Association of lung fluorodeoxyglucose uptake with radiation pneumonitis after concurrent chemoradiation for non-small cell lung cancer

Integrating 18 F-FDG PET/CT with lung dose-volume for assessing lung inflammatory changes after arc-based radiotherapy for esophageal cancer: A pilot study

OBJECTIVE

The incidence of radiation pneumonitis (RP) has a highly linear relationship with low-dose lung volume. We previously established a volume-based algorithm (VBA) method to improve low-dose lung volume in radiotherapy (RT). This study assessed lung inflammatory changes by integrating fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸ F-FDG PET/CT) with VBA for esophageal cancer patients undergoing arc-based RT.

METHODS

Thirty esophageal cancer patients received ¹⁸ F-FDG PET/CT imaging pre-RT and post-RT were included in a retrospective pilot study. We fused lung doses and parameters of PET/CT in RT planning. Based on VBA, we used the 5Gy isodose curve to define high-dose (HD) and low-dose (LD) regions in the lung volume. We divided patients into non-RP (nRP) and RP groups. The maximum, mean standardized uptake value (SUVmax, SUVmean), global lung glycolysis (GLG), mean lung dose (MLD) and V_5-30 in lungs were analyzed. Area under the curve values were utilized to identify optimal cut-off values for RP.

RESULTS

Eleven patients in the nRP group and 19 patients in the RP group were identified. In 30 RP lungs, post-RT SUVmax, SUVmean and GLG of HD regions showed significant increases compared to values for pre-RT lungs. There were no significant differences in values of 22 nRP lungs. Post-RT SUVmax and SUVmean of HD regions, MLD, and lung V₅ and V₁₀ in RP lungs were significantly higher than in nRP lungs. For detecting RP, the optimal cut-off values were post-RT SUVmax > 2.28 and lung V₅  > 47.14%.

CONCLUSION

This study successfully integrated ¹⁸ F-FDG PET/CT with VBA to assess RP in esophageal cancer patients undergoing RT. Post-RT SUVmax > 2.28 and lung V₅  > 47.14% might be potential indicators of RP.

Personalized mid-course FDG-PET based adaptive treatment planning for non-small cell lung cancer using machine learning and optimization

Objective. Traditional radiotherapy (RT) treatment planning of non-small cell lung cancer (NSCLC) relies on population-wide estimates of organ tolerance to minimize excess toxicity. The goal of this study is to develop a personalized treatment planning based on patient-specific lung radiosensitivity, by combining machine learning and optimization.Approach. Sixty-nine non-small cell lung cancer patients with baseline and mid-treatment [18]F-fluorodeoxyglucose (FDG)-PET images were retrospectively analyzed. A probabilistic Bayesian networks (BN) model was developed to predict the risk of radiation pneumonitis (RP) at three months post-RT using pre- and mid-treatment FDG information. A patient-specific dose modifying factor (DMF), as a surrogate for lung radiosensitivity, was estimated to personalize the normal tissue toxicity probability (NTCP) model. This personalized NTCP was then integrated into a NTCP-based optimization model for RT adaptation, ensuring tumor coverage and respecting patient-specific lung radiosensitivity. The methodology was employed to adapt the treatment planning of fifteen NSCLC patients.Main results. The magnitude of the BN predicted risks corresponded with the RP severity. Average predicted risk for grade 1-4 RP were 0.18, 0.42, 0.63, and 0.76, respectively (p< 0.001). The proposed model yielded an average area under the receiver-operating characteristic curve (AUROC) of 0.84, outperforming the AUROCs of LKB-NTCP (0.77), and pre-treatment BN (0.79). Average DMF for the radio-tolerant (RP grade = 1) and radiosensitive (RP grade ≥ 2) groups were 0.8 and 1.63,p< 0.01. RT personalization resulted in five dose escalation strategies (average mean tumor dose increase = 6.47 Gy, range = [2.67-17.5]), and ten dose de-escalation (average mean lung dose reduction = 2.98 Gy [0.8-5.4]), corresponding to average NTCP reduction of 15% [4-27].Significance. Personalized FDG-PET-based mid-treatment adaptation of NSCLC RT could significantly lower the RP risk without compromising tumor control. The proposed methodology could help the design of personalized clinical trials for NSCLC patients.

Radiation Versus Immune Checkpoint Inhibitor Associated Pneumonitis: Distinct Radiologic Morphologies

BACKGROUND

Patients with non-small cell lung cancer may develop pneumonitis after thoracic radiotherapy (RT) and immune checkpoint inhibitors (ICIs). We hypothesized that distinct morphologic features are associated with different pneumonitis etiologies.

