Vertebral body and splenic irradiation are associated with lymphopenia in localized pancreatic cancer treated with stereotactic body radiation therapy

NRG Oncology International Consensus Contouring Atlas on Target Volumes and Dosing Strategies for Dose-Escalated Pancreatic Cancer Radiation Therapy

PURPOSE

Dose-escalated radiation therapy is increasingly used in the treatment of pancreatic cancer; however, approaches to target delineation vary widely. We present the first North American cooperative group consensus contouring atlas for dose-escalated pancreatic cancer radiation therapy.

METHODS AND MATERIALS

An expert international panel comprising 15 radiation oncologists, 2 surgeons, and 1 radiologist was recruited. Participants used MimCloud software to contour high- and low-risk clinical target volumes (CTVs) on 3 pancreatic cancer cases: a borderline resectable head tumor, a locally advanced head tumor, and a medically inoperable tail tumor. Simultaneous Truth and Performance Level Estimation volumes were created, and contours were analyzed using Dice similarity coefficients.

RESULTS

The contoured gross tumor volume for the borderline head, locally advanced head, and unresectable tail tumor cases were 156.7, 58.2, and 9.0 cc, respectively, and the Dice similarity coefficients (SD) for the high- and low-risk CTV ranged from 0.45 to 0.82. Consensus volumes were agreed upon by authors. High-risk CTVs comprised the tumor plus abutting vessels. Low-risk CTVs started superiorly at (tail and distal body tumors) or 1 cm above (head, neck and proximal body tumors) the celiac takeoff and extended inferiorly to the superior mesenteric artery at the level of the first jejunal takeoff. For head, neck, and proximal body tumors, the lateral volume encompassed the entire pancreas head and 5 to 10 mm around the celiac, superior mesenteric artery, superior mesenteric vein, including the common hepatic artery and medial portal vein, consistent with a "Triangle" volume-based approach. For distal body and tail tumors, the entire tail was included, along with the splenic vessels and the takeoffs of celiac artery.

CONCLUSIONS

Through multidisciplinary collaboration, we created consensus contouring guidelines for dose-escalated pancreatic cancer radiation therapy. These volumes include not only gross disease, but also routine elective coverage, and can be used to standardize practice for future trials seeking to define the role of dose-escalated radiation therapy in pancreatic cancer.

Normal tissue complication probability model for severe radiation-induced lymphopenia in patients with pancreatic cancer treated with concurrent chemoradiotherapy

Background and purpose

Radiation-induced lymphopenia (RIL) may be associated with a worse prognosis in pancreatic cancer. This study aimed to develop a normal tissue complication probability (NTCP) model to predict severe RIL in patients with pancreatic cancer undergoing concurrent chemoradiotherapy (CCRT).

Materials and methods

We reviewed pancreatic cancer patients treated at our facility for model training and internal validation. Subsequently, we reviewed data from three other facilities to validate model fit externally. An absolute lymphocyte count (ALC) of ＜0.5 × 103/μL during CCRT was defined as severe RIL. An NTCP model was trained using a least absolute shrinkage and selection operator (LASSO)-based logistic model. The model's predictive performance was evaluated using the receiver operating characteristic area under the curve (AUC), scaled Brier score, and calibration plots.

Results

Among the 114 patients in the training set, 78 had severe RIL. LASSO showed that low baseline ALC, large planning target volume, and high percentage of bilateral kidneys receiving ≥ 5Gy were selected as parameters of the NTCP model for severe RIL. The AUC and scaled Brier score were 0.91 and 0.49, respectively. Internal validation yielded an average AUC of 0.92. In the external validation with 68 patients, the AUC and scaled Brier score was 0.83 and 0.30, respectively. Calibration plots showed good conformity.

Conclusions

The NTCP model for severe RIL during CCRT for pancreatic cancer, developed and validated in this study, demonstrated good predictive performance. This model can be used to evaluate and compare the risk of RIL.

Predictive value of bowel dose-volume for severe radiation-induced lymphopenia and survival in cervical cancer

Background

Radiation-induced lymphopenia (RIL) is closely related to the prognosis of cervical cancer patients and may affect the efficacy of immune checkpoint inhibitors (ICIs). However, the factors influencing RIL are not very clear. In addition to bone marrow (BM) dose-volume, animal studies indicate radiation-induced bowel injury may be a more crucial factor. Further clarification of the correlation between RIL and bowel dose-volume is important for cervical cancer treatment.

