Automated treatment planning as a dose escalation strategy for stereotactic radiation therapy in pancreatic cancer

Automated single-isocenter stereotactic body radiotherapy for multiple metastases from breast cancer: A case study

Oligometastatic breast cancer patients can today could benefit from a multimodal approach, combining systemic therapy with metastasis-directed treatment using stereotactic body radiotherapy (SBRT). However, the possibility to synchronously treat multiple lesions is still challenging, needing the ability to generate complex dose distributions with steep dose gradients outside the lesions and major sparing of surrounding organs at risk and accurately track and reproduce the patient's position before and during radiation therapy. We report the case of an oligometastatic patient from left breast cancer, which occurred after a full course of whole breast radiotherapy, treated using the potential of modern technology including single-isocenter setup, plan automation, breath-hold technique and surface guided tracking and reproducibility of patient's position before and during radiation therapy. A 44-year-old female patient with a history of left breast cancer, specifically a luminal-B-like invasive ductal carcinoma with Her2 overexpression, was admitted to our department. The patient previously underwent a left mastectomy (pT2N0M0), 4 cycles of adjuvant chemotherapy, adjuvant radiotherapy on the chest wall and lymph nodes drainage, and 5 years of hormonal therapy. A chest wall ultrasound and positron emission tomography revealed the presence of new lesions in the area of the surgical scar from the previous mastectomy, internal mammary, axillary and retropectoral levels. The 3 lesions were simultaneously treated with a mono-isocentric VMAT plan using SBRT technique with a total dose of 30 Gy delivered in 5 fractions. Due to the technical challenges, this treatment was supported by the use of planning automation, breath-hold technique and surface-guided radiation therapy to improve the accuracy of the dose delivery. Two different plans were generated and compared to pursue the best dosimetric result, including a summed plan obtained from 3 individual SBRT plans for each lesion with a separate isocenter placed in each of them (MIP), and a single-isocenter SBRT plan able to treat multiple lesions synchronously (SIP). Because of the advantages in terms of dosimetry and dose delivery efficiency, the patient was successfully treated with the SIP plan. The treatment time was reduced to about 4.5 minutes, allowing the comfortably use of breath-hold technique. After treatment, the condition of the patient was normal, and no toxicities have been observed in follow-up. SBRT with mono isocentric VMAT planning represents the recommended approach to simultaneously treat multiple lesions in close proximity in the thoracic district.

Feasibility-guided automated planning for stereotactic treatments of prostate cancer

Significant improvements in plan quality using automated planning have been previously demonstrated. The aim of this study was to develop an optimal automated class solution for stereotactic radiotherapy (SBRT) planning of prostate cancer using the new Feasibility module implemented in the pinnacle evolution. Twelve patients were retrospectively enrolled in this planning study. Five plans were designed for each patient. Four plans were automatically generated using the 4 proposed templates for SBRT optimization implemented in the new pinnacle evolution treatment planning systems, differing for different settings of dose-fallout (low, medium, high and veryhigh). Based on the obtained results, the fifth plan (feas) was generated customizing the template with the optimal criteria obtained from the previous step and integrating in the template the "a-priori" knowledge of OARs sparing based on the Feasibility module, able to estimate the best possible dose-volume histograms of OARs before starting optimization. Prescribed dose was 35 Gy to the prostate in 5 fractions. All plans were generated with a full volumetric-modulated arc therapy arc and 6MV flattening filter-free beams, and optimized to ensure the same target coverage (95% of the prescription dose to 98% of the target). Plans were assessed according to dosimetric parameters and planning and delivery efficiency. Differences among the plans were evaluated using a Kruskal-Wallis 1-way analysis of variance. The requests for more aggressive objectives for dose falloff parameters (from low to veryhigh) translated in a statistically significant improvement of dose conformity, but at the expense of a dose homogeneity. The best automated plans in terms of best trade-off between target coverage and OARs sparing among the 4 plans automatically generated by the SBRT module were the high plans. The veryhigh plans reported a significant increase of high-doses to prostate, rectum, and bladder that was considered dosimetrically and clinically unacceptable. The feas plans were optimized on the basis on high plans, reporting significant reduction of rectum irradiation; Dmean, and V18 decreased by 19% to 23% (p = 0.031) and 4% to 7% (p = 0.059), respectively. No statistically significant differences were found in femoral heads and penile bulb irradiation for all dosimetric metrics. feas plans showed a significant increase of MU/Gy (mean: 368; p = 0.004), reflecting an increased level of fluence modulation. Thanks to the new efficient optimization engines implemented in pinnacle evolution (L-BFGS and layered graph), mean planning time was decreased to less than 10 minutes for all plans and all techniques. The integration of dose-volume histograms a-priori knowledge provided by the feasibility module in the automated planning process for SBRT planning has shown to significantly improve plan quality compared to generic protocol values as inputs.

