Intensity-Modulated Radiation Therapy for Prostate Cancer

Impact on Late Toxicity of using Transabdominal Ultrasound for Prostate Cancer Patients Treated with Intensity Modulated Radiotherapy

An analysis of the effects of using the B-mode ultrasound Acquisition and Targeting (BAT) system for positioning of prostate cancer patients receiving external beam radiotherapy (EBRT) on late gastrointestinal (GI) and genitourinary (GU) toxicity is provided. The records of 49 consecutive patients treated using the BAT were reviewed; additionally, a comparison (No-BAT) group treated in a similar manner was identified, consisting of 49 patients treated immediately prior to this BAT group. There were no other fundamental differences between the two groups. The daily BAT movements were charted and late toxicity was scored for all patients using established toxicity scales. The results demonstrated similar GU toxicity rates between the two groups, but slightly lower rates of GI toxicity in the BAT group vs. the No-BAT group. However, regression analyses revealed that no factors, including BAT use, were significantly correlated with late GI or GU toxicity. Further efforts, perhaps better undertaken in a multi-institutional setting, are needed to determine whether BAT use can significantly reduce late GI toxicity.

Some computer graphical user interfaces in radiation therapy

In this review, five graphical user interfaces (GUIs) used in radiation therapy practices and researches are introduced. They are: (1) the treatment time calculator, superficial X-ray treatment time calculator (SUPCALC) used in the superficial X-ray radiation therapy; (2) the monitor unit calculator, electron monitor unit calculator (EMUC) used in the electron radiation therapy; (3) the multileaf collimator machine file creator, sliding window intensity modulated radiotherapy (SWIMRT) used in generating fluence map for research and quality assurance in intensity modulated radiation therapy; (4) the treatment planning system, DOSCTP used in the calculation of 3D dose distribution using Monte Carlo simulation; and (5) the monitor unit calculator, photon beam monitor unit calculator (PMUC) used in photon beam radiation therapy. One common issue of these GUIs is that all user-friendly interfaces are linked to complex formulas and algorithms based on various theories, which do not have to be understood and noted by the user. In that case, user only needs to input the required information with help from graphical elements in order to produce desired results. SUPCALC is a superficial radiation treatment time calculator using the GUI technique to provide a convenient way for radiation therapist to calculate the treatment time, and keep a record for the skin cancer patient. EMUC is an electron monitor unit calculator for electron radiation therapy. Instead of doing hand calculation according to pre-determined dosimetric tables, clinical user needs only to input the required drawing of electron field in computer graphical file format, prescription dose, and beam parameters to EMUC to calculate the required monitor unit for the electron beam treatment. EMUC is based on a semi-experimental theory of sector-integration algorithm. SWIMRT is a multileaf collimator machine file creator to generate a fluence map produced by a medical linear accelerator. This machine file controls the multileaf collimator to deliver intensity modulated beams for a specific fluence map used in quality assurance or research. DOSCTP is a treatment planning system using the computed tomography images. Radiation beams (photon or electron) with different energies and field sizes produced by a linear accelerator can be placed in different positions to irradiate the tumour in the patient. DOSCTP is linked to a Monte Carlo simulation engine using the EGSnrc-based code, so that 3D dose distribution can be determined accurately for radiation therapy. Moreover, DOSCTP can be used for treatment planning of patient or small animal. PMUC is a GUI for calculation of the monitor unit based on the prescription dose of patient in photon beam radiation therapy. The calculation is based on dose corrections in changes of photon beam energy, treatment depth, field size, jaw position, beam axis, treatment distance and beam modifiers. All GUIs mentioned in this review were written either by the Microsoft Visual Basic.net or a MATLAB GUI development tool called GUIDE. In addition, all GUIs were verified and tested using measurements to ensure their accuracies were up to clinical acceptable levels for implementations.

Individualized decision-making for older men with prostate cancer: balancing cancer control with treatment consequences across the clinical spectrum

Prostate cancer (PCa) is the most prevalent non-skin cancer among men and is the second leading cause of cancer death in men. PCa has an increased incidence and prevalence in older men. Age-associated incidence is on the rise due to increased screening in the older population. This has led to a sharp rise in the detection of early stage PCa. Given the indolent nature of many prostatic malignancies, a large proportion of older men with PCa will ultimately die from other causes. As a result, physicians and patients are faced with the challenge of identifying optimal treatment strategies for localized PCa, biochemically recurrent PCa and later-stage PCa. Age-related changes can impact tolerance of hormonal therapy and chemotherapy in men with metastatic disease and shift the risk-benefit ratio of these treatments. Tools such as the Comprehensive Geriatric Assessment (CGA) can help estimate remaining life expectancy and can help predict treatment-related morbidity and mortality in older men. Application of CGA in older men with PCa is important to help individualize and optimize treatment strategies. Research that integrates multidisciplinary and multidimensional assessment of PCa and the patient's overall health status is needed.

Case study of anti-1-amino-3-F-18 fluorocyclobutane-1-carboxylic acid (anti-[F-18] FACBC) to guide prostate cancer radiotherapy target design

PURPOSE OF THE REPORT

Anti-1-amino-3-F-18 fluorocyclobutane-1-carboxylic acid (FACBC) is a novel radiotracer, which has shown some promise for use with positron emission tomography (PET)/computed tomography (CT) for visualizing prostate cancer. Here we describe a case of a prostate cancer patient who underwent radiation treatment and had an FACBC scan obtained as part of a pilot study.

