Clinical and Dosimetric Predictors of Radiation Pneumonitis in Patients With Non-Small Cell Lung Cancer Undergoing Postoperative Radiation Therapy

[Prevention, Diagnosis, Therapy, and Follow-up of Lung Cancer - Interdisciplinary Guideline of the German Respiratory Society and the German Cancer Society - Abridged Version]

The current S3 Lung Cancer Guidelines are edited with fundamental changes to the previous edition based on the dynamic influx of information to this field:The recommendations include de novo a mandatory case presentation for all patients with lung cancer in a multidisciplinary tumor board before initiation of treatment, furthermore CT-Screening for asymptomatic patients at risk (after federal approval), recommendations for incidental lung nodule management , molecular testing of all NSCLC independent of subtypes, EGFR-mutations in resectable early stage lung cancer in relapsed or recurrent disease, adjuvant TKI-therapy in the presence of common EGFR-mutations, adjuvant consolidation treatment with checkpoint inhibitors in resected lung cancer with PD-L1 ≥ 50%, obligatory evaluation of PD-L1-status, consolidation treatment with checkpoint inhibition after radiochemotherapy in patients with PD-L1-pos. tumor, adjuvant consolidation treatment with checkpoint inhibition in patients withPD-L1 ≥ 50% stage IIIA and treatment options in PD-L1 ≥ 50% tumors independent of PD-L1status and targeted therapy and treatment option immune chemotherapy in first line SCLC patients.Based on the current dynamic status of information in this field and the turnaround time required to implement new options, a transformation to a "living guideline" was proposed.

Exploring causes and consequences of early discontinuation of durvalumab after chemoradiotherapy for non-small cell lung cancer

Introduction

For most locally advanced non-small cell lung cancer (LA-NSCLC) patients who complete definitive chemoradiotherapy (CRT) and do not experience disease progression, one year of adjuvant durvalumab is recommended. Here, we explore causes and consequences of early durvalumab discontinuation.

Materials and Methods

We reviewed patients treated for LA-NSCLC with definitive CRT who began adjuvant durvalumab between 2017 and 2021. Duration of durvalumab receipt and causes for early discontinuation were tabulated. Logistic regression models were utilized to evaluate predictors of early durvalumab discontinuation. Landmark analyses were performed to explore associations between early durvalumab discontinuation and clinical outcomes (progression-free survival (PFS), overall survival (OS)).

Results

Fifty-nine patients were included. Forty-one patients (69%) discontinued durvalumab early, most commonly for disease progression (n = 14) or lung toxicity (n = 10). Multivariable analysis revealed mean heart radiotherapy dose (MHD) was associated with risk of durvalumab discontinuation from progression (HR = 2.34 per 10 Gy, p = 0.052), and there was a trend suggesting an association between MHD and risk of durvalumab discontinuation from lung toxicity (HR = 2.16 per 10 Gy, p = 0.126). Median PFS duration following durvalumab initiation was 14 months, and median OS duration was 32 months. Landmark analyses that excluded patients with progression or death within one year of durvalumab initiation demonstrated improved outcomes for patients who completed one year of durvalumab (2-year PFS 100% v. 40%, p < 0.001; 2-year OS 100% v. 67%, p = 0.862). Improved outcomes were observed for patients who received MHD below the cohort median (9.3 Gy) compared to patients with higher MHD (median PFS 32 months v. 8 months, p < 0.001; 2-year OS 69% v. 44%, p = 0.088).

Conclusion

For LA-NSCLC patients treated with CRT followed by immunotherapy, extent of cardiac irradiation may be a risk factor for immunotherapy discontinuation, disease recurrence, and death.

Computed tomography and radiation dose images-based deep-learning model for predicting radiation pneumonitis in lung cancer patients after radiation therapy

PURPOSE

To develop a deep learning model that combines CT and radiation dose (RD) images to predict the occurrence of radiation pneumonitis (RP) in lung cancer patients who received radical (chemo)radiotherapy.