MATERIALS AND METHODS

We systematically compared computed tomography (CT) features of RT- versus ICI-pneumonitis. Clinical and imaging features were tested for association with pneumonitis severity. Lastly, we constructed an exploratory radiomics-based machine learning (ML) model to discern pneumonitis etiology.

RESULTS

Between 2009 and 2019, 82 patients developed pneumonitis: 29 after thoracic RT, 23 after ICI, and 30 after RT + ICI. Fifty patients had grade 2 pneumonitis, 22 grade 3, and 7 grade 4. ICI-pneumonitis was more likely bilateral (65% vs. 28%; p = .01) and involved more lobes (66% vs. 45% involving at least three lobes) and was less likely to have sharp border (17% vs. 59%; p = .004) compared with RT-pneumonitis. Pneumonitis morphology after RT + ICI was heterogeneous, with 47% bilateral, 37% involving at least three lobes, and 40% sharp borders. Among all patients, risk factors for severe pneumonitis included poor performance status, smoking history, worse lung function, and bilateral and multifocal involvement on CT. An ML model based on seven radiomic features alone could distinguish ICI- from RT-pneumonitis with an area under the receiver-operating curve of 0.76 and identified the predominant etiology after RT + ICI concordant with multidisciplinary consensus.

CONCLUSION

RT- and ICI-pneumonitis exhibit distinct spatial features on CT. Bilateral and multifocal lung involvement is associated with severe pneumonitis. Integrating these morphologic features in the clinical management of patients who develop pneumonitis after RT and ICIs may improve treatment decision-making.

IMPLICATIONS FOR PRACTICE

Patients with non-small cell lung cancer often receive thoracic radiation and immune checkpoint inhibitors (ICIs), both of which can cause pneumonitis. This study identified similarities and differences in pneumonitis morphology on computed tomography (CT) scans among pneumonitis due to radiotherapy (RT) alone, ICI alone, and the combination of both. Patients who have bilateral CT changes involving at least three lobes are more likely to have ICI-pneumonitis, whereas those with unilateral CT changes with sharp borders are more likely to have radiation pneumonitis. After RT and/or ICI, severe pneumonitis is associated with bilateral and multifocal CT changes. These results can help guide clinicians in triaging patients who develop pneumonitis after radiation and during ICI treatment.

Maximum standardized uptake value of primary tumor (SUVmax_PT) and horizontal range between two most distant PET-positive lymph nodes predict patient outcome in inoperable stage III NSCLC patients after chemoradiotherapy

Background

18F-FDG-positron emission tomography (PET)/computed tomography (CT) is a standard for initial staging in patients with locally advanced stage III non-small cell lung cancer (NSCLC). We evaluated a PET/CT staging score to characterize disease extension and patient outcome in this disease.

Methods

Ninety-nine consecutive patients with NSCLC stage IIIA–B (UICC 7th edition), who underwent 18F-FDG-PET/CT before the start of chemoradiotherapy (CRT) were analyzed. Maximum standardized uptake value of primary tumor (SUVmax_PT) and range between two most distant PET-positive (SUV ≥2.5) lymph nodes in two directions were analyzed for their correlation with patient outcome. The vertical distance was defined as A- and the horizontal as a B-line.

Results

According to the results of univariate analysis, score included the SUVmax_PT and horizontal B-line, patients were divided into three risk subgroups: low, intermediate and high-risk subgroups. Subgroups were defined as SUVmax_PT <8 and B-line <3.7 cm, SUVmax_PT >8 or B-line >3.7 cm and SUVmax_PT >8 plus B-line >3.7 cm, respectively. Twenty-eight (28%), 45 (46%) and 26 (26%) patients were assigned to the low, intermediate and high-risk subgroup, respectively. Median event-free survival (EFS) in low, intermediate and high-risk subgroups was 16 (95% CI: 7–25), 13 (95% CI: 12–15) and 10 (95% CI: 7–13) months (P=0.002, log-rank test). Median OS in the low, intermediate and high-risk subgroups was 40 (95% CI: 11–69), 23 (95% CI: 15–31) and 14 (95% CI: 13–14) months (P=0.0001, log-rank test). In the multivariate analysis, SUV, B-line and PET/CT score were significantly associated with EFS [harard ratio (HR) 2.12 (95% CI: 1.27–3.55) and intermediate risk HR 2.01 (95% CI: 1.13–3.59), P=0.003] and OS [high-risk HR 2.79 (95% CI: 1.16–4.55) and intermediate risk HR 2.30 (95% CI: 1.58–4.94), P=0.001].

Conclusions

A PET/CT score was developed for inoperable stage III NSCLC patients treated with CRT and was an independent predictor of patient outcome in the single-center cohort.