Personalized Automation of Treatment Planning for Linac-Based Stereotactic Body Radiotherapy of Spine Cancer

Purpose/Objective(s)

Stereotactic ablative body radiotherapy (SBRT) for vertebral metastases is a challenging treatment process. Planning automation has recently reported the potential to improve plan quality and increase planning efficiency. We performed a dosimetric evaluation of the new Personalized engine implemented in Pinnacle3 for full planning automation of SBRT spine treatments in terms of plan quality, treatment efficiency, and delivery accuracy.

Materials/Methods

The Pinnacle3 treatment planning system was used to reoptimize six patients with spinal metastases, employing two separate automated engines. These two automated engines, the existing Autoplanning and the new Personalized, are both template-based algorithms that employ a wishlist to construct planning goals and an iterative technique to replicate the planning procedure performed by skilled planners. The boost tumor volume (BTV) was defined as the macroscopically visible lesion on RM examination, and the planning target volume (PTV) corresponds with the entire vertebra. Dose was prescribed according to simultaneous integrated boost strategy with BTV and PTV irradiated simultaneously over 3 fractions with a dose of 30 and 21 Gy, respectively. Dose-volume histogram (DVH) metrics and conformance indices were used to compare clinically accepted manual plans (MP) with automated plans developed using both Autoplanning (AP) and Personalized engines (Pers). All plans were evaluated for planning efficiency and dose delivery accuracy.

Results

For similar spinal cord sparing, automated plans reported a significant improvement of target coverage and dose conformity. On average, Pers plans increased near-minimal dose D98% by 10.4% and 8.9% and target coverage D95% by 8.0% and by 4.6% for BTV and PTV, respectively. Automated plans provided significantly superior dose conformity and dose contrast by 37%–47% and by 4.6%–5.7% compared with manual plans. Overall planning times were dramatically reduced to about 15 and 23 min for Pers and AP plans, respectively. The average beam-on times were found to be within 3 min for all plans. Despite the increased complexity, all plans passed the 2%/2 mm γ-analysis for dose verification.

Conclusion

Automated planning for spine SBRT through the new Pinnacle3 Personalized engine provided an overall increase of plan quality in terms of dose conformity and a major increase in efficiency. In this complex anatomical site, Personalized strongly reduce the tradeoff between optimal accurate dosimetry and planning time.

Personalized Treatment Planning Automation in Prostate Cancer Radiation Oncology: A Comprehensive Dosimetric Study

Background

In radiation oncology, automation of treatment planning has reported the potential to improve plan quality and increase planning efficiency. We performed a comprehensive dosimetric evaluation of the new Personalized algorithm implemented in Pinnacle³ for full planning automation of VMAT prostate cancer treatments.

Material and Methods

Thirteen low-risk prostate (without lymph-nodes irradiation) and 13 high-risk prostate (with lymph-nodes irradiation) treatments were retrospectively taken from our clinical database and re-optimized using two different automated engines implemented in the Pinnacle treatment system. These two automated engines, the currently used Autoplanning and the new Personalized are both template-based algorithms that use a wish-list to formulate the planning goals and an iterative approach able to mimic the planning procedure usually adopted by experienced planners. In addition, the new Personalized module integrates a new engine, the Feasibility module, able to generate an “a priori” DVH prediction of the achievability of planning goals. Comparison between clinically accepted manually generated (MP) and automated plans generated with both Autoplanning (AP) and Personalized engines (Pers) were performed using dose-volume histogram metrics and conformity indexes. Three different normal tissue complication probabilities (NTCPs) models were used for rectal toxicity evaluation. The planning efficiency and the accuracy of dose delivery were assessed for all plans.

Results

For similar targets coverage, Pers plans reported a significant increase of dose conformity and less irradiation of healthy tissue, with significant dose reduction for rectum, bladder, and femurs. On average, Pers plans decreased rectal mean dose by 11.3 and 8.3 Gy for low-risk and high-risk cohorts, respectively. Similarly, the Pers plans decreased the bladder mean doses by 7.3 and 7.6 Gy for low-risk and high-risk cohorts, respectively. The integral dose was reduced by 11–16% with respect to MP plans. Overall planning times were dramatically reduced to about 7 and 15 min for Pers plans. Despite the increased complexity, all plans passed the 3%/2 mm γ-analysis for dose verification.

