PurposeThe aim of the study was to compare the dose differences between two kinds of materials (silica gel and hydrogel) used to prepare boluses based on three‐dimensional (3D) printing technologies and commercial bolus in head phantoms simulating nose, ear, and parotid gland radiotherapy.Methods and materialsWe used 3D printing technology to make silica gel and hydrogel boluses. To evaluate the clinical feasibility, intensity modulated radiation therapy (IMRT) plans were created for head phantoms that were bolus‐free or had a commercial bolus, a silica gel bolus, or a hydrogel bolus. Dosimetry differences were compared in simulating nose, ear, and parotid gland radiotherapy separately.ResultsThe air gaps were smaller in the silica gel and hydrogel bolus than the commercial one. In nose plans, it was shown that the V 95% (relative volume that is covered by at least 95% of the prescription dose) of the silica gel (99.86%) and hydrogel (99.95%) bolus were better than the commercial one (98.39%) and bolus‐free (87.52%). Similarly, the homogeneity index (HI) and conformity index (CI) of the silica gel (0.06; 0.79) and hydrogel (0.058; 0.80) bolus were better than the commercial one (0.094; 0.72) and bolus‐free (0.59; 0.53). The parameters of results (HI, CI, V 95%) were also better in 3D printing boluses than in the commercial bolus or without bolus in ear and parotid plans.ConclusionsSilica gel and hydrogel boluses were not only good for fit and a high level of comfort and repeatability, but also had better parameters in IMRT plans. They could replace the commercial bolus for clinical use.

Patients with metastatic cancer refractory to standard systemic therapies have a poor prognosis and few therapeutic options. Radiotherapy can shape the tumor microenvironment (TME) by inducing immunogenic cell death and promoting tumor recognition by natural killer cells and T lymphocytes. Granulocyte macrophage-colony stimulating factor (GM-CSF) was known to promote dendric cell maturation and function, and might also induce the macrophage polarization with anti-tumor capabilities. A phase II trial (ChiCTR1900026175) was conducted to assess the clinical efficacy and safety of radiotherapy, PD-1 inhibitor and GM-CSF (PRaG regimen). This trial was registered at http://www.chictr.org.cn/index.aspx. A PRaG cycle consisted of 3 fractions of 5 or 8 Gy delivered for one metastatic lesion from day 1, followed by 200 μg subcutaneous injection of GM-CSF once daily for 2 weeks, and intravenous infusion of PD-1 inhibitor once within one week after completion of radiotherapy. The PRaG regimen was repeated every 21 days for at least two cycles. Once the PRaG therapy was completed, the patient continued PD-1 inhibitor monotherapy until confirmed disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). A total of 54 patients were enrolled with a median follow-up time of 16.4 months. The ORR was 16.7%, and the disease control rate was 46.3% in intent-to-treat patients. Median progression-free survival was 4.0 months (95% confidence interval [CI], 3.3 to 4.8), and median overall survival was 10.5 months (95% CI, 8.7 to 12.2). Grade 3 treatment-related adverse events occurred in five patients (10.0%) and grade 4 in one patient (2.0%). Therefore, the PRaG regimen was well tolerated with acceptable toxicity and may represent a promising salvage treatment for patients with chemotherapy-refractory solid tumors. It is likely that PRaG acts via heating upthe TME with radiotherapy and GM-CSF, which was further boosted by PD-1 inhibitors.

Immune checkpoint inhibitors (ICIs) targeting programmed cell death protein-1 (PD-1), and programmed cell death ligand-1 (PD-L1) have been approved for a variety of malignant tumors and are widely used to treat patients with metastatic disease. However, the efficacy of PD-1 inhibitors is limited due to tumor heterogeneity, high tumor burden, and “cold” tumor microenvironment. Radiotherapy can improve the anti-tumor effects of PD-1/PD-L1 inhibitors in various ways. As a new radiotherapy method, stereotactic body radiotherapy (SBRT) or hypofractionated radiotherapy (HFRT) provides higher doses per fraction to the target lesions, thus achieving immune activation effects and overcoming tumor resistance to anti-PD-1/PD-L1 treatment, which significantly improves the local and distant control of tumors. However, for different metastatic situations, radiotherapy plays different roles in the combination therapy. In oligometastatic status, radiotherapy can be used as a local radical treatment aiming to eliminate cancers in cooperation with systemic PD-1 inhibitors. In other circumstances, like bulky metastasis or multiple metastatic tumors, radiotherapy can be used as adjuvant to systemic immunotherapy. This review focuses on the underlying mechanisms and optimization strategies for the combination of radiotherapy and anti-PD-1/PD-L1 therapy in metastatic disease.

Esophageal squamous cell carcinoma (ESCC) is a malignancy with poor prognosis, which is often diagnosed at a late stage. Effective treatment options are limited when patients fail standard systemic therapy. The application of PD-1 inhibitors have led to a paradigm shift in the treatment of ESCC, but its efficacy as monotherapy is limited. Previous studies have shown that the antitumor effects may be reinforced when a PD-1 inhibitor is combined with radiotherapy or GM-CSF. This study aimed to report a case of a patient about advanced unresectable ESCC negative expression of PD-L1, who experienced tumor progression after chemoradiotherapy and targeted therapy.A significant systemic effect was seen after PD-1 inhibitor combined with GM-CSF and stereotactic body radiotherapy (SBRT) for metastatic lesions, however, severe pneumonia occurred after the triple-combination therapy. This study also reviewed several reports about the efficacy and safety of combination therapy.

