IMRT For Prostate Cancer Research Articles

P107-3 SBRT and IMRT in localized prostate cancer: genitourinary toxicity comparison

P107-3 SBRT and IMRT in localized prostate cancer: genitourinary toxicity comparison

Evolving Prostate Cancer Radiotherapy: Exploring Gonadal Doses in 3DCRT and IMRT with Testicular Shielding

Objective: To compare the dosimetry of IMRT versus 3DCRT in prostate cancer, with a focus on testicular dose using lead testicular shielding. Materials and Methods: From January 2021 to January 2022, twenty patients with localized prostate cancer underwent IMRT treatment. Plans for 3DCRT were generated for each patient. Comparison was made between 3D-CRT and IMRT regarding target volume dose uniformity, sparing of critical organs, and testicular doses. Results: Significant differences were observed in dose uniformity and sparing of critical organs between the two modalities (p<0.005), demonstrating the superiority of IMRT over 3DCRT. However, with lead testicular shielding, comparable testicular doses were achieved with both techniques. Conclusion: IMRT offers superior dosimetric advantages compared to 3DCRT. Nevertheless, the testicular dose remains nearly equivalent between the two techniques when utilizing lead testicular shielding.

Intensity modulated radiation therapy with stereotactic body radiation therapy boost for unfavorable prostate cancer: five-year outcomes

PurposeIntensity-modulated radiation therapy (IMRT) with brachytherapy boost for unfavorable prostate cancer has been shown to improve biochemical relapse-free survival compared to IMRT alone. Stereotactic body radiation therapy (SBRT) is a less-invasive alternative to brachytherapy. Early outcomes utilizing SBRT boost suggest low rates of high-grade toxicity with a maintained patient-reported quality of life. Here, we report the 5-year progression-free survival (PFS) and prostate cancer-specific survival (PCSS) of patients treated with IMRT plus SBRT boost.Materials and methodsBetween 2008 and 2020, 255 patients with unfavorable prostate cancer were treated with robotic SBRT (19.5 Gy in three fractions) followed by fiducial-guided IMRT (45–50.4 Gy) according to an institutional protocol. For the first year, the patient’s PSA level was monitored every 3 months, biannually for 2 years, and annually thereafter. Failure was defined as nadir + 2 ng/mL or a rising PSA with imaging suggestive of recurrence. Detection of recurrence also included digital rectal examination and imaging studies, such as MRI, CT, PET/CT, and/or bone scans. PFS and PCSS were calculated using the Kaplan–Meier method.ResultsThe median follow-up period was 71 months. According to the NCCN risk classification, 5% (13/255) of the patients had favorable intermediate-risk disease, 23% (57/255) had unfavorable intermediate-risk disease, 40% (102/255) had high-risk disease, and 32% (83/255) had very high-risk disease. Androgen deprivation therapy was administered to 80% (204/255) of the patients. Elective pelvic lymph node IMRT was performed in 28 (10%) patients. The PFS for all patients at 5 years was 81% (favorable intermediate risk, 91%; unfavorable intermediate risk, 89%; high-risk, 78%; and very-high risk, 72%). The PCSS for all patients at 5 years was 97% (favorable intermediate risk, 100%; unfavorable intermediate risk, 100%; high risk, 100%; and very high risk, 89%).ConclusionThe incidence of failure following IMRT plus SBRT for unfavorable prostate cancer remains low at 5 years.

Effect of Daikenchuto Therapy on Risk of Rectal Bleeding after IMRT for Prostate Cancer

