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

Comparison of rectal dose reduction by a hydrogel spacer among 3D conformal radiotherapy, volumetric-modulated arc therapy, helical tomotherapy, CyberKnife and proton therapy

This study aimed to evaluate the rectal dose reduction with hydrogel spacer in 3D conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), helical tomotherapy (HT), CyberKnife (CK) and proton therapy. Twenty patients who had hydrogel spacer for prostate radiotherapy were retrospectively enrolled. Computed tomography (CT) images with or without hydrogel spacer were used to evaluate rectal dose reduction. In total, 200 plans (20 patients × 2 CT images × 5 techniques) were created using the following criteria: 3DCRT, VMAT and HT [76 Gy/38 fractions (Fr), planning target volume (PTV) D50%], CK (36.25 Gy/5 Fr, PTV D95%) and proton therapy (63 GyE/21 Fr, PTV D50%). Rectal dose reduction was evaluated using low-/middle-dose (D20%, D50% and D80%) and high-dose (D2%) ranges. Rectal dose reduction of each dose index was compared for each technique. Significant rectal dose reduction (P < 0.001) between the treatment plans on pre- and post-CT images were achieved for all modalities for D50%, D20% and D2%. In particular, the dose reduction of high-dose (D2%) ranges were -40.61 ± 11.19, -32.44 ± 5.51, -25.90 ± 9.89, -13.63 ± 8.27 and -8.06 ± 4.19%, for proton therapy, CK, HT, VMAT and 3DCRT, respectively. The area under the rectum dose-volume histogram curves were 34.15 ± 3.67 and 34.36 ± 5.24% (P = 0.7841) for 3DCRT with hydrogel spacer and VMAT without hydrogel spacer, respectively. Our results indicated that 3DCRT with hydrogel spacer would reduce the medical cost by replacing the conventional VMAT without spacer for prostate cancer treatment, from the point of view of the rectal dose. For the high-dose gradient region, proton therapy and SBRT with CK showed larger rectal dose reduction than other techniques.

Impact of image guidance on toxicity and tumour outcome in moderately hypofractionated external-beam radiotherapy for prostate cancer

To report toxicity and efficacy outcome of moderately hypofractionated image-guided external-beam radiotherapy in a large series of patients treated for prostate cancer (PCa). Between 10/2006 and 12/2015, 572 T1-T3N0M0 PCa patients received 70.2 Gy in 26 fractions at 2.7 Gy/fraction: 344 patients (60%) with three-dimensional conformal radiotherapy (3D-CRT) and 228 (40%) with intensity-modulated radiotherapy (IMRT). Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria and Houston definition (nadir + 2) were used for toxicity and biochemical failure evaluation, respectively. Median age was 74 years (interquartile range 69-77). Compared with 3D-CRT, in IMRT group more high-risk patients (29% vs 18%; P = 0.002) and more high-volume target (75% vs 60%; P < 0.001) were included. Acute gastro-intestinal (GI) toxicity G > 1 were registered in 8% and in 11% IMRT and 3D-CRT patients, respectively, whereas late GI G > 1 were observed in 2% and 16% IMRT and 3D-CRT patients, respectively. Acute genito-urinary (GU) toxicity G > 1 were registered in 26% and 40% IMRT and 3D-CRT patients, respectively, whereas late GU G > 1 occurred in 5% IMRT and 15% 3D-CRT patients. Multivariate proportional hazard Cox models confirmed significantly greater risk of late toxicity with 3D-CRT compared to IMRT for GU > 1 (P = 0.004) and for GI > 1 (P < 0.001). With a median 4-year follow-up, overall survival (OS), clinical progression-free survival (cPFS) and biochemical PFS (bPFS) for the whole series were 91%, 92% and 91%, respectively. cPFS and bPFS were significantly different by risk groups. Multivariate Cox models for bPFS and cPFS showed no difference between irradiation techniques and a significant impact of risk group and initial PSA. Moderately hypofractionated radiotherapy is a viable treatment option for localized PCa with excellent tumour control and satisfactory toxicity profile. IMRT seems associated with a reduction in toxicity, whereas tumour control was equal between IMRT and 3D-CRT patients and depended mainly on the risk category.

Late toxicity of image-guided hypofractionated radiotherapy for prostate: non-randomized comparison with conventional fractionation

PURPOSE

To evaluate the incidence and predictors for late toxicity and tumor outcome after hypofractionated radiotherapy using three different image-guided radiotherapy (IGRT) systems (hypo-IGRT) compared with conventional fractionation without image guidance (non-IGRT).