METHODS

We explored the potential impact of FACBC on treatment planning. We registered the FACBC acquisition with the PET/CT, which required a simple translation. Then, we did a deformable image registration of the PET/CT with the planning CT-this process allowed the FACBC-defined gross tumor volume (GTVFACBC) to be projected into the planning CT. An intensity-modulated radiotherapy (IMRT) plan (plan A) not including GTVFACBC (with final dose to 81.0 Gy) was generated, as was an IMRT plan including the GTVFACBC to a final dose of 86.4 Gy (plan B). Target coverage and normal tissue dose volume histogram (DVH) endpoints were tabulated.

RESULTS

In this particular patient, bladder constraints could not be met on any plan due to anatomic limitations. However, the impact on the rectal DVH could be assessed, and inclusion of the GTVFACBC did permit rectal DVH constraints to be met in plan B while maintaining target coverage and inhomogeneity constraints.

CONCLUSION

In our test case, it was feasible to use FACBC to guide IMRT, and highlights the role of deformable image registration of the PET/CT with the planning CT. These findings can guide future studies incorporating FACBC into treatment planning.

Dose–Volume Comparison of Proton Therapy and Intensity-Modulated Radiotherapy for Prostate Cancer

PURPOSE

The contrast in dose distribution between proton radiotherapy (RT) and intensity-modulated RT (IMRT) is unclear, particularly in regard to critical structures such as the rectum and bladder.

METHODS AND MATERIALS

Between August and November 2006, the first 10 consecutive patients treated in our Phase II low-risk prostate proton protocol (University of Florida Proton Therapy Institute protocol 0001) were reviewed. The double-scatter proton beam plans used in treatment were analyzed for various dosimetric endpoints. For all plans, each beam dose distribution, angle, smearing, and aperture margin were optimized. IMRT plans were created for all patients and simultaneously analyzed. The IMRT plans were optimized through multiple volume objectives, beam weighting, and individual leaf movement. The patients were treated to 78 Gray-equivalents (GE) in 2-GE fractions with a biologically equivalent dose of 1.1.

RESULTS

All rectal and rectal wall volumes treated to 10-80 GE (percentage of volume receiving 10-80 GE [V(10)-V(80)]) were significantly lower with proton therapy (p < 0.05). The rectal V(50) was reduced from 31.3% +/- 4.1% with IMRT to 14.6% +/- 3.0% with proton therapy for a relative improvement of 53.4% and an absolute benefit of 16.7% (p < 0.001). The mean rectal dose decreased 59% with proton therapy (p < 0.001). For the bladder and bladder wall, proton therapy produced significantly smaller volumes treated to doses of 10-35 GE (p < 0.05) with a nonsignificant advantage demonstrated for the volume receiving < or =60 GE. The bladder V(30) was reduced with proton therapy for a relative improvement of 35.3% and an absolute benefit of 15.1% (p = 0.02). The mean bladder dose decreased 35% with proton therapy (p = 0.002).

CONCLUSION

Compared with IMRT, proton therapy reduced the dose to the dose-limiting normal structures while maintaining excellent planning target volume coverage.

Chronic genitourinary and gastrointestinal toxicity of prostate cancer patients undergoing pelvic radiotherapy with intensity-modulated versus 4-field technique

PURPOSE

To compare chronic GU and GI toxicity of pelvic radiotherapy delivered using intensity-modulated radiotherapy (IMRT) versus conventional 4-field technique.

METHODS

The records of consecutive prostate cancer patients receiving RT at a single institution with a minimum follow-up of 120 days were reviewed; 48 of these patients received a prostate boost preceded by pelvic radiotherapy (PRT), 14 with IMRT (IM-PRT), and 34 with 4-field (4F-PRT). Dosimetric endpoints for the bladder, rectum, composite, and target for the PRT plans were compared using the 2-tailed t test. Late RTOG GU and GI toxicity were compared using the chi test. Ordered logit regression analyses were performed using all major patient, disease, and treatment factors as covariates.

RESULTS

IM-PRT demonstrated superior bladder and rectum dosimetric endpoints over 4F-PRT for the PRT portion of the treatment and for the composite treatment at the expense of higher target inhomogeneity in the PRT portion of the treatment plan. Late GU toxicity was significantly lower in the IM-PRT group (P < 0.001), whereas late GI toxicity was similar in both groups (P = 0.44). When considering a similar follow-up interval in both groups, however, the difference in GU toxicity only reached a trend (P = 0.10). The regression analyses showed that no factor, including IMRT, reached significance in predicting GU or GI toxicity.

CONCLUSION

Use of pelvic IMRT for prostate cancer patients was not associated with reduction of late GI toxicity but was associated with a small reduction of late GU toxicity. This reduction of late GU toxicity warrants further exploration in consortium studies.

