Bahar Dirican

External Radiotherapy in Macular Degeneration: Our Technique, Dosimetric Calculation, and Preliminary Results

PURPOSE This study was performed to determine the toxicity and efficacy of external-beam radiotherapy in patients with age-related subfoveal neovascularization. METHODS AND MATERIALS Between January 1996 and September 1996, 25 patients with a mean age of 70.5 (60-84) years were enrolled. All patients underwent fluorescein angiographic evaluation and documentation of their neovascular disease prior to irradiation. A total of 25 patients were treated with a total dose of 12 Gy in 6 fractions over 8 days. We used a lens-sparing technique and patients were treated with a single lateral 6-MV photon beam. To assess the risk of radiation carcinogenesis after treatment of age-related subfoveal neovascularization, we estimated the effective dose for a standard patient on the basis of tissue-weighting factors as defined by the International Commission on Radiological Protection (ICRP). The calculations were made with TLD on a male randophantom. The lens dose was found to be 0.217 Gy per fraction. RESULTS No significant acute morbidity was noted. Visual acuity was maintained or improved in 76% and 80% of treated patients at their 1- and 3-month follow-up examinations, respectively. On angiographic imaging, there was stabilization of subfoveal neovascular membranes in 23 patients (92%) at 3 months after irradiation. CONCLUSION Our observations on these 25 patients in this study indicate that many patients will have improved or stable vision after radiotherapy treatment with low-dose irradiation.

Spinal Implants and Radiation Therapy: The Effect of Various Configurations of Titanium Implant Systems in a Single-Level Vertebral Metastasis Model

BACKGROUND The combination of surgery and radiation therapy is a common clinical practice in the treatment of spinal tumors. Although it is known that metallic implants disturb radiation therapy beams, it is not known what kind of dose distributions appear with spinal irradiation in the presence of a spinal implant. The aim of the present study was to investigate the effect of various spinal implant constructs on the dose of radiation delivered to the spinal canal in a single-level metastasis model. METHODS We performed four spinal implant reconstructions on standard sawbones spine models: posterior instrumentation without anterior column reconstruction, posterior instrumentation with anterior column reconstruction with use of a titanium cage, anterior instrumentation with anterior column reconstruction with use of a titanium cage, and anterior instrumentation with anterior column reconstruction with use of chest tubes filled with bone cement. Irradiation with two different radiation therapy units (a cobalt-60 teletherapy unit and a linear accelerator) was performed twice for each model in a posterior-to-anterior direction, and thermoluminescent dosimeters were used to measure the dose changes in the anterior, middle, and posterior portions of the spinal canal. RESULTS Compared with the sawbones-only model, the posterior instrumentation reconstructions resulted in a 5% to 7% decrease in the radiation dose delivered to the spinal canal with both radiation therapy units, whereas the anterior instrumentation reconstructions resulted in a 1% decrease in the dose delivered with the linear accelerator unit and a < or = 2% increase in the dose delivered with the cobalt-60 teletherapy unit. When thermoluminescent dosimeters in the middle of the spinal canal were evaluated individually, anterior instrumentation with anterior column reconstruction with use of bone cement-filled chest tubes resulted in a 5.5% increase in the radiation dose delivered with the cobalt-60 teletherapy unit, whereas all of the other instrumentation models resulted in a <1% disturbance in the radiation dose delivered with both radiation therapy units. CONCLUSIONS The posterior instrumentation systems did not result in the delivery of an increased dose of radiation to the spinal cord, suggesting that current radiation therapy regimens may be performed without additional harm. The anterior instrumentation systems also appeared to be relatively safe when irradiation was performed with the linear accelerator unit. However, when irradiation was performed with use of the cobalt-60 teletherapy unit, there was an increase in the dose of radiation delivered to the spinal canal in the presence of the anterior instrumentation systems, particularly the anterior column reconstruction with use of bone cement-filled chest tubes. These dose-perturbation characteristics might be important to consider during the calculation of radiation therapy protocols for patients who are going to receive high doses or recurrent treatments that would reach the tolerance limits of the spinal cord.