METHODS AND MATERIALS

We compared the late rectal and urinary toxicity and outcome in 179 prostate cancer patients treated with hypo-IGRT (70.2 Gy/26 fractions) and 174 non-IGRT patients (80 Gy/40 fractions). Multivariate analysis was performed to define predictors for late toxicity. 5- and 8-year recurrence-free survival (RFS) and overall survival (OS) were analyzed.

RESULTS

Mean follow-up was 81 months for hypo-IGRT and 90 months for non-IGRT group. Mainly mild late toxicity was observed: Hypo-IGRT group experienced 65 rectal (30.9% G1/G2; 6.3% G3/G4) and 105 urinary events (56% G1/G2; 4% G3/G4). 5- and 8-year RFS rates were 87.5% and 86.8% (hypo-IGRT) versus 80.4% and 66.8% (non-IGRT). 5- and 8-year OS rates were 91.3% and 82.7% in hypo-IGRT and 92.2% and 84% in non-IGRT group. Multivariate analysis showed that hypo-IGRT is a predictor for late genitourinary toxicity, whereas hypo-IGRT, acute urinary toxicity and androgen deprivation therapy are predictors for late rectal toxicity. Advanced T stage and higher Gleason score (GS) were correlated with worse RFS.

CONCLUSIONS

A small increase in mild late toxicity, but not statistically significant increase in severe late toxicity in the hypo-IGRT group when compared with conventional non-IGRT group was observed. Our study confirmed that IGRT allows for safe moderate hypofractionation, offering a shorter overall treatment time, a good impact in terms of RFS and providing potentially more economic health care.

Planning study to compare dynamic and rapid arc techniques for postprostatectomy radiotherapy of prostate cancer

PURPOSE

To compare our standard technique for postprostatectomy radiotherapy of prostate cancer, i.e. using two lateral conformal dynamic arcs with volumetric-modulated arc therapy (VMAT) performed with the RapidArc(®) (Varian Medical Systems, Palo Alto, CA, USA). The plans were referred to as DA and RA, respectively.

MATERIALS AND METHODS

The treatment plans of 44 patients receiving adjuvant/salvage radiotherapy in the first months of 2010 were compared. In all cases, the prescribed total dose was 66-68.2 Gy (2.2 Gy per fraction). Both DA and RA plans were optimized in terms of dose coverage and constraints.

RESULTS

Small differences between the techniques were observed for planning target volume (PTV) dose distribution, whereas significant differences in sparing of organs at risk (OARs) were recorded (p < 0.0001). The OAR values (median; 95 % confidence interval, CI) were: rectum: D30 % = 60.7 Gy (59.40-62.04 Gy) and 48.2 Gy (46.40-52.72 Gy), D60 % = 34.1 Gy (28.50-38.92 Gy) and 27.7 Gy (21.80-31.51 Gy); bladder: D30 % = 57.3 Gy (45.83-64.53 Gy) and 46.4 Gy (33.23-61.48 Gy), D50 % = 16.4 Gy (11.89-42.38 Gy) and 17.2 Gy (10.97-27.90 Gy), for DA and RA, respectively. Treatment times were very similar, whereas the monitor units (MU) were 550 ± 29 versus 277 ± 3 for RA and DA, respectively.

CONCLUSION

Dose-volume histograms (DVHs) show improvements in OAR sparing with RA. However, the RA technique is associated with almost double the number of MUs compared to DA. Regarding the PTV, DA is slightly superior in terms of D2 % and dose homogeneity. On the whole, the results suggest that RA be the favorable technique.

Evaluation of the dynamic conformal arc therapy in comparison to intensity-modulated radiation therapy in prostate, brain, head-and-neck and spine tumors

To evaluate dynamic conformal arc therapy (DAT) dose distribution and clinical applicability in comparison to intensity‐modulated radiotherapy (IMRT) in different types of tumors and locations, twelve patients with prostate cancer with no node involvement and three patients with single tumors in the pituitary, in the neck and in the thoracic spinal region treated with IMRT, were retrospectively planned with DAT using Eclipse (V8.1). The prostate cases were also planned with three‐dimensional conformal radiation therapy (3DCRT). Dose distributions were evaluated through comparisons of dose‐volumetric histograms and in‐house IMRT protocol constraints, as well as validated via ion chamber array measurements. DAT plans for prostate showed a statistically comparable achievement of tumor conformity and dose sparing for bladder and rectum when compared to IMRT. Dose on femoral heads were similar to those achieved using 3DCRT. DAT could be planned with similar results to those obtained in IMRT for the dose constraints of the defined structures by using a 360° arc for the brain lesion and several arcs including noncoplanar ones for the head‐and‐neck and spinal tumors. Experimental validation of the calculated dose distributions via gamma analysis of composite distributions for DAT provided that more than 95% of the pixels satisfy the criteria 3 mm–3%, which was similar to that of IMRT. The average number of monitor units was approximately five times lower than IMRT. In conclusion, DAT is capable of providing conformal dose distributions to the targets accomplishing many of the IMRT dose constraints simultaneously. Experimental dose‐validation accuracy, ease of planning and reduced treatment times make DAT both acceptable and attractive for clinical use.