Rectal bleeding due to radiation proctitis after treatment in radiation therapy for prostate cancer is a typical late toxicity symptom. The rate of rectal bleeding has been reduced by using IMRT, IGRT and peri-rectal hydrogel spacer. On the other hand, few reports have attempted to reduce the rate of rectal bleeding by medication. It has been reported that Daikenchuto (DKT), a traditional Japanese herbal medicine, has the effects of accelerating gastrointestinal motility and anti-fibrosis. We retrospectively investigated the rate of rectal bleeding in patients between concurrently administered and not administered DKT for bowel control during IMRT for prostate cancer. The subjects were 102 patients who underwent definitive IMRT for prostate cancer between 2014 and 2021 in our hospital. The DKT therapy concurrent use group were included 46 patients (45%), who were administered DKT per 10.0 g / day or 15.0 g / day. The irradiation was carried out, confirming the rectal volume every time by the image-guided radiotherapy using cone beam CT in all cases. The curative doses fractionation of IMRT were 78 Gy in 2 Gy per fraction (40%) or 70 Gy in 2.5 Gy per fraction (60%). We compared the rate of rectal bleeding after IMRT with and without DKT. Late rectal bleeding toxicity was scored using the Common Terminology Criteria for Adverse Events ver. 5.0 criteria. The associated factors of rectal bleeding were examined using the Cox proportional hazard model for multivariate analysis. In the DKT therapy group, the median follow-up period was 31 months (Range: 17-84 months), and the rectal bleeding rate was Grade 1 in 2 patients (4%) and Grade ≥ 2 in none. The median observation period in the non-DKT therapy group was 48 months (Range: 17-101 months), and the rectal bleeding rate was Grade 1 in 12 patients (21%), Grade 2 in 6 patients (10%), and there were no events of Grade ≥ 3. In univariate analysis, DKT therapy, dose fractionation and planned rectal doses (V50, V55, V60, V65, V70 and V75 converted to EQD23) were significant factors for rectal bleeding. Multivariate analysis showed that the DKT therapy was a significant independent factor in reducing the rate of rectal bleeding (HR: 0.105, 95% CI: 0.01-0.50, P = 0.003). It was statistically suggested in this study that the DKT therapy further reduced the rate of rectal bleeding in IMRT for prostate cancer.

Optimized Hybrid Arc for Improved Sparing of Organs at Risk: Balanced Combination of IMRT and VMAT in Prostate Cancer

Optimized Hybrid Arc for Improved Sparing of Organs at Risk: Balanced Combination of IMRT and VMAT in Prostate Cancer

VMAT partial arc technique decreases dose to organs at risk in whole pelvic radiotherapy for prostate cancer when compared to full arc VMAT and IMRT.

Whole pelvic radiotherapy (WPRT) can sterilize microscopic lymph node metastases in treatment of prostate cancer. WPRT, compared to prostate only radiotherapy (PORT), is associated with increased acute gastrointestinal, and hematological toxicities. To further explore minimizing normal tissue toxicities associated with WPRT in definitive IMRT for prostate cancer, this planning study compared dosimetric differences between static 9-field-IMRT, full arc VMAT, and mixed partial-full arc VMAT techniques. In this retrospective study, 12 prostate cancer patients who met the criteria for WPRT were randomly selected for this study. The initial volume, PTV46, included the prostate, seminal vesicles, and pelvic nodes with margin and was prescribed to 4600cGy. The cone-down volume, PTV78, included the prostate and proximal seminal vesicles with margin to a total dose of 7800cGy. For each CT image set, 3 plans were generated for each of the PTVs: an IMRT plan, a full arc (FA) VMAT plan, and a mixed partial-full arc (PFA) VMAT plan, using 6MV photons energy. According to RTOG protocols none of the plans had a major Conformity Index (CI) violation by any of the 3 planning techniques. PFA plan had the best mean CI index of 1.00 and significantly better than IMRT (p = 0.03) and FA (p = 0.007). For equivalent PTV coverage, the average composite gradient index of the PFA plans was better than the IMRT and the FA plans with values 1.92, 2.03, and 2.01 respectively. The defference was statistically significant between PFA/IMRT and PFA/FA, with p- values of < 0.001. The IMRT plans and the PFA plans provided very similar doses to the rectum, bladder, sigmoid colon, and femoral heads, which were lower than the dose in the FA plans. There was a significant decrease in the mean dose to the rectum from 4524 cGy with the FA to 4182cGy with the PFA and 4091cGy with IMRT (p < 0.001). The percent of rectum receiving 4000cGy was also the highest with FA at 66.1% compared to 49.9% (PFA) and 47.5% (IMRT). There was a significant decrease in the mean dose to the bladder from 3922cGy (FA) to 3551cGy (PFA) and 3612cGy (IMRT) (p < 0.001). The percent of bladder receiving 4000cGy was also the highest with FA at 45.4% compared to 36.6% (PFA) and 37.4% (IMRT). The average mean dose to the sigmoid colon decreased from 4177cGy (FA) to 3893cGy (PFA) and 3819cGy (IMRT). The average mean dose to the femoral heads decreased from 2091cGy (FA) to 2026cGy (PFA) and 1987cGy (IMRT). Considering the improvement in plan quality indices recorded in this study including the dose gradient and the dose to organs at risk, mixed partial-full arc plans may be the preferred VMAT treatment technique over full arc plans for prostate cancer treatments that include nodal volumes.