The Risk of Radiation-Induced Carcinogenesis after External Beam Radiotherapy of Graves’ Orbitopathy

Purpose: In order to estimate the risk of radiation-induced carcinogenesis after external beam radiotherapy of Graves’ orbitopathy, we made dosimetric measurements with thermoluminescent dosimeters in a male Rando phantom using our treatment technique. Methods: We produced dose-volume histograms from 5-mm CT slices using our treatment planning system. In this way we estimated the irradiation dose received by the main surrounding organs such as the brain, the bone and the eyeball. We use 6-MV X-ray for the treatment of Graves’ orbitopathy and our total dose is 2,000 cGy, 200 cGy per fraction. Clinical target volume was limited to the retrobulbar orbital content and medial rectus muscle, sparing the lenses, lacrimal glands and the sella turcica. All dosimetric measurements with thermoluminescent dosimeters were made 3 times. Results: We found that the dose to the right lens was 101.6 mGy and to left lens 103.4 mGy. Average absorbed doses to red bone marow, thyroid, lung, esophagus, bone surface, skin and brain, respectively, were estimated to be 523, 21, 4, 5, 81, 29, 47 mGy. Then, using tissue weighting factors specified by the International Commission of Radiation Protection, the resulting total effective dose was calculated to be 66.8 mSv. Conclusion: The risk factor for fatal cancer development derived from human epidemiological data is presently assumed to be 10% per Gy. In patients treated by our method of retro-orbital external beam radiotherapy for Graves’ orbitopathy, there is a 0.0067 (or 7 per 1,000 persons or 0.7%) risk of developing fatal radiation-induced cancer.

Dosimetric comparison of left-sided whole-breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and volumetric arc therapy

PURPOSE This study evaluated the dose distribution and homogeneity of four different types of intensity-modulated radiotherapy (IMRT) in comparison with standard wedged tangential-beam three-dimensional conformal radiotherapy (3DCRT) of the left breast in patients who had undergone lumpectomy. MATERIALS AND METHODS Five radiotherapy treatment plans, including 3DCRT, forward-planned IMRT (for-IMRT), inverse IMRT (inv-IMRT), helical tomotherapy (HT) and volumetric-modulated arc therapy (VMAT), were created for 15 consecutive patients. RESULTS All modalities presented similar target coverage. Target max doses were reduced with for-IMRT compared to 3DCRT, and these doses were further reduced with inv-IMRT and HT. HT resulted in the lowest max doses delivered to the heart, left anterior descending artery (LAD), and ipsilateral lung, but had higher mean, max, and low doses delivered to contralateral breast. HT resulted in increased low doses to a large volume of healthy tissue. Compared to other techniques, all inverse-planned modalities significantly improved conformity number; however, VMAT had worse homogeneity. The for-IMRT plan significantly lowered monitor unit (MU) compared to the inverse-planned techniques. CONCLUSION All modalities evaluated provide adequate coverage of the whole breast. For-IMRT improves target homogeneity compared with 3DCRT, but to a lesser degree than the inverse-planned inv-IMRT and HT. HT decreases the ipsilateral OAR volumes receiving higher and mean doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies.

Management of patients with recurrent glioblastoma using hypofractionated stereotactic radiotherapy.

Background Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. The chance of cure is very limited due to treatment-refractory disease course with frequent recurrences despite aggressive multimodality management. In this retrospective study, we evaluated treatment outcomes of hypofractionated stereotactic radiotherapy (HFSRT) in the management of recurrent GBM and report our single-center experience. Methods Twenty-eight patients receiving HFSRT for recurrent GBM between September 2008 and February 2014 were retrospectively assessed. Total radiotherapy dose was 25 Gy delivered in 5 fractions over 5 consecutive days for all patients. High-precision, image-guided volumetric modulated arc therapy was delivered with a linear accelerator using 6-MV photons using the frameless technique. Analyzed prognostic factors were age, gender, Karnofsky performance status (KPS), tumor location, planning target volume (PTV) size, overall survival (OS), progression-free survival (PFS), time interval between completion of treatment with Stupp protocol at primary diagnosis and recurrence. Results Median follow-up time was 42 months (range 2–68). Median time interval between primary chemoradiotherapy and HFSRT was 11.2 months (range 4–57.9). Median OS and PFS calculated from reirradiation was 10.3 months and 5.8 months, respectively. Longer interval between initial treatment and recurrence (p = 0.01), smaller PTV size (p = 0.001), KPS ≥70 (p = 0.005) and younger age (p = 0.004) were associated with longer OS on statistical analysis. Conclusion HFSRT offers a feasible and effective salvage treatment option for recurrent GBM management. Prognostic factors associated with longer OS in our study were longer interval between initial treatment and recurrence, smaller PTV size, KPS ≥70 and younger age.