The role of indium-111 radioimmunoscintigraphy in post-radical retropubic prostatectomy management of prostate cancer patients

Indium-111 radioimmunoscintigraphy (RIS) has an increasing role in the treatment of prostate cancer and is most commonly performed at this disease site using labeled monoclonal antibody against prostate-specific membrane antigen. There are many limitations of RIS, including low spatial resolution, low diagnostic yield and limited availability. Despite these limitations, the efficacy of RIS has been demonstrated in many clinical studies, including multi-institutional investigations. The highest sensitivity and specificity of RIS appears to be in the post-radical retropubic prostatectomy (post-RRP) setting. RIS has recently been explored for its role in clinical radiotherapy decision-making, and was found to have a significant impact in selecting patients for radiotherapy and for the general radiotherapy treatment volume definition. RIS has also recently been explored for its role in radiotherapy planning and was found to impact clinical target volume design. However, manual editing of the RIS volume is still necessary when projected into the radiotherapy-planning scan, as there is often overlap in the RIS-defined uptake regions with normal structures (rectum, bladder and symphysis bone marrow). The impact of RIS on biochemical control has been explored, with studies in this area yielding conflicting results. It appears that the maximum impact of RIS is possible when areas of labeled antibody uptake regions are co-registered with the radiotherapy-planning computed tomography scan. The larger RIS-guided target volumes do not appear to be prohibitive in increasing radiotherapy-related toxicity. Future directions of the use of RIS for post-RRP prostate cancer are discussed.

Influence of intensity-modulated radiotherapy on acute genitourinary and gastrointestinal toxicity in the treatment of localized prostate cancer

The objective of this investigation is to compare acute genitourinary (GU) and gastrointestinal (GI) toxicity results of radiotherapy to localized fields delivered using intensity-modulated radiotherapy (IMRT) versus conventional radiotherapy (ConvRT). The records of 481 consecutive prostate cancer patients receiving RT to localized fields at a single institution were reviewed; 108 received IMRT and 373 received ConvRT. Acute GU and GI toxicity, as defined by the Radiation Therapy Oncology Group (RTOG) grading system, were compared using the chi-square test. Ordered logit regression analyses were performed using all major disease and treatment factors as covariates. Acute GU grade 0, 1, 2, 3, and 4 toxicity rates were 23%, 40%, 34%, 3%, and 0%, respectively, in the IMRT cohort and 31%, 37%, 30%, 1%, and 1%, respectively, in the ConvRT cohort -- these rates were not significantly different (p=0.118). Acute GI grade 0, 1, 2, 3, and 4 toxicity rates were 42%, 37%, 22%, 0%, and 0%, respectively, in the IMRT cohort and 33%, 32%, 35%, 0%, and 0%, respectively, in the ConvRT cohort--this lower toxicity in the IMRT group was significant (p=0.013). The regression analyses showed that only IMRT use (p=0.046) predicted reduction in acute GI toxicity but no factors correlated with acute GU toxicity rate. In conclusion, in our retrospective single-institution analysis, IMRT was not associated with reduction of acute GU toxicity but was associated with a reduction of acute GI toxicity over ConvRT in the treatment of prostate cancer to localized fields.

Intensity modulated radiation therapy with irregular multileaf collimated field: a dosimetric study on the penumbra region with different leaf stepping patterns

Using a Varian 21 EX linear accelerator with a multileaf collimator (MLC) of 120 leaves, the penumbra regions of beam profiles within an irregular multileaf collimated fields were studied. MLC fields with different leaf stepping angles from 21.8 degrees to 68.2 degrees were used. Beam profiles in different directions: (1) along the cross-line and in-line axis, (2) along the leaf stepping edges of the field, and (3) parallel to the stepping edges but in the middle of the field, were measured and calculated using Kodak XV radiographic film and Pinnacle3 treatment planning system version 7.4f. These beam profiles were measured and calculated at source to axis distance= 100 cm with 5 cm of solid water slab on top. On the one hand, for both cross-line and in-line beam profiles, the penumbra widths of 20%-80% did not vary with the leaf stepping angles and were about 0.4 cm. On the other hand, the penumbra widths of 10%-90% of the above two profiles varied with the stepping angles and had maximum widths of about 1.9 cm (cross-line) and 1.65 cm (in-line) for stepping angles of 38.7 degrees and 51.3 degrees , respectively. For profiles crossing the "rippled" stepping edges of the field, the penumbra widths (10%-90%) at the regions between two opposite leaves (i.e., profile end at the Y1/Y2 jaw position) decreased with the stepping angles. At the penumbra regions between two leaf edges with the tongue-and-groove structure of the same bank (i.e., profile end at the X1/X2 jaw position), the penumbra widths increased with the stepping angles. When the penumbra widths were measured between two opposite leaf edges and at corners between two leaves, the widths first decreased with the stepping angles and then increased beyond the minimum width point at stepping angle of 45 degrees. The penumbra width (10%-90%) measured at the leaf edge was larger than that at the corner. For the beam profiles calculated using Pinnacle3, it is found that the results agreed well with the measurements along the cross-line and in-line axis, while there was a deviation for the profiles along the leaf stepping edge of the field compared to the film measurements. The measured results in this study can help us to understand the dosimetric effect of the leaf stepping (due to finite leaf width), tongue-and-groove and rounded leaf end structure in the penumbra region of an irregular MLC field. A more dedicated penumbra model can be developed for the treatment planning system.

