Hippocampal Sparing Whole Brain Radiotherapy and Integrated Simultaneous Boost vs Stereotactic Radiosurgery Boost: A Comparative Dosimetric Planning Study.

BACKGROUND: Whole brain radiotherapy (WBRT) and stereotactic radiosurgery were frequently used to palliate patients with brain metastases. It remains controversial which modality or combination of therapy is superior especially in the setting of limited number of brain metastases. The availability of newer medical therapy that improves survival highlighted the importance of reducing long term radiation toxicity associated with WBRT. In this study, we aim to demonstrate the hippocampal sparing technique with whole brain and integrated simultaneous boost Materials and Methods: Planning data from 10 patients with 1-5 brain metastases treated with SRS were identified. Based on the contouring guideline from RTOG atlas, we identified and contoured the hippocampus with 5mm isocentric expansion to form the hippocampal avoidance structure. The plan was to deliver hippocampal sparing whole brain radiotherapy (HSWBRT) of 30 Gy in 10 fractions and simultaneous boost to metastatic lesions of 30 Gy in 10 fractions each. RESULTS: The PTV, hippocampus and hippocampal avoidance volumes ranges between 1.00 - 39.00 cc., 2.50 - 5.30 cc and 26.47 - 36.30 cc respectively. The mean hippocampus dose for the HSWBRT and HSWBRT and SIB plans was 8.06 Gy and 12.47 respectively. The max dose of optic nerve, optic chiasm and brainstem were kept below acceptable range of 37.5 Gy. CONCLUSIONS: The findings from this dosimetric study demonstrated the feasibility and safety of treating limited brain metastases with HSWBRT and SIB. It is possible to achieve the best of both worlds by combining HSWBRT and SIB to achieve maximal local intracranial control while maintaining as low a dose as possible to the hippocampus thereby preserving memory and quality of life.

Role of genetic & environment risk factors in the aetiology of colorectal cancer in Malaysia.

BACKGROUND & OBJECTIVES: Colorectal cancer (CRC) is second only to breast cancer as the leading cause of cancer-related deaths in Malaysia. In the Asia-Pacific area, it is the highest emerging gastrointestinal cancer. The aim of this study was to identify single nucleotide polymorphisms (SNPs) and environmental factors associated with CRC risk in Malaysia from a panel of cancer associated SNPs. METHODS: In this case-control study, 160 Malaysian subjects were recruited, including both with CRC and controls. A total of 768 SNPs were genotyped and analyzed to distinguish risk and protective alleles. Genotyping was carried out using Illumina's BeadArray platform. Information on blood group, occupation, medical history, family history of cancer, intake of red meat and vegetables, exposure to radiation, smoking and drinking habits, etc was collected. Odds ratio (OR), 95% confidence interval (CI) were calculated. RESULTS: A panel of 23 SNPs significantly associated with colorectal cancer risk was identified (P<0.01). Of these, 12 SNPs increased the risk of CRC and 11 reduced the risk. Among the environmental risk factors investigated, high intake of red meat (more than 50% daily proportion) was found to be significantly associated with increased risk of CRC (OR=6.52, 95% CI :1.93-2.04, P=0.003). Two SNPs including rs2069521 and rs10046 in genes of cytochrome P450 (CYP) superfamily were found significantly associated with CRC risk. For gene-environment analysis, the A allele of rs2069521 showed a significant association with CRC risk when stratified by red meat intake. INTERPRETATION & CONCLUSIONS: In this preliminary study, a panel of SNPs found to be significantly associated with CRC in Malaysian population, was identified. Also, red meat consumption and lack of physical exercise were risk factors for CRC, while consumption of fruits and vegetables served as protective factor.

Treatment outcome with brachytherapy for recurrent nasopharyngeal carcinoma.

BACKGROUND: To evaluate the treatment outcome and major late complications of all patients with recurrent nasopharyngeal carcinoma (NPC) treated with intracavitary brachytherapy (ICBT) in Hospital Kuala Lumpur. MATERIALS AND METHODS: This retrospective study was conducted at the Department of Radiotherapy and Oncology, Hospital Kuala Lumpur, Malaysia. All patients with histologically confirmed recurrent NPC in the absence of distant metastasis treated in the period 1997-2010 were included in this study. These patients were treated with ICBT alone or in combination with external beam radiotherapy (EBRT). Treatment outcomes measured were local recurrence free survival (LRFS), disease free survival (DFS) and overall survival (OS). RESULTS: Thirty three patients were eligible for this study. The median age at recurrence was 56 years with a median time to initial local recurrence of 27 months. Majority of patients were staged as rT1-2 (94%) or rN0 (82%). The proportion of patients categorised as stage III-IV at first local recurrence was only 9%. Twenty one patients received a combination of ICBT and external beam radiotherapy while 12 patients were treated with ICBT alone. Median interval of recurrence post re-irradiation was 32 months (range: 4-110 months). The median LRFS, DFS and OS were 30 months, 29 months and 36 months respectively. The 5 year LRFS, DFS and OS were 44.7%, 38.8% and 28.1% respectively. The N stage at recurrence was found to be a significant prognostic factor for LRFS and DFS after multivariate analysis. Major late complications occurred in 34.9% of our patients. CONCLUSIONS: Our study shows ICBT was associated with a reasonable long term outcome in salvaging recurrent NPC although major complications remained a significant problem. The N stage at recurrence was a significant prognostic factor for both LRFS and DFS.