PACS numbers: 87.55.D‐, 87.55.dk, 87.55.Qr, 87.56.bd, 87.56.Fc, 87.53.Kn, 87.55. de, 87.55.kd

Dosimetric comparison of three-dimensional conformal radiotherapy in salvage radiotherapy for PSA relapse after radical prostatectomy

The purpose of this study is to compare three-dimensional conformal radiotherapy (3D-CRT) plans in a setting of salvage radiotherapy after radical prostatectomy (RP) and to simulate whether dose escalation is possible with the most adequate 3D-CRT technique. This study included consecutive 10 patients underwent salvage radiotherapy (RT) for biochemical relapse of prostate cancer after RP. Normal structures included the rectum, bladder, and femoral head. For each patient, four different treatment plans including four fields RT (4F-RT), dynamic conformal arc radiotherapy (DCAT), six fields RT (6F-RT), and DCAT with rectum hollow-out technique (DCAT-HO), were created to entire the prostate bed. The parameters of the maximum and mean doses received by organs at risk (OAR), target coverage, dose homogeneity for the planning target volume (PTV) were compared. All plans were considered to be clinically tolerable for PTV coverage and dose homogeneity. The rectum sparing at the high dose area for DCAT-HO was considered to be the most superior to those for other three techniques by comparison of the dose delivered to a 1%, 5%, and 10% volume of the rectum. In the simulation of dose escalation to 70 Gy with DCAT-HO, OAR met a requirement of the dose-volume constraints. However, in the simulation of dose escalation to 72 Gy, the rectum that receives 60 to 65 Gy and bladder that receives 65 Gy exceeded the optimal dose-volume constraints. DCAT-HO was considered to be one of the most appropriate techniques in 3D-CRT if dose escalation to 70 Gy might be needed in a setting of salvage RT after RP in the future.

Acute toxicity of image-guided hypofractionated radiotherapy for prostate cancer: nonrandomized comparison with conventional fractionation

OBJECTIVES

To compare acute toxicity of prostate cancer image-guided hypofractionated radiotherapy (hypo-IGRT) with conventional fractionation without image-guidance (non-IGRT). To test the hypothesis that the potentially injurious effect of hypofractionation can be counterbalanced by the reduced irradiated normal tissue volume using IGRT approach.

MATERIALS AND METHODS

One hundred seventy-nine cT1-T2N0M0 prostate cancer patients were treated within the prospective study with 70.2 Gy/26 fractions (equivalent to 84 Gy/42 fractions, α/β 1.5 Gy) using IGRT (transabdominal ultrasound, ExacTrac X-Ray system, or cone-beam computer tomography). Their prospectively collected data were compared with data of 174 patients treated to 80 Gy/40 fractions with non-IGRT. The difference between hypo-IGRT and non-IGRT cohorts included fractionation (hypofractionation vs. conventional fractionation), margins (hypo-IGRT margins: 7 mm and 3 mm, for all but posterior margins; respectively; non-IGRT margins: 10 and 5 mm, for all but posterior margins, respectively), and use of image-guidance or not. Multivariate analysis was performed to define the tumor-, patient-, and treatment-related predictors for acute toxicity.

RESULTS

All patients completed the prescribed radiotherapy course. Acute toxicity in the hypo-IGRT cohort included rectal (G1: 29.1%; G2: 11.2%; G3: 1.1%) and urinary events (G1: 33.5%; G2: 39.1%; G3: 5%). Acute toxicity in the non-IGRT patients included rectal (G1: 16.1%; G2: 6.3%) and urinary events (G1: 36.2%; G2: 20.7%; G3: 0.6%). In 1 hypo-IGRT and 2 non-IGRT patients, radiotherapy was temporarily interrupted due to acute toxicity. The incidence of mild (G1-2) rectal and bladder complications was significantly higher for hypo-IGRT (P = 0.0014 and P < 0.0001, respectively). Multivariate analysis showed that hypo-IGRT (P = 0.001) and higher PSA (P = 0.046) are correlated with higher acute urinary toxicity. No independent factor was identified for acute rectal toxicity. No significant impact of IGRT system on acute toxicity was observed.

