Avascular Necrosis of the Femoral Head After Palliative Radiotherapy in Metastatic Prostate Cancer: Absence of a Dose Threshold?

Avascular necrosis (AVN) is the final common pathway resulting from insufficient blood supply to bone, commonly the femoral head. There are many postulated etiologies of non-traumatic AVN, including corticosteroids, bisphosphonates, and radiotherapy (RT). However, it is unclear whether there is a dose threshold for the development of RT-induced AVN. In this case report, we describe a patient with prostate cancer metastatic to bone diagnosed with AVN after receiving single-fraction palliative RT to the left femoral head. Potential contributing factors are discussed, along with a review of other reported cases. At present, the RT dose threshold below which there is no risk for AVN is unknown, and therefore detrimental impact from the RT cannot be excluded. Given the possibility that RT-induced AVN is a stochastic effect, it is important to be aware of the possibility of this diagnosis in any patient with a painful hip who has received RT to the femoral head.

An evaluation of the Clarity 3D ultrasound system for prostate localization.

The purpose of this study is to evaluate the accuracy and precision of the Clarity 3D ultrasound system to track prostate gland positional variations due to setup error and organ motion. Seventeen patients (n = 17) undergoing radical external beam radiation therapy for localized prostate cancer were studied. Subsequent to initial reference ultrasound and planning CT scans, each patient underwent seven repeat weekly tracking CT and ultrasound (US) scans during the course of treatment. Variations in the location of the prostate between reference and tracking scans were measured. Differences reported by CT and ultrasound scans are compared. Ultrasound tracking was initially performed clinically by a group of trained general users. Retrospective prostate localization was then performed by a trained dedicated user upon the original raw data set and also a reduced data set derived from the original by an expert user from Resonant Medical. Correlation accuracy between ultrasound and CT shifts acquired and delineated by a pool of trained general users was deemed unacceptable for radiotherapy purposes. A mean discrepancy between CT and US localizations of greater than 10 mm, with a 5 mm or greater discrepancy rate of nearly 90%, was observed. Retrospective analysis by a dedicated user of both the original and Resonant Medical reduced data sets yielded mean CT-Us discrepancies of 8.7 mm and 7.4 mm, respectively. Unfortunately, the 5 mm or greater CT-US discord rate for these retrospective analyses failed to drop below 80%. The greatest disparity between CT and ultrasound was consistently observed in the superior-inferior direction, while greatest agreement was achieved in the lateral dimension. Despite an expert reanalysis of the original data, the Clarity ultrasound system failed to deliver an acceptable level of geometric accuracy required for modern radiotherapy purposes.

Skin-sparing radiation using intensity-modulated radiotherapy after conservative surgery in early-stage breast cancer: a planning study.

PURPOSE: To evaluate the feasibility of skin-sparing by configuring it as an organ-at-risk (OAR) while delivering whole-breast intensity-modulated radiotherapy (IMRT) in early breast cancer. METHODS AND MATERIALS: Archival computed tomography scan images of 14 left-sided early-breast tumor patients who had undergone lumpectomy were selected for this study. Skin was contoured as a 4- to 5-mm strip extending from the patient outline to anterior margin of the breast planning target volume (PTV). Two IMRT plans were generated by the helical tomotherapy approach to deliver 50 Gy in 25 fractions to the breast alone: one with skin dose constraints (skin-sparing plan) and the other without (non-skin-sparing plan). Comparison of the plans was done using a two-sided paired Student t test. RESULTS: The mean skin dose and volume of skin receiving 50 Gy were significantly less with the skin-sparing plan compared with non-skin-sparing plan (42.3 Gy vs. 47.7 Gy and 12.2% vs. 57.8% respectively; p < 0.001). The reduction in skin dose was confirmed by TLD measurements in anthropomorphic phantom using the same plans. Dose-volume analyses for other OARs were similar in both plans. CONCLUSIONS: By configuring the skin as an OAR, it is possible to achieve skin dose reduction while delivering whole-breast IMRT without compromising dose profiles to PTV and OARs.