A Dosimetrical Analysis of the Magnitude of Isocenter Shifts Using CT-on-Rails Guided Online Adaptive Planning for Left Breast Cancer Patients Treated by Intensity Modulated Radiation Therapy

Introduction:

This study was conducted to check the accuracy and validity of an automated adaptive planning (AAP) method which combines automated re-contouring and re-planning to check for inter-fractional anatomical changes in breast cancer patients receiving intensity modulated radiation therapy (IMRT) based on a weekly computed tomography (CT)-on rails images dosimetrically viewing the magnitude of difference in isocenter shifts and the degree of dose deviations regarding target coverage and dose received by organs at risk.

Methods and Materials:

Twenty left sided conservative breast cancer patients were selected for IMRT treatment. Automatic generation of the contours on each repeat CT image was performed by mapping the contours from the planning CT image using deformable image registration. 3D- CRT and IMRT plans were automatically recalculated for each patient. The magnitude of isocenter shifts in postero-anterior (PA), cranio-caudal (CC) and right-left (RL) directions was calculated and the degree of dose deviations regarding target coverage and dose received by organs at risk.

Results:

In the PA,CC and RL directions, 9.2%, 11.4% and 6.4% of the 100 CT scans didn’t require any position adjustments. The mean isocenter shifts and standard deviation (SD) were 0.5 & 0.6 +/- 1.1mm, 0.3 &0.4 +/- 0.5mm and 0.2 & 0.4+/- 0.6mm for the IMRT and 3D-CRT plans in the PA,CC and RL directions, respectively. 74.1%, 65.1%, and 55.8% required a shift of 1 - 3 mm; 10.5%, 23.9%, and 33.2% required a shift of 3 - 5mm; and 1.5%, 3.3%, and 5.4% required a shift of more than 5 mm, respectively. With respect to target coverage, the D90[Gy] for the breast CTV was 46.2 Gy and 45.6 for the IMRT and 3D-CRT plans. The mean doses to the heart and left lung were reduced by 5.5 %, 3.7 Gy and 4.1%, 2.6 Gy using the AAP method.

Conclusions:

The fully automated AAP method using CT on rails for online re-planning was effective in reducing the magnitude of isocenter shifts and compensating for target volume coverage underdosing and higher doses perceived by risk organs caused by anatomical inter-fractional changes in breast cancer patients.

Osteonecrosis of the jaw (ONJ): diagnosis and management in 2015

Osteonecrosis of the jaw (ONJ) has been associated with the use of aminobisphosphonates and denosumab. The vast majority (>90%) of cases occur in the oncology patient population receiving high doses of intravenous bisphosphonates or subcutaneous denosumab. The incidence of ONJ in the osteoporosis patient population is very low and is estimated at 1-90 per 100,000 patient-years of exposure. In the oncology patient population the incidence appears to be related to dose and duration of exposure, and prevalence has been estimated to be as high as 18.6%. A number of risk factors in addition to antiresorptive therapy have been identified. These include the presence of periodontal disease, oral surgical procedures with extractions or implants, radiation therapy, chemotherapy, diabetes, glucocorticoid use, and smoking. Antiangiogenic agents appear to contribute to the risk of ONJ, however, data at this time are limited and further evidence is required prior to confirming a causal relationship. ONJ may be prevented with optimization of oral hygiene, the use of oral antimicrobial mouth rinses, as well as systemic antibiotic therapy. Individuals not responding to conservative management or in the advanced stages of ONJ may be considered for surgery, as data over the past several years have demonstrated surgical success in this patient population. Case reports have indicated that teriparatide may enhance healing. A number of experimental therapies are being evaluated and include the use of bone marrow stem cell intralesional transplantation, local application of platelet-derived growth factor, hyperbaric oxygen, tissue grafting, and low-level laser therapy. This paper summarizes the current research as well as the international consensus on the diagnosis and management of ONJ.