Sinisa Stanic

Failure Mode and Effect Analysis for Delivery of Lung Stereotactic Body Radiation Therapy

PURPOSE To improve the quality and safety of our practice of stereotactic body radiation therapy (SBRT), we analyzed the process following the failure mode and effects analysis (FMEA) method. METHODS The FMEA was performed by a multidisciplinary team. For each step in the SBRT delivery process, a potential failure occurrence was derived and three factors were assessed: the probability of each occurrence, the severity if the event occurs, and the probability of detection by the treatment team. A rank of 1 to 10 was assigned to each factor, and then the multiplied ranks yielded the relative risks (risk priority numbers). The failure modes with the highest risk priority numbers were then considered to implement process improvement measures. RESULTS A total of 28 occurrences were derived, of which nine events scored with significantly high risk priority numbers. The risk priority numbers of the highest ranked events ranged from 20 to 80. These included transcription errors of the stereotactic coordinates and machine failures. CONCLUSION Several areas of our SBRT delivery were reconsidered in terms of process improvement, and safety measures, including treatment checklists and a surgical time-out, were added for our practice of gantry-based image-guided SBRT. This study serves as a guide for other users of SBRT to perform FMEA of their own practice.

Gamma Knife Radiosurgery for Recurrent Glossopharyngeal Neuralgia after Microvascular Decompression

Background: We report the first application of Gamma Knife radiosurgery (GKR) for recurrent glossopharyngeal neuralgia (GN) after microvascular decompression (MVD). The patient is a 51-year-old male with left-sided GN. He underwent MVD and did well for almost 4 years. Later on, the patient started to experience recurrent intolerable throat pain, frequently 10/10 in intensity. Based on the application of radiosurgery for trigeminal neuralgia, GKR was offered to the patient. Methods: After careful identification of the nerve with the assistance of a neuroradiologist, we targeted the nerve root complex, which is the cisternal portion of the nerve, using the Coherent Oscillatory State Acquisition for the Manipulation of Image Contrast (COSMIC) pulse sequence with contiguous 1-mm slices obtained by an 1.5 Tesla MRI. The radiosurgery was planned utilizing the Leksell Gamma Plan version 8.1. A single shot with a 4-mm collimator was used to deliver 80 Gy to the 100% isodose line. Results: Four weeks after the treatment, the patient began to notice significant pain relief. At the 12-month follow-up, the patient’s pain, which was intolerable prior to radiosurgery, was mild and occasional. Conclusion: GKR, which is now widely used for refractory trigeminal neuralgia, can be considered for refractory or recurrent GN. With a multidisciplinary approach and advanced neuroimaging, GKR is feasible for GN after MVD, despite the shortness of the intracranial cisternal nerve portion. Further studies are necessary to establish the role of GKR for refractory GN after MVD; however, given its rarity and the lack of experience with GKR for this condition, retrospective studies with dozens of patients are almost impossible at this time.

Tolerance of the Small Bowel to Therapeutic Irradiation: A Focus on Late Toxicity in Patients Receiving Para-aortic Nodal Irradiation for Gynecologic Malignancies

Objective The recently published Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) recommends dose constraints for acute small-bowel toxicity but does not fully address dose constraints for late small-bowel toxicity and the maximum dose tolerance of the small bowel. Radiation oncologists in practice frequently face a challenge when deciding what maximum point dose to accept in a patient’s treatment plan. Given this lack of guidance for maximum radiation dose tolerance on the small bowel, we performed a literature search on the topic. Methods We searched PubMed for English language publications up to December 2012 on pelvic and para-aortic lymph node (PALN) irradiation for gynecologic malignancies. The search was performed using the following key words: late small-bowel toxicity, cervical cancer, endometrial cancer, ovarian cancer, gynecologic malignancies, pelvic irradiation, PALN irradiation, extended-field radiation therapy. Relevant references were selected, and full articles were obtained for review. The predetermined criteria for deciding which studies to include were used. Results With photon irradiation, the incidence of grade 3 or greater late small-bowel toxicity, including small-bowel obstruction, is 9% ± 7% after a median follow-up of 5 years and with mean pelvic and para-aortic/whole abdominal prescription doses of 50 ± 5 Gy and 40 ± 10 Gy, respectively. Our estimate for the small-bowel T10/5 would be the maximum point dose of 55 Gy. Conclusions If possible, it is prudent to try to keep the maximum point dose to the small bowel at 55 Gy or less. Given the lack of substantial data to make firm guidelines, further studies are needed to clarify the dose-volume relationship for late toxicity. Dose escalation to PALN should continue to be used with caution.

Evaluation of hippocampus dose for patients undergoing intensity-modulated radiotherapy for nasopharyngeal carcinoma.