Evaluation of stereotactic body radiation therapy in the management of adrenal metastases from non-small cell lung cancer.

Aims and Background In this retrospective analysis, we evaluated the use of stereotactic body radiation therapy in the management of adrenal metastases from non-small cell lung cancer and report our single center experience. Methods and Study design Fifteen non-small cell lung cancer patients (9 male, 6 female) with 17 adrenal metastases referred to Gulhane Military Medical Academy Radiation Oncology Department were treated using active breathing control-guided stereotactic body radiation therapy between December 2009 and October 2013. Dose per fraction was 10 Gy to deliver a total dose of 30 Gy over 3 consecutive days for all metastatic adrenal lesions. The mean gross tumor volume was 28.4 cc (range 6.6-101.5) and mean planning target volume was 57.4 cc (range 16.5-143.8). Results At a median follow-up of 16 months, local control was 86.7% and overall survival was 33.3%. Median disease-free survival was 10 months. Treatment response according to RECIST was categorized as complete response in 3 patients (20%), partial response in 5 patients (33.3%), stable disease in 5 patients (33.3%), and progressive disease in 2 patients (13.3%). Most common acute toxicity was grade 1 nausea (n = 7) and grade 1 fatigue (n = 12). There was no case of grade ≥3 acute or late toxicity. Conclusions Stereotactic body radiation therapy offers a safe and efficacious management strategy for adrenal metastases from non-small cell lung cancer by providing excellent local control with negligible treatment related toxicity.

Evaluation of linear accelerator-based stereotactic radiosurgery in the management of glomus jugulare tumors.

AIMS AND BACKGROUND Although mostly benign and slow-growing, glomus jugulare tumors have a high propensity for local invasion of adjacent vascular structures, lower cranial nerves and the inner ear, which may result in substantial morbidity and even mortality. Treatment strategies for glomus jugulare tumors include surgery, preoperative embolization followed by surgical resection, conventionally fractionated external beam radiotherapy, radiosurgery in the form of stereotactic radiosurgery or fractionated stereotactic radiation therapy, and combinations of these modalities. In the present study, we evaluate the use of linear accelerator (LINAC)-based stereotactic radiosurgery in the management of glomus jugulare tumors and report our 15-year single center experience. METHODS AND STUDY DESIGN Between May 1998 and May 2013, 21 patients (15 females, 6 males) with glomus jugulare tumors were treated using LINAC-based stereotactic radiosurgery at the Department of Radiation Oncology, Gulhane Military Medical Academy. The indication for stereotactic radiosurgery was the presence of residual or recurrent tumor after surgery for 5 patients, whereas 16 patients having growing tumors with symptoms received stereotactic radiosurgery as the primary treatment. RESULTS Median follow-up was 49 months (range, 3-98). Median age was 55 years (range, 24-77). Of the 21 lesions treated, 13 (61.9%) were left-sided and 8 (38.1%) were right-sided. Median dose was 15 Gy (range, 10-20) prescribed to the 85%-100% isodose line encompassing the target volume. Local control defined as either tumor shrinkage or the absence of tumor growth on periodical follow-up neuroimaging was 100%. CONCLUSIONS LINAC-based stereotactic radiosurgery offers a safe and efficacious management strategy for glomus jugulare tumors by providing excellent tumor growth control with few complications.