Study on surface dose generated in prostate intensity-modulated radiation therapy treatment

The surface doses of 6- and 15-MV prostate intensity-modulated radiation therapy (IMRT) irradiations were measured and compared to those from a 15-MV prostate 4-beam box (FBB). IMRT plans (step-and-shoot technique) using 5, 7, and 9 beams with 6- and 15-MV photon beams were generated from a Pinnacle treatment planning system (version 6) using computed tomography (CT) scans from a Rando Phantom (ICRU Report 48). Metal oxide semiconductor field effect transistor detectors were used and placed on a transverse contour line along the Phantom surface at the central beam axis in the measurement. Our objectives were to investigate: (1) the contribution of the dynamic multileaf collimator (MLC) to the surface dose during the IMRT irradiation; (2) the effects of photon beam energy and number of beams used in the IMRT plan on the surface dose. The results showed that with the same number of beams used in the IMRT plan, the 6-MV irradiation gave more surface dose than that of 15 MV to the phantom. However, when the number of beams in the plan was increased, the surface dose difference between the above 2 photon energies became less. The average surface dose of the 15-MV IMRT irradiation increased with the number of beams in the plan, from 0.86% to 1.19%. Conversely, for 6 MV, the surface dose decreased from 1.33% to 1.24% as the beam number increased from 7 to 9. Comparing the 15-MV FBB and 6-MV IMRT plans with 2 Gy/fraction, the IMRT irradiations gave generally more surface dose, from 15% to 30%, depending on the number of beams in the plan. It was found that the increase in surface dose for the IMRT technique compared to the FBB plan was predominantly due to the number of beams and the calculated monitor units required to deliver the same dose at the isocenter in the plans. The head variation due to the dynamic MLC movement changing the surface dose distribution on the patient was reflected by the IMRT dose-intensity map. Although prostate IMRT in this study had an average higher surface dose than that of FBB, the more even distribution of relatively lower surface dose in IMRT field could avoid the big dose peaks at the surface positions directly under the FBB fields. Such an even and low surface dose distribution surrounding the patient in IMRT is believed to give less skin complication than that of FBB with the same prescribed dose.

Comparison of late gastrointestinal and genitourinary toxicity of prostate cancer patients undergoing intensity-modulated versus conventional radiotherapy using localized fields

To compare late genitourinary (GU) and gastrointestinal (GI) toxicity of radiotherapy (RT) to localized fields for prostate cancer delivered using intensity-modulated RT (IMRT) versus conventional RT (ConvRT). The records of 461 patients were reviewed; 355 patients received IMRT and 106 received ConvRT. Late GU and GI toxicity were compared. Late GU toxicity rates were not significantly different (P=0.166); however, late GI toxicity rates were lower with IMRT (P=0.001). Regression analyses demonstrated that only IMRT use (P=0.006) predicted reduction in late GI toxicity but no factors correlated with late GU toxicity. IMRT did not influence late GU toxicity but was associated with a reduction of late GI toxicity over ConvRT.

SWIMRT: a graphical user interface using sliding window algorithm to construct a fluence map machine file

A custom‐made computer program, SWIMRT, to construct “multileaf collimator (MLC) machine” file for intensity‐modulated radiotherapy (IMRT) fluence maps was developed using MATLAB® and the sliding window algorithm. The user can either import a fluence map with a graphical file format created by an external treatment‐planning system such as Pinnacle3 or create his or her own fluence map using the matrix editor in the program. Through comprehensive calibrations of the dose and the dimension of the imported fluence field, the user can use associated image‐processing tools such as field resizing and edge trimming to modify the imported map. When the processed fluence map is suitable, a “MLC machine” file is generated for our Varian 21 EX linear accelerator with a 120‐leaf Millennium MLC. This machine file is transferred to the MLC console of the LINAC to control the continuous motions of the leaves during beam irradiation. An IMRT field is then irradiated with the 2D intensity profiles, and the irradiated profiles are compared to the imported or modified fluence map. This program was verified and tested using film dosimetry to address the following uncertainties: (1) the mechanical limitation due to the leaf width and maximum traveling speed, and (2) the dosimetric limitation due to the leaf leakage/transmission and penumbra effect. Because the fluence map can be edited, resized, and processed according to the requirement of a study, SWIMRT is essential in studying and investigating the IMRT technique using the sliding window algorithm. Using this program, future work on the algorithm may include redistributing the time space between segmental fields to enhance the fluence resolution, and readjusting the timing of each leaf during delivery to avoid small fields. Possible clinical utilities and examples for SWIMRT are given in this paper.

PACS numbers: 87.53.Kn, 87.53.St, 87.53.Uv

Management Strategies for Locally Advanced Prostate Cancer

Locally advanced prostate cancer represents a subpopulation of prostate cancer diagnosed in patients who are either untouched by screening efforts or whose disease has an unusually rapidly progressive natural history. The diagnostic work-up for the locally advanced patient is distinct from that of early stage disease in several respects in that it is related principally to ruling out metastases. The typical metastatic work-up consists of a serum alkaline phosphatase, bone scan, CT of the abdomen/pelvis, and chest x-ray. Once metastatic disease has been ruled out, individual components of the management of locally advanced prostate cancer patients may include surgery (palliative or curative), external beam radiation therapy (with photons or particles) or brachytherapy (with low-dose rate/permanent or high-dose rate/temporary radiation sources), and hormone therapy. Unlike in early stage disease, observation/watchful waiting is typically not a treatment option in locally advanced prostate cancer. Of the curative local control modalities, the one most commonly used, and the one which has emerged as the clinical standard, is photon external beam radiotherapy (EBRT). Numerous randomised studies have shown that androgen ablation has an established role in conjunction with radiotherapy for locally advanced disease--the current standard of care is thus photon EBRT plus neoadjuvant and adjuvant androgen ablation. Long-term androgen ablation appears to be better than short-term ablation, even when hormone complications are considered. EBRT is typically delivered to the prostate, seminal vesicles and pelvic lymph nodes, although in some circumstances local fields to the prostate and seminal vesicles may be adequate. New treatment planning and delivery techniques, such as intensity-modulated radiotherapy and organ motion tracking, are being developed to reduce the morbidity of radiotherapy while permitting a higher delivered dose. Further work is necessary to determine the precise sequencing and duration of hormone therapy in conjunction with radiotherapy and the optimum radiotherapy treatment volume. Additional work is also needed to determine the precise groups benefiting from other local control modalities such as surgery and brachytherapy. Finally, novel investigational strategies such as chemotherapy and gene therapy are being applied in an attempt to improve outcomes of locally advanced prostate cancer patients.

