Comparisons of the impact of systematic uncertainties in patient setup and prostate motion on doses to the target among different plans for definitive external-beam radiotherapy for prostate cancer

Assessment of interfractional prostate motion in patients immobilized in the prone position using a thermoplastic shell

The aim of this study was to evaluate the interfractional prostate motion of patients immobilized in the prone position using a thermoplastic shell. A total of 24 patients with prostate calcifications detectable using a kilo-voltage X-ray image-guidance system (ExacTrac X-ray system) were examined. Daily displacements of the calcification within the prostate relative to pelvic bony structures were calculated by the ExacTrac X-ray system. The average displacement and standard deviation (SD) in each of the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were calculated for each patient. Based on the results of interfractional prostate motion, we also calculated planning target volume (PTV) margins using the van Herk formula and examined the validity of the PTV margin of our institute (a 9-mm margin everywhere except posteriorly, where a 6-mm margin was applied). In total, 899 data measurements from 24 patients were obtained. The average prostate displacements ± SD relative to bony structures were 2.8 ± 3.3, -2.0 ± 2.0 and 0.2 ± 0.4 mm, in the SI, AP and LR directions, respectively. The required PTV margins were 9.7, 6.1 and 1.4 mm in the SI, AP and LR directions, respectively. The clinical target volumes of 21 patients (87.5%) were located within the PTV for 90% or more of all treatment sessions. Interfractional prostate motion in the prone position with a thermoplastic shell was equivalent to that reported for the supine position. The PTV margin of our institute is considered appropriate for alignment, based on bony structures.

Long-term outcomes of dynamic conformal arc irradiation combined with neoadjuvant hormonal therapy in Japanese patients with T1c-T2N0M0 prostate cancer: case series study

OBJECTIVE

There are few reports of the outcomes of external beam radiotherapy in Asian males with localized prostate cancer. The aim of this study is to evaluate the long-term outcomes of external beam irradiation using three-dimensional two-dynamic conformal arc therapy, combined with neoadjuvant hormonal therapy, in patients with T1c-T2N0M0 prostate cancer.

METHODS

Between March 2003 and August 2007, 150 Japanese patients with T1c-T2N0M0 prostate cancer were definitively treated with three-dimensional two-dynamic conformal arc therapy. The median age, pretreatment prostate-specific antigen values and neoadjuvant hormonal therapy period were 73 years, 9.4 ng/ml and 6 months, respectively. In principle, 74 Gy was delivered to the planning target volume, although the total dose was reduced to 70 Gy in patients with unfavorable risk factors, such as severe diabetes mellitus or anticoagulant therapy. No adjuvant hormonal therapy was given to any patient. Salvage hormonal therapy was started when the prostate-specific antigen value exceeded 4 ng/ml in a monotonically increasing manner.

RESULTS

The median follow-up period was 79 months. Salvage hormonal therapy was initiated in 10 patients and the median prostate-specific antigen value at the initiation was 4.7 ng/ml. The 5-year Kaplan-Meier estimates of the biochemical relapse-free survival rate, the salvage hormonal therapy -free rate and the overall survival rate were 83.3% (95% confidence interval = 77.1-89.6%), 94.3% (95% confidence interval = 90.4-98.1%) and 96.3% (95% confidence interval = 93.1-99.5%), respectively. The 5-year cumulative incidence rates of developing more than Grade 2 late rectal and urinary toxicities were 5.5 and 2.9%, respectively.

CONCLUSIONS

Three-dimensional two-dynamic conformal arc therapy, with up to 74 Gy, in patients with T1c-T2N0M0 prostate cancer with neoadjuvant hormonal therapy was well tolerated and achieved good biochemical control and survival outcomes.

Long-term outcomes of three-dimensional conformal radiation therapy combined with neoadjuvant hormonal therapy for Japanese patients with T1c-T2N0M0 prostate cancer

BACKGROUND

The outcomes of three-dimensional conformal radiation therapy (3D-CRT) combined with neoadjuvant hormonal therapy (NAHT) in Japanese patients with T1c-T2N0M0 prostate cancer, with initiation of salvage hormonal therapy (SHT) at a relatively early phase, were analyzed.

METHODS

Fifty-nine Japanese patients with T1c-T2N0M0 prostate cancer who received radical 3D-CRT between January 1999 and January 2003 were evaluated. The median age, initial prostate-specific antigen (PSA) level, and duration of NAHT were: 72 years, 9.4 ng/ml, and 6 months, respectively. Seventy Gy was given in 35 fractions confined to the prostate ± seminal vesicles. AHT was not administered after 3D-CRT in any patients.

RESULTS

The median follow-up period was 89 months. The median PSA value at the time of initiation of SHT was 4.7 ng/ml (range 0.1-21.6 ng/ml). The overall, disease-specific, PSA failure-free (based on the Phoenix definition), and SHT-free survival rates at 8 years were 82.8% (95% confidence interval [CI] 72.4-93.2), 100%, 62.4% (47.1-77.8), and 82.6% (71.3-94.0), respectively. Only one patient developed grade 3 late toxicity.