Evaluation of Treatment Outcomes of Early-Stage Endometrial Cancer Radiotherapy: A Single Center Experience

BACKGROUND Postoperative adjuvant radiotherapy (RT) in the management of early stage endometrial cancer (EC) is still controversial. Here we report our institutional experience with patients who received postoperative RT for stage I-II EC over a period of 35 years and assess potential predictors of local recurrence (LR), distant metastasis (DM), and overall survival (OS). MATERIALS AND METHODS A total of 188 patients undergoing postoperative RT for stage IA-II EC between 1977 and 2012 were evaluated. Some 96 received median 46 Gy whole pelvic radiotherapy (WPRT) (range: 40-60 Gy), 37 were given WPRT with vaginal cuff therapy (VCT), and 55 received only VCT either with brachytherapy (BT) or stereotactic body radiotherapy (SBRT). Chemotherapy was given to 5 patients with uterine papillary serous carcinoma (UPSC). Logistic regression analysis was used to assess the effect of clinicopathological factors on LR, DM, and OS. RESULTS Median follow-up time was 11 years (range: 1-35 years). At the time of analysis, 34 patients were not alive. Of the 15 patients with LR, 7 (46.7%) recurred in the vaginal stump, 5 (33.3%) in the pelvic region, and 3 (20%) in the paraaortic nodal region, while 12 had distant metastasis. UPSC histology (p=0.027), sole VCT (p=0.041), high histologic grade (p=0.034), and age≥71 (p=0.04) were poor prognostic factors on univariate analysis. CONCLUSIONS In our patients receiving radiotherapy for early-stage EC, grade III disease and age≥71 were associated with shorter OS whereas UPSC histology was an independent predictor for both LR and DM.

Dosimetric evaluation of critical organs at risk in mastectomized left-sided breast cancer radiotherapy using breath-hold technique

AIMS AND BACKGROUND The aim of the study was to evaluate the dosimetric impact of the active breathing control-moderate deep inspiration breath-hold (ABC-mDIBH) technique on normal tissue sparing in locally advanced left-sided breast cancer radiotherapy. METHODS AND STUDY DESIGN Twenty-seven consecutive patients with left-sided locally advanced breast cancer referred to our department for adjuvant radiotherapy were enrolled in the study. Each patient was scanned at free breathing and ABC-mDIBH for radiation treatment planning. Two separate radiotherapy treatment plans were generated with and without ABC-mDIBH to investigate the dosimetric impact of ABC-mDIBH in breast cancer radiotherapy. RESULTS Between June 2011 and February 2012, 27 consecutive patients with left-sided locally advanced breast cancer referred to our department for adjuvant radiotherapy were enrolled in the study. Dose-volume parameters of left anterior descending coronary artery, lungs, heart, contralateral breast, esophagus and spinal cord were significantly reduced with the use of ABC-mDIBH (P <0.001). CONCLUSIONS Our study revealed that the use of ABC-mDIBH in the practice of locally advanced mastectomized left-sided breast cancer radiotherapy improves normal tissue sparing with the expected potential of decreasing treatment-related morbidity and mortality. Moreover, the resultant reduction achieved with ABC in doses to the left anterior descending coronary artery, which plays a central role in cardiac perfusion, may have implications for decreasing the potential of radiation-induced cardiac morbidity and mortality.

Adaptive splenic radiotherapy for symptomatic splenomegaly management in myeloproliferative disorders.

Aims and Background Symptomatic, massive splenomegaly is a debilitating complication of myeloproliferative disorders. In the study, we evaluated the use of a contemporary, individualized radiotherapeutic approach for splenic irradiation, including 3-dimensional computed tomography-based treatment planning, individualized treatment margins based on splenic motion assessment, online setup verification with volumetric image guidance at each fraction, and adaptive radiation treatment planning to account for changes in splenic size during the fractionated radiotherapy course. Methods and Study design Between December 2008 and January 2014, 18 patients (13 males, 5 females) with myeloproliferative disorders referred to Gulhane Military Medical Academy Radiation Oncology Department underwent 22 courses of splenic irradiation using 3-dimensional computed tomography-based treatment planning and volumetric image guidance for palliation of symptomatic splenomegaly. Results Median age was 64 years (range 28-79). Significant pain relief was achieved in 20 of the 22 splenic irradiation courses (90.9%). Improvement in hematological parameters was achieved in 8 of the 11 splenic irradiation courses applied for cytopenia (72.7%). At least a 50% reduction in splenic size was achieved in 18 of the 22 splenic irradiation courses (81.8%). Toxicity was manageable with supportive treatment including antiemetics and platelet or red blood cell transfusions. Conclusions Splenic irradiation with a contemporary radiotherapeutic approach offers safe and effective palliation of symptomatic splenomegaly in myeloproliferative disorders.