Multi-Criteria Optimization and RapidPlan for Improved Organs at Risk Sparing in Treatment Planning of Malignant Pleural Mesothelioma

PURPOSE/OBJECTIVE(S)

Treatment planning for malignant pleural mesothelioma is complex and time-consuming owing to the large volume of the target as well as its overlap and proximity to critical organs. Knowledge-based planning (KBP) model using RapidPlan (RP) was previously developed and clinically tested at our institution for treatment planning of these cases that had undergone pleurectomy-decortication, and therefore had two intact-lungs. The aim of this work is to investigate if multi-criteria optimization (MCO) can further improve the RP model with respect to organ at risk (OAR) sparing without compromising target coverage.

MATERIALS/METHODS

The RP model was trained with clinically accepted plans of 57 patients that used Volumetric Modulated Arc Therapy (VMAT) with 2 partial arcs and 6 MV photons. The dose volume histogram (DVH) estimation model was trained to estimate doses to the heart, ipsilateral lung, total lung, contralateral lung, stomach, esophagus, kidneys and liver. Clinical treatment plans for 12 patients were re-planned using RP as well as a combination of RP and MCO. Application of MCO was after RP and used tradeoff exploration to navigate to the improved dose distribution on a Pareto surface. Selection of a plan that further improved OAR sparing while maintaining coverage constraints of PTV D95 and V95 ≥ 94% was made. Dosimetric parameters for clinical plans (CP), plans using RP as well as plans generated with RP and MCO were all compared for 12 new validation cases. Wilcoxon sign-rank test was used for statistical significance testing.

RESULTS

The mean heart dose was reduced from 20.9 Gy ± 3.2 Gy for CP to 17.1 Gy ± 4.2 Gy with RP and further to 13.8 Gy ± 3.3 Gy with RP and MCO. The heart V30 Gy was reduced from 23.7% ± 8% to 18.2% ± 9.4% with RP and further to 13.6% ± 5.7% with RP and MCO. The corresponding results for contralateral lung V5 Gy were 68.6% ± 14.1% with CP, 50% ± 26.3% with RP and 45.3% ± 22.8% with RP and MCO, while the mean esophagus dose was reduced from 26.5 Gy ± 3.1 Gy to 21.5 Gy ± 4.7 Gy with RP and further to 19.1 Gy ± 4.2 Gy with RP and MCO. All these dosimetric improvements were statistically significant (p<0.001). However, improvements with RP and MCO for the total lung mean and V20 Gy, liver mean, stomach mean and kidney V18 Gy were marginal over the RP. Sparing of ipsilateral lung V20 Gy was maintained at ≥ 50 cc on average for all plans. PTV D95 and V95 were both normalized at 94%.

CONCLUSION

Combination of RP and MCO significantly improved sparing of the OARs, especially the heart, contralateral lung and esophagus without compromising coverage or doses to other structures. Since doses to the heart, and contralateral lung are known to correlate with incidence of radiation pneumonitis, it would be prudent to consider planning with both RP and MCO to help determine the optimal treatment plan for the individual patient's anatomy.

Long-Term Outcomes of Multidisciplinary Radiation Oncology Equity and Inclusion Committee Programming at an Academic Health System

PURPOSE/OBJECTIVE(S)

Academic radiation oncology departments are increasingly implementing educational programs to promote diversity, equity, and inclusion, but data on their impact remains sparse. This study aimed to assess learning outcomes and perceived impact of the programming of a multidisciplinary radiation oncology equity and inclusion committee (EIC).

MATERIALS/METHODS

Since August 2020, a committee of radiation therapists (RTTs), physicians (MDs), nurses (RNs), and administrators (ADs) has led an alternate-monthly online EIC meeting open to all radiation oncology employees at one health system. Learning goals of EIC programming are (1) to understand disparities in healthcare practice and outcomes for marginalized populations, (2) to discuss current events relevant to marginalized groups, and (3) to identify and address personal bias. EIC has featured expert guest speakers, open discussion, cultural events, and individual storytelling. In February 2023, we conducted a department-wide survey evaluating participation in one or more EIC meetings. EIC participants also completed an evaluation focused on learning goal achievement and program strengths/weaknesses. Multiple choice responses and 5-point Likert scale survey items were descriptively analyzed; open responses were qualitatively coded and categorized into themes.