Methods

Cervical cancer patients treated with postoperative radiotherapy or radical radiotherapy were eligible for this retrospective study. Clinical characteristics, dose parameters of bowel and BM, planning target volume (PTV) size, overall survival (OS) and progression-free survival (PFS) were recorded. The absolute lymphocyte count<0.5×109/L at radiotherapy end was defined as severe RIL (sRIL). Hazard ratio (HR) and 95% confidence interval (Cl)were estimated using Cox regression models. Survival curve was plotted using the Kaplan-Meier method. On this basis, the receiver operating characteristics (ROC) curve was used to calculate the area under the curve (AUC) for radiation parameters with sRIL as the state variable.

Result

A total of 118 cervical cancer patients were included in this study, with a median follow-up time of 57.6 months. In multivariable Cox regression analysis, international Federation of Gynecology and obstetrics (FIGO) stage (HR, 11.806; 95% CI, 3.256-42.809; p<0.001), concurrent chemotherapy (HR, 0.200; 95% CI, 0.054-0.748; p=0.017), sRIL after radiotherapy (HR, 6.009; 95% CI, 1.361-26.539; p=0.018), and pathological type (HR, 2.261; 95% CI, 1.043-4.901; p=0.039) were significantly correlated with OS. Patients with sRIL had significantly decreased OS (79.1% vs 94.1%; HR, 3.81; 95%CI, 1.46-9.92; p=0.023). In binary logistic regression analysis, sRIL was significantly correlated with bowel V45 (Odds radio (OR), 1.025; 95%CI, 1.007-1.044; p=0.007), BM V10 (OR, 0.987; 95%CI, 0.978-0.997; p=0.011), BM V20 (OR, 1.017; 95%CI, 1.002-1.031, p=0.027), and PTV size (OR, 0.998; 95%CI, 0.996-1.000; p=0.026). The ROC curve showed, bowel V45 (AUC=0.787, p<0.001) was the best indicator for predicting sRIL.

Conclusion

SRIL after radiotherapy could significantly predict decreased OS. In addition, sRIL is associated with higher bowel, BM dose-volume, PTV size, indicating that the bowel may be an important organ leading to an increased risk of sRIL.

The impact of different modalities of chemoradiation therapy and chemotherapy regimens on lymphopenia in patients with locally advanced non-small cell lung cancer

BACKGROUND

Chemotherapy and radiotherapy (RT) would induce lymphopenia, leading to a poor prognosis. This study investigated whether chemotherapy increased lymphopenia during RT and explored the impacts of different chemotherapy regimens on the lymphocyte counts of patients receiving RT.

METHODS

Clinical parameters and lymphocyte data were collected from 215 patients with locally advanced non-small cell lung cancer (LA-NSCLC). Severe lymphopenia (SRL) was defined as an absolute lymphocyte count (ALC) of ≤0.2×103 cells/μL. Patient overall survival (OS) was analyzed using the Kaplan-Meier method. The predictors of SRL were extracted using univariate and multivariate regression analyses with backward likelihood ratio elimination.

RESULTS

Compared with patients without SRL, patients with SRL with LA-NSCLC showed a poorer prognosis in terms of OS (P=0.003). Of the 215 patients, 130 underwent concurrent chemoradiotherapy (CCRT) and 85 underwent sequential chemoradiotherapy (SCRT). The OS was better in patients without SRL (in the CCRT group, P=0.01 and in the SCRT group, P=0.08). The mean ALCs for CCRT and SCRT did not differ significantly (P=0.27). The minimum ALC of CCRT was significantly lower than that of SCRT (P<0.0001). CCRT was a predictor of SRL (P=0.008). However, multivariate analysis showed that the different chemotherapy regimens were not predictors of SRL (all P>0.1).

CONCLUSIONS

In LA-NSCLC, the outcomes of patients with SRL were poorer than those without SRL. RT and chemotherapy were the main factors affecting SRL development, while different chemotherapy regimens were not significantly associated with lymphocyte counts in LA-NSCLC.

Pelvic bone marrow dose-volume predictors of late lymphopenia following pelvic lymph node radiation therapy for prostate cancer

BACKGROUND AND PURPOSE

Given the substantial lack of knowledge, we aimed to assess clinical/dosimetry predictors of late hematological toxicity on patients undergoing pelvic-nodes irradiation (PNI) for prostate cancer (PCa) within a prospective multi-institute study.

