Analysis of predictive factors for lung injury after forward-planned intensity-modulated radiotherapy in whole breast irradiation

Anatomy-dependent lung doses from 3D-conformal breast-cancer radiotherapy

This study aims to identify key anatomic features that govern the individual variability of lung doses from breast-cancer radiotherapy. 3D conformal, intensity-modulated and hybrid techniques with 50.4 Gy whole-breast dose were planned for 128 patients. From their CT images, 17 anatomic measures were assessed and tested as predictors for lung dose-volume characteristics. Tangential techniques yielded mean ipsilateral lung doses in the range of 3–11 Gy. This inter-patient variability was explained to almost 40% by central lung distance, and to almost 60% if this measure was complemented by midplane lung width and maximum heart distance. Also the variability in further dose-volume metrics such as volume fractions receiving 5, 20 or 40 Gy could be largely explained by the anatomy. Multi-field intensity-modulated radiotherapy reduced high-exposed lung volumes, but resulted in higher mean ipsilateral lung doses and larger low-dose burden. Contralateral lung doses ranged from 0.3 to 1 Gy. The results highlight that there are large differences in lung doses among breast-cancer patients. Most of this inter-individual variability can be explained by a few anatomic features. The results will be implemented in a dedicated software tool to provide personalized estimates of long-term health risks related to breast-cancer radiotherapy. The results may also be used to identify favourable as well as problematic anatomies, and serve as a quick quantitative benchmark for individual treatment plans.

Imaging features of radiation-induced lung disease and its relationship with clinical and dosimetric factors in breast cancer patients

Aim

The aim is to extensively evaluate imaging features of radiation induced lung disease in breast cancer patients and to determine the relationship of imaging alterations with dosimetric parameters and patient related characteristics.

Materials and Methods

A total of 76 breast cancer patients undergoing radiotherapy (RT) were studied retrospectively by case notes, treatment plans, dosimetric parameters, and chest computed tomography (CT) scans. Time intervals, that chest CT scans were acquired, were grouped as 1-6 months, 7-12 months, 13-18 months and more than 18 months after RT. Chest CTs (one or more for each patient) were assessed for the presence of ground glass opacity, septal thickening, consolidation/patchy pulmonary opacity/alveolar infiltrates, subpleural air cyst, air bronchogram, parenchymal bands, traction bronchiectasis, pleural/subpleural thickening and pulmonary volume loss. These alterations were scored by applying a system devised by Nishioka et al. Nishioka scores were analyzed for the relationship with clinical and dosimetric factors.

Statistical Analysis Used

IBM SPSS Statistics for Windows, version 22.0 (IBM Corp., Armonk, N.Y., USA) was used to analyze data.

Results

Median follow-up time was 49 months. Advanced age and aromatase inhibitor intake were correlated with higher Nishioka scores for 1-6 months' period. However, both were found nonsignificant in multivariate analysis. Nishioka scores of CT scans acquired more than 12 months after RT were positively correlated with mean lung dose, V5, V20, V30, and V40. Receiver operating characteristic analysis revealed that V5 for ipsilateral lung was the most robust dosimetric parameter predicting chronic lung injury. V5 >41% indicates the development of radiological lung changes.

Conclusions

Keeping V5 ≤41% for ipsilateral lung could provide avoiding chronic lung sequelae.

Pneumonitis and fibrosis after breast cancer radiotherapy: occurrence and treatment-related predictors

BACKGROUND

Radiation pneumonitis (RP) and radiation fibrosis (RF) are common side effects after breast cancer (BC) radiotherapy (RT). However, there is a great variation in the frequency of RP and RF. This study presents the occurrence of- and the treatment-related predictors for RP and RF. Further, physician- and patient-reported pulmonary symptoms during the first year after postoperative RT for BC are demonstrated.

MATERIALS AND METHODS

From 2007 to 2008, 250 BC patients referred for postoperative RT were included in a prospective cohort study and followed during the first year after RT. High-resolution computed tomography of the lungs and symptom registration were performed before RT and 3, 6, and 12 months after RT. Patient-reported symptoms were registered by standard quality of life questionnaires. Logistic regression analyses were applied to estimate treatment-related predictors for radiological RP (rRP), clinical RP (cRP), radiological RF (rRF), and clinical RF (cRF).