The development of a deep reinforcement learning network for dose-volume-constrained treatment planning in prostate cancer intensity modulated radiotherapy

Although commercial treatment planning systems (TPSs) can automatically solve the optimization problem for treatment planning, human planners need to define and adjust the planning objectives/constraints to obtain clinically acceptable plans. Such a process is labor-intensive and time-consuming. In this work, we show an end-to-end study to train a deep reinforcement learning (DRL) based virtual treatment planner (VTP) that can behave like a human to operate a dose-volume constrained treatment plan optimization engine following the parameters used in Eclipse TPS for high-quality treatment planning. We considered the prostate cancer IMRT treatment plan as the testbed. The VTP took the dose-volume histogram (DVH) of a plan as input and predicted the optimal strategy for constraint adjustment to improve the plan quality. The training of VTP followed the state-of-the-art Q-learning framework. Experience replay was implemented with epsilon-greedy search to explore the impacts of taking different actions on a large number of automatically generated plans, from which an optimal policy can be learned. Since a major computational cost in training was to solve the plan optimization problem repeatedly, we implemented a graphical processing unit (GPU)-based technique to improve the efficiency by 2-fold. Upon the completion of training, the established VTP was deployed to plan for an independent set of 50 testing patient cases. Connecting the established VTP with the Eclipse workstation via the application programming interface, we tested the performance the VTP in operating Eclipse TPS for automatic treatment planning with another two independent patient cases. Like a human planner, VTP kept adjusting the planning objectives/constraints to improve plan quality until the plan was acceptable or the maximum number of adjustment steps was reached under both scenarios. The generated plans were evaluated using the ProKnow scoring system. The mean plan score (± standard deviation) of the 50 testing cases were improved from 6.18 ± 1.75 to 8.14 ± 1.27 by the VTP, with 9 being the maximal score. As for the two cases under Eclipse dose optimization, the plan scores were improved from 8 to 8.4 and 8.7 respectively by the VTP. These results indicated that the proposed DRL-based VTP was able to operate the in-house dose-volume constrained TPS and Eclipse TPS to automatically generate high-quality treatment plans for prostate cancer IMRT.

PD-0322 Artificial intelligence organ-at-risk dose prediction for high-risk prostate cancer IMRT

PD-0322 Artificial intelligence organ-at-risk dose prediction for high-risk prostate cancer IMRT

Long-term safety of high-dose whole pelvic IMRT for high-risk localized prostate cancer through 10-year follow-up.

The aim of this study was to evaluate the long-term efficacy and safety of whole pelvic intensity-modulated radiation therapy with a simultaneous-integrated boost (WP-SIB-IMRT) for locally advanced prostate cancer (LAPCa). All patients with cT3-4N0M0 prostate cancer treated with WP-SIB-IMRT between February 2006 and September 2009 at our institution were analyzed retrospectively. The prescribed dose was 78Gy to the prostate and 58.5Gy to the prophylactic pelvic lymph nodal area in 39 fractions delivered using the simultaneous-integrated boost technique. All patients received short-term neoadjuvant androgen-deprivation therapy alone (median 8.3months). Propensity-score matching (PSM) analysis was performed to evaluate the additional benefit of prophylactic whole pelvic radiation therapy (WPRT), using the cohort of 203 LAPCa patients treated with prostate-only IMRT (PO-IMRT). In total, 47 consecutive patients were analyzed. The median estimated risk of pelvic lymph node involvement was 57.5%. The median follow-up period was 10.5years. The 10year prostate cancer-specific survival and biochemical failure (BF) rates were 92.2 and 54.8%, respectively. The 10year cumulative incidence rates of ≥ grade 2 late genitourinary and gastrointestinal toxicities were 21.6 and 17.2%, respectively. From a total of 250 patients, PSM analysis identified 76 patients with similar characteristics, and no significant difference in BF rates was observed between WP-SIB-IMRT and PO-IMRT cohorts (p = 0.261). WP-SIB-IMRT for LAPCa was safe over long-term observation, although no clear benefit of WPRT was observed among our small and highly selected cohort. Regarding the additional efficacy of WPRT, further investigations are needed.

