Young Kee Oh

Is Prophylactic Irradiation to Para-aortic Lymph Nodes in Locally Advanced Cervical Cancer Necessary?

Purpose This study evaluated the efficacy of extended field irradiation (EFI) in patients with locally advanced cervical cancer without para-aortic nodal involvement. Materials and Methods A total of 203 patients with locally advanced cervical cancer (International Federation of Gynecology and Obstetrics [FIGO] stage, IB2-IIIB) treated with radiotherapy at Keimyung University Dongsan Medical Center from 1996 to 2010 were retrospectively analyzed. The median patient age was 59 years (range, 29 to 83 years). None of the patients had para-aortic node metastases. Of the 203 patients, 88 underwent EFI and 115 underwent irradiation of the pelvis only. Concurrent chemoradiotherapy (CCRT) was administered to 133 patients. EFI field was used for treatment of 26 patients who received radiotherapy alone and 62 who received CCRT. Results The median follow-up period was 60 months. The 2- and 5-year overall survival (OS) rates were 87.8% and 73.5%, respectively, and the 2- and 5-year disease-free survival rates were 81.7% and 75.0%, respectively, however, no survival differences were observed between the two treatment field groups. EFI tended to increase OS in the radiotherapy alone group, but not in the CCRT group. Conclusion These findings suggest that EFI does not have a significant effect in patients with locally advanced cervical cancer, especially in patients receiving CCRT. Conduct of additional studies will be required in order to confirm these findings.

Clinical significance of the lymph node ratio in N1 breast cancer

Purpose The purpose of this study was to evaluate the prognostic value of the lymph node ratio (LNR), which was defined as the proportion of involved nodes of all dissected nodes, in pN1 breast cancer. Materials and Methods We retrospectively analyzed the clinical data of patients with pN1 breast cancer (N = 144) treated at Keimyung University Dongsan Medical Center, Daegu, Korea between 2001 and 2010. The median age was 46 years (range, 27 to 66 years). The LNR was 0.01–0.15 (low LNR) in 130 patients and >0.15 (high LNR) in 14 patients. Sixty-five patients (45.1%) had T1 tumors, 74 (51.4%) had T2 tumors, and 5 (3.5%) had T3 tumors. Eighty-eight patients (61.1%) underwent total mastectomy and 56 (38.9%) underwent partial mastectomy. Fifty-nine patients (41.0%) underwent radiotherapy and 12 (8.3%) underwent regional radiotherapy. The median follow-up period was 65 months. Results The 5- and 10-year disease-free survival (DFS) rates were 92.7% and 82.4%, respectively. Univariate analyses revealed that high LNR (p = 0.004), total mastectomy (p = 0.006), no local radiotherapy (p = 0.036), and stage T2 or T3 (p = 0.010) were associated with worse DFS. In multivariable analysis, only high LNR (p = 0.015) was associated with worse DFS. Conclusion High LNR is an independent prognostic factor in pN1 breast cancer and could be an indication for adjuvant radiotherapy in these patients.

Long-term outcomes of surgery and radiotherapy for secreting and non-secreting pituitary adenoma

Purpose: To investigate treatment outcome and long term complication after surgery and radiotherapy (RT) for pituitary adenoma. Materials and Methods: From 1990 to 2009, 73 patients with surgery and RT for pituitary adenoma were analyzed in this study. Median age was 51 years (range, 25 to 71 years). Median tumor size was 3 cm (range, 1 to 5 cm) with suprasellar (n = 21), cavernous sinus extension (n = 14) or both (n = 5). Hormone secreting tumor was diagnosed in 29 patients; 16 patients with prolactin, 12 patients with growth hormone, and 1 patient with adrenocorticotrophic hormone. Impairment of visual acuity or visual field was presented in 33 patients at first diagnosis. Most patients (n = 64) received RT as postoperative adjuvant setting. Median RT dose was 45 Gy (range, 45 to 59.4 Gy). Results: Median follow-up duration was 8 years (range, 3 to 22 years). In secreting tumors, hormone normalization rate was 55% (16 of 29 patients). For 25 patients with evaluable visual field and visual acuity test, 21 patients (84%) showed improvement of visual disturbance after treatment. The 10-year tumor control rate for non-secreting and secreting adenoma was 100% and 58%, respectively (p < 0.001). Progression free survival rate at 10 years was 98%. Only 1 patient experienced endocrinological recurrence. Following surgery, 60% (n = 44) suffered from pituitary function deficit. Late complication associated with RT was only 1 patient, who developed cataract. Conclusion: Surgery and RT are very effective and safe in hormonal and tumor growth control for secreting and non-secreting pituitary adenoma.

