I.A. Kim

Dosimetric effects of the acuros XB and anisotropic analytical algorithm on volumetric modulated arc therapy planning for prostate cancer using an endorectal balloon

BackgroundTo compare the dosimetric effects of Acuros XB (AXB) and Anisotropic Analytical Algorithm (AAA) on volumetric modulated arc therapy (VMAT) planning for postoperative prostate cancer patients irradiated using an endorectal balloon (ERB).MethodsWe measured central axis doses with film in a phantom containing an air cavity, and compared measurements with calculations of the AAA and AXB. For clinical study, 10 patients who had undergone whole pelvic radiotherapy (WPRT) followed by prostatic bed-only radiotherapy (PBRT) using VMAT were enrolled. An ERB was used for PBRT but not for WPRT. To compare dosimetric parameters, the cumulative dose-volume histograms, mean, maximum, and minimum doses were measured for the planning target volume. Homogeneity of plans were confirmed using V95%, V107% (VX%, percentage volumes receiving at least X% of prescribed doses) and conformity indices (homogeneity index [HI], conformity index [CI], and conformation number [CN]). We compared volumes of the organ-at-risk receiving 10% to 100% (10-tier at 10% interval) of prescribed doses (V10% – V100%).ResultsIn the phantom study, the AAA showed larger disagreement with the measurements, and overestimated the dose in the air cavity, comparing with the AXB. For WPRT planning, the AAA predicted a lower maximum dose and V107% than the AXB. For PBRT planning, the AAA estimated a higher minimum dose, lower maximum dose, and smaller V107%, and larger V95% than the AXB. Regarding the conformity indices, the AAA was estimated to be more homogenous than the AXB for PBRT planning (HI, 0.088 vs. 0.120, pu2009=u20090.005; CI, 1.052 vs. 1.038, pu2009=u20090.022; and CN, 0.920 vs. 0.900, pu2009=u20090.007) but not for WPRT planning. Among V10% to V100% of the rectum, the PBRT exhibited significant discrepancies in V30%, V40%, V70%, V80%, and V90%; while the WPRT did in V20% and V30%.ConclusionsThe phantom study demonstrated that the AXB calculates more accurately in the air cavity than the AAA. In the clinical setting, the AXB exhibited different dosimetric distributions in the VMAT plans for PBRT containing an ERB. The AXB should be considered for prostate cancer patients irradiated with an ERB for better applying of heterogeneous condition.

Epidemiology of Intracranial Metastases in Korea: A National Cohort Investigation

Purpose To investigate the epidemiologic features of intracranial metastases (ICMET) in Korea, we performed a cohort study using the National Health Insurance Service–National Sample Cohort database, which comprised healthcare usage information of approximately 1 million Korean individuals over 12 years. Materials and Methods We enrolled 998,602 subjects, after excluding 18,218 subjects diagnosed with any cancer during the washout period (2002-2004). The observation period was 9 years (2005-2013; 8,725,438 person-years). The initial diagnosis date of ICMET and the primary cancer was recorded. The incidence was determined based on the number of incident cases and observation size, whereas survival was estimated using death statistics from the database. Results Through observation period, a total 776 subjects developed ICMET. The age-standardized incidence of ICMET was 8.2 per 100,000 person-years. The mean interval between the initial diagnosis date of the primary cancer and ICMET was 13.1 months. Patients with ICMET had shorter survival than those without ICMET (30.9 months vs. 81.4 months, p < 0.001). The ICMET incidence among the cancer patients was 5.0 per 1,000 person-years; it was highest in lung cancer cases, followed by breast and liver cancer cases. Moreover, ICMET from lung cancer was the most common metastasis type, followed by ICMET from liver and breast cancer. Conclusion The incidence of ICMET was 8.2 per 100,000 person-years among the Korean population and 5.0 per 1,000 person-years among cancer patients. Most of the ICMET cases arose from lung cancer. ICMET also critically influenced survival in cancer patients.