Thomas E. Merchant, DO, PhD
Thomas E. Merchant, DO, PhD

Thomas E. Merchant, DO, PhD

Member, St. Jude Faculty

  • Chair, Radiation Oncology Department
  • Baddia J. Rashid Endowed Chair in Radiation Oncology
  • Chairman, Radiation Oncology Discipline, Children's Oncology Group



BS – University of Michigan, Ann Arbor, Michigan
DO – Chicago College of Osteopathic Medicine, Chicago, Illinois
PhD – University of Utrecht, The Netherlands

Research Interests

I am currently Chair of Radiation Oncology at St. Jude Children’s Research Hospital in Memphis, Tennessee where I have practiced since 1996. Prior to my appointment at St. Jude, I was an attending physician in the Department of Radiation Oncology at the Memorial Sloan-Kettering Cancer Center in New York, New York. I was originally trained as a nuclear engineer at the University of Michigan. After completing my engineering degree, and prior to attending medical school at the Chicago College of Osteopathic Medicine, I worked in the area of radiation protection and safety for the French Atomic Energy Commission in Fontenay-aux-Roses, France. After medical school, I was a Fulbright Scholar to the Netherlands at the University of Utrecht where I received my Ph.D., cum laude, in experimental pathology. I interned at the Chicago Osteopathic Hospital and performed my residency at the Memorial Sloan-Kettering Cancer Center. As a part of my formal medical and residency training, I spent time at the Massachusetts Eye and Ear Infirmary in Boston and Curie Institute in Paris. In the latter part of my residency training, I was awarded a fellowship and spent time at the Joint Center for Radiation Therapy and Children’s Hospital Boston.

The subject of my research has been the application of advanced radiotherapy methods in the treatment of children with cancer. My focus has been in pediatric neuro-oncology where I have designed new treatments for children with brain tumors and modeled radiation-related CNS effects. The broad long-term goal of my research has been to increase the cure rates for the most common brain tumors and reduce or eliminate the side effects of radiation therapy. My work in the area of conformal radiation therapy for pediatric CNS tumors has provided the basis for the dose, volume and normal tissue tolerance guidelines used in most of the national cooperative group brain tumor trials for children with medulloblastoma, ependymoma, low-grade glioma and craniopharyngioma. My work has recently been highlighted in a number of oncology journals including Lancet OncologyJournal of Clinical Oncology, and the International Journal of Radiation Oncology, Biology and Physics.

In the Children’s Oncology Group, I served as the Chair of the Radiation Oncology Discipline and Vice-chair of the CNS Disease Committee from 2006-2016. I was the Principal Investigator for the most recent national ependymoma study. My current efforts include leading the development of new guidelines to implement and research the role of intensity-modulated radiation therapy and proton beam therapy in the treatment of children with all types of brain and solid tumors. To that end, I completed a sabbatical at the Paul Scherrer Institute in Villigen, Switzerland, where I studied proton spot scanning. My goal is to lead the effort to develop institutional and collaborative protocols for St. Jude patients to receive proton beam therapy at established protons centers.


  • Ependymoma
  • Craniopharyngioma
  • Medulloblastoma
  • Low-grade glioma
  • Retinoblastoma

Special Interests

  • Brain tumors in young children
  • Side effects of radiation therapy
  • Re-irradiation
  • Proton therapy

Selected Publications

Jacola L, Conklin H, Scoggins M, Ashford J, Merchant TE, Mandrell B, Ogg R, Curtis E, Wise M, Indelicato D, Crabtree V. Investigating the role of hypothalamic tumor involvement in sleep and cognitive outcomes among children treated for craniopharyngioma. J Ped Psych 2016 (in press).

Conklin H, Ogg R, Ashford J, Scoggins M, Zou P, Clark K, Martin-Elbahesh K, Hardy K, Merchant T, Jeha S, Huang L, Zhang H. Computerized Cognitive Training for Amelioration of Cognitive Late Effects Among Childhood Cancer Survivors: A Randomized Controlled Trial. J Clin Oncol 33(33):3894-902, 2015. doi:10.1200/JCO.2015.61.6672. PMID:26460306, PMCID:PMC4652013.