Concurrent chemoradiotherapy improves survival outcome in muscle-invasive bladder cancer

Purpose To evaluate survival rates and prognostic factors related to treatment outcomes after bladder preserving therapy including transurethral resection of bladder tumor, radiotherapy (RT) with or without concurrent chemotherapy in bladder cancer with a curative intent. Materials and Methods We retrospectively studied 50 bladder cancer patients treated with bladder-preserving therapy at Keimyung University Dongsan Medical Center from January 1999 to December 2010. Age ranged from 46 to 89 years (median, 71.5 years). Bladder cancer was the American Joint Committee on Cancer (AJCC) stage II, III, and IV in 9, 27, and 14 patients, respectively. Thirty patients were treated with concurrent chemoradiotherapy (CCRT) and 20 patients with RT alone. Nine patients received chemotherapy prior to CCRT or RT alone. Radiation was delivered with a four-field box technique (median, 63 Gy; range, 48.6 to 70.2 Gy). The follow-up periods ranged from 2 to 169 months (median, 34 months). Results Thirty patients (60%) showed complete response and 13 (26%) a partial response. All patients could have their own bladder preserved. Five-year overall survival (OS) rate was 37.2%, and the 5-year disease-free survival (DFS) rate was 30.2%. In multivariate analysis, tumor grade and CCRT were statistically significant in OS. Conclusion Tumor grade was a significant prognostic factor related to OS. CCRT is also considered to improve survival outcomes. Further multi-institutional studies are needed to elucidate the impact of RT in bladder cancer.

Interval between Surgery and Radiation Therapy Is an Important Prognostic Factor in Treatment of Rectal Cancer

Purpose The purpose of this study is to evaluate survival and prognostic factors for rectal cancer, including interval between surgery and radiation therapy after surgery, radiation therapy, and chemotherapy. Materials and Methods We conducted a retrospective study of 153 patients with rectal cancer who were treated with surgery, radiotherapy with/without chemotherapy at Keimyung University Dongsan Medical Center from January, 1988 to December, 2005. The study included 89 males and 64 females, with a median age of 56 years (range, 23 to 81 years). Tumor, node and metastasis (TNM) was I in 23 patients, II in 39, and III in 91. Radiation therapy was performed on pelvic fields using a median dose of 54 Gy five days per week, 1.8 Gy once per day. Ninety two patients were treated with radiotherapy, 43 with concurrent chemo-radiation therapy and 18 with sequential therapy after surgery. The median follow-up period was 52 months (range, 4 to 272 months). The interval between surgery and radiation was 1-25 weeks (median, 5 weeks). Results Two-year and five-year overall survival rate was 64.7% and 46.4%, respectively. Two-year and five-year disease-free-survival (DFS) rate was 58.6% and 43.1%, respectively. Median DFS was 39 months. Loco-regional failure was evident in 10.5% of patients, 8.4% had distant metastasis, and 9.2% had both. In multivariate analysis, TNM stage and interval between surgery and radiation therapy (≤5 weeks vs. >5 weeks; 95% confidence interval, 1.276 to 2.877; hazard ratio, 1.916; p=0.002) were significant prognostic factors of DFS. Conclusion Survival rates for rectal cancer after surgery, chemotherapy, and radiation therapy were similar to those reported in previous studies. Starting radiation therapy as soon as possible after surgery, especially within the first five weeks after surgery, is suggested.

Dose comparison between prescription methods according to anatomical variations in intracavitary brachytherapy for cervical cancer