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

OBJECTIVES

To provide a single-institution analysis of the influence of pelvic intensity-modulated radiotherapy (RT) on acute genitourinary (GU) and gastrointestinal (GI) toxicity.

METHODS

The records of 610 consecutive patients with prostate cancer receiving RT were reviewed. Of these 610 patients, 49 had received a prostate boost preceded by pelvic RT (PRT), 15 intensity-modulated PRT (IM-PRT), and 34 four-field PRT (4F-PRT). The dosimetric endpoints for the bladder, rectum, and target for the PRT plans were compared using the paired t test; similar dosimetric analyses were done for the composite plans. Acute GU and GI toxicity were compared using the chi-square test. Ordered logit regression analyses were performed using all major treatment factors as covariates.

RESULTS

The bladder and rectum dosimetric endpoints were improved for IM-PRT compared with 4F-PRT for the PRT portion of the treatment plan (P = 0.06 and P = 0.03, respectively) and for the composite treatment plan (P = 0.04 and P = 0.01, respectively), at the expense of greater target inhomogeneity in the PRT portion of the treatment plan (P < 0.01). GU toxicity was significantly lower in the IM-PRT group (P < 0.001), and GI toxicity was similar in both groups (P = 0.637). The regression analyses showed that intensity-modulated RT for the pelvic portion of treatment was the only factor significantly predicting for GU toxicity (P = 0.05); no major treatment factor reached significance in predicting GI toxicity.

CONCLUSIONS

Compared with 4F-PRT, the use of IM-PRT improved dosimetric outcomes, was not associated with a reduction in acute GI toxicity, and was associated with a reduction in acute GU toxicity in the treatment of prostate cancer.

Intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer: toxicity and clinical outcome

PURPOSE

To assess survival, local control, and toxicity of intensity modulated radiation therapy (IMRT) in squamous cell carcinoma of the anal canal.

METHODS AND MATERIALS

Seventeen patients were treated with nine-field IMRT plans. Thirteen received concurrent 5-fluorouracil and mitomycin C, whereas 1 patient received 5-fluorouracil alone. Seven patients were planned with three-dimensional anteroposterior/posterior-anterior (AP/PA) fields for dosimetric comparison to IMRT.

RESULTS

Compared with AP/PA, IMRT reduced the mean and threshold doses to small bowel, bladder, and genitalia. Treatment was well tolerated, with no Grade > or =3 acute nonhematologic toxicity. There were no treatment breaks attributable to gastrointestinal or skin toxicity. Of patients who received mitomycin C, 38% experienced Grade 4 hematologic toxicity. IMRT did not afford bone marrow sparing, possibly resulting from the clinical decision to prescribe 45 Gy to the whole pelvis in most patients, vs. the Radiation Therapy Oncology Group-recommended 30.6 Gy whole pelvic dose. Three of 17 patients, who did not achieve a complete response, proceeded to an abdominoperineal resection and colostomy. At a median follow-up of 20.3 months, there were no other local failures. Two-year overall survival, disease-free survival, and colostomy-free survival are: 91%, 65%, and 82% respectively.

CONCLUSIONS

In this hypothesis-generating analysis, the acute toxicity and clinical outcome with IMRT in the treatment of anal cancer is encouraging. Compared with historical controls, local control is not compromised despite efforts to increase conformality and reduce normal structure dose.

Late radiotherapy toxicity after prostate cancer treatment: Influence of hormonal therapy

OBJECTIVES

To analyze the impact of hormonal therapy (HT) on late gastrointestinal (GI) and genitourinary (GU) toxicity from external beam radiotherapy (RT).

METHODS

The records of 445 consecutive patients with prostate cancer undergoing RT with or without HT were reviewed. Late toxicity rates, using established toxicity scoring guidelines, were tabulated in the two groups and compared using the chi-square test. Ordered logit regression analyses were performed that included the major demographic, disease, and treatment factors.

RESULTS

The chi-square analyses demonstrated lower rates of GI toxicity (P = 0.013) and GU toxicity (P = 0.041) in the cohort receiving HT; this reduction in toxicity appeared to be consistent across different toxicity grades. However, on regression analysis, the only factor reaching statistical significance in predicting late GI and late GU toxicity was the radiation dose (P = 0.004 and P = 0.047, respectively). In particular, on regression analysis, HT did not reach statistical significance in predicting late GI toxicity (P = 0.229) or late GU toxicity (P = 0.910).

CONCLUSIONS

Observed late RT toxicity rates were generally similar in patients who did and did not receive HT. Thus, increased late RT toxicity should not be a major concern when deciding to add HT to RT for treatment of localized prostate cancer.