RESULTS

The occurrence of rRP and cRP at three months was 78% and 19%, while 12 months after RT rRF and cRF was 89% and 16%, respectively; all reported as grade 1. In multivariable analyses, mastectomy predicted cRP at three months (OR = 2.48, p = .03) and cRF at six months, ipsilateral lung volume receiving 20 Gray or more (V20), V30, and mean lung dose (MLD) predicted rRP at six months (OR = 1.06, p = .0003; OR = 1.10, p = .001; and OR = 1.03, p = .01, respectively). Endocrine treatment predicted cRF at 12 months (OR = 2.48, p = .02). Physicians reported significant more dyspnea at 3 months (p = .003) and patients reported 'a little dyspnea' more at 3 and 12 months compared to baseline (p = .007).

CONCLUSION

RP and RF are prevalent in the first year after BC radiation. Mastectomy predicted cRP at three months. V20, V30, D25, and MLD predicted rRP at 6 months, and endocrine treatment predicted cRF at 12 months. Patients and physicians reported dyspnea differently.

Internal Mammary Chain Sentinel Nodes in Early-Stage Breast Cancer Patients: Toward Selective Removal

BACKGROUND

Removal of internal mammary chain sentinel nodes (IMCSNs) affects prognosis and treatment of breast cancer, and internal mammary chain radiotherapy (IMCRT) can improve survival for selected patients. This study aimed to determine the effect of IMCSN biopsy on recurrence-free survival (RFS) and overall survival (OS) and to identify predictive factors for IMCSN and distant metastasis.

METHODS

Patients with IMCSNs were selected from a prospective database for the period 1999-2007. Lymphoscintigraphy was performed after intratumoral technetium-99 m injection, and all sentinel nodes were removed. Both RFS and OS were calculated for subgroups with tumor-positive, tumor-negative, or non-removed IMCSNs. Predictive factors were identified for tumor-positive IMCSNs and distant metastasis by regression analysis.

RESULTS

For 287 (85%) of 336 patients, IMCSN biopsy was performed, and metastasis was detected in 38 patients (13%). The patients with tumor-positive IMCSNs had poorer OS than the patients with no IMCSN metastasis or non-removed IMCSNs (p = 0.002). These patients also had worse RFS due to distant metastasis (p = 0.002). Axillary metastasis was predictive for tumor-positive IMCSNs (positive predictive value, 38.5%). The predictive factors for distant metastasis were tumor-positive IMCSNs (hazard ratio [HR], 2.5), non-removed IMCSNs (HR, 2.3), tumor diameter greater than 1.5 cm (HR, 3.5), and age older than 65 years (HR, 3.1; reference, < 50 years).

CONCLUSIONS

Patients with IMCSNs have worse survival due to distant metastasis. The clinically relevant predictive factor for distant metastasis is tumor larger than 1.5 cm. According to the authors' current protocol, IMCSN biopsy is performed for patients younger than 70 years who have a tumor larger than 1.5 cm, with the cardiotoxicity of the adjuvant IMCRT weighed against the survival benefit.

Identification of molecular signatures involved in radiation-induced lung fibrosis

