effects of unrecognized selection bias for or against the ADT group. The prostate specific antigen (PSA) nadir plus 2.0 ng/ml (nadir + 2) was used as the biochemical control end point. Local control, PSA progression-free survival, distant metastasis free survival, and cause-specific survival were compared.

RESULTS

The 10 year PSA-PFS (nadir + 2) for all 411 patients was 81%. The results stratified by risk group were: low 92%, intermediate 87%, and high 63%. The low and intermediate risk groups were not statistically different from one another but they were both significantly better than the high risk group. ADT versus No ADT 10-year survival showed no significant differences for any outcome variable: PSA-PFS (83% vs. 81% ns), local control (97% vs. 99%), distant metastasis free survival (94% vs. 97%), and cause-specific survival (97% vs. 97%). A subset analysis of PSA-PFS (nadir + 2) stratified by risk group revealed no difference between the ADT and No ADT groups.

CONCLUSIONS

high dose rate brachytherapy and external beam radiation therapy resulted in high rates of local control, PSA progression-free survival, distant metastasis free survival, and cause-specific survival in all risk groups. Improved outcome from the use of androgen deprivation was not observed.

EUS-guided fiducial placement before targeted radiation therapy for prostate cancer

BACKGROUND

Image-guided radiation therapy allows the delivery of precisely aimed radiation beams to tumors while minimizing radiation to adjacent normal tissue. This is particularly important in the prostate, a moving target whose positioning depends on the dynamics of its neighboring bladder and rectum. Targeted radiation therapy can be achieved by using implantable radiographic markers, or fiducials, which serve as reference points to accurately delineate tumors.

OBJECTIVE

To determine the feasibility and safety of placing fiducials in the prostate under linear array EUS guidance to facilitate targeted radiation therapy.

DESIGN

Retrospective analysis of a prospective database.

SETTING

University of Miami Hospital and Clinics, a tertiary cancer referral center.

PATIENTS

Localized prostate cancer patients scheduled to undergo intensity-modulated radiation therapy.

INTERVENTIONS

A total of 16 patients underwent EUS-guided fiducial placement to delineate the prostate before planned radiation therapy.

RESULTS

Fiducial placement was successful in all patients (100%). A total of 71 gold markers were deployed in a 4-quadrant manner outlining the prostate. Seven of 16 patients had an additional fiducial placed to ensure adequate prostate delineation. Patients tolerated the procedure well with minimal discomfort. No complications developed from the procedure.

LIMITATIONS

Single-center experience, small sample size.

CONCLUSIONS

EUS-guided placement of fiducials to facilitate image-guided radiation therapy for prostate cancer is a feasible alternative to transperineal or transrectal US approaches, thereby adding to the expanding list of indications for linear EUS. This procedure can be safely performed by endosonographers familiar with perirectal anatomy and transrectal FNA technique.

A prediction study on radiation-induced second malignancies for IMRT treatment delivery

Low-level peripheral organ dose and its effect on second malignancies for patients undergoing radiation therapy have been reported in the literature. However, a comprehensive database outlining the treatment modalities, the tumor location, and a quantification of the overall relative risk of second malignancies is rather limited. In this work, we quantify the relative risks or percent likelihood of second malignancies for patients undergoing IMRT and conventional radiotherapy for four different tumor sites: breast, head and neck, lung, and prostate. We utilize Monte Carlo methods based on actual patient plans to compute the whole body effective dose equivalent for each plan and then deduce the percent likelihood of the occurrence of second malignancy. Based on an evaluation of over 30 actual patient plans and Monte Carlo simulations using 6, 10, and 18MV photon beam energies, we observed that the IMRT patients treated for head and neck cancer showed a 40% increase in risk for developing a second malignancy compared to those treated with conventional radiotherapy. The increase in risk for prostrate patients was 30% while the IMRT lung patients gave the highest relative risk almost tripling that observed in their conventionally treated counterparts. There was negligible difference in risk between breast patients undergoing IMRT treatment versus conventional therapy. The overall relative risk of radiation induced malignancy observed was below 6% in all treatment plans considered.