MATERIALS AND METHODS

Clinical/dosimetry/blood test data were prospectively collected including lymphocytes count (ALC) at baseline, mid/end-PNI, 3/6 months and every 6 months up to 5-year after PNI. DVHs of the Body, ileum (BMILEUM), lumbosacral spine (BMLS), lower pelvis (BMPELVIS), and whole pelvis (BMTOT) were extracted. Current analysis focused on 2-year CTCAEv4.03 Grade ≥ 2 (G2+) lymphopenia (ALC < 800/μL). DVH parameters that better discriminate patients with/without toxicity were first identified. After data pre-processing to limit overfitting, a multi-variable logistic regression model combining DVH and clinical information was identified and internally validated by bootstrap.

RESULTS

Complete data of 499 patients were available: 46 patients (9.2 %) experienced late G2+ lymphopenia. DVH parameters of BMLS/BMPELVIS/BMTOT and Body were associated to increased G2+ lymphopenia. The variables retained in the resulting model were ALC at baseline [HR = 0.997, 95 %CI 0.996-0.998, p < 0.0001], smoke (yes/no) [HR = 2.9, 95 %CI 1.25-6.76, p = 0.013] and BMLS-V ≥ 24 Gy (cc) [HR = 1.006, 95 %CI 1.002-1.011, p = 0.003]. When acute G3+ lymphopenia (yes/no) was considered, it was retained in the model [HR = 4.517, 95 %CI 1.954-10.441, p = 0.0004]. Performances of the models were relatively high (AUC = 0.87/0.88) and confirmed by validation.

CONCLUSIONS

Two-year lymphopenia after PNI for PCa is largely modulated by baseline ALC, with an independent role of acute G3+ lymphopenia. BMLS-V24 was the best dosimetry predictor: constraints for BMTOT (V10Gy < 1520 cc, V20Gy < 1250 cc, V30Gy < 850 cc), and BMLS (V24y < 307 cc) were suggested to potentially reduce the risk.

The Role of Thoracic Vertebral Body Dosimetry in Minimizing Acute Hematologic Toxicities of Patients With Non-Small Cell Lung Cancer Receiving Lung Radiation Therapy and Immunotherapy

PURPOSE

Hematologic toxicities (HTs) are among the most common toxicities of combined immunotherapy and radiation therapy (RT). It remains essential to prevent RT-induced HTs because they can cause treatment discontinuation (influencing antitumoral effects) and because lymphopenia might dampen the effects of immunotherapy. To date, there are no studies examining the effect of thoracic vertebral body (TVB) RT dose on HTs in patients with non-small cell lung cancer receiving combined lung RT and programmed cell death (ligand) 1 immunotherapy.

METHODS AND MATERIALS

For standardization, all doses were reported as 2-Gy equivalents (EQD2). Mirroring publications before the immunotherapy era, TVB volumes referred to T1-T10, and specific dosimetric parameters (DmeanEQD2, V5EQD2-V60EQD2) were analyzed. Logistic regression estimated associations between grade ≥3 HTs (HT3+) and dosimetric/clinical parameters. Normal tissue complication probability (NTCP) models were constructed by logistic regression analysis modeling for HT3+. Receiver operating characteristic (ROC) analysis delineated TVB dosimetric thresholds, the stratification of which was able to evaluate post-RT absolute lymphocyte count and immunotherapy responses. Areas under the curve (AUCs) for NTCP models were corroborated by bootstrapping (optimism-corrected) methodology.

RESULTS

In 132 patients, there were 26 (19.7%) instances of HT3+. On multivariate analysis, DmeanEQD2 and V5EQD2 to V20EQD2 were associated with HT3+ (P < .05 for all). The NTCP models illustrated a 50% probability of HT3+ at a DmeanEQD2 = 39.8 Gy, V5EQD2 = 87.4%, V10EQD2 = 77.0%, and V20EQD2 = 68.4%. ROC analysis delineated optimal thresholds of HT3+ with DmeanEQD2 ± 30.2 Gy, V5EQD2 ± 69.1%, V10EQD2 ± 64.6%, and V20EQD2 ± 53.5%. Patients treated with values above those cutoffs had over double the risk of HT3+, with significant differences in post-RT absolute lymphocyte count and immunotherapy responses (P < .05 for all). AUCs for each individual parameter ranged from 0.743 to 0.798, and combining all 4 aforementioned cutoffs into a ROC curve resulted in a qualitatively higher AUC (0.836).