PO-1655: Dosimetric impact of the anatomical pelvic organs variations during prostate cancer IMRT

PO-1655: Dosimetric impact of the anatomical pelvic organs variations during prostate cancer IMRT

PH-0232: Metabolic profiles do not recover to normal after pelvic IMRT for high-risk prostate cancer.

PH-0232: Metabolic profiles do not recover to normal after pelvic IMRT for high-risk prostate cancer.

PSA Levels after IMRT for Prostate Cancer: Discriminating Second Plateau from PSA Failure

After IMRT combined with androgen deprivation therapy (ADT) for prostate cancer, PSA levels generally decrease to the nadir; by withdrawing ADT, the PSA level gradually rises and reaches a plateau after a while. Following IMRT alone, the PSA level gradually decreases and reaches a plateau. In the present study, this plateau is named as “first plateau (P1)”. In some cases, however, PSA rises after the first plateau and reaches a second plateau (P2) without cancer recurrence. We assume this phenomenon reflects the recovery of normal prostate cells. The objective of this study is to investigate clinical features of the second plateau and to compare patients who experienced PSA failure to those who settled at the second plateau phase. Of 348 patients with T1-3N0M0 prostate cancer treated by IMRT with or without neoadjuvant/adjuvant ADT, 35 patients receiving ADT for > 3 years or intermittent ADT were excluded, and 313 patients followed for 79-129 (median 106) months were analyzed. The total dose was 72.6-78 Gy with daily fractions of 2.0, 2.1, or 2.2 Gy. PSA failure was defined as PSA rise of > 2.0 ng/mL above the nadir. “Plateau” was defined algorithmically as an interval where PSA value at any measurement point falls into a range of the preceding three values and “elevation” as a consequent PSA rise without satisfying the criteria of “plateau”. Cox proportional-hazard models were used to find predictors for P2. The slope of elevation after P1 (E1) was calculated as a regression coefficient in a linear regression. Mean PSA nadir, P1 and P2 levels were compared between the PSA-failure and non-failure groups. Of 313 patients, P1 was observed in 177 patients (56.5%). In 67 (21.4%), PSA levels did not elevate above nadir and in 69 (22.0%) PSA levels increased after nadir without satisfying the criteria of plateau. Eventually, PSA failure was observed in 50 patients (16.0%). P2 was observed in 52 (16.6%) and elevation after P2 (E2) was observed in 24 (7.7%). T3 and neoadjuvant ADT were associated with lower likelihood of the occurrence of P2 on multivariate analysis. In fully-analyzable cases (n = 93), mean PSA nadir, P1 and P2 levels, and E1 slope for the non-PSA-failure group (n = 74) were 0.11, 0.31, and 0.41 ng/mL, and 0.11 ng/mL/year, respectively. Those for the PSA-failure group (n = 19) were 0.26, 0.54, and 0.82 ng/mL, and 0.48 ng/mL/year, respectively. All these factors except the mean P2 level were significantly higher in the PSA-failure group. The ROC curve identified the E1 slope of 0.28 ng/mL/year as an optimal cut-off value predicting risks of PSA failure with the highest accuracy (AUC:0.88, 95% CI: 0.79-0.96). By applying the criteria of “plateau” proposed in this study, 52 of 313 patients (16.6%) treated by IMRT experienced the second plateau. A comparison of the E1 slope indicated PSA rise of >0.28 ng/mL/year after P1 could be a predictor discriminating PSA failure from second plateau.

EP-2196 Dosimetric impact of anatomical changes during IMRT for prostate cancer

EP-2196 Dosimetric impact of anatomical changes during IMRT for prostate cancer

EP-1567 Prospective longitudinal evaluation of quality of life after prostate cancer IMRT

EP-1567 Prospective longitudinal evaluation of quality of life after prostate cancer IMRT

EP-1521 IMRT for prostate cancer with seminal vesicle involvement : A multicentric retrospective analysis

EP-1521 IMRT for prostate cancer with seminal vesicle involvement : A multicentric retrospective analysis