Proton therapy for locally advanced non-small cell lung cancer

Radiation therapy is an essential component of treatment for locally advanced non-small cell lung cancer (NSCLC) but can be technically challenging because of the proximity of lung tumors to nearby critical organs or structures. The most effective strategy for reducing radiation-induced toxicity is to reduce unnecessary exposure of normal tissues by using advanced technology; examples from photon (X-ray) therapy have included three-dimensional conformal radiation therapy versus its predecessor, two-dimensional radiation therapy, and intensity-modulated photon radiation therapy versus its predecessor, three-dimensional conformal therapy. Using particle-beam therapy rather than photons offers the potential for further advantages because of the unique depth-dose characteristics of the particles, which can be exploited to allow still higher dose escalation to tumors with greater sparing of normal tissues, with the ultimate goal of improving local tumor control and survival while preserving quality of life by reducing treatment-related toxicity. However, the costs associated with particle therapy with protons are considerably higher than the current state of the art in photon technology, and evidence of clinical benefit from protons is increasingly being demanded to justify the higher financial burden on the healthcare system. Some such evidence is available from preclinical studies, from retrospective, single-institution clinical series, from analyses of national databases, and from single-arm prospective studies in addition to several ongoing randomized comparative trials. This review summarizes the rationale for and challenges of using proton therapy to treat thoracic cancers, reviews the current clinical experience, and suggests topics for future research.

Particle therapy in non-small cell lung cancer

The finite range of proton beams in tissues offers unique dosimetric advantages that theoretically allow the dose to the target to be escalated while minimizing exposure of surrounding tissues and thereby minimizing radiation-induced toxicity. These theoretical advantages have led to widespread adoption of proton therapy around the world for a wide variety of tumors at different anatomic sites. Many treatment-planning comparisons have shown that proton therapy has substantial dosimetric advantages over conventional photon (X-ray) radiation therapy. However, given the typically significant difference in cost between proton therapy versus conventional photon therapy, strong evidence of proton therapy's clinical benefits in terms of toxicity and survival is warranted. Some findings from retrospective studies, single-arm prospective studies, and a very few randomized clinical trials comparing these modalities are beginning to emerge. In this review, we examine the available data on proton therapy for (non-small cell lung cancer NSCLC). We begin by discussing the unique challenges involved in treating moving targets with significant tissue heterogeneity and the technologic efforts underway to overcome these challenges. We then discuss the rationale for minimizing normal tissue toxicity, particularly pulmonary, cardiac, and hematologic toxicity, within the context of previously unsuccessful attempts at dose escalation for lung cancer. Finally, we explore strategies for accelerating the development of trials aimed at measuring meaningful clinical endpoints and for maximizing the value of proton therapy by personalizing its use for individual patients.

Patient-reported lung symptoms as an early signal of impending radiation pneumonitis in patients with non-small cell lung cancer treated with chemoradiation: an observational study

PURPOSE

Clinician ratings of concurrent chemoradiation (CRT)-induced radiation pneumonitis (RP) in patients with non-small cell lung cancer (NSCLC) are based on both imaging and patient-reported lung symptoms. We compared the value of patient-reported outcomes versus normal-lung uptake of ¹⁸F-fluoro-2-deoxyglucose in positron emission computed tomography (FDG PET/CT) during the last week of treatment, for indicating the development of grade ≥ 2 RP within 4 months of CRT completion.

METHODS

132 patients with NSCLC-reported RP-related symptoms (coughing, shortness of breath) repeatedly using the validated MD Anderson Symptom Inventory lung cancer module. Of these patients, 68 had FDG PET/CT scans that were analyzed for normal-lung mean standardized FDG uptake values (SUV_mean) before, during, and up to 4 months after CRT. Clinicians rated RP using CTCAE version 3. Logistic regression models examined potential predictors for developing CTCAE RP ≥ 2.

RESULTS

For the entire sample, patient-rated RP-related symptoms during the last week of CRT correlated with clinically meaningful CTCAE RP ≥ 2 post-CRT (OR 2.74, 95% CI 1.25-5.99, P = 0.012), controlled for sex, age, mean lung radiation dose, comorbidity, and baseline symptoms. Moderate/severe patient-rated RP-related symptom score (≥ 4 on a 0-10 scale, P = 0.001) and normal-lung FDG uptake (SUV_mean > 0.78, P = 0.002) in last week of CRT were equally strong predictors of post-CRT CTCAE RP ≥ 2 (C-index = 0.78, 0.77).

CONCLUSIONS

During the last week of CRT, routine assessment of moderate-to-severe RP-related symptoms provides a simple way to identify patients with NSCLC who may be at risk for developing significant post-CRT RP, especially when PET/CT images of normal-lung FDG uptake are not available.