Difficulties and potential of correlating local recurrences in prostate cancer with the delivered local dose

In the previous decades the distinction between a local relapse and distant metastases was difficult to accomplish in an early stage. As a consequence, a failure could only be coarsely related to the original radiotherapy treatment. Currently, due to better imaging and position verification techniques, the actual dose within the prostate can be estimated, taking position uncertainties into account. Furthermore, advanced functional MRI techniques, such as MR spectroscopy (MRS) and dynamic contrast-enhanced MRI (DCE-MRI), increase the chance of localizing a local recurrence within the prostate. With this information the correlation between the actual previously delivered dose and a local relapse can be established, using non-rigid registration of the planning CT and the post-recurrence MRI. The current study describes the possibilities and problems in obtaining this correlation. This serves as a framework for investigating a reliable dose effect relationship in the future.

Development of a prostate cancer metagram: a solution to the dilemma of which prediction tool to use in patient counseling

Many treatment options are available to the human with clinically localized prostate cancer, including surgery, radiation, and even active surveillance. To the authors' knowledge, there is no consensus on the optimal management of this patient population, with most clinicians tending to recommend the treatment with which they are most familiar. Effective patient counseling allowing informed decision making can be best achieved with a formalized system that offers accurate predictions of outcomes for all available treatment approaches. The authors organized the currently available prostate cancer prediction tools toward the formation of a metagram that can be used to tailor management to the individual patient. A comprehensive review of the literature was performed to identify published prediction tools intended for use in prostate cancer. Tools were categorized by a combination of treatment modality and the outcome being predicted, and incorporated into a metagram constructed of 16 different treatment options and 10 outcomes related to cancer control, survival, and morbidity. A search of the literature revealed 44 prostate cancer prediction tools that assessed at least 1 of the 160 treatment/outcome combinations that comprise the metagram. Only 31 cells of the metagram were populated with currently available tools. Prediction tools offer the most accurate estimates of outcomes in prostate cancer, but their current role in patient counseling is complicated by the large number of existing tools, as well as a lack of comparative data. To address this, the authors incorporated the most relevant prediction tools currently available into a prostate cancer metagram that may offer evidence-based and individualized predictions for multiple endpoints after all available treatment options in clinically localized prostate cancer. The metagram also reveals areas of deficiency in the current catalog of prediction tools. Many more prediction tools are needed. Cancer 2009;115(13 suppl):3039-45. (c) 2009 American Cancer Society.

Radiobiological model comparison of 3D conformal radiotherapy and IMRT plans for the treatment of prostate cancer

The main aim of radiotherapy is to deliver a dose of radiation that is high enough to destroy the tumour cells while at the same time minimising the damage to normal healthy tissues. Clinically, this has been achieved by assigning a prescription dose to the tumour volume and a set of dose constraints on critical structures. Once an optimal treatment plan has been achieved the dosimetry is assessed using the physical parameters of dose and volume. There has been an interest in using radiobiological parameters to evaluate and predict the outcome of a treatment plan in terms of both a tumour control probability (TCP) and a normal tissue complication probability (NTCP). In this study, simple radiobiological models that are available in a commercial treatment planning system were used to compare three dimensional conformal radiotherapy treatments (3D-CRT) and intensity modulated radiotherapy (IMRT) treatments of the prostate. Initially both 3D-CRT and IMRT were planned for 2 Gy/fraction to a total dose of 60 Gy to the prostate. The sensitivity of the TCP and the NTCP to both conventional dose escalation and hypo-fractionation was investigated. The biological responses were calculated using the Källman S-model. The complication free tumour control probability (P+) is generated from the combined NTCP and TCP response values. It has been suggested that the alpha/beta ratio for prostate carcinoma cells may be lower than for most other tumour cell types. The effect of this on the modelled biological response for the different fractionation schedules was also investigated.

Dose escalation to the dominant intraprostatic lesion defined by sextant biopsy in a permanent prostate I-125 implant: a prospective comparative toxicity analysis

PURPOSE

Using real-time intraoperative inverse-planned permanent seed prostate implant (RTIOP/PSI), multiple core biopsy maps, and three-dimensional ultrasound guidance, we planned a boost volume (BV) within the prostate to which hyperdosage was delivered selectively. The aim of this study was to investigate the potential negative effects of such a procedure.