A case study of radiotherapy planning for a bilateral metal hip prosthesis prostate cancer patient

The purpose of this report is to communicate the observed advantage of intensity-modulated radiotherapy (IMRT) in a patient with bilateral metallic hip prostheses. In this patient with early-stage low-risk disease, a dose of 74 Gy was planned in two phases--an initial 50 Gy to the prostate and seminal vesicles and an additional 24 Gy to the prostate alone. Each coplanar beam avoided the prosthesis in the beam's eye view. Using the same target expansions for each phase, IMRT and 3D-conformal radiotherapy (CRT) plans were compared for target coverage and inhomogeneity as well as dose to the bladder and rectum. The results of the analysis demonstrated that IMRT provided superior target coverage with reduced dose to normal tissues for both individual phases of the treatment plan as well as for the composite treatment plan. The dose to the rectum was significantly reduced with the IMRT technique, with a composite V 80 of 35% for the IMRT plan versus 70% for 3D-CRT plan. Similarly, the dose to the bladder was significantly reduced with a V 80 of 9% versus 20%. Overall, various dosimetric parameters revealed the corresponding 3D-CRT plan would not have been acceptable. The results indicate significant success with IMRT in a clinical scenario where there were no curative alternatives for local treatment other than external beam radiotherapy. Therefore, definitive external beam radiation of prostate cancer patients with bilateral prosthesis is made feasible with IMRT. The work described herein may also have applicability to other groups of patients, such as those with gynecological or other pelvic malignancies.

Dosimetric effect of collimating jaws for small multileaf collimated fields

The dosimetric effects from the jaw positioned close to the small field (0.5 x 0.5, 1 x 1, and 2 x 2 cm2) side-edge generated by a single-focused multileaf collimator (MLC) were measured and studied. The measurement is important in intensity modulated radiotherapy (IMRT) because generally the jaw cannot perfectly cover all the leaf-ends in a segment of irregular field. This leads to additional dose contributed by (1) the end surface of the jaw, (2) the leaf-end, and (3) the inter- and intraleaf leakage/transmissions during the dosimetric measurement. Moreover, most of the conventional treatment planning systems ignore these effects in the dose calculation. In this study, measurements were made using a Varian 21 EX linear accelerator with 6 MV photon beam through a MLC containing 120 leaves. Percentage depth dose, beam profile, and output for small fields were measured by varying the jaw at different positions away from the leaf-ends in the field side-edge. Moving the jaw away from the leaf-ends increases the output and penumbra width for the small fields. Such increase is particularly significant when the field size is small (0.5 x 0.5 cm2) and the degree of increase changes quickly when the jaw-end is at about 1-2 cm from the leaf-end. It is suggested that measurements should be carried out in the IMRT commissioning to provide information to physicists in reviewing the treatment planning system's accuracy regarding leaf leakage/transmission and jaw effects.

Analysis of impact of age and race on biochemical control after radiotherapy in different prostate cancer settings

OBJECTIVES

To provide a single-institution analysis of the impact of age and race on biochemical control after radiotherapy (RT) administered in different prostate cancer scenarios. Age and race are among the most controversial prognostic factors in determining outcome after RT. Proper understanding of these prognostic factors can assist in both treatment decision-making and the general understanding of the natural history of prostate cancer.

METHODS

The records of 527 consecutive nonmetastatic patients undergoing RT at a single institution and for whom demographic, disease, treatment, and follow-up information were available were reviewed. The cohort was divided into two categories: locally advanced/localized (458 patients) and postprostatectomy (69 patients). Biochemical failure-free survival (BFFS) curves were compared within each group to determine the influence of age and race on biochemical control.

RESULTS

BFFS curves for the entire study population did not reveal any statistically significant difference when separated by age (younger than 60 years versus 60 to 69 years versus 70 years or older; 4-year BFFS 75% versus 70% versus 72%, respectively; P = 0.773) or by race (African American versus white; 4-year BFFS 74% versus 70%, respectively; P = 0.469). Additionally, no statistically significant differences were observed as a function of stage or age within either category (intact prostate or postprostatectomy).

CONCLUSIONS

Age and race did not, in our study, independently influence biochemical control after RT for nonmetastatic prostate cancer. On the basis of the results of this study, age and race should not be used as independent factors in treatment decision-making and in patient counseling concerning prostate cancer.

Impact of hormone therapy on acute radiotherapy toxicity in the treatment of prostate cancer

PURPOSE

To analyze the impact of neoadjuvant hormone therapy (HT) on acute gastrointestinal (GI) and genitourinary (GU) toxicity from radiotherapy (RT).

SCOPE

The toxicity rates of 480 consecutive prostate cancer patients were reviewed and compared using the chi2 test. Ordered logit regression analyses were performed including the major demographic, disease, and treatment factors. Although no reduction in acute GI toxicity from HT use was observed (P=0.067), a lower rate of acute GU toxicity was observed (P=0.002). No factor reached statistical significance on regression analysis.

CONCLUSIONS

Observed toxicity rates were similar or lower in patients receiving HT. Thus, increased RT toxicity should not be a concern when deciding to add neoadjuvant HT to RT for prostate cancer.

Analysis of influence of age on acute and chronic radiotherapy toxicity in treatment of prostate cancer

OBJECTIVES

To provide a single-institution analysis of the influence of age on acute and late genitourinary (GU) and gastrointestinal (GI) toxicity after radiotherapy (RT) administered in different prostate cancer scenarios. Improved understanding of the influence of age on toxicity outcome after RT for prostate cancer can assist in treatment decision-making.

