Dosimetric analysis of the alopecia preventing effect of hippocampus sparing whole brain radiation therapy.

Abstract

BACKGROUND: Whole brain radiation therapy (WBRT) is widely used for the treatment of brain metastases. Cognitive decline and alopecia are recognized adverse effects of WBRT. Recently hippocampus sparing whole brain radiation therapy (HS-WBRT) has been shown to reduce the incidence of memory loss. In this study, we found that multi-field intensity modulated radiation therapy (IMRT), with strict constraints to the brain parenchyma and to the hippocampus, reduces follicular scalp dose and prevents alopecia. METHODS: Suitable patients befitting the inclusion criteria of the RTOG 0933 trial received Hippocampus sparing whole brain radiation. On follow up, they were noticed to have full scalp hair preservation. 5 mm thickness of follicle bearing scalp in the radiation field was outlined in the planning CT scans. Conventional opposed lateral WBRT radiation fields were applied to these patient-specific image sets and planned with the same nominal dose of 30 Gy in 10 fractions. The mean and maximum dose to follicle bearing skin and Dose Volume Histogram (DVH) data were analyzed for conventional and HS-WBRT. Paired t-test was used to compare the means. RESULTS: All six patients had fully preserved scalp hair and remained clinically cognitively intact 1-3 months after HS-WBRT. Compared to conventional WBRT, in addition to the intended sparing of the Hippocampus, HS-WBRT delivered significantly lower mean dose (22.42 cGy vs. 16.33 cGy, p < 0.0001), V24 (9 cc vs. 44 cc, p < 0.0000) and V30 (9 cc vs. 0.096 cc, p = 0.0106) to follicle hair bearing scalp and prevented alopecia. There were no recurrences in the Hippocampus area. CONCLUSIONS: HS-WBRT, with an 11-field set up as described, while attempting to conserve hippocampus radiation and maintain radiation dose to brain inadvertently spares follicle-bearing scalp and prevents alopecia.

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10.1186/s13014-015-0555-9

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Mahadevan, Anand, Carrie Sampson, Salvatore LaRosa, Scott R Floyd, Eric T Wong, Erik J Uhlmann, Soma Sengupta, Ekkehard M Kasper, et al. (2015). Dosimetric analysis of the alopecia preventing effect of hippocampus sparing whole brain radiation therapy. Radiat Oncol, 10. p. 245. 10.1186/s13014-015-0555-9 Retrieved from https://hdl.handle.net/10161/15934.

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Floyd

Scott Richard Floyd

Gary Hock and Lyn Proctor Associate Professor of Radiation Oncology

Diseases of the brain carry particular morbidity and mortality, given the fundamental function of the brain for human life and quality of life. Disease of the brain are also particularly difficult to study, given the complexity of the brain. Model systems that capture this complexity, but still allow for experiments to test therapies and mechanisms of disease are badly needed.  We have developed an experimental model system that uses slices made from rat and mouse brains to create a test platform to research new treatments for brain diseases such as stroke, Alzheimer's disease, Huntington's disease and brain tumors. This model system reduces the number of experimental animals used, and streamlines experiments so that final testing in laboratory animals is more efficient. We use this brainslice system and limited numbers of experimental animals to test drugs and genetic pathways to treat stroke, Alzheimer's disease, Huntington's disease and brain tumors. As many brain tumors are treated with radiation therapy, we have a particular interest in the cellular response to DNA damage caused by radiation. DNA damage signaling and repair are fundamental processes necessary for cells to maintain genomic integrity. Problems with these processes can lead to cancer. As many cancer cells have altered DNA damage and repair pathways, we can apply DNA damage as cancer therapy. Our knowledge of how normal and neoplastic cells handle DNA damage is still incomplete. A deeper understanding can lead to improved cancer treatment, and to better protection from the harmful effects of DNA damaging agents like radiation. To this end, we plan experiments that test the effects of radiation on normal animal tissues and animal models of cancer, as well as molecular pathways in brain diseases such as Alzheimer’s, Huntington’s and stroke.


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