METHODS

CT, RD images and clinical parameters were obtained from 314 retrospectively-collected patients (training set) and 35 prospectively-collected patients (test-set-1) who were diagnosed with lung cancer and received radical radiotherapy in the dose range of 50 Gy and 70 Gy. Another 194 (60 Gy group, test-set-2) and 158 (74 Gy group, test-set-3) patients from the clinical trial RTOG 0617 were used for external validation. A ResNet architecture was used to develop a prediction model that combines CT and RD features. Thereafter, the CT and RD weights were adjusted by using 40 patients from test-set-2 or 3 to accommodate cohorts with different clinical settings or dose delivery patterns. Visual interpretation was implemented using a gradient-weighted class activation map (grad-CAM) to observe the area of model attention during the prediction process. To improve the usability, ready-to-use online software was developed.

RESULTS

The discriminative ability of a baseline trained model had an AUC of 0.83 for test-set-1, 0.55 for test-set-2, and 0.63 for test-set-3. After adjusting CT and RD weights of the model using a subset of the RTOG-0617 subjects, the discriminatory power of test-set-2 and 3 improved to AUC 0.65 and AUC 0.70, respectively. Grad-CAM showed the regions of interest to the model that contribute to the prediction of RP.

CONCLUSION

A novel deep learning approach combining CT and RD images can effectively and accurately predict the occurrence of RP, and this model can be adjusted easily to fit new cohorts.

Trimodality therapy of malignant pleural mesothelioma with helical tomotherapy

OBJECTIVE

The purpose of this study was to determine the efficacy and tolerability of hemithoracic radiotherapy implemented with helical tomotherapy (HTT) in malignant pleural mesothelioma (MPM) patients.

METHODS

Between October 2018 and December 2020, data from 11 MPM patients who received trimodality therapy, including lung-sparing surgery (pleurectomy-decortication, P/D), adjuvant chemotherapy (cisplatin+ pemetrexed), and radiotherapy, were retrospectively reviewed. HTT was used to deliver a total of 30 Gy, 50-54 Gy or 59.4-60 Gy to R2 disease with 1.8-2 Gy daily doses. Descriptive data are presented in number (percentage) or median (minimum- maximum). The Kaplan-Meier method was used to calculate survival data. In patients with toxicities, the risk organ doses were compared using the Mann-Whitney U test.

RESULTS

The median follow-up was 20.5 (12-30) months. Two-year local control, disease-free, and overall survival rates were 48.5%, 49%, and 77.9%, respectively. The median prescribed dose for planning target volume (PTV) was 50.4±8.7 (30-60) Gy. Mean dose (D_mean) of total lung was 19.9±6 (10.4-26) Gy; the V20 (%) of ipsilateral and contralateral lungs were 89.±11.2 (62.7-100) and 0.7±2.1 (0.49-5.9), respectively. Esophageal D_mean and maximum doses (D_max) were found as 21.7±8.4 (7.4-34) and 53.1±10.4 (25.4-64.4) Gy, respectively. V30 (%) and Dmean of heart were 22.3%±13.4% (3.9-47) and 21±5.7 (10.8-29.3) Gy, respectively. D_max of medulla spinalis (MS) was 38.6± 1.3 (13.7-48) Gy. Grade 1-2 radiation pneumonitis (RP) developed in 4 (36.4%) and esophagitis in 2 (18.2%) patients. RP was found to be associated with MS and esophageal doses (p<0.05). Myelitis was diagnosed in 1 (9.1%) patient (MS D_max: 29 Gy).

CONCLUSION

HTT can be used as part of trimodality therapy for MPM patients with acceptable toxicities. MS and esophageal doses should be considered for radiation pneumonitis risk, and new dose constraints for these organs should be defined.

Association of cardiac calcium burden with overall survival after radiotherapy for non-small cell lung cancer

Background and purpose

Coronary calcifications are associated with coronary artery disease in patients undergoing radiotherapy (RT) for non-small cell lung cancer (NSCLC). We quantified calcifications in the coronary arteries and aorta and investigated their relationship with overall survival (OS) in patients treated with definitive RT (Def-RT) or post-operative RT (PORT).

Materials and methods

We analyzed 263 NSCLC patients treated from 2004 to 2017. Calcium burden was ascertained with a Hounsfield unit (HU) cutoff of > 130 in addition to a deep learning (DL) plaque estimator. The HU cutoff volumes were defined for coronary arteries (Plaque_Coro) and coronary arteries and aorta combined (Plaque_Coro+Ao), while the DL estimator ranged from 0 (no plaque) to 3 (high plaque). Patient and treatment characteristics were explored for association with OS.