RESULTS

There were 84 survey respondents, corresponding to a department response rate of 53%. Of these, 37 (44%) indicated participation in at least one EIC meeting. Participants were 35% RTTs, 16% MDs, 14% ADs, 3% physicists/dosimetrists, 3% RNs, and 19% undisclosed profession; 46% identified as a racial, ethnic, sexual, and/or gender minority. 41% of participants attended 5 or more sessions. Participants reported high overall value of the EIC meeting (mean value 3.7 / 5, SD 1.2) and 89% would recommend participation. There was strong agreement with achievement of EIC learning goals (mean agreement [MA] 3.9 / 5, SD 0.91), and most participants reported improved capability to understand (61%, MA 3.72 / 5, SD 0.99) and address (61%, MA 3.75 / 5, SD 0.83) the specific needs of their patients from marginalized groups. The three most common themes of EIC strengths were educational value, speaker quality, and improved work relationships. Commonly requested improvements included more practice scenarios, increasing participation, and giving more equitable attention to all minority groups. Among EIC non-participants, 75% reported non-participation due to scheduling, 71% felt that having an EIC was valuable, and 59% reported a desire to attend an EIC meeting in the future.

CONCLUSION

Nearly 3 years since implementation, EIC programming is highly valued. The majority of participants report achievement of learning goals and perceive self-improvement in care for marginalized groups as a result of participation. Further research is needed to externally validate the impact of this programming on learning and patient care domains.

Frequent Friers: Outcomes in Patients Who Receive Multiple Courses of Lung SBRT

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) is a definitive therapy for early-stage non-small cell lung cancer and solitary pulmonary metastases with high tolerability and excellent survival rates. With longer survival and patients developing subsequent primaries or oligometastatic disease, patients are receiving multiple repeat lung SBRT courses. This study aims to assess safety and efficacy of high-frequency SBRT (HF-SBRT) to the lung, defined as >3 courses.

MATERIALS/METHODS

A retrospective review was performed of patients who received >3 courses of lung SBRT. Logistic regression was performed to identify predictors of radiation pneumonitis (RP) and worsening pulmonary function (WPF). Local control (LC) and overall survival (OS) were evaluated using the Kaplan-Meier method.

RESULTS

Ninety-four courses of HF-SBRT to the lung were identified among 28 patients. 78% of patients received 3 SBRT courses, 12% received 4 courses, and 7.1% received >5 courses. Median follow-up was 4.4 years. Median age at time of treatment was 73 years-old; 58% males; 42% had an underlying pulmonary comorbidity; 39% prior lung surgery; 52% history of cardiac disease; 52% prior tobacco use; median ECOG 0. Median SBRT dose was 48 Gy. Median interval between courses was 5.6 months. Zero patients experienced greater than grade 2 acute CTCAE v5 toxicity. 7.2% (7) of patients developed RP at median time of 2.6 months [IQR: 1.4,7.4]; grade 1: 3 patients, grade 2: 1 patient, grade 3: 2 patients. Of patients who developed RP, 42% (3) went on to receive further SBRT without experiencing significant adverse events (AEs). History of pulmonary disease, prior lung surgery, and history of tobacco use strongly correlated with WPF but not RP (WPF p-values: <0.001, 0.003, <0.001, respectively). History of cardiac disease did not correlate with WPF or RP. Receiving bilateral lung SBRT treatment (vs unilateral) trended towards correlation with WPF (p = 0.06) and RP (p = 0.08). Time between SBRT courses did not significantly differ for those who developed RP (p = 0.62) or WPF (p = 0.42). No individual or plan sum dosimetric constraint (GTV, PTV, unilateral lung V5, lung V10, lung V20, unilateral mean lung dose, or total lung V20) significantly differed in those who experienced RP. WPF correlated with the plan sum unilateral lung V10 (p = 0.05). LC at 1-year was 100%, 1 local failure occurred at 13 months; 2-year OS was 91.7%, median OS 5.4 years.

CONCLUSION

Overall, HF-SBRT was well tolerated. Development of RP did not correlate with a specific individual or plan sum dosimetric parameter, with patients receiving subsequent courses of SBRT without increased AEs. WPF increasingly occurred with subsequent SBRT courses and correlated with unilateral plan sum V10. This study suggests that in appropriately selected patients, SBRT after RP can still be provided as definitive care, while further studies should validate this and focus attention on mitigating long-term WPF in patients who receive HF-SBRT.

Decision Regret among Patients with Early-stage Lung Cancer Undergoing Radiation Therapy or Surgical Resection

AIMS

Clinical equipoise exists regarding early-stage lung cancer treatment among patients as trials comparing stereotactic body radiation therapy (SBRT) and surgical resection are unavailable. Given the potential differences in treatment effectiveness and side-effects, we sought to determine the associations between treatment type, decision regret and depression.

