Dosimetric Evaluation of a Set of Specifically Designed Grids for Treating Subcutaneous Superficial Tumor with 6 and 18 MeV Electron Beam External Radiotherapy

Background: Conventional electron beam radiotherapy used for treating superficial cancer tumors suffers from the disadvantage of low skin sparing effect. Furthermore, increasing electron energy for treating deeper-seated tumors leads to significant increase of skin dose. To overcome this, various grids are recommended for electron beam radiotherapy of subcutaneous tumors. However, appropriate grids are required to be designed for decreasing skin dose while delivering uniform high doses to deep-seated superficial tumors. Our goal was to design, examine and propose appropriate grid(s) for optimum electron beam radiotherapy of subcutaneous tumors with the best skin sparing with 6 and 18 MeV energies.Materials and Methods: Relevant dosimetric characteristics were determined and analyzed for five grids manufactured from dry lead having various cavity diameters (1.5, 2.0, 2.5, 3.0, 3.5 cm) and shielded areas (0.3, 0.4, 0.5, 0.6, 0.7 cm) among the cavities but the same fraction of cavity/open (68%) and shielded/closed (38%) areas under the grid plates. Isodose distributions and dose profiles resulted from the grids were investigated using EDR2 films and MATLAB software. Results: The grids with 2 and 2.5 cm diameter cavities and 0.4 and 0.5 cm shielded areas were the most appropriate grids for 6 and 18 MeV radiotherapy, respectively. With these grids, the 100% PDDs (percentage depth doses) located at 1.25 and 2.5 cm for an open filed (without the grids) were moved down to 1.87 and 5.4 cm for 6 and 18 MeV energies, respectively. Furthermore, the proposed grids provided the least peak to valley dose variations hence the most uniform doses delivered at their relevant depths of treatment. Conclusions: To decrease the skin dose in 6 and 18 MeV electron beam radiotherapy of superficial subcutaneous tumors, various home-made grids were designed and investigated. The most appropriate grids (having 2 and 2.5 cm cavity diameters for 6 and 18 MeV, respectively) provided the optimum dose delivery for superficial subcutaneous tumors locating around 1.5 and 5 cm depth for 6 and 18 MeV energies. Our comprehensive study provides reliable results that could be considered and developed more for a wider range of MeV electron grid therapies in routine clinical practices.

Resection of primary central nervous system lymphoma: impact of patient selection on overall survival

OBJECTIVEPrimary central nervous system lymphoma (PCNSL) is a rare CNS tumor with a poor prognosis. It is usually diagnosed by needle biopsy and treated mainly with high-dose chemotherapy. Resection is currently not considered a standard treatment option. A possible prolonged survival after resection of PCNSL lesions in selected patients has been suggested, but selection criteria for surgery, especially for solitary lesions, have never been established.METHODSThe authors retrospectively searched their patient database for records of adult patients (≥ 18 years) who were diagnosed and treated for a solitary PCNSL between 2005 and 2019. Patients were divided into groups according to whether they underwent resection or needle biopsy. Statistical analyses were performed in an attempt to identify variables affecting outcome and possible survival advantage and to characterize subgroups of patients who would benefit from resection of their tumor compared with undergoing biopsy only.RESULTSA total of 113 patients with a solitary lesion of PCNSL were identified; 36 patients underwent resection, and 77 had a diagnostic stereotactic biopsy only. The statically significant preoperative risk factors included age ≥ 70 years (adjusted HR 9.61, 95% CI 2.42–38.11; p = 0.001), deep-seated lesions (adjusted HR 3.33, 95% CI 1.13–9.84; p = 0.030), and occipital location (adjusted HR 4.26, 95% CI 1.08–16.78; p = 0.039). Having a postoperative Karnofsky Performance Scale (KPS) score < 80 (adjusted HR 3.21, 95% CI 1.05–9.77; p = 0.040) and surgical site infection (adjusted HR 4.27, 95% CI 1.18–15.47; p = 0.027) were significant postoperative risk factors after the adjustment and selection by means of other possible risk factors. In a subgroup analysis, patients younger than 70 years who underwent resection had a nonsignificant trend toward longer survival than those who underwent needle biopsy (median survival 35.0 months vs 15.2 months, p = 0.149). However, patients with a superficial tumor who underwent resection had significantly longer survival times than those who underwent needle biopsy (median survival 34.3 months vs 8.9 months, p = 0.014). Patients younger than 70 years who had a superficial tumor and underwent resection had significantly prolonged survival, with a median survival of 35.0 months compared with 8.9 months in patients from the same group who underwent needle biopsy (p = 0.007).CONCLUSIONSSpecific subgroups of patients with a solitary PCNSL lesion might gain a survival benefit from resection compared with undergoing only a diagnostic biopsy.

SURG-30. SURGICAL RESECTION OF PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA: IMPACT OF PATIENT SELECTION ON OVERALL SURVIVAL

OBJECTIVE A possible prolonged survival after surgical resection for primary central nervous system lymphoma (PCNSL) lesions in selected patients has been suggested, but selection criteria for surgery, especially for solitary lesions, have never been established. METHODS We retrospectively searched our patient database for records of adult patients (≥18 years) who were diagnosed and treated for a solitary lesion of PCNSL between 2005 and 2019. Patients were divided into groups according to whether they underwent surgical resection or needle biopsy. Statistical analyses were performed in an attempt to identify variables affecting outcome and possible survival advantage and to characterize subgroups of patients who would benefit from resection of their tumor compared to undergoing biopsy only. RESULTS 113 patients with a solitary lesion of PCNSL were identified, 36 underwent surgical resection and 77 a diagnostic stereotaxic biopsy only. Pre-operative risk factors were found to include age &gt; 70 years ([HR] 9.61, 95% [CI] 2.42-38.11, p=0.001) and deep seated lesions (adjusted HR 3.33, 95% CI 1.13-9.84, p=0.030). Having a postoperative Karnofsky Performance Scale (KPS) under 80 (adjusted HR 3.21, 95% CI 1.05-9.77, p=0.040) or surgical-site infections (adjusted HR 4.27, 95% CI 1.18-15.47, p=0.027) were significant postoperative risk factors. In a subgroup analysis, patients with a superficial tumor who underwent surgical resection had significantly longer survival times compared with those who underwent needle biopsy (median survival 34.3 months versus 8.9 months, p=0.014). Patients under 70 years who had a superficial tumor and underwent surgical resection had significantly prolonged survival, with a median survival of 35.0 months versus 8.9 months in patients from the same group who underwent needle biopsy (p=0.007). CONCLUSION Specific subgroups of patients with a solitary PCNSL lesion might gain a survival benefit from surgical resection compared to undergoing only a diagnostic biopsy.

A two-dimensional MXene potentiates a therapeutic microneedle patch for photonic implantable medicine in the second NIR biowindow

A soluble microneedle system loaded with two-dimensional MXene has been successfully fabricated, which can achieve in-situ photothermal therapy towards superficial tumor models with minimal invasion and high efficiency of drug delivery.