METHODS AND MATERIALS

Patients treated with RTIOP/PSI for localized prostate cancer with topographic biopsy results received an intraprostatic boost (boost group [BG]). They were compared with patients treated with a standard plan (reference group [RG]). Plans were generated using a simulated annealing inverse planning algorithm. Prospectively recorded urinary, rectal, and sexual toxicities and dosimetric parameters were compared between groups.

RESULTS

The study included 120 patients treated with boost technique who were compared with 70 patients treated with a standard plan. Boost technique did not significantly change the number of seeds (55.1/RG vs. 53.6/BG). The intraoperative prostate V150 was slightly higher in BG (75.2/RG vs. 77.2/BG, p = 0.039). Urethra V100, urethra D90, and rectal D50 were significantly lower in the BG. No significant differences were seen in acute or late urinary, rectal, or sexual toxicities.

CONCLUSIONS

Because there were no differences between the groups in acute and late toxicities, we believe that BV can be planned and delivered to the dominant intraprostatic lesion without increasing toxicity. It is too soon to say whether a boost technique will ultimately increase local control.

Higher-than-conventional radiation doses in localized prostate cancer treatment: a meta-analysis of randomized, controlled trials

PURPOSE

To determine in a meta-analysis whether the outcomes in men with localized prostate cancer treated with high-dose radiotherapy (HDRT) are better than those in men treated with conventional-dose radiotherapy (CDRT), by quantifying the effect of the total dose of radiotherapy on biochemical control (BC).

METHODS AND MATERIALS

The MEDLINE, EMBASE, CANCERLIT, and Cochrane Library databases, as well as the proceedings of annual meetings, were systematically searched to identify randomized, controlled studies comparing HDRT with CDRT for localized prostate cancer. To evaluate the dose-response relationship, we conducted a meta-regression analysis of BC ratios by means of weighted linear regression.

RESULTS

Seven RCTs with a total patient population of 2812 were identified that met the study criteria. Pooled results from these RCTs showed a significant reduction in the incidence of biochemical failure in those patients with prostate cancer treated with HDRT (p < 0.0001). However, there was no difference in the mortality rate (p = 0.38) and specific prostate cancer mortality rates (p = 0.45) between the groups receiving HDRT and CDRT. However, there were more cases of late Grade >2 gastrointestinal toxicity after HDRT than after CDRT. In the subgroup analysis, patients classified as being at low (p = 0.007), intermediate (p < 0.0001), and high risk (p < 0.0001) of biochemical failure all showed a benefit from HDRT. The meta-regression analysis also detected a linear correlation between the total dose of radiotherapy and biochemical failure (BC = -67.3 + [1.8 x radiotherapy total dose in Gy]; p = 0.04).

CONCLUSIONS

Our meta-analysis showed that HDRT is superior to CDRT in preventing biochemical failure in low-, intermediate-, and high-risk prostate cancer patients, suggesting that this should be offered as a treatment for all patients, regardless of their risk status.

Assessing prostate, bladder and rectal doses during image guided radiation therapy--need for plan adaptation?

The primary application of Image‐Guided Radiotherapy (IGRT) in the treatment of localized prostate cancer has been to assist precise dose delivery to the tumor. With the ability to use in‐room Computed Tomography (CT) imaging modalities, the prostate, bladder and rectum can be imaged before each treatment and the actual doses delivered to these organs can be tracked using anatomy of the day. This study evaluates the dosimetric uncertainties caused by interfraction organ variation during IGRT for 10 patients using kilovoltage cone beam CT (kvCBCT) on the Elekta Synergy system and megavoltage CT (MVCT) on the TomoTherapy Hi·Art System. The actual delivered doses to the prostate, bladder and rectum were based on dose recomputation using CT anatomy of the day. The feasibility of dose calculation accuracy in kvCBCT images from the Elekta Synergy system was investigated using the ComTom phantom. Additionally, low contrast resolution, image uniformity, and spatial resolution between the three imaging modalities of kilovoltage CT (kvCT), kvCBCT and MVCT images, were quantitatively evaluated using the Catphan 600 phantom. The Planned Adaptive software was used on the TomoTherapy Hi·Art system to construct a cumulative Dose Volume Histogram (DVH), incorporating anatomical information provided by the daily MVCT scans. The cumulative DVH was examined to identify large deviation (10% or greater) between the planned and delivered mean doses. The study proposes a framework that applies the cumulative DVH to evaluate and adapt plans that are based on actual delivered doses. Due to the large deviation in CT number (›300 HU) between the kvCBCT images and the kvCT, a direct dose recomputation on the kvCBCT images from the Elekta Synergy system was found to be inaccurate. The maximum deviation to the prostate was only 2.7% in our kvCBCT study, when compared to the daily prescribed dose. However, there was a large daily variation in rectum and bladder doses based on the anatomy of the day. The maximum variation in rectum and bladder volumes receiving the percentage of prescribed dose was 12% and 40%, respectively. We have shown that by using Planned Adaptive software on the TomoTherapy Hi·Art system, plans can be adapted based on the image feedback from daily MVCT scans to allow the actual delivered doses to closely track the original planned doses.

