Prostate intensity-modulated radiotherapy planning in seven mouse clicks: Development of a class solution for cancer

Implementation of automatic plan optimization in Italy: Status and perspectives

PURPOSE

To investigate and report on the diffusion and clinical use of automated radiotherapy planning systems in Italy and to assess the perspectives of the community of Italian medical physicists involved in radiotherapy on the use of these tools.

MATERIALS AND METHODS

A survey of medical physicists (one per Institute) of 175 radiotherapy centers in Italy was conducted between February 21st and April 1st, 2021. The information collected included the institute's characteristics, plan activity, availability/use of automatic tools and related issues regarding satisfaction, criticisms, expectations, and perceived professional modifications. Responses were analysed, including the impact of a few variables such as the institute type and experience.

RESULTS

125 of the centers (71%) answered the survey, with regional variability (range: 47%-100%); among these, 49% have a TPS with some automatic option. Clinical use of automatic planning is present in 33% of the centers, with 13% applying it in >50% of their plans. Among the 125 responding centres the most used systems are Pinnacle (16%), Raystation (9%) and Eclipse (4%). The majority of participants consider the use of automated techniques to be beneficial, while only 1% do not see any advantage; 83% of respondents see the possibility of enriching their professional role as a potential benefit, while 3% see potential threats.

CONCLUSIONS

Our survey shows that 49% of the responding centres have an automatic planning solution although clinically used in only 33% of the cases. Most physicists consider the use of automated techniques to be beneficial and show a prevalently positive attitude.

Automated planning through robust templates and multicriterial optimization for lung VMAT SBRT of lung lesions

Purpose

To develop and validate a robust template for VMAT SBRT of lung lesions, using the multicriterial optimization (MCO) of a commercial treatment planning system.

Methods

The template was established and refined on 10 lung SBRT patients planned for 55 Gy/5 fr. To improve gradient and conformity a ring structure around the planning target volume (PTV) was set in the list of objectives. Ideal fluence optimization was conducted giving priority to organs at risk (OARs) and using the MCO, which further pushes OARs doses. Segmentation was conducted giving priority to PTV coverage. Two different templates were produced with different degrees of modulation, by setting the Fluence Smoothing parameter to Medium (MFS) and High (HFS).

Each template was applied on 20 further patients. Automatic and manual plans were compared in terms of dosimetric parameters, delivery time, and complexity. Statistical significance of differences was evaluated using paired two‐sided Wilcoxon signed‐rank test.

Results

No statistically significant differences in PTV coverage and maximum dose were observed, while an improvement was observed in gradient and conformity. A general improvement in dose to OARs was seen, which resulted to be significant for chest wall V_30 Gy, total lung V_20 Gy, and spinal cord D_0.1 cc. MFS plans are characterized by a higher modulation and longer delivery time than manual plans. HFS plans have a modulation and a delivery time comparable to manual plans, but still present an advantage in terms of gradient.

Conclusion

The automation of the planning process for lung SBRT using robust templates and MCO was demonstrated to be feasible and more efficient.

Late toxicities of prostate cancer radiotherapy with and without hydrogel SpaceAOR insertion

INTRODUCTION

To investigate whether the implantation of a hydrogel spacer (SpaceOAR) reduces long-term rectal toxicity for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT).

METHODS

Patients with localised prostate cancer treated with 81 Gy in 45 fx of IMRT over 9 weeks were retrospectively compared: 65 patients with SpaceOAR and 56 patients without SpaceOAR. Planning aims restricted rectal doses to V40 Gy < 35%, V65 Gy < 17%, V75 Gy < 10%. Toxicities were evaluated between 3 months and 3 years after the completion of radiotherapy and were based on the common terminology criteria for adverse events (CTCAE) assessment tool for diarrhoea, haemorrhoids, faecal incontinence and proctitis.

RESULTS

The cumulative incidence of low-grade diarrhoea (G1) was significantly higher in the non-SpaceOAR group (21.4% vs 6.2%; P = 0.016). The cumulative incidence of proctitis (grades G1 and G2) was also higher in the non-SpaceOAR group (26.7% vs 9.2%; P = 0.015); the cumulative incidence of G2 proctitis was higher in the latter group (P = 0.043). There were no differences between the treatment groups for cumulative incidences of faecal incontinence and/or haemorrhoids. Three years after IMRT, diarrhoea and proctitis were higher in the non-SpaceOAR group, without reaching statistical significance. This finding was unchanged after correcting for baseline symptoms.

CONCLUSION

SpaceOAR is of benefit in reducing the cumulative incidence of low-grade diarrhoea and proctitis for up to 3 years after intensity-modulated radiotherapy.

Treatment planning for proton therapy: what is needed in the next 10 years?

