Background: Radiotherapy (RT) is a mainstay for the treatment of lung cancer, but the effective dose is often limited by the development of radiation-induced pneumonitis and pulmonary fibrosis. Transforming growth factor β (TGFβ) and platelet-derived growth factor (PDGF) play crucial roles in the development of these diseases, but the effects of dual growth factor inhibition on pulmonary fibrosis development remain unclear. Methods: C57BL/6 mice were treated with 20 Gy to the thorax to induce pulmonary fibrosis. PDGF receptor inhibitors SU9518 and SU14816 (imatinib) and TGFβ receptor inhibitor galunisertib were applied individually or in combinations after RT. Lung density and septal fibrosis were measured by high-resolution CT and MRI. Lung histology and gene expression analyses were performed and Osteopontin levels were studied. Results: Treatment with SU9518, SU14816 or galunisertib individually attenuated radiation-induced pulmonary inflammation and fibrosis and decreased radiological and histological signs of lung damage. Combining PDGF and TGFβ inhibitors showed to be feasible and safe in a mouse model, and dual inhibition significantly attenuated radiation-induced lung damage and extended mouse survival compared to blockage of either pathway alone. Gene expression analysis of irradiated lung tissue showed upregulation of PDGF and TGFβ-dependent signaling components by thoracic irradiation, and upregulation patterns show crosstalk between downstream mediators of the PDGF and TGFβ pathways. Conclusion: Combined small-molecule inhibition of PDGF and TGFβ signaling is a safe and effective treatment for radiation-induced pulmonary inflammation and fibrosis in mice and may offer a novel approach for treatment of fibrotic lung diseases in humans. Translational statement: RT is an effective treatment modality for cancer with limitations due to acute and chronic toxicities, where TGFβ and PDGF play a key role. Here, we show that a combined inhibition of TGFβ and PDGF signaling is more effective in attenuating radiation-induced lung damage compared to blocking either pathway alone. We used the TGFβ-receptor I inhibitor galunisertib, an effective anticancer compound in preclinical models and the PDGFR inhibitors imatinib and SU9518, a sunitinib analog. Our signaling data suggest that the reduction of TGFβ and PDGF signaling and the attenuation of SPP1 (Osteopontin) expression may be responsible for the observed benefits. With the clinical availability of similar compounds currently in phase-I/II trials as cancer therapeutics or already approved for certain cancers or idiopathic lung fibrosis (IPF), our study suggests that the combined application of small molecule inhibitors of TGFβ and PDGF signaling may offer a promising approach to treat radiation-associated toxicity in RT of lung cancer.

Radio-resistant mesenchymal stem cells: mechanisms of resistance and potential implications for the clinic

Background: Head-and-neck squamous cell carcinoma (HNSCC) is one of the most common malignancies globally, and the number of elderly patients diagnosed with HNSCC is increasing. However, as elderly HNSCC patients are underrepresented in clinical trials, current clinical decision making for this cohort largely lacks clinical evidence.Methods: Elderly patients (≥65 years) with HNSCC undergoing (chemo)radiotherapy from 2010 to 2018 at Freiburg University Medical Center were assessed for patterns of care, locoregional control (LRC), progression-free (PFS) and overall survival (OS) regarding definitive and adjuvant treatments. Acute and late therapy-associated toxicities were quantified according to CTCAE v5.0.Results: Two hundred forty-six patients were included in this analysis, of whom 166 received definitive and 80 adjuvant treatment. Two-year rates for OS, PFS and LRC were 56.9, 44.9 and 75.5%, respectively. Survival differed significantly between age groups with an OS of 40 and 22 months and a PFS of 23 and 12 months for patients aged 65–74 or ≥ 75 years, respectively (p < 0.05). Concomitant chemotherapy resulted in improved OS in patients aged 65–74 years compared to radiotherapy alone (p < 0.05) for definitive treatments, while patients ≥75 years did not benefit (p = 0.904). For adjuvant chemoradiotherapy, a trend towards superior OS rates was observed for patients aged 65–74 years (p = 0.151). Low performance status (HR = 2.584, 95% CI 1.561–4.274;p < 0.001) and smoking (HR = 1.960, 95% CI 1.109–3.464,p < 0.05) were the strongest independent prognostic factor in the multivariate analysis for decreased OS. One hundred thirty-eight patients (56.1%) experienced acute grade 3/4 and 45 patients (19.9%) chronic grade 3 toxicities.Conclusion: Radiotherapy is a feasible treatment modality for elderly HNSCC patients. The relatively low OS compared to high LRC may reflect age and comorbidities. Concomitant chemotherapy should be critically discussed in elderly HNSCC patients.

To report our experience with increased dose intensity-modulated radiation and concurrent systemic chemotherapy as definitive treatment of locally advanced esophageal cancer. We analyzed 27 consecutive patients with histologically proven esophageal cancer, who were treated with increased-dose IMRT as part of their definitive therapy. The majority of patients had T3/4 and/or N1 disease (93%). Squamous cell carcinoma was the dominating histology (81%). IMRT was delivered in step-and-shoot technique in all patients using an integrated boost concept. The boost volume was covered with total doses of 56-60 Gy (single dose 2-2.14 Gy), while regional nodal regions received 50.4 Gy (single dose 1.8 Gy) in 28 fractions. Concurrent systemic therapy was scheduled in all patients and administered in 26 (96%). 17 patients received additional adjuvant systemic therapy. Loco-regional control, progression-free and overall survival as well as acute and late toxicities were retrospectively analyzed. In addition, quality of life was prospectively assessed according to the EORTC QLQs (QLQ-OG25, QLQ-H&N35 and QLQ-C30). Radiotherapy was completed as planned in all but one patient (96%), and 21 patients received more than 80% of the planned concurrent systemic therapy. We observed ten locoregional failures, transferring into actuarial 1-, 2- and 3-year-locoregional control rates of 77%, 65% and 48%. Seven patients developed distant metastases, mainly to the lung (71%). The actuarial 1-, 2- and 3-year-disease free survival rates were 58%, 48% and 36%, and overall survival rates were 82%, 61% and 56%. The concept was well tolerated, both in the clinical objective examination and also according to the subjective answers to the QLQ questionnaire. 14 patients (52%) suffered from at least one acute CTC grade 3/4 toxicity, mostly hematological side effects or dysphagia. Severe late toxicities were reported in 6 patients (22%), mostly esophageal strictures and ulcerations. Severe side effects to skin, lung and heart were rare. IMRT with concurrent systemic therapy in the definitive treatment of esophageal cancer using an integrated boost concept with doses up to 60 Gy is feasible and yields good results with acceptable acute and late overall toxicity and low side effects to skin, lung and heart.