PACS number: 87.53.Tf

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.

3-D conformal treatment of prostate cancer to 74 Gy vs. high-dose-rate brachytherapy boost: a cross-sectional quality-of-life survey

The effects of two modalities of dose-escalated radiotherapy on health-related quality of life (HRQOL) were compared. Forty-one consecutive patients were treated with a 3-D conformal (3-DC) boost to 74 Gy, and 43 with high-dose rate (HDR) brachytherapy boost (2x9 Gy), following 3-D conformal treatment to 46 Gy. Median age was 70 years in both groups, median initial PSA was 7.9 microg/l in 3-DC boost patients and 8.1 microg/l in HDR boost patients. Stage was <or=T2 in 66% and 67% and Gleason score was >or=7 in 52% and 47%, respectively. HRQOL was assessed cross-sectionally using EORTC QLQ-C30 and organ-specific PR25 modules 3--32 (median 19) and 4--25 (median 14) months after treatment, respectively. Questionnaires were completed by 93% and 97% of patients, respectively. Diarrhea and insomnia scores were significantly increased in both groups. In the PR25 module, scores of 3-DC boost and HDR boost patients for urinary, bowel and treatment-related symptoms were similar. Among responders, 34% of 3-DC boost patients and 86% of HDR boost patients had severe erectile problems. Dose escalation in prostate cancer by either 3-DC boost to 74 Gy or HDR brachytherapy boost appears to result in similar HRQOL profiles.

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

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

2D versus 3D radiation therapy for prostate carcinoma: a direct comparison of dose volume parameters

That three dimensional (3D) planning for radiation therapy (RT) of carcinoma of the prostate (CaP) improves radiation dosimetry to the tumour and reduces dose to the rectum and bladder compared with 2D planning, has not been properly evaluated. We addressed this by downloading the CT data files of twenty-two patients who had completed 2D planned RT for CaP onto a 3D planning system and re-planning RT using the same four field technique and dose prescription as the 2D technique. The radiation dose at 100%, 90%, 50% and 0% volumes (D100, D90, D50 and D0) of the Dose Volume Histograms (DVH's) of the GTV, PTV, rectum and bladder, the area under the curves of each DVH and the field sizes were evaluated and compared between the two sets of plans. Repeated measured t-tests were used to compare the means of the different measurements. The D100, D90 and D50 of the GTV, PTV and rectum were increased for the 3D versus the 2D plans (p < 0.05 for each parameter). The area under the rectal DVH was also greater for the 3D plans (p < 0.05). These changes are attributable to the larger field sizes, particularly the length in the 3D compared with the 2D plans.