Purpose We compared how doses delivered via two-dimensional (2D) intracavitary brachytherapy (ICBT) and three-dimensional (3D) ICBT varied anatomically. Materials and Methods A total of 50 patients who received 30 Gy of 3D ICBT after external radiotherapy (RT) were enrolled. We compared the doses of the actual 3D and 2D ICBT plans among patients grouped according to six anatomical variations: differences in a small-bowel V2Gy, small bowel circumference, the direction of bladder distension, bladder volume, sigmoid V3.5Gy, and sigmoid circumference. Seven dose parameters were measured in line with the EMBRACE recommendations. Results In terms of bladder volume, the bladder and small-bowel D2cc values were lower in the 150–250 mL bladder volume subgroup; and the rectum, sigmoid, and bladder D2mL values were all lower in the >250 mL subgroup, for 3D vs. 2D ICBT. In the sigmoid V3.5Gy >2 mL subgroup, the sigmoid and bladder D2mL values were significantly lower for 3D than 2D ICBT. The bladder D2mL value was also significantly lower for 3D ICBT, as reflected by the sigmoid circumference. In patients with a small bowel V2.0Gy >10 mL or small bowel circumference >15%, most dose parameters were significantly lower for 3D than 2D ICBT. The bladder distension direction did not significantly affect the doses. Conclusion Compared to 2D ICBT, a greater bladder volume can reduce the internal 3D ICBT organ dose without affecting the target dose.

Design and Characteristics of Parallel Plate Type Ionization Chamber for the Measurement of High Energy Photon and Electron Beam

The dosimetric system consisting of parallel plate type of air-filled ionization chamber and charge to voltage converter was designed to do constancy check of the high energy photon and electron beam of clinical linear accelerator. The ionization chamber had been fabricated using an acrylic plate for the air cavity and two printed circuit boards for electrical configuration. The air gap between two electrodes ranged from 3 mm, 6 mm and 10 mm. The sensitive volume of the chambers were 0.9 cc, 1.9 cc and 3.1 cc respectively. The major parameters of the chamber characteristics such as zero drift current, leakage current, saturation voltage, reproducibility, linearity, EPM(Effective Point of Measurement), dose rate effect and polarity effect were measured. The experimental results are as followings. Zero drift currents were 0.23 pA for the volume of 0.9 cc, 1.9 cc and 0.45 pA for 3.1 cc. Leakage currents were 0.38 pAfor the volume of 0.9 cc, 1.9 cc and 0.56 pAfor 3.1 cc. Saturation voltages were 300 V, 400 V and 500 V for three kinds of chambers with volume of 0.9 cc, 1.9 cc and 3.1 cc respectively. Standard deviation of reproducibility was less than 0.003, and the linearity was measured within0.5% for all kinds of chambers. EPM(effective point of measurement) shifted towards the geometric center of the chamber as the plate separation increased. These data were comparable to those of commercially available dosimetric system for QA-purpose. This dosimetric system consisting of the ionization chamber, the PCB, and RF coaxial cables is satisfactory for the purpose of the constancy check of the high energy photon and electron beam from the medical linear accelerator.

Development of Multi-Channel Dosimeter System for Measurement of Dose Distribution in Therapeutic Photon Beams

We investigated the characteristics of the multi-channel dosimeter (MCD) system for dose distribution by the moving wedge in clinical photon beams. Also we developed an electrometer for the multi-channel dosimeter system for radiation therapy. In dynamic field irradiation, the virtual wedge technique and its fraction methods are available through the computer-controlled asymmetric independent collimator. The modified MCD system consists of an electrometer, a solid detector and an array phantom. The MCD is used for the point dose measurement and the field size scanning. Thus, we evaluated the dosimetric characteristics of the virtual wedge and the conventional fixed wedge by the radiation field analyzer (RFA). In our analysis for the 6 and 10 MV photon beams, the maximum dose in the virtual-wedge and the fixed-wedge factors varied from 1.2 % to 1.6 % for square collimator setting ranging from 10 to 20 cm, respectively. We constructed the modified MCD system with the developed electrometer for radiation therapy to improve on the analytical expressions describing the dose distributions for the virtual wedge and the wedge fraction method in 6 and 10 MV clinical photon beams.

A Test code to Calculate the trajectory of Charged Particals in a Medium under External Electric and Magnetic Fields

A computer code to calculate the trajectory of charged particles in a medium under external electric and magnetic fields was designed. Using this code, the trajectories considered the energy loss and the direction change of the primary particles determined by stopping power and Lorentz force respectively could be calculated. The results show the variation of trajectories as a function of kinetic energy and external fields. The code can be useful for finding the information about the enhancement of energy deposition in a medium irradiated by charged particle beam. Since only the energy loss and the direction change for primary particles are considered, there are errors in this calculation. However, the results can be applied to the study of dose enhancement in radiation therapy. More accurate calculations can be achieved by considering multiple scattering of primary particles and the effect of secondary particles.