OBJECTIVE To evaluate the dose received by the hippocampus among patients undergoing intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer. METHODS 10 patients with biopsy-proven, locally advanced nasopharyngeal cancer constituted the study population. The total prescribed dose to the planning target volume (PTV) was 70 Gy (D95%) delivered in 2.12-Gy daily fractions using IMRT. Using established anatomical guidelines, MRI co-registration and the assistance of a board-certified neuroradiologist, the right and left hippocampi were delineated on axial imaging from the CT scan obtained at simulation for each patient beginning at the most anterior portion of the lateral ventricle. IMRT treatment plans were generated without dose-volume constraints to the hippocampus. A range of dose-volume statistics was calculated. RESULTS The mean hippocampus volume was 6.01 ± 2.61 cm(3). The mean V20 was 72.2%; V40 was 22.0%; V50 was 10.2%; and V60 was 5.5%. The average mean, minimum and maximum hippocampus doses were 30.27 Gy (range, 19.08-47.99 Gy); 17.54 Gy (range, 11.66-33.17 Gy); and 54.95 Gy (range, 35.59-75.57 Gy), respectively. The hippocampus received a maximum dose exceeding 70 Gy in 30% of cases. CONCLUSION Our dosimetric analysis suggests that, for patients undergoing IMRT for nasopharyngeal cancer, the hippocampus routinely receives significantly high doses. ADVANCES IN KNOWLEDGE The hippocampus receives a fair amount of incidental radiation during treatment for nasopharyngeal cancer. Given the importance of this structure with respect to memory and neurocognitive function, consideration should be given to identifying the hippocampus as a critical organ at risk in the IMRT optimization process.

Rib fracture following stereotactic body radiotherapy: a potential pitfall.

Although the incidence of rib fractures after conventional radiotherapy is generally low (<2%), rib fractures are a relatively common complication of stereotactic body radiotherapy. For malignancy adjacent to the chest wall, the incidence of rib fractures after stereotactic body radiotherapy is as high as 10%. Unrecognized bone fractures can mimic bone metastases on bone scintigraphy, can lead to extensive workup, and can even lead to consideration of unnecessary systemic chemotherapy, as treatment decisions can be based on imaging findings alone. Nuclear medicine physicians and diagnostic radiologists should always consider rib fracture in the differential diagnosis.

Addition of a third field significantly increases dose to the brachial plexus for patients undergoing tangential whole-breast therapy after lumpectomy.

Our goal was to evaluate brachial plexus (BP) dose with and without the use of supraclavicular (SCL) irradiation in patients undergoing breast-conserving therapy with whole-breast radiation therapy (RT) after lumpectomy. Using the standardized Radiation Therapy Oncology Group (RTOG)-endorsed guidelines delineation, we contoured the BP for 10 postlumpectomy breast cancer patients. The radiation dose to the whole breast was 50.4 Gy using tangential fields in 1.8-Gy fractions, followed by a conedown to the operative bed using electrons (10 Gy). The prescription dose to the SCL field was 50.4 Gy, delivered to 3-cm depth. The mean BP volume was 14.5 ± 1.5 cm(3). With tangential fields alone, the median mean dose to the BP was 0.57 Gy, the median maximum dose was 1.93 Gy, and the irradiated volume of the BP receiving 40, 45, and 50 Gy was 0%. When the third (SCL field) was added, the dose to the BP was significantly increased (P = .01): the median mean dose to the BP was 40.60 Gy, and the median maximum dose was 52.22 Gy. With 3-field RT, the median irradiated volume of the BP receiving 40, 45, and 50 Gy was 83.5%, 68.5%, and 24.6%, respectively. The addition of the SCL field significantly increases dose to the BP. The possibility of increasing the risk of BP morbidity should be considered in the context of clinical decision making.

Relationship Between Pelvic Organ-at-Risk Dose and Clinical Target Volume in Postprostatectomy Patients Receiving Intensity-Modulated Radiotherapy

PURPOSE To investigate dose-volume consequences of inclusion of the seminal vesicle (SV) bed in the clinical target volume (CTV) for the rectum and bladder using biological response indices in postprostatectomy patients receiving intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS We studied 10 consecutive patients who underwent prostatectomy for prostate cancer and subsequently received adjuvant or salvage RT to the prostate fossa. The CTV to planning target volume (PTV) expansion was 7 mm, except posterior expansion, which was 5 mm. Two IMRT plans were generated for each patient, including either the prostate fossa alone or the prostate fossa with the SV bed, but identical in all other aspects. Prescription dose was 68.4 Gy in 1.8-Gy fractions prescribed to ≥95% PTV. RESULTS With inclusion of the SV bed in the treatment volume, PTV increased and correlated with PTV-bladder and PTV-rectum volume overlap (Spearman ρ 0.91 and 0.86, respectively; p < 0.05). As a result, the dose delivered to the bladder and rectum was higher (p < 0.05): mean bladder dose increased from 11.3 ± 3.5 Gy to 21.2 ± 6.6 Gy, whereas mean rectal dose increased from 25.8 ± 5.5 Gy to 32.3 ± 5.5 Gy. Bladder and rectal equivalent uniform dose correlated with mean bladder and rectal dose. Inclusion of the SV bed in the treatment volume increased rectal normal tissue complication probability from 2.4% to 4.8% (p < 0.01). CONCLUSIONS Inclusion of the SV bed in the CTV in postprostatectomy patients receiving IMRT increases bladder and rectal dose, as well as rectal normal tissue complication probability. The magnitude of PTV-bladder and PTV-rectal volume overlap and subsequent bladder and rectum dose increase will be higher if larger PTV expansion margins are used.

Conventional Radiation Therapy in Early Stage Non-small-cell Lung Cancer

Surgery is standard treatment approach in patients with early stage (I-II) nonsmall cell lung cancer. However, there are patients who do not undergo surgery due to existing comorbidities, advanced age or refusal. They have traditionally been treated with radiation therapy which provided median survival times of [ 30 months and 5-year survival rates of [ 30% in stage I disease.