Conklin H, Ogg R, Ashford J, Scoggins M, Zou P, Clark K, Martin-Elbahesh K, Hardy K, Merchant T, Jeha S, Huang L, Zhang H. Computerized Cognitive Training for Amelioration of Cognitive Late Effects Among Childhood Cancer Survivors: A Randomized Controlled Trial. J Clin Oncol 33(33):3894-902, 2015. doi:10.1200/JCO.2015.61.6672. PMID:26460306. PMCID:PMC4652013.

Green DM, Merchant TE, Billups C, Stokes DC, Broniscer A, Bartels U, Chintogumpala M, Hassall TE, Gururangan S, McCowage GB, Heath JA, Cohn RJ, Fisher MJ, Srinivasan A, Robinson GW, Gajjar A. Pulmonary Function after Treatment for Embryonal Brain Tumors on SJMB03 That Included Craniospinal Irradiation. Int J Radiat Oncol Biol Phys 93(1):47-53, 2015. doi:10.1016/j.ijrobp.2015.05.019.

Uh J, Merchant TE, Li Y, Li X, Sabin ND, Indelicato DJ, Ogg RJ, Boop FA, Hua CH. Effects of Surgery and Proton Therapy on Cerebral White Matter of Craniopharyngioma Patients. Int J Radiat Oncol Biol Phys 93(1):64-71, 2015. doi:10.1016/j.ijrobp.2015.05.017. PMID:26279025.

Klimo P Jr, Venable GT, Boop FA, Merchant TE. Recurrent Craniopharyngioma After Conformal Radiation in Children and the Burden of Treatment. J Neurosurg Pediatric 15(5):499-505, 2015. doi:10.3171/2015.10.PEDS14384. PMID:25700121.

Hua CH, Merchant TE, Li X, Li Y, Shulkin, BL. Establishing Age-Associated Normative Ranges of the Cerebral 18F-FDG Uptake Ratio in Children. J Nucl Med 56(4):575-579, 2015.

Murphy ES, Xie H, Merchant TE, Yu JS, Chao ST, Suh JH. Review of Cranial Radiotherapy-Induced Vasculopathy. J Neurooncol 122(3):421-9, 2015. doi:10.1007/s11060-015-1732-2. PMID:25670390.

Tsui K, Gajjar A, Li C, Srivastava D, Broniscer A, Wetmore C, Kun LE, Merchant TE, Ellison DW, Orr BA, Boop FA, Klimo P, Ross J, Robison LL, Armstrong GT. Subsequent neoplasms in survivors of childhood central nervous system tumors: risk after modern multimodal therapy. Neuro Oncol 17(3):448-56, 2015. doi:10.1093/neuonc/nou279. PMID:25395462. PMCID:PMC4483102.

Willard VW, Conklin HM, Wu S, Merchant TE. Prospective longitudinal evaluation of emotional and behavioral functioning in pediatric patients with low-grade glioma treated with conformal radiation therapy. J Neurooncol 122(1):161-8, 2015. doi:10.1007/s11060-014-1696-7. PMID:25573605. PMCID: PMC4654414.

Chemaitilly W, Li Z2, Huang S, Ness KK, Clark KL, Green DM, Barnes N, Armstrong GT, Krasin MJ, Srivastava DK, Pui CH, Merchant TE, Kun LE, Gajjar A, Hudson MM, Robison LL, Sklar CA. Anterior hypopituitarism in adult survivors of childhood cancers treated with cranial radiotherapy: a report from the St Jude Lifetime Cohort study. J Clin Oncol 33(5):492-500, 2015. doi:10.1200/JCO.2014.56.7933. PMID:25559807.  PMCID:PMC4314596. 

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Armstrong GT, Conklin HM, Huang S, Srivastava D, Sanford R, Ellison DW, Merchant TE, Hudson MM, Hoehn ME, Robison LL, Gajjar A, Morris EB. Survival and long-term health and cognitive outcomes after low-grade glioma. Neuro Oncol 13(2):223-34, 2010.

