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Background: This study investigated whether the dose distribution of lung cancer can be improved by dynamic arc conformal radiotherapy (dynamic CRT) compared with static multiple-beam radiotherapy (static CRT). Materials and methods: A dummy study of static CRT and dynamic CRT was performed, designed to meet the predetermined dose constraints. A dose of 60 Gy in 30 fractions was administered using two dose prescription methods: dose prescribed to the isocenter (IC prescription), and dose prescribed to > 50% of the planning target volume (D50 prescription). Dose-volume parameters were compared between the plans. Results: Among 20 patients with locally advanced lung cancer, dose conformity was significantly better with dynamic CRT than static CRT (median conformity index: 1.3 vs. 2.2; p < 0.01). As for the lung dose, compared with static CRT, dynamic CRT did not increase the percentage lung volume receiving ≥ 20 Gy (18.9% vs. 19.3%, p = 0.09). The maximum spinal cord dose was significantly reduced by dynamic CRT (static vs. dynamic CRT: 44.1 vs. 25.2 Gy, p < 0.001). With the change from IC to D50 prescription, the 95% isodose volume increased by 18.3 cc in static CRT and by 4.1 cc in dynamic CRT, while doses to the lung and spinal cord remained within the acceptable ranges. Conclusion: The dynamic CRT technique showed better target coverage and lower doses to the spinal cord in exchange for increased low-dose lung area, compared with static CRT. Dynamic CRT with D50 prescription instead of prescription to the isocenter has excellent dose distribution profiles without compromising doses to organs at risk for lung cancer at favorable locations.
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Background Malignant lumbosacral plexopathy is caused by a direct extension of an intrapelvic malignancy to involve the plexus nerves. In this report, we describe the effect of radiotherapy on patients with malignant lumbosacral plexopathy. Patients and methods We performed a retrospective review of the medical records of patients who underwent radiation therapy for pain caused by malignant lumbosacral plexopathy between 2017 and 2020 at our institution. The pain was measured using a numeric rating scale (0-10) at initiation and completion of radiotherapy or at the time when the maximum response was observed. Results A total of 12 tumor sites in 11 patients were included. Eight of the tumors invaded the iliopsoas muscle, and the remaining four invaded or abutted the piriformis muscle. The mean duration of follow-up was 215 days (31-675 days). All patients achieved pain relief at the end of radiotherapy, with complete resolution of pain in nine patients. The maximum effect was seen at a mean of three weeks (1-12 weeks) after the initiation of radiotherapy. Toxicities related to radiotherapy included grade 1 diarrhea in four patients and grade 1 frequent urination in one patient. Two patients experienced a relapse of pain at one and two months, respectively, after achieving their maximal response. Conclusion Radiotherapy provides significant pain relief for patients with the malignant lumbosacral syndrome. The recognition and diagnosis of this syndrome, and the use of radiation therapy as a therapeutic option, are important. Patients should be offered all possible therapies, regardless of curative or palliative intent.
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BACKGROUND: In stereotactic radiosurgery (SRS), fixation devices are secured to the patient's head with pins. However, there have been no standards for the use of such pins, which must be inserted with appropriate torque based on the surgeon's clinical judgment. Therefore, the pins may sometimes be tightened excessively and penetrate too deeply into the patient's skull. PURPOSE: To improve safety in SRS, a torque wrench was used for pin insertion. The usefulness of the torque wrench was then evaluated by examining the relationships between the pins and skull bone and identifying differences according to the wrench used and the patient's bone thickness. METHODS: CT images of patients who had previously undergone SRS were used to assess the relationships between the pins and skull bone. Differences according to the wrench used and pin insertion site were investigated. RESULTS: Compared with a standard wrench, use of the torque wrench decreased the insertion depth of pins in the skull bone. In terms of site, pins in the forehead were inserted more deeply. No differences related to the frontal sinus were observed. CONCLUSION: The use of a torque wrench improved safety during pin insertion for SRS procedures.