Results

The median Plaque_Coro and Plaque_Coro+Ao was 0.75 cm³ and 0.87 cm³ in the Def-RT group and 0.03 cm³ and 0.52 cm³ in the PORT group. The median DL estimator was 2 in both cohorts. In Def-RT, large Plaque_Coro (HR:1.11 (95%CI:1.04-1.19); p = 0.008), and Plaque_Coro+Ao (HR:1.06 (95%CI:1.02-1.11); p = 0.03), and poor Karnofsky Performance Status (HR: 0.97 (95%CI: 0.94-0.99); p = 0.03) were associated with worse OS. No relationship was identified between the plaque volumes and OS in PORT, or between the DL plaque estimator and OS in either Def-RT or PORT.

Conclusions

Coronary artery calcification assessed from RT planning CT scans was significantly associated with OS in patients who underwent Def-RT for NSCLC. This HU thresholding method can be straightforwardly implemented such that the role of calcifications can be further explored.

Predictors of high-grade radiation pneumonitis following radiochemotherapy for locally advanced non-small cell lung cancer: analysis of clinical, radiographic and radiotherapy-related factors

Purpose:

In this study, the relation between radiation pneumonitis (RP) and a wide spectrum of clinical, radiographic and treatment-related factors was investigated. As scoring of low-grade RP can be subjective, RP grade ≥3 (RP ≥ G3) was chosen as a more objective and clinically significant endpoint for this study.

Methods and Materials:

105 consecutive patients with locally advanced non-small cell lung cancer underwent conventionally fractionated radio-(chemo-)therapy to a median dose of 64 Gy. A retrospective analysis of 25 clinical (gender, race, pulmonary function, diabetes, statin use, smoking history), radiographic (emphysema, interstitial lung disease) and radiotherapy dose- and technique-related factors was performed to identify predictors of RP ≥ G3. Following testing of all variables for statistical association with RP using univariate analysis (UVA), a forward selection algorithm was implemented for building a multivariate predictive model (MVA) with limited sample size.

Results:

Median follow-up of surviving patients was 33 months (9–132 months). RP ≥ G3 was diagnosed in 10/105 (9·5%) patients. Median survival was 28·5 months. On UVA, predictors for RP ≥ G3 were diabetes, lower lobe location, planning target volume, volumetric modulated arc therapy (VMAT), lung V5 Gy (%), lung Vspared5 Gy (mL), lung V20 Gy (%) and heart V5 Gy (% and mL). On MVA, VMAT was the only significant predictor for RP ≥ G3 (p = 0·042). Lung V5 Gy and lung V20 Gy were borderline significant for RP ≥ G3. Patients with RP ≥ 3 had a median survival of 10 months compared to 29·5 months with RP < G3 (p = 0·02).

Conclusions:

In this study, VMAT was the only factor that was significantly correlated with RP ≥ G3. Avoiding RP ≥ G3 is important as a toxicity per se and as a risk factor for poor survival. To reduce RP, caution needs to be taken to reduce low-dose lung volumes in addition to other well-established dose constraints.

High-Risk Non-Small Cell Lung Cancer Treated With Active Scanning Proton Beam Radiation Therapy and Immunotherapy

Purpose

Non-small cell lung cancer (NSCLC) is a deadly malignancy that is frequently diagnosed in patients with significant medical comorbidities. When delivering local and regional therapy, an exceedingly narrow therapeutic window is encountered, which often precludes patients from receiving aggressive curative therapy. Radiation therapy advances including particle therapy have been employed in an effort to expand this therapeutic window. Here we report outcomes with the use of proton therapy with curative intent and immunotherapy to treat patients diagnosed with high-risk NSCLC.

Methods and Materials

Patients were determined to be high risk if they had severe underlying cardiopulmonary dysfunction, history of prior thoracic radiation therapy, and/or large volume or unfavorable location of disease (eg, bilateral hilar involvement, supraclavicular involvement). As such, patients were determined to be ineligible for conventional x-ray-based radiation therapy and were treated with pencil beam scanning proton beam therapy (PBS-PBT). Patients who demonstrated excess respiratory motion (ie, greater than 1 cm in any dimension noted on the 4-dimensional computed tomography simulation scan) were deemed to be ineligible for PBT. Toxicity was reported using the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. Overall survival and progression-free survival were calculated using the Kaplan-Meier method.