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

ObjectivesNo study has reported clinical results of external-beam radiotherapy specifically for T3b prostate cancer. The possibility of escalating the dose to the involved seminal vesicles (ISV) while respecting the dose constraints in the organs at risk is thus so far not clearly demonstrated. The objective of the study was to analyze the dose distribution and the clinical outcome in a large series of patients who received IMRT for T3b prostate cancer.Materials and methodsThis retrospective analysis included all patients who received IMRT and androgen deprivation therapy for T3b prostate cancer, between 2008 and 2017, in six French institutions, with available MRI images and dosimetric data.ResultsA total of 276 T3b patients were included. The median follow-up was 26 months. The median (range) prescribed doses (Gy) to the prostate and to the ISV were 77 (70–80) and 76 (46–80), respectively. The dose constraint recommendations were exceeded in less than 12% of patients for the rectum and the bladder. The 5-year risks of biochemical and clinical recurrences and cancer-specific death were 24.8%, 21.7%, and 10.3%, respectively. The 5-year risks of local, pelvic lymph node, and metastatic recurrences were 6.4%, 11.3%, and 15%, respectively. The number of involved lymph nodes (≤ 2 or ≥ 3) on MRI was the only significant prognostic factor in clinical recurrence (HR 9.86) and death (HR 2.78). Grade ≥ 2 acute and 5-year late toxicity rates were 13.2% and 12% for digestive toxicity, and 34% and 31.5% for urinary toxicity, respectively. The dose to the pelvic lymph node and the age were predictive of late digestive toxicity.ConclusionIMRT for T3b prostate cancer allows delivery of a curative dose in the ISV, with a moderate digestive toxicity but a higher urinary toxicity. Lymph node involvement increases the risk of recurrence and death.

47. Dependence from dose and fractionation of late severe urinary toxicities after radical radiotherapy for prostate cancer

Purpose Development of NTCP models of late severe urinary symptoms after radical RT for prostate cancer (PCa). Methods Patients were enrolled in a prospective, multicentre, observational trial in 2010–2014 and treated with conventional (74–80 Gy at 1.8–2 Gy/fr) or moderately hypofractionated IMRT (65–75.2 Gy at 2.2–2.7 Gy/fr). Bladder dose-surface histograms were corrected to 2 Gy/fr equivalent doses (EQD2) and reduced to Equivalent Uniform Doses at varying α / β and n. Urethral stricture requiring urethrotomy and bleeding (assessed by the physicians) and late obstructive symptoms and incontinence (through ICIQ and IPSS questionnaires) were evaluated before RT, at its completion and every 6 months until 5 years of follow-up. Incidence of late obstructive symptoms was defined as an increase of ⩾10 points with respect to baseline in the IPSS, at least once between 6–36 months after RT; incidence of incontinence as the sum ICIQ3 + ICIQ4 > 5, with the same timing, in continent patients before RT (ICIQ3 + ICIQ4 = 0). Maximum likelihood estimation (MLE) was employed for calculating the best-fit NTCP parameters (EUD50 and k) of all symptoms. Results 319 patients were followed for ⩾36 months with at least 3 follow-up evaluations. 27/319 (23%) patients exhibited at least one severe late urinary symptom (details in Table). Bleeding, obstructive symptoms and incontinence showed greater incidence for hypofractionation and EQD2 > 78 Gy. The highest likelihood was obtained for very low n in all cases; low α / β was found for all the endpoints except stricture. Figure shows the best-fit NTCP parameters: incontinence and bleeding curves were steeper with rising EUD. Conclusions Incidence of late severe urinary symptoms in patients treated with IMRT for PCa was about 20%. Bladder seems to act as a serial organ and all the symptoms significantly depend on the prescribed dose. In addition, all the symptoms, except for stenosis, show a surprisingly important effect of hypofractionation.

EP183 - Superiority of coverage probability concept compared to standard IMRT in prostate cancer - results of a prospective pre-adaptive study

EP183 - Superiority of coverage probability concept compared to standard IMRT in prostate cancer - results of a prospective pre-adaptive study

Associations between MRI Findings and Urinary Tract Symptoms after IMRT for Prostate Cancer

Associations between MRI Findings and Urinary Tract Symptoms after IMRT for Prostate Cancer

PV-0624: Longitudinal analysis of the microbiota by GI toxicity during IMRT for high-risk prostate cancer

PV-0624: Longitudinal analysis of the microbiota by GI toxicity during IMRT for high-risk prostate cancer