It is difficult to study the intestinal damage induced by space radiation to astronauts directly, and few prediction models exist. However, we can simulate it in patients with pelvic tumor radiotherapy (RT). Radiation-induced intestinal injury (RIII) is common in cancer patients who receieved pelvic and abdominal RT. We dynamically analyzed gut microbiota and metabolites alterations in 17 cervical and endometrial cancer patients after pelvic RT. In patients who later developed grade 2 RIII, dysbiosis of gut microbiota and metabolites were observed. Univariate analysis showed that Erysipelatoclostridium and ptilosteroid A were related to the occurrence of grade 2 RIII. Notably, a strong positive correlation between gut bacteria Erysipelatoclostridium relative abundance and gut metabolite ptilosteroid A expression was found. Furthermore, combinations of Erysipelatoclostridium and ptilosteroid A could provide good diagnostic markers for grade 2 RIII. In conclusion, gut bacteria Erysipelatoclostridium and its related metabolite ptilosteroid A may collaboratively predict RIII, and could be diagnostic biomarkers for RIII and space radiation injury.

e15173 Background: Patients with refractory metastatic solid tumors have poor prognoses and few therapeutic options. The application of PD-1 inhibitor has led to a paradigm shift in the treatment of advanced cancer, but its efficacy as a monotherapy is limited. Previous evidence has shown that the anti-tumor effects might be reinforced when PD-1 inhibitor combines with radiotherapy or granulocyte macrophage-colony stimulating factor (GM-CSF). An exploratory study was conducted to assess the clinical efficacy and safety of PD-1 inhibitor combined with radiotherapy and GM-CSF (PRaG regimen) for the treatment of refractory patients. Methods: Participants had multimetastatic solid tumors progressing beyond at least first-line chemotherapy.They were treated with hyperfractionated radiotherapy (3 doses of 8Gy or 5 doses of 5Gy) for each metastatic site. On the second day after radiotherapy, PD-1 inhibitor 200 mg once was intravenously administered and GM-CSF 200 µg daily was subcutaneously injected for 2 weeks. This course was repeated every 3 weeks, targeting a second metastatic site. Triple-combination therapy. (PRaG regimen) was given for at least 2 cycles. After combination therapy, maintenance with PD-1 inhibitor was administered until disease progression or unacceptable toxicity. The main outcome measures included safety, toxicity, progression-free survival (PFS) and objective response rate (ORR) after three cycles of treatment. Results: A total of 16 patients were enrolled.The median number of metastatic lesions was 7.5(95%CI, 5.3 to 19.5) and the median sum of the longest diameter of all measurable lesions was 161.7mm (95%CI, 104.1 to 279.3mm).All patients completed two cycles or more of triple-combination therapy. The ORR was 20% and the median PFS was 3.3 months (95%CI, 2.3to 7.2months) at the time of evaluation. Treatment-related adverse events of any grade occurred in 13 (81%) patients, and grade 3 and higher adverse event like pneumonitis occurred in 2 (11.0%) patients. Conclusions: The PRaG regimen is well tolerated with acceptable toxicity. For patients with resistant metastatic solid tumors, low efficacy and high cytotoxicity are commonly observed in conventional therapy. With the new chemo-free PRaG regimen, myelosuppression was not observed and gastrointestinal side effects remained low. So, PRaG regimen is considered as a promising salvage treatment for patients with chemotherapy-refractory metastatic solid tumor. The suggested mechanism might involve radiosensitization of immunotherapy. Clinical trial information: ChiCTR1900020175 .

Females with HPV-negative head and neck squamous cell carcinoma (HNSCC) have worse outcomes compared to men in The Cancer Genome Atlas (TCGA). Our primary aim was to determine if females have an increased frequency of destructive TP53 mutations and divergent mRNA gene expression of immune markers. Our secondary aim was to determine if females have poor progression-free survival (PFS) and overall survival (OS) after controlling for TP53 mutations, immune markers, and clinicopathologic factors. Materials/Methods: We identified 461 patients in TCGA with non-metastatic HNSCC (stages I-IVB) treated with radiotherapy (RT) +/-chemotherapy (CT) (N = 51) or surgery +/-adjuvant RT and CT (N = 410). We performed descriptive statistics on sex, TP53 mutations, and immune markers. We used Mann-Whitney U and Fisher's exact tests to evaluate differences in continuous log2 transformed mRNA counts for immune markers and the presence of destructive TP53 mutations, respectively. We performed Cox regression on OS and PFS according to sex, presence of destructive TP53 mutations, and a gene signature of immune markers (as a weighted sum of genes). We controlled for demographic and clinicopathologic factors. All tests were two-tailed. Final model was derived from primary covariates and confounders with P-value thresholds of < 0.05 and < 0.10, respectively. Data were extracted using open-source software packages and analyzed using statistical software. Results: In females, we observed increased mRNA gene expression of PD1, PDL1, IDO1, CXCL11, TIGIT, and TIM3 (all P-values < 0.05). We did not observe differences in TP53 mutations or L1CAM, SAA1, CTLA4, and LAG3 mRNA gene expression. On adjusted Cox regres-

Significant differences were found between those in SC and FC and those in SC and TC (p Z 0.036 and 0.031, respectively). All the fractures were predicted to occur on the femoral neck in SC but at the border with the fixation site in FC and TC. The ratios of predicted fracture loads of affected side to unaffected side increased after irradiation compared to those before irradiation in 4 cases in SC. The ratios in patients with osteolytic changes of the bone cortex changed from 0.86 to 1.11 in 6 months and from 0.72 to 1.12 in 12 months. The ratios in those with thinning of the bone cortex in the lesser trochanter changed from 0.95 to 1.00 in 6 months, and in those with soft tissue density in the bone marrow, from 0.96 to 1.05 in 3 months. Conclusion: The predicted fracture loads on the affected side recovered to the same level as those on the unaffected side after radiotherapy in 4 of 6 cases in SC. The finite element method could quantitatively evaluate changes in bone strength in radiotherapy for bone metastases based on predicted fracture loads.