Results

A total of 29 patients with high-risk NSCLC diagnoses were treated with PBS-PBT. The majority (55%) of patients were defined as high risk due to severe cardiopulmonary dysfunction. Most commonly, patients were treated definitively to a total dose of 6000 cGy (relative biological effectiveness) in 30 fractions with concurrent chemotherapy. Overall, there were a total of 6 acute grade 3 toxicities observed in our cohort. Acute high-grade toxicities included esophagitis (n = 4, 14%), dyspnea (n = 1, 3.5%), and cough (n = 1, 3.5%). No patients developed grade 4 or higher toxicity. The majority of patients went on to receive immunotherapy, and high-grade pneumonitis was rare. Two-year progression-free and overall survival was estimated to be 51% and 67%, respectively. COVID-19 was confirmed or suspected to be responsible for 2 patient deaths during the follow-up period.

Conclusions

Radical PBS-PBT treatment delivered in a cohort of patients with high-risk lung cancer with immunotherapy is feasible with careful multidisciplinary evaluation and rigorous follow-up.

Effects of Tumor Mutational Burden and Gene Alterations Associated with Radiation Response on Outcomes of Postoperative Radiation Therapy in Non-Small Cell Lung Cancer

PURPOSE

Postoperative radiation therapy (PORT) in resected non-small cell lung cancer (NSCLC) improves locoregional outcomes, but recent randomized data do not support its unselected use. We assessed if tumor mutational burden (TMB) and mutations in genes associated with radiation sensitivity can select patients for PORT.

METHODS AND MATERIALS

Patients with resected NSCLC treated with and without PORT who underwent tumor genomic profiling were examined. The incidence of locoregional failures (LRFs) in patients with deleterious mutations in DNA damage response and repair (DDR) genes and genes associated with radiation resistance (KEAP1/NFE2L2/STK11/PIK3CA) were investigated. Cox modeling and receiver operating characteristic curve (ROC) analysis assessed the relationship between TMB and locoregional control (LRC).

RESULTS

Eighty-nine patients with NSCLC treated with PORT were analyzed, with a 2-year LRF rate of 19% (95% confidence interval, 10%-27%). Among patients treated with PORT, those with mutations in radiation resistance genes (n = 16 [18%]) had significantly more LRFs than patients without mutations (2-year LRF rate: 60% vs 11%; P < .001). On multivariate analysis, radiation-resistance mutations were associated with LRF after PORT (hazard ratio, 7.42; P < .001). Patients with mutations identified in DDR genes (n = 15 [17%]) had significantly improved LRC (P = .048) and no LRF events after PORT. On multivariate analysis, a higher TMB was associated with improved LRC after PORT (hazard ratio, 0.86; P = .01), and TMB was associated with PORT outcomes (area under ROC curve, 0.67-0.77). These genomic markers were not similarly associated with LRF in patients not treated with PORT.

CONCLUSIONS

The data suggest that patients with radiation-resistance gene alterations may derive minimal benefit from PORT, whereas patients with high TMB and/or alterations in DDR genes may benefit from PORT and be suited for future precision-RT strategies. Prospective studies are necessary to validate these findings.

GOECP/SEOR radiotheraphy guidelines for non-small-cell lung cancer

Non-small cell lung cancer (NSCLC) is a heterogeneous disease accounting for approximately 85% of all lung cancers. Only 17% of patients are diagnosed at an early stage. Treatment is multidisciplinary and radiotherapy plays a key role in all stages of the disease. More than 50% of patients with NSCLC are treated with radiotherapy (curative-intent or palliative). Technological advances-including highly conformal radiotherapy techniques, new immobilization and respiratory control systems, and precision image verification systems-allow clinicians to individualize treatment to maximize tumor control while minimizing treatment-related toxicity. Novel therapeutic regimens such as moderate hypofractionation and advanced techniques such as stereotactic body radiotherapy (SBRT) have reduced the number of radiotherapy sessions. The integration of SBRT into routine clinical practice has radically altered treatment of early-stage disease. SBRT also plays an increasingly important role in oligometastatic disease. The aim of the present guidelines is to review the role of radiotherapy in the treatment of localized, locally-advanced, and metastatic NSCLC. We review the main radiotherapy techniques and clarify the role of radiotherapy in routine clinical practice. These guidelines are based on the best available evidence. The level and grade of evidence supporting each recommendation is provided.