CONCLUSIONS

The acute toxicity rates were low and similar in both study groups with some increase in mild acute urinary injury in the hypo-IGRT patients (most probably due to the under-reporting in the retrospectively analyzed non-IGRT cohort). The higher incidence of acute bowel reactions observed in hypo-IGRT group was not significant in the multivariate analysis. Further investigation is warranted in order to exclude the bias due to the nonrandomized character of the study.

Sooner or later? Outcome analysis of 431 prostate cancer patients treated with postoperative or salvage radiotherapy

PURPOSE

To evaluate the outcome of postoperative radiotherapy (PORT) and salvage RT (SART) using a three-dimensional conformal two-dynamic arc (3D-ART) or 3D six-field technique in 431 prostate cancer patients.

METHODS AND MATERIALS

Of the 431 patients, 258 underwent PORT (started <6 months after radical prostatectomy) and 173 underwent SART because of biochemical failure after radical prostatectomy. The median patient age, preoperative prostate-specific antigen level, and Gleason score was 66 years, 9.4 ng/mL, and 7, respectively. The median radiation dose was 70 Gy in 35 fractions for both PORT and SART. The 3D six-field and 3D-ART techniques were used in 25.1% and 74.9% of patients, respectively. Biochemical failure was defined as a post-RT prostate-specific antigen nadir plus 0.1 ng/mL.

RESULTS

Acute toxicity included rectal events (PORT, 44.2% and 0.8% Grade 1-2 and Grade 3, respectively; SART, 42.2% and 1.2% Grade 1-2 and Grade 3, respectively) and urinary events (PORT, 51.2% and 2.3% Grade 1-2 and Grade 3-4, respectively; SART, 37.6% and 0% Grade 1-2 and Grade 3, respectively). Late toxicity also included rectal events (PORT, 14.7% and 0.8% Grade 1-2 and Grade 3-4, respectively; SART, 15.0% and 0.6% Grade 1-2 and Grade 3, respectively) and urinary events (PORT, 28.3% and 3.7% Grade 1-2 and Grade 3-4, respectively; SART, 19.3% and 0.6% Grade 1-2 and Grade 3, respectively). After a median follow-up of 48 months, failure-free survival, including biochemical and clinical failure, was significantly longer in the PORT patients (79.8% vs. 60.5%, p < 0.0001). Multivariate analysis showed that a prostate-specific antigen level postoperatively but before RT of >/=0.2 ng/mL (p < 0.001), Gleason score >6 (p = 0.025) and use of preoperative androgen deprivation (p = 0.002) correlated significantly with shorter failure-free survival. Multivariate analysis showed that PORT and the 3D-ART technique correlated with greater late urinary toxicity.

CONCLUSION

PORT and early referral for SART offer better disease control after radical prostatectomy. The greater urinary toxicity occurring after PORT and 3D-ART requires further investigation to improve the therapeutic index.

Evidence-based radiation oncology: Definitive, adjuvant and salvage radiotherapy for non-metastatic prostate cancer

The standard treatment options based on the risk category (stage, Gleason score, PSA) for localized prostate cancer include surgery, radiotherapy and watchful waiting. The literature does not provide clear-cut evidence for the superiority of surgery over radiotherapy, whereas both approaches differ in their side effects. The definitive external beam irradiation is frequently employed in stage T1b-T1c, T2 and T3 tumors. There is a pretty strong evidence that intermediate- and high-risk patients benefit from dose escalation. The latter requires reduction of the irradiated normal tissue (using 3-dimensional conformal approach, intensity modulated radiotherapy, image-guided radiotherapy, etc.). Recent data suggest that prostate cancer may benefit from hypofractionation due to relatively low alpha/beta ratio; these findings warrant confirmation though. The role of whole pelvis irradiation is still controversial. Numerous randomized trials demonstrated a clinical benefit in terms of biochemical control, local and distant control, and overall survival from the addition of androgen suppression to external beam radiotherapy in intermediate- and high-risk patients. These studies typically included locally advanced (T3-T4) and poor-prognosis (Gleason score >7 and/or PSA >20 ng/mL) tumors and employed neoadjuvant/concomitant/adjuvant androgen suppression rather than only adjuvant setting. The ongoing trials will hopefully further define the role of endocrine treatment in more favorable risk patients and in the setting of the dose escalated radiotherapy. Brachytherapy (BRT) with permanent implants may be offered to low-risk patients (cT1-T2a, Gleason score <7, or 3+4, PSA <or=10 ng/mL), with prostate volume of <or=50 ml, no previous transurethral prostate resection and a good urinary function. Some recent data suggest a benefit from combining external beam irradiation and BRT for intermediate-risk patients. EBRT after radical prostatectomy improves disease-free survival and biochemical and local control rates in patients with positive surgical margins or pT3 tumors. Salvage radiotherapy may be considered at the time of biochemical failure in previously non-irradiated patients.