Developments in radiotherapy

A systematic assessment of radiotherapy for cancer was conducted by The Swedish Council on Technology Assessment in Health Care (SBU) in 2001. The assessment included a review of future developments in radiotherapy and an estimate of the potential benefits of improved radiotherapy in Sweden. The conclusions reached from this review can be summarized as: Successively better knowledge is available on dose-response relationships for tumours and normal tissues at different fractionation schedules and treated volumes. Optimization of dose levels and fractionation schedules should improve the treatment outcome. Improved treatment results may be expected with even more optimized fractionation schedules. The radiosensitivity of the tumour is dependent on the availability of free oxygen in the cells. The oxygen effect has been studied for a long time and new knowledge has emerged, but there is still no consensus on the best way to minimize its negative effect in the treatment of hypoxic tumours. Development in imaging techniques is rapid, improving accuracy in outlining targets and organs at risk. This is a prerequisite for advanced treatment planning. More accurate treatment can be obtained using all the computer techniques that are successively made available for calculating dose distributions, controlling the accelerator and multileaf collimator (MLC) and checking patient set-up. Optimized treatment plans can be achieved using inverse dose planning and intensity modulation radiation therapy (IMRT). Optimization algorithms based on biological data from clinical trials could be a part of future dose planning. New genetic markers might be developed that give a measure of the radiation responsiveness of tumours and normal tissue. This could lead to more individualized treatments. New types of radiation sources may be expected: protons, light ions, and improved beams (and compounds) for boron neutron capture therapy (BNCT). Proton accelerators with scanned-beam systems and energy modulation give good dose distribution. The results reported with carbon ions from Japan and Germany are promising. An interesting development is to verify the dose and position for the irradiated volume with PET on line. Safer margins are obtained and the treatment volume can thus be limited. Very large accelerators are needed to accelerate the carbon ions. Still, it should be possible to keep the costs per patient at the same level as those for other types of advanced radiotherapy, since far fewer treatments per patient are needed. It might also be possible to treat new groups of patients. Increased resources are needed to introduce all the currently available techniques. New types of particle accelerators require large investments and a new structure of radiotherapy in Sweden.

Long-term results of a phase II trial of high-dose radiotherapy (60 Gy) and UFT/l-leucovorin in patients with non-resectable locally advanced rectal cancer (LARC)

BACKGROUND

Preoperative radiochemotherapy is a cornerstone in patients with non- resectable locally advanced rectal cancer (LARC). To improve outcome (number of R0 resections and survival) high-dose radiotherapy (RT) was combined with oral UFT/l-leucovorin to allow tumour regression before radical intended surgery.

METHODS

Pelvic RT was delivered with megavoltage photons using a 5 field technique. RT was CT-based, given 5 days a week through one posterior field and two lateral fields (48.6 Gy/27 fractions) to encompass the primary tumour and the regional lymph nodes. In addition, the tumour bed received a concurrent boost (5.4 Gy/27 fractions) and a final boost (6 Gy/3 fractions); thus GTV received 60 Gy/30 fractions. Concurrent with RT patients received a daily dose of oral UFT 300 mg/m(2) plus l-leucovorin 22.5 mg 5/7 days (divided in three doses).

RESULTS

From September 2000 to November 2004, 52 patients (median age 60 years (32-83); median PS 0 (0-2)) with LARC (36 primary, 16 recurrent) were included in this phase II study. All but three patients received the planned 60 Gy, median duration of RT was 42 days (25-49). Toxicity was very modest; only four patients had a dose reduction of UFT. No hematological toxicity of clinical significance was seen. Non-hematological toxicity grade 1 (GI-toxicity, fatigue and/or dysuria) was frequently observed but only four patients experienced grade 3 toxicity (diarrhoea and/or nausea/vomiting). Forty patients (77%) were operated (30 R0, 5 R1, 5 R2) median 55 days (27-112) after completion of RT. Seven (13%) patients had a pathological complete response (pCR). Thirty-one patients (60%) died after median 25.4 months (1.6-45.2 months). Twenty-one patients (40%) are still alive June 2007.

CONCLUSIONS

Preoperative high-dose RT and concomitant UFT produces major regression in most patients with non-resectable LARC and thus a good chance of cure.

Subjective and objective measures of late genitourinary morbidity following hypofractionated radiotherapy in men with prostate cancer

To value the late genitourinary (GU) morbidity in men treated with a hypofractionated radiotherapy regimen for prostate cancer. Patients with intermediate risk factors according to D'Amico's criteria were selected. The hypofractionated schedule consisted of 15 fractions of 3.63 Gy delivered three times per week for a total dose of 54.3 Gy. Significant changes in storage-symptoms were not found. A significant transient worsening in the score of late effects of normal tissue late effects normal tissue task force (LENT)-subjective, objective, management, analytic (SOMA) urinary-function domain was observed at 12 months with subsequent improvement at 28 months. The assessment of voiding-symptoms and maximum urinary flow rate (Qmax) showed that no significant difference was measurable at 12 and 28 months. For PVR, a transient increase at 12 months with a subsequent decrease at 28 months was measured. No significant increase in alpha-blockers usage and in the percentage of men with pathological nonintubated uroflowmetry (NIF) was observed at 12 and 28 months. Finally, patients did not perceive any clinical worsening in their quality of life (QoL) as attested by the International Prostate Symptom Score (IPSS)-QoL. Our study seems to suggest that our hypofractionated radiotherapy schedule for the treatment of prostate cancer is safe in terms of late urinary morbidity. Further study will be required to confirm our results.