Indications and Parameters Around Postoperative Radiation Therapy for Lung Cancer

Patients with locally advanced resected non-small-cell lung cancer present a high risk of relapse. Although adjuvant platinum-based chemotherapy has become the standard of care, the role of postoperative radiation therapy (PORT) has been controversial for years. In patients with incomplete resection, PORT should be proposed, on the basis of a strong consensus, despite the absence of randomized evidence. In patients with completely resected (R0) non-small-cell lung cancer, a meta-analysis showed poorer outcomes after PORT in the absence of mediastinal involvement (pN0 and pN1). In patients with pN2, the role of PORT was less clear and required further research. The meta-analysis included trials using older radiation techniques and poorer quality of surgery according to today's standards, and selection of patients was not positron emission tomography-based. Newer retrospective and nonrandomized studies and subgroup analyses of randomized trials evaluating adjuvant chemotherapy suggested a survival benefit of PORT in patients with pN2 R0. Two recent randomized trials (Lung ART and PORT-C) evaluating conformal PORT versus no PORT retrieved no disease-free survival advantage for stage IIIA-N2 patients, even if mediastinal relapse was significantly decreased with PORT. PORT had no effect on survival, possibly given the high rate of distant relapse and risk of additional cardiopulmonary toxicity. Ongoing and future analyses are planned in Lung ART to identify patients for whom PORT could be recommended. Incorporation of newer systemic treatments (immune checkpoint inhibitors or targeted therapy in oncogene-addicted patients) is underway in the neoadjuvant and/or adjuvant setting. Better identification of patients at a high risk of disease recurrence, with analysis of circulating tumor DNA, on the basis of the detection of postsurgical minimal (or molecular) residual disease is warranted in future studies.

Postoperative radiotherapy in resected non-small cell lung cancer: The never-ending story

This manuscript collects in a joint and orderly manner the existing evidence at the present time about postoperative treatment with radiotherapy in non-small cell lung cancer. It also systematically reviews the current evidence, the international recommendations in the most relevant guidelines, the most controversial aspects in clinical and pathological staging, the specific technical aspects of radiotherapy treatment, and also collects all the potential risk factors that have been postulated as significant in the prognosis of these patients, evaluating the possibility of segmenting a particularly sensitive subpopulation with a high risk of relapse on which an adjuvant treatment with radiotherapy could have an impact on their clinical evolution. Finally, currently active trials that aspire to provide more evidence on this topic are reviewed.

Post-operative radiation therapy for non-small cell lung cancer: A comparison of radiation therapy techniques

OBJECTIVES

Post-operative radiation therapy (PORT) in locally advanced non-small cell lung cancer (LA-NSCLC) has historically been associated with toxicity. Conformal techniques like intensity modulated radiation therapy (IMRT) have the potential to reduce acute and long-term toxicity from radiation therapy. Among patients receiving PORT for LA-NSCLC, we identified factors associated with receipt of IMRT and evaluated the association between IMRT and toxicity.

METHODS

We queried the Surveillance, Epidemiology, and End Results (SEER)-Medicare database between January 1, 2006 to December 31, 2014 to identify patients diagnosed with Stage II or III NSCLC and who received upfront surgery and subsequent PORT. Baseline differences between patients receiving 3-dimentional conformal radiation therapy (3D-CRT) and IMRT were assessed using the chi-squared test for proportions and the t-test for means. Multivariable logistic regression was used to identify predictors of receipt of IMRT and pulmonary, esophageal, and cardiac toxicity. Propensity-score matching was employed to reduce the effect of known confounders.

RESULTS

A total of 620 patients met the inclusion criteria, among whom 441 (71.2%) received 3D-CRT and 179 (28.8%) received IMRT. The mean age of the cohort was 73.9 years and 54.7% were male. The proportion of patients receiving IMRT increased from 6.2% in 2006 to 41.4% in 2014 (P < 0.001). IMRT was not associated with decreased pulmonary (OR 0.89; 95% CI, 0.62-1.29), esophageal (OR 1.09; 95% CI, 0.0.75-1.58), or cardiac toxicity (OR 1.02; 95% CI, 0.69-1.51). These findings held on propensity-score matching. Clinical risk factors including comorbidity and prior treatment history were associated with treatment toxicity.