MATERIALS AND METHODS

A multicentre, prospective study of patients with stage IA-IIA non-small cell lung cancer (NSCLC) with planned treatment with SBRT or surgical resection was conducted. Decision regret and depression were measured using the Decision Regret Scale (DRS) and Patient Health Questionnaire-4 (PHQ-4) at 3, 6 and 12 months post-treatment, respectively. Mixed linear regression modelling examined associations between treatment and decision regret adjusting for patient sociodemographics.

RESULTS

Among 211 study participants with early-stage lung cancer, 128 (61%) patients received SBRT and 83 (39%) received surgical resection. The mean age was 73 years (standard deviation = 8); 57% were female; 79% were White non-Hispanic. In the entire cohort at 3 months post-treatment, 72 (34%) and 57 (27%) patients had mild and severe decision regret, respectively. Among patients who received SBRT or surgery, 71% and 46% of patients experienced at least mild decision regret at 3 months, respectively. DRS scores increased at 6 months and decreased slightly at 12 months of follow-up in both groups. Higher DRS scores were associated with SBRT treatment (adjusted mean difference = 4.18, 95% confidence interval 0.82 to 7.54) and depression (adjusted mean difference = 3.49, 95% confidence interval 0.52 to 6.47). Neither patient satisfaction with their provider nor decision-making role concordance was associated with DRS scores.

CONCLUSIONS

Most early-stage lung cancer patients experienced at least mild decision regret, which was associated with SBRT treatment and depression symptoms. Findings suggest patients with early-stage lung cancer may not be receiving optimal treatment decision-making support. Therefore, opportunities for improved patient-clinician communication probably exist.

Frequency of use and outcome of surgical resection in the management of malignant mesothelioma in a community-based population: Results in 5,937 patients

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Background: Multimodality therapy of mesothelioma patients treated at specialized tertiary hospitals report surgical resection rates of 42% (Flores RM et al. Prognostic Factors in the Treatment of Malignant Pleural Mesothelioma at a Large Tertiary Referral Center. J Thorac Oncol 2007;2(10):957–965.). Treatment strategies in the community are less well defined and surgical expertise is not readily available. We undertook this study to evaluate the rate of surgical resection and its association with survival in a non-tertiary based population. Methods: The Surveillance, Epidemiology, and End Results (SEER) database was searched from 1990 - 2004. Variables analyzed included age, sex, race, year of diagnosis, laterality, vital status, stage, surgery, and reasons for no surgery. The association of resection on overall survival was estimated by the Kaplan-Meier method and examined in a Cox proportional hazards model adjusting for covariates. Results: Pathologically proven malignant pleural mesothelioma was identified in 5,937 patients: 1,166 women, 4,771 men; median age was 70 years. Surgical resection rate was 11% (n=636). Univariate analysis demonstrated a median survival of 13 months with surgical resection and a median survival of 7 months in the non-resected group (p<0.0001). Multivariate analysis demonstrated improved survival for surgically resected patients (HR 0.7, p<0.0001), controlling for age, gender, and stage. Conclusions: Surgical resection was associated with improved survival when controlling for age, stage, and gender. However, the rate of surgical resection was much lower in the community when compared to tertiary referral centers. Treatment efforts should be focused on a multidisciplinary approach which includes surgical evaluation.

No significant financial relationships to disclose.

A multicenter U.S. trial of neoadjuvant pemetrexed plus cisplatin (PC) followed by extrapleural pneumonectomy (EPP) and hemithoracic radiation (RT) for stage I-III malignant pleural mesothelioma (MPM)

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Background: The optimal management for fit patients with early stage MPM remains controversial. One approach involves neoadjuvant chemotherapy followed by EPP and hemithoracic RT and prior trials using gemcitabine and cisplatin have been reported (Weder JCO 2004, Flores JTO 2006). We administered PC, followed by EPP and RT to further assess feasibility and survival of trimodality therapy in a larger, multicenter study. Methods: Eligibility criteria: Stage T1–3 N0–2, no prior surgical resection, adequate organ function (including predicted post-op FEV1 >35%) and PS 0–1. Pts received pemetrexed 500 mg/m2 plus cisplatin 75 mg/m2 with vitamin supplementation for 4 cycles. Pts without disease progression underwent EPP followed by RT (54 Gy). The primary endpoint was pathologic complete response (pCR) rate. Enrollment was completed in March, 2006. Results: 77 patients were enrolled and 72 are evaluable. Median age 63.5 (range 34–78), M:F = 51:21, Clinical stage I:II:III:IV = 5:31:33:1, epithelial:nonepithelial = 58:15, ECOG PS 0:1:2 = 28:42:2. 83% of patients completed all four cycles of PC. Grade 3/4 events related to chemotherapy included: neutropenia (4%), febrile neutropenia (3%), nausea (1%), vomiting (3%), pneumonia (6%), pulmonary embolism (1%), and chest pain (3%). Of 73 pts assessed for radiologic response, 3 CRs, 21 PRs, 36 SDs, 3 PDs, and 10 were unevaluable; (RR= 33% [95% CI, 0.22, 0.45]). Of 54 pts who underwent surgery, EPP completion rate was 87% (47/54); that is 47/77 (61%) by ITT. Pathologic stage I:II:III:IV:NE = 4:12:24:3:11. One pCR was confirmed. 35/39 completed RT. Preliminary TTP =13.1 mo (95% CI=9.6, 15.9; 48% censored) and median survival=16.6 mo (95% CI=13.9, 19.3; 55% censored;1-yr survival = 68%). Conclusions: This multicenter trial testing trimodality therapy in MPM showed that it is feasible with a high rate of chemotherapy delivery. One pCR was observed. Preliminary survival is below that reported by single institutions for patients undergoing EPP but with a high censorship rate at this early time point. Further analyses are necessary to identify a cohort of patients most likely to benefit. This study was sponsored by Eli Lilly & Company.