METHODS

The records of 527 consecutive nonmetastatic patients receiving RT at a single institution and for whom demographic, disease, treatment, and follow-up information were available were reviewed. The cohort was divided into four major categories as a function of age: younger than 60 years, 60 to 69 years, 70 to 74 years, and 75 years and older. The toxicity rates in each of these categories were tabulated according to the Radiation Therapy Oncology Group toxicity scales and compared using the chi-square test. Additionally, an ordered logit regression analysis was performed for each of these categories using all major patient, disease, and treatment factors.

RESULTS

The toxicity rates were not significantly different as a function of age for either acute GU (P = 0.10) or acute GI (P = 0.19) toxicity or for either late GU (P = 0.22) or late GI (P = 0.09) toxicity. The ordered logit regression analysis showed that age was not a factor that correlated with toxicity in any setting (acute GU, P = 0.44; acute GI, P = 0.55; late GU, P = 0.65; late GI, P = 0.14).

CONCLUSIONS

Patient age did not independently influence GI or GU toxicity after RT for nonmetastatic prostate cancer and should not be used as an independent factor in treatment decision-making or in patient counseling with regard to GI and GU toxicity outcomes after RT.

Opacity transfer function optimization for volume-rendered computed tomography images of the prostate

RATIONALE AND OBJECTIVES

The selection of an opacity transfer function is essential for volume visualization. Computed tomography (CT) scans of the pelvis were used to determine an optimal opacity transfer function for use in radiotherapy.

MATERIALS AND METHODS

On sample datasets (a mathematical phantom and a patient pelvis CT scan), standard viewing orientations were selected to render the prostate. Opacity functions were selected via (1) trapezoidal manual selection, (2) trapezoidal semiautomatic selection, and (3) histogram volume-based selection. Using an established metric, the errors using each of these methods were computed.

RESULTS

Trapezoidal manual opacity function optimization resulted in visually acceptable images, but the errors were considerable (6.3-9.1 voxel units). These errors could be reduced with the use of trapezoidal semiautomatic selection (4.9-6.2 voxel units) or with histogram volume-based selection (4.8-7.9 voxel units). As each visualization algorithm focused on enhancing the boundary of the prostate using a different approach, the scene information was considerably different using the three techniques.

CONCLUSION

Improved volume visualization of soft tissue interfaces was achieved using automated optimal opacity function determination, compared with manual selection.

Hormone therapy and radiotherapy for early prostate cancer: a utility-adjusted number needed to treat (NNT) analysis

PURPOSE

To quantify, using the number needed to treat (NNT) methodology, the benefit of short-term (< or =6 months) hormone therapy adjuvant to radiotherapy in the group of patients with early (clinical stage T1-T2c) prostate cancer.

METHODS AND MATERIALS

The absolute biochemical control benefit for the use of hormones adjuvant to radiotherapy in early-stage disease was determined by literature review. A model was developed to estimate the utility-adjusted survival detriment due to the side effects of hormone therapy. The NNTs before and after the incorporation of hormone sequelae were computed; the sign and magnitude of the NNTs were used to gauge the effect of the hormones.

RESULTS

The absolute NNT analysis, based on summarizing the results of 8 reports including a total of 3652 patients, demonstrated an advantage to the addition of hormones for the general early-stage prostate cancer population as well as for all prognostic groups. After adjustment for hormone-induced functional loss, the advantage of hormones remained considerable in the high- and intermediate-risk groups, with the utility-adjusted NNT becoming weakened in the low-risk group when the utility compromise from complications of hormones was assumed to be considerable.

CONCLUSIONS

Short-term hormone therapy seems to be beneficial for selected early-stage prostate cancer patients. The advantage seems to be greatest in the intermediate- and high-risk groups; with current follow-up, the side effects of hormones may outweigh their benefit in certain clinical situations in the favorable group. The present investigation demonstrates the significant role of the NNT technique for oncologic and radiotherapeutic management decisions when treatment complications need to be considered and balanced with the beneficial effects of the treatment.

Analysis of acute toxicity with use of transabdominal ultrasonography for prostate positioning during intensity-modulated radiotherapy

OBJECTIVES

To analyze the effects of the B-mode ultrasound acquisition and targeting (BAT) system for positioning of patients with prostate cancer receiving intensity-modulated radiotherapy on acute gastrointestinal (GI) and genitourinary (GU) toxicity.

METHODS

The records of 50 consecutive patients treated using the BAT system were reviewed. Additionally, a comparison (no-BAT) group (ie, a group without a BAT study) treated in a similar manner was identified. The no-BAT group consisted of 49 patients treated immediately before the BAT group. For the two groups, the target definitions and dose prescriptions were identical, the treatment plan acceptance criteria were identical, and intensity-modulated radiotherapy was used for all patients. The daily BAT movements were charted in each of the three principal directions. Acute toxicity was scored for all patients according to the Radiation Therapy Oncology Group GI and GU acute toxicity scales.

RESULTS

The GU toxicity rates for the BAT versus no-BAT groups were grade 0 in 20% versus 14%; grade 1 in 38% versus 47%; grade 2 in 38% versus 39%; and grade 3 in 4% versus 0%, respectively (P = 0.284). The corresponding GI toxicity rates were grade 0 in 42% versus 27%; grade 1 in 28% versus 29%; and grade 2 in 30% versus 45% (P = 0.040). The incidence of GU and GI toxicity did not correlate with the directions or size of the BAT moves. Regression analysis revealed that for acute GI toxicity, the only variable reaching statistical significance was BAT use; no variable, including BAT use, reached statistical significance for acute GU toxicity.