In radiotherapy, radiation (IR)-induced lung fibrosis has severe and dose-limiting side effects. To elucidate the molecular effects of IR fibrosis, we examined the fibrosis process in irradiated mouse lung tissues. High focal IR (90 Gy) was exposed to a 3-mm volume of the left lung in C57BL6 mice. In the diffused irradiation, 20 Gy dose delivered with a 7-mm collimator almost covered the entire left lung. Histological examination for lung tissues of both irradiated and neighboring regions was done for 4 weeks after irradiation. Long-term effects (12 months) of 20Gy IR were compared on a diffuse region of the left lung and non-irradiated right lung. Fibrosis was initiated as early as 2 weeks after IR in the irradiated lung region and neighboring region. Upregulation of gtse1 in both 90Gy-irradiated and neighboring regions was observed. Upregulation of fgl1 in both 20Gy diffused irradiated and non-irradiated lungs was identified. When gtse1 or flg1 was knock-downed, TGFβ or IR-induced epithelial-mesenchymal transition was inhibited, accompanied with the inhibition of cellular migration, suggesting fibrosis responsible genes. Immunofluorescence analysis using mouse fibrotic lung tissues suggested that fibrotic regions showed increased expressions of Gtse1 and Fgl1, indicating novel molecular signatures of gtse1and fgl1 for IR-induced lung fibrosis. Even though their molecular mechanisms and IR doses or irradiated volumes for lung fibrosis may be different, these genes may be novel targets for understanding IR-induced lung fibrosis and in treatment strategies. KEY MESSAGES: Upregulation of gtse1 by 90Gy focal irradiation and upregulation of fgl1 by 20Gy diffused irradiation are identified in mouse lung fibrosis model. Gtse1 and Fgl1 are involved in radiation or TGFβ-induced epithelial-mesenchymal transition. Radiation-induced fibrotic regions of mouse lungs showed increased expressions of Gtse1 and Fgl1. Gtse1 and Fgl1 are suggested to be novel targets for radiation-induced lung fibrosis.

Exposure of the lungs in breast cancer radiotherapy: A systematic review of lung doses published 2010-2015

BACKGROUND AND PURPOSE

We report a systematic review of lung radiation doses from breast cancer radiotherapy.

METHODS AND MATERIALS

Studies describing breast cancer radiotherapy regimens published during 2010-2015 and reporting lung dose were included. Doses were compared between different countries, anatomical regions irradiated, techniques and use of breathing adaptation.

RESULTS

471 regimens from 32 countries were identified. The average mean ipsilateral lung dose (MLDipsi) was 9.0 Gy. MLDipsi for supine radiotherapy with no breathing adaption was 8.4 Gy for whole breast/chest wall (WB/CW) radiotherapy, 11.2 Gy when the axilla/supraclavicular fossa was irradiated, and 14.0 Gy with the addition of internal mammary chain irradiation; breathing adaptation reduced MLDipsi by 1 Gy, 2 Gy and 3 Gy respectively (p < 0.005). For WB/CW radiotherapy, MLDipsi was lowest for tangents in prone (1.2 Gy) or lateral decubitus (0.8 Gy) positions. The highest MLDipsi was for IMRT in supine position (9.4 Gy). The average mean contralateral lung dose (MLDcont) for WB/CW radiotherapy was higher for IMRT (3.0 Gy) than for tangents (0.8 Gy).

CONCLUSIONS

Lung doses from breast cancer radiotherapy varied substantially worldwide, even between studies describing similar regimens. Lymph node inclusion and IMRT use increased exposure, while breathing adaptation and prone/lateral decubitus positioning reduced it.

Myeloid differentiation primary response gene 88-leukotriene B4 receptor 2 cascade mediates lipopolysaccharide-potentiated invasiveness of breast cancer cells

Inflammation and local inflammatory mediators are inextricably linked to tumor progression through complex pathways in the tumor microenvironment. Lipopolysaccharide (LPS) exposure to tumor cells has been suggested to promote tumor invasiveness and metastasis. However, the detailed signaling mechanism involved has not been elucidated. In this study, we showed that LPS upregulated the expression of leukotriene B₄ receptor-2 (BLT2) and the synthesis of BLT2 ligands in MDA-MB-231 and MDA-MB-435 breast cancer cells, thereby promoting invasiveness. BLT2 depletion with siRNA clearly attenuated LPS-induced invasiveness. In addition, we demonstrated that myeloid differentiation primary response gene 88 (MyD88) lies upstream of BLT2 in LPS-potentiated invasiveness and that this ‘MyD88-BLT2’ cascade mediates activation of NF-κB and the synthesis of IL-6 and IL-8, which are critical for the invasiveness and aggression of breast cancer cells. LPS-driven metastasis of MDA-MB-231 cells was also markedly suppressed by the inhibition of BLT2. Together, our results demonstrate, for the first time, that LPS potentiates the invasiveness and metastasis of breast cancer cells via a ‘MyD88-BLT2’-linked signaling cascade.