Systemic Abscopal Effect of Low-dose Radiotherapy (2 Gy ×2) against Palatine Tonsil Follicular Lymphoma

Highly Radiosensitive Diffuse Large B-cell Lymphoma of the Skull Treated With Low-Dose CyberKnife Radiotherapy: A Case Report

Diffuse large B-cell lymphoma (DLBCL) of the skull is rare, and there are no reports of treatment using CyberKnife (CK). Here, we report the case of a patient with skull DLBCL treated with low-dose CK radiotherapy (CKR), resulting in effective local control. The patient was a 75-year-old man who was initially diagnosed with multiple skull metastases (frontal, occipital, right orbital bones) from renal pelvic cancer. We initially created a CKR treatment plan for the frontal bone lesion with a marginal dose of 35 Gy and a maximum of 64.8 Gy in five fractions every other day. Because the frontal bone lesion shrank rapidly from the start of the treatment, we completed CKR with a marginal dose of 21 Gy and a maximum of 38.9 Gy in three fractions over five days. At six weeks after CKR, the MRI showed complete resolution of not only the frontal bone lesion but also the occipital and orbital bone lesions that we did not directly target for irradiation. The maximum doses irradiated to the occipital and orbital bone lesions were 0.31 Gy and 0.34 Gy. Because of the marked shrinkage of the skull lesions, we suspected that the patient had a radiosensitive neoplastic disease. FDG-PET/CT revealed multiple lymph nodes and bone metastases. The patient underwent a scrotal biopsy, and the histologic diagnosis was DLBCL. The patient subsequently received chemotherapy for DLBCL. Ten months after CKR and six months after the start of chemotherapy for DLBCL, the patient died due to gastrointestinal bleeding. The skull lesions were well-controlled locally without adverse events due to CKR until the end of the life. Our present case suggests the importance of diagnosis and the effectiveness of low-dose CKR in the skull DLBCL.

Radiotherapy, photodynamic therapy, and cryoablation-induced abscopal effect: Challenges and future prospects

Local therapy modalities such as radiation therapy, photodynamic therapy, photothermal therapy, and cryoablation have been used to treat localized tumors for decades. The discovery of the abscopal effect causes a paradigm shift where local therapy also causes systemic effects and leads to the remission of nonirradiated tumors. The abscopal effect of radiation therapy, alone or in combination with other treatments, has been extensively studied over the last six decades. However, the results are unsatisfactory in producing robust, reproducible, and long-lasting systemic effects. Although immunotherapy and radiation therapy are promising in producing the abscopal effect, the abscopal effect's mechanism is still unclear, owing to various factors such as irradiation type and dose and cancer type. This article reviews the research progress, clinical and preclinical evidence of the abscopal effect by various local therapies alone and in combination with chemotherapy and immunotherapy, case reports, and the current challenges in producing the abscopal effect by various local therapies, focusing on radiotherapy, photodynamic therapy, cryoablation, and the prospects for obtaining a robust, reproducible, and long-lasting abscopal effect.