CONCLUSIONS

This hypothesis-generating work suggests that TVB dosimetry may equate with HT3+ in patients with non-small cell lung cancer undergoing combined lung RT/immunotherapy. Applying TVB dose constraints in this population could reduce HT3+ and avoid dampening of immunotherapy responses, but prospective validation is required.

Proton and Carbon Ion Radiation Therapy Decreased Severe Lymphopenia by Reducing Thoracic Vertebra and Aortic Doses in Non-Small Cell Lung Cancer Versus Intensity Modulated Radiation Therapy

PURPOSE

Lymphopenia is a common adverse effect of radiation therapy (RT). Little is known about the difference in lymphopenia between intensity modulated (photon) radiation therapy (IMRT) and proton and carbon ion radiation therapy (PCIRT). This study aimed to investigate lymphopenia differences between IMRT and PCIRT in non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

Clinical and dosimetric parameters were collected from 343 patients who received definitive IMRT or PCIRT for NSCLC. Severe lymphopenia (SRL) was defined as an absolute lymphocyte count (ALC) ≤0.5 × 103 cells/μL. Overall survival (OS) was analyzed using the Kaplan-Meier method. Propensity score matching was performed between the IMRT and PCIRT groups. Least absolute shrinkage and selection operator analysis was used to select appropriate dosimetric parameters. Univariate and multivariate logistic regression analyses were conducted to identify the predictors of SRL.

RESULTS

Compared with the IMRT group, the PCIRT group was less likely to develop SRL (P < .001). Compared with the non-SRL group, the SRL group showed significant association with poorer OS, with a median survival time of 29.2 versus 15.0 months (P = .046). IMRT was an independent risk factor of SRL (P = .004). A lower ALC before RT (P = .030) and larger planning target volume (PTV) (P = .002) were also significant independent risk factors for SRL. Moreover, the majority of dosimetric parameters of organs at risk in PCIRT were lower than those in IMRT (P < .001). Thoracic vertebra V5 (P = .002) and aorta V5 (P = .026) were identified as independent risk predictors of SRL after adding dosimetric parameters to the regression model.

CONCLUSIONS

Compared with IMRT, PCIRT could reduce SRL incidence, possibly by limiting thoracic vertebra and aortic doses, and SRL was associated with poor outcomes in patients with NSCLC.

Emerging evidence for adapting radiotherapy to immunotherapy

Immunotherapy has revolutionized the clinical management of many malignancies but is infrequently associated with durable objective responses when used as a standalone treatment approach, calling for the development of combinatorial regimens with superior efficacy and acceptable toxicity. Radiotherapy, the most commonly used oncological treatment, has attracted considerable attention as a combination partner for immunotherapy owing to its well-known and predictable safety profile, widespread clinical availability, and potential for immunostimulatory effects. However, numerous randomized clinical trials investigating radiotherapy-immunotherapy combinations have failed to demonstrate a therapeutic benefit compared with either modality alone. Such a lack of interaction might reflect suboptimal study design, choice of end points and/or administration of radiotherapy according to standard schedules and target volumes. Indeed, radiotherapy has empirically evolved towards radiation doses and fields that enable maximal cancer cell killing with manageable toxicity to healthy tissues, without much consideration of potential radiation-induced immunostimulatory effects. Herein, we propose the concept that successful radiotherapy-immunotherapy combinations might require modifications of standard radiotherapy regimens and target volumes to optimally sustain immune fitness and enhance the antitumour immune response in support of meaningful clinical benefits.

Neoadjuvant chemoradiotherapy induced lymphopenia in gastric cancer and associations with spleen dosimetry and survival outcomes

Background

Few studies concentrate on spleen dosimetry of radiotherapy for gastric cancer (GC). Although there is no consensus on the spleen dose-volume threshold for lymphopenia, several studies indicated that the higher the spleen dose, the higher the risk of lymphopenia. This study aimed to identify the appropriate spleen dosimetric parameters for predicting grade 4 + lymphopenia in patients with locally advanced GC.

Material and methods

A total of 295 patients treated with nCRT and nChT from June 2013 to December 2021 at two major centers were included, of whom 220 were assigned to the training cohort and 75 to the external validation cohort.