Conclusions

The Personalized engine provided an overall increase of plan quality, in terms of dose conformity and sparing of normal tissues for prostate cancer patients. The Feasibility “a priori” DVH prediction module provided OARs dose sparing well beyond the clinical objectives. The new Pinnacle Personalized algorithms outperformed the currently used Autoplanning ones as solution for treatment planning automation.

A comprehensive evaluation of the quality and complexity of prostate IMRT and VMAT plans generated by an automated inverse planning tool

Introduction:

The Pinnacle3 Auto-Planning (AP) package is an automated inverse planning tool employing a multi-sequence optimisation algorithm. The nature of the optimisation aims to improve the overall quality of radiotherapy plans but at the same time may produce higher modulation, increasing plan complexity and challenging linear accelerator delivery capability.

Methods and materials:

Thirty patients previously treated with intensity-modulated radiotherapy (IMRT) to the prostate with or without pelvic lymph node irradiation were replanned with locally developed AP techniques for step-and-shoot IMRT (AP-IMRT) and volumetric-modulated arc therapy (AP-VMAT). Each case was also planned with VMAT using conventional inverse planning. The patient cohort was separated into two groups, those with a single primary target volume (PTV) and those with dual PTVs of differing prescription dose levels. Plan complexity was assessed using the modulation complexity score.

Results:

Plans produced with AP provided equivalent or better dose coverage to target volumes whilst effectively reducing organ at risk (OAR) doses. For IMRT plans, the use of AP resulted in a mean reduction in bladder V50Gy by 4·2 and 4·7 % (p ≤ 0·01) and V40Gy by 4·8 and 11·3 % (p < 0·01) in the single and dual dose level cohorts, respectively. For the rectum, V70Gy, V60Gy and V40Gy were all reduced in the dual dose level AP-VMAT plans by an average of 2·0, 2·7 and 7·3 % (p < 0·01), respectively. A small increase in plan complexity was observed only in dual dose level AP plans.

Findings:

The automated nature of AP led to high quality treatment plans with improvement in OAR sparing and minimised the variation in achievable dose planning metrics when compared to the conventional inverse planning approach.

Challenges in lung and heart avoidance for postmastectomy breast cancer radiotherapy: Is automated planning the answer?

Postmastectomy radiotherapy (PMRT) has been shown to improve the overall survival for invasive breast cancer patients. However, it represents a challenging treatment geometry and individualized planning strategies with complex field arrangements are usually adopted to decrease radiotoxicity to heart and lungs. Automated treatment planning has the potential to improve plan quality consistency and planning efficiency. Herein, we describe the application of the Pinnacle³ Autoplanning engine as a valuable technological resource able to allow the treatment of challenging patients theoretically unfit for radiotherapy for major cardiac and pulmonary comorbidities. Treatment was planned for three left-sided chest wall and regional lymph-nodes postmastectomy breast cancer patients. A deep inspiration breath-hold (DIBH) technique was used aiming to reduce the OARs irradiation. Three manually generated plans (hybrid-IMRT (HMRT), hybrid-VMAT (HVMAT) and full VMAT (MP-VMAT) and a fully automated plan created by the Autoplanning engine (AP-VMAT) were optimized in order to ensure a safe radiation therapy to the patients. The plans were evaluated based on planning target volumes (PTVs) coverage, dose homogeneity index (HI), conformity index (CN), dose to organs at risk (OARs) and normal tissue complication probabilities (NTCPs) of pericarditis, long term mortality and pneumonitis. Despite the use of deep moderated breath-hold, all human-driven plans failed to reach the stringent dose objectives for OARs. All plans provided an optimal coverage for chest wall and lymph-nodal area. AP-VMAT delivered the lowest mean dose to the heart (3.4 to 4.9 Gy) and ipsilateral lung (7.5 to 12.5 Gy) reporting the lowest NTCP for pneumonitis (<1%), confirming the only chance to comply the dose objectives. Moreover, AP-VMAT reported a decrease of the integral dose, which was lower by about 4-8% with respect to manual plans. AP-VMAT plan resulted in up to 58% increase of MUs with respect to manual plans, suggesting a more pronounced fluence modulation and plan complexity. A major difference was found for the planning time which was reduced to less than 30 minutes by using the Auto-Planning module. With improved planning quality and efficiency, Auto-planning is an effective tool to enable high-quality plans in challenging postmastectomy breast cancer radiotherapy.