CONCLUSION

In a cohort of elderly patients, the use of IMRT in the setting of PORT for LA-NSCLC was not associated with a difference in toxicity compared to 3D-CRT. This finding suggests that outcomes from PORT may be independent of radiotherapy treatment technique.

Increasing Heart Dose Reduces Overall Survival in Patients Undergoing Postoperative Radiation Therapy for NSCLC

Introduction

Given the concern for cardiopulmonary toxicity in patients with NSCLC undergoing postoperative radiation therapy (PORT), the purpose of this study was to evaluate the association between heart dose and overall survival (OS) in patients undergoing PORT with modern techniques.

Methods

This is a retrospective study of consecutive patients with NSCLC treated with PORT between May 2004 and January 2017. Clinical records were reviewed and radiation dose distributions were analyzed for association with OS.

Results

A total of 284 patients were analyzed. At the time of surgery, most patients had pathologic American Joint Committee on Cancer seventh edition stage III disease (91.2 %) and received either preoperative or adjuvant chemotherapy (92.3 %). Most patients underwent a lobectomy (81.3 %) and had R0 (80.6 %) or R1 (19.4 %) resection. PORT was delivered with a median radiation dose of 54 Gy, and 70.4 % of patients were treated with intensity-modulated radiation therapy. Dosimetric variables across a large range of doses to the heart were highly significant (p < 0.05) for OS. The volume of the heart receiving 8 Gy (HV8) was the most significant dosimetric variable (p < 0.001), and the median HV8 was 35.5 %. The median OS was 33.2 versus 53.6 months (p < 0.005) for patients with HV8 above or below 35.5 %, respectively. On multivariable analysis accounting for other potential prognostic confounders, HV8 remained highly significant (p < 0.001).

Conclusions

The data reveal a strong correlation between increasing heart dose and OS in patients with NSCLC undergoing PORT. Taken together with the recently presented LungART trial, lowering heart dose in PORT patients may help to decrease the risk of morbidity and mortality and improve the therapeutic ratio of PORT.

Predictors of Pneumonitis After Conventionally Fractionated Radiotherapy for Locally Advanced Lung Cancer

PURPOSE

Multiple factors influence the risk of developing pneumonitis after radiation therapy (RT) for lung cancer, but few resources exist to guide clinicians in predicting risk in an individual patient treated with modern techniques. We analyzed toxicity data from a state-wide consortium to develop an integrated pneumonitis risk model.

METHODS AND MATERIALS

All patients (N = 1302) received conventionally fractionated RT for stage II-III non-small cell lung cancer between April 2012 and July 2019. Pneumonitis occurring within 6 months of treatment was graded by local practitioners and collected prospectively from 27 academic and community clinics participating in a state-wide quality consortium. Pneumonitis was modeled as either grade ≥2 (G2+) or grade ≥3 (G3+). Logistic regression models were fit to quantify univariable associations with dose and clinical factors, and stepwise Akaike information criterion-based modeling was used to build multivariable prediction models.

RESULTS

The overall rate of pneumonitis of any grade in the 6 months following RT was 16% (208 cases). Seven percent of cases (n = 94) were G2+ and <1% (n = 11) were G3+. Adjusting for incomplete follow-up, estimated rates for G2+ and G3+ were 14% and 2%, respectively. In univariate analyses, gEUD, V5, V10, V20, V30, and mean lung dose (MLD) were positively associated with G2+ pneumonitis risk, whereas current smoking status was associated with lower odds of pneumonitis. G2+ pneumonitis risk of ≥22% was independently predicted by MLD of ≥20 Gy, V20 of ≥35%, and V5 of ≥75%. In multivariate analyses, the lung V5 metric remained a significant predictor of G2+ pneumonitis, even when controlling for MLD, despite their close correlation. For G3+ pneumonitis, MLD and V20 were statistically significant predictors. Number of patient comorbidities was an independent predictor of G3+, but not G2+ pneumonitis.

CONCLUSIONS

We present an analysis of pneumonitis risk after definitive RT for lung cancer using a large, prospective dataset. We incorporate comorbidity burden, smoking status, and dosimetric parameters in an integrated risk model. These data may guide clinicians in assessing pneumonitis risk in individual patients.