[Ectopic Injection of Hydrogel Spacer in IMRT for Prostate Cancer-A Case Study].

A hydrogel spacer injection between the prostate and rectum is reported to reduce the risk of rectal toxicity in radiotherapy for prostate cancer. We present a case of an ectopic injection of hydrogel spacer. The patient was a 77-year-old male with intermediate-risk prostate cancer. It was planned that he would receive intensity modulated radiation therapy(IMRT), and a hydrogel spacer was inserted. Three days after insertion, the patient had a fever of 38.6℃ and presented frequent urination and perineal pain. Swelling and heat sensation were observed in the perineum. CRP was 12.00 mg/dL and the white blood cell count was as high as 9,300/µL. T2-weighted images showed a 5.3×1.9 cm high-intensity area around the lower urethra. Ectopic injection of hydrogel spacer and concomitant infection were diagnosed. Upon administering antibiotic treatment, his symptoms and inflammation improved immediately. Four months after hydrogel spacer insertion, T2-weighted images showed a high-intensity area in the lower urethra and around the ischial bone, which was attributed to the remaining hydrogel spacer. The hydrogel spacer and his symptoms completely disappeared at 9 months after hydrogel spacer insertion.

Symptomatic radiation-induced rib fractures after stereotactic body radiotherapy for early-stage non-small cell lung cancer.

Background and purpose: The present study investigated the relationships between the risk of radiation-induced rib fractures (RIRF) and clinical and dosimetric factors in stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). We also examined dosimetric parameters associated with symptomatic or asymptomatic RIRF and the dosimetric threshold for symptomatic RIRF. Materials and methods: We reviewed 244 cases of early-stage NSCLC treated with SBRT. Gray's test and the Fine-Gray model were performed to examine the relationships between clinical and dosimetric factors and grade ≥ 2 (i.e., symptomatic) RIRF. The effects of each dose parameter on grade ≥ 1 and ≥ 2 RIRF were assessed with the Fine-Gray model. The t-test was used to compare each dose parameter between the grade 1 and grade ≥ 2 groups. Optimal thresholds were tested using receiver operating characteristic (ROC) curves. Results: With a median follow-up period of 48 months, the 4-year cumulative incidence of grade ≥ 1 and grade ≥ 2 RIRF were 26.4 % and 8.0 %, respectively. Regarding clinical factors, only age was associated with the development of grade ≥ 2 RIRF (p = 0.024). Among dosimetric parameters, only V40Gy significantly differed between the grade 1 and grade ≥ 2 groups (p = 0.015). The ROC curve analysis of grade ≥ 2 RIRF showed that the optimal diagnostic thresholds for D3cc, D4cc, D5cc, and V40Gy were 45.86 Gy (area under the curve [AUC], 0.706), 39.02 Gy (AUC, 0.705), 41.62 Gy (AUC, 0.702), and 3.83 cc (AUC, 0.730), respectively. These results showed that V40Gy ≤ 3.83 cc was the best indicator of grade ≥ 2 RIRF. The 4-year incidence of grade ≥ 2 RIRF in the V40Gy ≤ 3.83 cc vs. > 3.83 cc groups was 1.8 % vs. 14.2 % (p = 0.001). Conclusion: The present results recommend V40Gy ≤ 3.83 cc as the threshold for grade ≥ 2 RIRF in SBRT.