Neoadjuvant androgen deprivation for prostate volume reduction: the optimal duration in prostate cancer radiotherapy

OBJECTIVES

For locally advanced prostate cancer, the results of radiotherapy are improved by combination with androgen deprivation therapy. Volume reduction achieved with neoadjuvant hormonal treatment can facilitate dose escalation without increasing the toxicity. The optimal duration of hormonal treatment, however, is unknown. The endpoint of this study is the optimal duration of androgen deprivation for prostate volume reduction in a cohort of patients scheduled for external beam radiotherapy.

PATIENTS AND METHODS

Twenty patients scheduled for external beam radiotherapy with cT2-3No/xMo prostate cancer were treated with a luteinizing hormone releasing hormone agonist (busereline) and nonsteroidal anti-androgen (nilutamide) for 9 months consecutively. Repeated CT scan examination was performed 3-monthly to measure prostate volumes until the start of radiation therapy. The analysis of volume reduction was performed with the Wilcoxon signed ranks test.

RESULTS

The baseline median prostate volume for the cohort of patients was 82 cc (95% CI: 61-104 cc) with a median volume reduction of 31% (95% CI: 26%-35%) (P < 0.0001) after 3 months of androgen deprivation. Between 3 and 6 months, a median volume reduction of 9% (95% CI: 4%-14%) (P < 0.0001) was observed. The effect was more pronounced in large prostates (>60 cc) than in small prostates (≤60 cc). In the total cohort of patients no significant volume reduction occurred between 6 and 9 months of maximal androgen blockade (MAB).

CONCLUSIONS

In this study, we have shown that the most significant prostate volume reduction is achieved after 3 months of MAB with a maximum reduction after 6 months. Therefore, the optimal duration of neoadjuvant androgen deprivation to reduce prostate volume before prostate cancer radiotherapy is 6 months. In small prostates 3 months of hormonal treatment may be enough for maximal volume reduction.

Biochemical Control and Toxicity after Intensity-Modulated Radiation Therapy for Prostate Cancer

Intensity modulated radiation therapy (IMRT) has achieved widespread use for prostate cancer; however, in relation to this use, outcomes studies are still relatively sparse. We report a single-institutional experience in outcomes analysis with the use of IMRT for the primary management of prostate cancer. One hundred thirty consecutive patients with adenocarcinoma of the prostate were treated at a single institution using IMRT with curative intent. Thirty-six (28%) patients were classified as low-risk, 69 (53%) as intermediate-risk, and 25 (19%) as high-risk. The median dose prescription was 76 Gy to the planning target volume. Sixty-five (50%) patients received androgen deprivation therapy (ADT) for a median 4 months, starting 2 months prior to IMRT. Biochemical failure was defined as PSA > post-treatment nadir+2. Gastrointestinal (GI) and Genitourinary (GU) toxicity were defined by RTOG criteria. Median follow-up was 53 months. By NCCN risk category, 4-year biochemical control was 97%, 94%, and 87% for low, intermediate, and high-risk patients, respectively. Among disease factors, multivariable analysis demonstrated the strongest association between biochemical control and Gleason score ≤6 (p=0.0371). Therapy was well tolerated with no Grade 4 toxicity and limited grade 3 GI or GU toxicity. Acute Grade 3+ GI and GU toxicity rates were 0% and 2%, and maximal late Grade 3+ GI and GU toxicity rates were 5% and 6%, respectively. Late rectal toxicity was associated with higher volumes of RT to the rectum. By last follow-up late Grade 3+ toxicity was 2% for both GI and GU systems. In conclusion, patients treated with IMRT for prostate cancer have excellent rates of biochemical control and low rates of severe toxicity of treatment.