No significant financial relationships to disclose.

Reduction of organ motion effects in IMRT and conformal 3D radiation delivery by using gating and tracking techniques

Respiration-gated radiotherapy offers a significant potential for improvement in the irradiation of tumour sites affected by respiratory motion such as lung, breast and liver tumours. An increased conformality of irradiation fields leading to decreased complications rates of organs at risk (lung, heart) is expected. Four main strategies are used to reduce respiratory motion effects: integration of respiratory movements into treatment planning, breath-hold techniques, respiratory gating techniques, and tracking techniques. Measurements of respiratory movements can be performed either in a representative sample of the general population, or directly on the patient before irradiation. The measured amplitude could be applied to a geometrical margin or integrated into dosimetry. However, these strategies remain limited for very mobile tumours, in which this approach results in larger irradiated volumes. Reduction of breathing motion can be achieved by using either breath-hold techniques or respiration synchronized gating techniques. Breath-hold can be achieved with active techniques, in which a valve temporarily blocks airflow of the patient, or passive techniques, in which the patient voluntarily breath-holds. Synchronized gating techniques use external devices to predict the phase of the respiration cycle while the patient breaths freely. Another category is tumour tracking, which consists of two major aspects: real-time localization of, and real-time beam adaptation to, a constantly moving tumour. These techniques are presently being investigated in several medical centres worldwide. Although promising, the first results obtained in lung and liver cancer patients require confirmation. This paper describes the most frequently used gating and tracking techniques and the main published clinical reports.

Evaluation of an automated deformable image matching method for quantifying lung motion in respiration-correlated CT images

We have evaluated an automated registration procedure for predicting tumor and lung deformation based on CT images of the thorax obtained at different respiration phases. The method uses a viscous fluid model of tissue deformation to map voxels from one CT dataset to another. To validate the deformable matching algorithm we used a respiration-correlated CT protocol to acquire images at different phases of the respiratory cycle for six patients with nonsmall cell lung carcinoma. The position and shape of the deformable gross tumor volumes (GTV) at the end-inhale (EI) phase predicted by the algorithm was compared to those drawn by four observers. To minimize interobserver differences, all observers used the contours drawn by a single observer at end-exhale (EE) phase as a guideline to outline GTV contours at EI. The differences between model-predicted and observer-drawn GTV surfaces at EI, as well as differences between structures delineated by observers at EI (interobserver variations) were evaluated using a contour comparison algorithm written for this purpose, which determined the distance between the two surfaces along different directions. The mean and 90% confidence interval for model-predicted versus observer-drawn GTV surface differences over all patients and all directions were 2.6 and 5.1 mm, respectively, whereas the mean and 90% confidence interval for interobserver differences were 2.1 and 3.7 mm. We have also evaluated the algorithm's ability to predict normal tissue deformations by examining the three-dimensional (3-D) vector displacement of 41 landmarks placed by each observer at bronchial and vascular branch points in the lung between the EE and EI image sets (mean and 90% confidence interval displacements of 11.7 and 25.1 mm, respectively). The mean and 90% confidence interval discrepancy between model-predicted and observer-determined landmark displacements over all patients were 2.9 and 7.3 mm, whereas interobserver discrepancies were 2.8 and 6.0 mm. Paired t tests indicate no significant statistical differences between model predicted and observer drawn structures. We conclude that the accuracy of the algorithm to map lung anatomy in CT images at different respiratory phases is comparable to the variability in manual delineation. This method has therefore the potential for predicting and quantifying respiration-induced tumor motion in the lung.