CONCLUSIONS

The use of the BAT system did not change the rate of acute GU toxicity but did reduce the rate of acute GI toxicity.

The effectiveness of combining hormone therapy and radiotherapy in the treatment of prostate cancer

Hormone therapy is commonly used for many patients with prostate cancer. Radiotherapy occupies a prominent role in the treatment of locally-advanced, localised, and postsurgical prostate cancer. Hormone therapy and radiotherapy are often used in combination. In this article, the major features of the hormone/radiotherapy interactions are reviewed, with emphasis on the role of combination treatment for locoregional disease. The reported results suggest a biochemical survival advantage to the use of hormone therapy with radiotherapy, in virtually all settings of non-metastatic disease, with the weakest database being in the setting of low-risk, early-stage disease. Further data are needed in order to identify the optimum target population, combination of agents, and hormone duration, as a function of patient and disease factors.

Postprostatectomy adjuvant versus salvage radiotherapy

BACKGROUND

Radiotherapy (RT) has been used with success after radical retropubic prostatectomy (RRP), both in the adjuvant and salvage settings. The purpose of the current investigation was to systematically compare adjuvant versus salvage RT in a manner that incorporates both treatment efficacy and complications.

METHODS

A literature review was performed of reports of post-RRP salvage and adjuvant RT, and 12 trials comprising 1060 patients met the appropriate inclusion criteria. The biochemical failure-free survival in each study/arm was tabulated, and these values were entered into a model to compute an unadjusted number-needed-to treat (NNT). RT complications were then considered, accounting for differences in toxicity incidences in the salvage versus adjuvant setting, to compute complication-adjusted NNTs. In all the trials, the signs and magnitudes of the NNTs obtained were used to compare adjuvant with salvage RT.

RESULTS

The absolute NNT analysis showed an advantage of adjuvant compared with salvage RT. After adjustment for RT complications, however, the advantage shifted to salvage RT. This transition point from superiority of adjuvant RT to superiority of salvage RT was sensitive to the estimated incidence and severity of RT side effects.

CONCLUSIONS

Adjuvant post-RRP RT was advantageous in comparison to salvage RT if the side effects of RT were estimated to be negligible. However, with moderate incidence/severity of RT side effects, salvage RT was advantageous. The findings herein must be tested in a prospective study in which both health-related quality of life and cancer control are documented in patients receiving adjuvant versus salvage post-RRP RT. Further work is needed to better estimate parameters entered into the model to determine the precise transition point between adjuvant and salvage RT with modern RT techniques.

Androgen ablation adjuvant to postprostatectomy radiotherapy: Complication-adjusted number needed to treat analysis

OBJECTIVES

To quantify the benefits and harm of androgen ablation (AA) adjuvant to radiotherapy in the postprostatectomy setting. AA is commonly used in the management of prostate cancer.

METHODS

A literature review was performed to estimate the absolute biochemical control advantage for the use of AA concomitant with postprostatectomy external beam radiotherapy. Additionally, a model was developed, with supporting published data, to estimate the utility-adjusted survival detriment due to the side effects of AA, using the number needed to treat (NNT) technique. Using these data, the unadjusted NNTs and the utility-adjusted NNTs for the addition of AA were computed. In all cases, the sign and magnitude of the NNTs obtained were used to gauge the effects of AA.

RESULTS

The unadjusted NNT analysis demonstrated very low values (far less than 20), suggesting a strong benefit for the use of AA, in both adjuvant and salvage radiotherapy settings. Even after adjustment for hormone-induced functional loss, a significant advantage of AA was demonstrated.

CONCLUSIONS

Using the complication-adjusted NNT method, AA appears to be advantageous in both adjuvant and salvage postprostatectomy radiotherapy settings. The results of the present investigation demonstrated the significant role of the NNT technique for uro-oncologic management decisions when treatment complications need to be considered and balanced against the beneficial effects of the treatment.

Biological effective dose for comparison and combination of external beam and low-dose rate interstitial brachytherapy prostate cancer treatment plans

We report a methodology for comparing and combining dose information from external beam radiotherapy (EBRT) and interstitial brachytherapy (IB) components of prostate cancer treatment using the biological effective dose (BED). On a prototype early-stage prostate cancer patient treated with EBRT and low-dose rate I-125 brachytherapy, a 3-dimensional dose distribution was calculated for each of the EBRT and IB portions of treatment. For each component of treatment, the BED was calculated on a point-by-point basis to produce a BED distribution. These individual BED distributions could then be summed for combined therapies. BED dose-volume histograms (DVHs) of the prostate, urethra, rectum, and bladder were produced and compared for various combinations of EBRT and IB. Transformation to BED enabled computation of the relative contribution of each modality to the prostate dose, as the relative weighting of EBRT and IB was varied. The BED-DVHs of the prostate and urethra demonstrated dramatically increased inhomogeneity with the introduction of even a small component of IB. However, increasing the IB portion relative to the EBRT component resulted in lower dose to the surrounding normal structures, as evidenced by the BED-DVHs of the bladder and rectum. Conformal EBRT and low-dose rate IB conventional dose distributions were successfully transformed to the common "language" of BED distributions for comparison and for merging prostate cancer radiation treatment plans. The results of this analysis can assist physicians in quantitatively determining the best combination and weighting of radiation treatment modalities for individual patients.