Results

Grade 4 + lymphopenia was more common in the nCRT than in the nChT group (49.5% vs. 0, P < 0.001 in the training cohort; 25.0% vs. 0, P = 0.001 in the external validation cohort). Age ≥ 60 years (P = 0.006), lower pretreatment absolute lymphocyte count (P = 0.001), higher spleen volume (SPV) (P = 0.001), and higher V₂₀ (P = 0.003) were significant risk factors of grade 4 + lymphopenia for patients treated with nCRT. Patients with grade 4 + lymphopenia had significantly worse PFS (P = 0.043) and showed a negative correlation trend with OS (P = 0.07). Limiting V₂₀ to < 84.5% could decrease the incidence of grade 4 + lymphopenia by 35.7%. The predictive effectiveness of the multivariable model in the training and external validation cohorts was 0.880 and 0.737, respectively.

Conclusion

Grade 4 + lymphopenia during nCRT was more common than nChT, and was associated with a worse PFS in GC patients. Constraining the spleen V₂₀ to < 84.5% may indirectly improve outcomes through lymphocyte preservation.

Splenic irradiation contributes to grade ≥ 3 lymphopenia after adjuvant chemoradiation for stomach cancer

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Severe lymphopenia occurs commonly after adjuvant chemoradiation for gastric cancer.

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High splenic radiation doses increase the chances of severe lymphopenia.

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Severe lymphopenia predicts a poorer overall survival and higher risk of infections.

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The spleen is not routinely considered an organ-at-risk with dosimetric constraint.

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Applying dose constraints to the spleen might lower the risk of severe lymphopenia.

Introduction

Adjuvant chemoradiation therapy (CRT) in gastric cancer inevitably results in an unintentional spleen radiation dose. We aimed to determine the association between the spleen radiation dose and the observed severity of lymphopenia which may affect the clinical outcomes (survival time and infection risk).

Methods

Patients who received adjuvant CRT for gastric cancer between January 2015 and December 2020 were analyzed. The splenic dose-volume histogram (DVH) parameters were reported as mean splenic dose (MSD) and percentage of splenic volume receiving at least × Gray (Gy). Peripheral blood counts were recorded pre- and post-CRT. The development of severe (Common Terminology Criteria for Adverse Events, version 5.0, grade ≥ 3) post-CRT lymphopenia (absolute lymphocyte count [ALC] < 0.5 K/μL) was assessed by multivariable logistic regression using patient and dosimetric factors. Overall survival (OS), recurrence-free survival (RFS), and cumulative incidence of infectious events were estimated and analyzed using the Cox model or competing risk analysis.

Results

Eighty-four patients with a median follow-up duration of 42 months were analyzed. Pre- and post-CRT median ALC values were 1.8 K/μL (0.9–3.1 K/μL) and 0.9 K/μL (0.0–4.9 K/μL), respectively (P < 0.001). MSD > 40 Gy (odds ratio [OR], 1.13; 95 % confidence interval [CI], 1.01–1.26; P = 0.041), sex (OR for male to female, 0.25; 95 % CI, 0.09–0.70; P = 0.008), and baseline absolute neutrophil count (OR per 1 unit increase, 1.61; 95 % CI, 1.02–2.58; P = 0.040) were associated with the development of severe post-CRT lymphopenia, which was a risk factor for poorer OS (hazard ratio [HR] = 2.47; 95 % CI, 1.24–4.92; P = 0.010) and RFS (HR = 2.27; 95 % CI, 1.16–4.46; P = 0.017). The cumulative incidence of infections was higher among severe post-CRT lymphopenia patients (2.53, 95 % CI, 1.03–6.23, P = 0.043).

Conclusion

High splenic radiation doses increase the odds of severe post-CRT lymphopenia, an independent predictor of lower OS and higher risks of recurrence and infections in gastric cancer patients receiving adjuvant CRT. Therefore, optimizing the splenic DVH parameters may decrease the risk of severe post-CRT lymphopenia.

Proton Therapy in the Management of Pancreatic Cancer

Radiation therapy plays a central role in the treatment of pancreatic cancer. While generally shown to be feasible, proton irradiation, particularly when an ablative dose is planned, remains a challenge, especially due to tumor motion and the proximity to organs at risk, like the stomach, duodenum, and bowel. Clinically, standard doses of proton radiation treatment have not been shown to be statistically different from photon radiation treatment in terms of oncologic outcomes and toxicity rates as per non-randomized comparative studies. Fractionation schedules and concurrent chemotherapy combinations are yet to be optimized for proton therapy and are the subject of ongoing trials.