CONCLUSIONS

The PSA control rates in our series of Japanese patients with stage T1c-T2N0M0 prostate cancer treated with the standard dose of 3D-CRT combined with NAHT seemed at least comparable to those reported from Western countries; as well, the patients had excellent outcomes. The present outcomes can be used as basic data for evaluating the impact of dose escalation with intensity-modulated radiation therapy for Japanese patients with prostate cancer in the future.

Acurácia na reprodutibilidade do posicionamento diário de pacientes submetidos a radioterapia conformada (RT3D) para câncer de próstata

OBJETIVO: Avaliar a reprodutibilidade do posicionamento de pacientes com diagnóstico de câncer de próstata submetidos a radioterapia conformada. MATERIAIS E MÉTODOS: Foram avaliados 960 (posições anterior e lateral) filmes radiológicos, de um total de 120 pacientes que receberam radioterapia conformada na próstata com técnica isocêntrica. As imagens foram obtidas em acelerador linear de partículas 6 MV. Aplicou-se protocolo específico para planejamento e tratamento da próstata, com o paciente em posição supina, mãos colocadas sobre o tórax, pés apoiados em suporte apropriado. Diariamente, os pacientes foram posicionados conforme demarcações na pele, coincidentes com os lasers da sala. Os filmes radiológicos foram comparados com as radiografias reconstruídas digitalmente (digitally reconstructed radiography - DRR) em sistema de planejamento computadorizado Eclipse, a partir das tomografias. As radiografias de posicionamento foram realizadas no primeiro dia e após, semanalmente, até o término do tratamento. RESULTADOS: As médias dos deslocamentos observados foram de 1,99 ± 1,25 mm no sentido crânio-caudal, 1,37 ± 0,84 mm no látero-lateral e 1,94 ± 1,10 mm no ântero-posterior. CONCLUSÃO: O uso de protocolos específicos para posicionamento dos pacientes é possível na prática clínica, possibilita reprodutibilidade adequada e rápida correção dos possíveis erros.

The effect of interfraction prostate motion on IMRT plans: a dose-volume histogram analysis using a Gaussian error function model

The Gaussian error function model, containing pairs of error and complementary error functions, was used to carry out cumulative dose-volume histogram (cDVH) analysis on prostate intensity modulated radiation therapy (IMRT) plans with interfraction prostate motion. Cumulative DVHs for clinical target volumes (CTVs) shifted in the anterior-posterior directions based on a 7-beam IMRT plan were calculated and modeled using the Pinnacle3 treatment planning system and a Gaussian error function, respectively. As the parameters in the error function model, namely, a, b and c were related to the shape of the cDVH curve, evaluation of cDVHs corresponding to the prostate motion based on the model parameters becomes possible as demonstrated in this study. It was found that deviations of the cDVH for the CTV were significant, when the CTV-planning target volume (PTV) margin was underestimated in the anterior-posterior directions, particularly in the posterior direction for a patient with relatively small prostate volume (39 cm3). Analysis of the cDVH for the CTV shifting in the anterior-posterior directions using the error function model showed that parameters a1,2, which were related to the maximum relative volume of the cDVH, changed symmetrically when the prostate was shifted in the anterior and posterior directions. This change was more significant for the larger prostate. For parameters b related to the slope of the cDVH, b1,2 changed symmetrically from the isocenter, when the CTV was within the PTV. This was different from parameters c (c1,2 are related to the maximum dose of the cDVH), which did not vary significantly with the prostate motion in the anterior-posterior directions and prostate volume. Using the patient data, this analysis validates the error function model, and further verified the clinical application of this mathematical model on treatment plan evaluations.

IMRT of prostate cancer: a comparison of fluence optimization with sequential segmentation and direct step-and-shoot optimization

BACKGROUND AND PURPOSE

Intensity-modulated radiation therapy (IMRT) has shown its superiority to three-dimensional conformal radiotherapy in the treatment of prostate cancer. Different optimization algorithms are available: algorithms which first optimize the fluence followed by a sequencing (IM), and algorithms which involve the machine parameters directly in the optimization process (DSS). The aim of this treatment-planning study is to compare both of them regarding dose distribution and treatment time.

PATIENTS AND METHODS

Ten consecutive patients with localized prostate cancer were enrolled for the planning study. The planning target volume and the rectum volume, urinary bladder and femoral heads as organs at risk were delineated. Average doses, the target dose homogeneity H, D(5), D(95), monitor units per fraction, and the number of segments were evaluated.

RESULTS

While there is only a small difference in the mean doses at rectum and bladder, there is a significant advantage for the target dose homogeneity in the DSS-optimized plans compared to the IM-optimized ones. Differences in the monitor units (nearly 10% less for DSS) and the number of segments are also statistically significant and reduce the treatment time.

CONCLUSION

Particularly with regard to the tumor control probability, the better homogeneity of the DSS-optimized plans is more profitable. The shorter treatment time is an improvement regarding intrafractional organ motion. The DSS optimizer results in a higher target dose homogeneity and, simultaneously, in a lower number of monitor units. Therefore, it should be preferred for IMRT of prostate cancer.