Treatment planning is the process where the prescription of the radiation oncologist is translated into a deliverable treatment. With the complexity of contemporary radiotherapy, treatment planning cannot be performed without a computerized treatment planning system. Proton therapy (PT) enables highly conformal treatment plans with a minimum of dose to tissues outside the target volume, but to obtain the most optimal plan for the treatment, there are a multitude of parameters that need to be addressed. In this review areas of ongoing improvements and research in the field of PT treatment planning are identified and discussed. The main focus is on issues of immediate clinical and practical relevance to the PT community highlighting the needs for the near future but also in a longer perspective. We anticipate that the manual tasks performed by treatment planners in the future will involve a high degree of computational thinking, as many issues can be solved much better by e.g. scripting. More accurate and faster dose calculation algorithms are needed, automation for contouring and planning is required and practical tools to handle the variable biological efficiency in PT is urgently demanded just to mention a few of the expected improvements over the coming 10 years.

Analysis of a volumetric-modulated arc therapy (VMAT) single phase prostate template as a class solution

Aim

To assess a class solution template for volumetric-modulated arc therapy (VMAT) for prostate cancer using plan analysis software.

Background

VMAT is a development of intensity-modulated radiotherapy (IMRT) with potential advantages for the delivery of radiotherapy (RT) in prostate cancer. Class solutions are increasingly used for facilitating RT planning. Plan analysis software provides an objective tool for evaluating class solutions.

Materials and methods

The class solution for VMAT was based on the current static field IMRT template. The plans of 77 prostate cancer patients were evaluated using a set of in-house plan quality metrics (scores) (PlanIQ™, Sun Nuclear Corporation). The metrics compared the class solution for VMAT planning with the IMRT template and the delivered clinical plan (CP). Eight metrics were associated with target coverage and ten with organs-at-risk (OAR). Individual metrics were summed and the combined scores were subjected to non-parametric analysis. The low-dose wash for both static IMRT and VMAT plans were evaluated using 40 Gy and 25 Gy isodose volumes.

Results

VMAT plans were of equal or better quality than the IMRT template and CP for target coverage (combined score) and OAR combined score. The 40 Gy isodose volume was marginally higher with VMAT than IMRT (4.9%) but lower than CP (-6.6%)(P = 0.0074). The 25 Gy volume was significantly lower with VMAT than both IMRT (-32.7%) and CP (-34.4%)(P < 0.00001).

Conclusions

Automated VMAT planning for prostate cancer is feasible and the plans are equal to or better than the current IMRT class solution and the delivered clinical plan.

Software-based evaluation of a class solution for prostate IMRT planning

AIM

To use plan analysis software to evaluate a class solution for prostate intensity modulated radiotherapy (IMRT) planning.

BACKGROUND

Class solutions for radiotherapy planning are increasingly being considered for streamlining planning. Plan analysis software provides an objective approach to evaluating radiotherapy plans.

MATERIALS AND METHODS

Three iterations of a class solution for prostate IMRT planning (T1, T2 and Tfinal) were compared to the clinical plan of 74 prostate patients using radiotherapy plan analysis software (Plan IQ™, Sun Nuclear Corporation). A set of institution-specific plan quality metrics (scores) were established, based on best practice guidelines.

RESULTS

For CTV coverage, Tfinal was not significantly different to the clinical plan. With the exception of 95% PTV coverage, Tfinal metrics were significantly better than the clinical plan for PTV coverage. In the scoring analysis, mean dose, 95% and 107% isodose coverage scores were similar for all the templates and clinical plan. 100% coverage of the CTV clinical plan was similar to Tfinal but scored higher than T1 and T2. There were no significant differences between Tfinal and the clinical plan for the metrics and scores associated with organs at risk. The total plan score was similar for Tfinal and the clinical plan, although the scores for volume receiving total dose outside the PTV were higher for Tfinal than for the clinical plan (P < 0.0001).

CONCLUSIONS

The radiotherapy plan analysis software was useful for evaluating a class solution for prostate IMRT planning and provided evidence that the class solution produced clinically acceptable plans for these patients.

Can a peri-rectal hydrogel spaceOAR programme for prostate cancer intensity-modulated radiotherapy be successfully implemented in a regional setting?

INTRODUCTION

The aim of this study was to investigate whether the implementation of a hydrogel spacer (SpaceOAR) programme for patients treated with 81 Gy prostate intensity-modulated radiotherapy (IMRT) in a regional setting can reduce rectal doses and toxicity.

METHODS

In this retrospective study, 125 patients with localised prostate cancer treated between April 2014 (programme commencement) and June 2015 were compared: 65 with SpaceOAR (inserted by five different urologists) and 60 patients treated over the same time period without SpaceOAR. Patients were treated with 81 Gy in 45Fx of IMRT over 9 weeks. Planning aims included restricting rectal doses to V40 Gy < 35%, V65 Gy < 17%, V75 Gy < 10%. Acute toxicity was assessed weekly during radiotherapy and at 12 weeks.

RESULTS

Rectal volume parameters were all significantly lower in the SpaceOAR group, with an associated reduction in acute diarrhoea (13.8% vs 31.7%). There were no significant differences in the very low rates of acute and late faecal incontinence or proctitis, however, there was a trend towards increased haemorrhoid rate in the SpaceOAR group (11.7% vs 3.1%, P = 0.09).

CONCLUSION

A SpaceOAR programme in a regional setting with urologists performing low volumes of insertions (<1 per month on average) is of clinical benefit, and was associated with significantly lower radiation doses to the rectum and lower rates of acute diarrhoea.