Tendulkar RD, Pai Panandiker AS, Wu S, Kun LE, Broniscer A, Sanford RA, Merchant TE. Irradiation of pediatric high-grade spinal cord tumors. Int J Radiat Oncol Biol Phys 78(5):1451-1456, 2010.

Broniscer A, Baker JN, Tagen M, Onar-Thomas A, Gilbertson RJ, Davidoff AM, Panandiker AP, Leung W, Chin TK, Stewart CF, Kocak M, Rowland C, Merchant TE, Kaste SC, Gajjar A. Phase I study of vandetanib during and after radiotherapy in children with diffuse intrinsic pontine glioma. J Clin Oncol 28(31):4762-4768, 2010.

Crom DB, Smith D, Xiong Z, Onar A, Hudson MM, Merchant TE, Morris EB. Health status in long-term survivors of pediatric craniopharyngiomas. J Neurosci Nurs 42(6):323-328, 2010.

Beltran C, Naik M, Merchant TE. Dosimetric effect of setup motion and target volume margin reduction in pediatric ependymoma. Radiother Oncol 96(2):216-22, 2010.

Di Pinto M, Conklin HM, Li C, Xiong X, Merchant TE. Investigating verbal and visual auditory learning after conformal radiation therapy for childhood ependymoma. Int J Radiat Oncol Biol Phys 77(4):1002-8, 2010.

Beltran C, Krasin MJ, Merchant TE. Inter- and intrafractional positional uncertainties in pediatric radiotherapy patients with brain and head and neck tumors. Int J Radiat Oncol Biol Phys Epub ahead of print, June 2010.

Beltran C, Trussell J, Merchant TE. Dosimetric impact of intrafractional patient motion in pediatric brain tumor patients. Med Dosim 35(1):43-8, 2010.

Kiehna EN, Merchant TE. Radiation therapy for pediatric craniopharyngioma. Neurosurg Focus 28(4):E10, 2010.

Pai Panandiker AS, McGregor L, Krasin MJ, Wu S, Xiong X, Merchant TE. Locoregional tumor progression after radiation therapy influences overall survival in pediatric patients with neuroblastoma. Int J Radiat Oncol Biol Phys 76(4):1161-5, 2010.

Mayo CS, Yorke ED, Merchant TE. Radiation-associated brainstem injury. Int J Radiat Oncol Biol Phys 76(Suppl 3):S36-41, March 2010.

Aquilina K, Merchant TE, Rodriguez-Galindo C, Ellison DW, Sanford RA, Boop FA. Malignant transformation of irradiated craniopharyngioma in children: report of two cases. J Neurosurg Pediatr 5(2):155-61, 2010.

Merchant TE, Chitti RM, Li C, Xiong X, Sanford RA, Khan RB. Factors associated with neurological recovery of brainstem function following post-operative conformal radiation therapy for infratentorial ependymoma. Int J Radiat Oncol Biol Phys 76(2):496-503, February 2010.

Merchant TE, Pollack IF, Loeffler JS. Brain tumors across the age spectrum: biology, therapy, and late effects. Semin Radiat Oncol 20(1):58-66, 2010.

Merchant TE. Three-dimensional conformal radiation therapy for ependymoma. Childs Nerv Syst25(10):1261-8, October 2009.

Sanford R, Merchant TE, Zwienenberg-Lee M, Kun LE, Boop FA. Advances in surgical techniques for resection of childhood cerebellopontine angle ependymomas are key to survival. Child Nerv Sys 25(10):1229-40, 2009.

Morris BE, Li C, Khan RB, Sanford RA, Boop F, Pinlac R, Xiong X, Merchant TE. Evolution of neurological impairment in pediatric infratentorial ependymoma patients. J Neurooncol 94(3):391-8, September 2009.

Merchant TE, Kun LE, Wu S, Xiong X, Sanford RA, Boop FA. Phase II trial of conformal radiation therapy for pediatric low-grade glioma. J Clin Oncol 27(22):3598-604, 2009.

Merchant TE, Conklin HM, Wu S, Lustig RH, Xiong X. Late effects of conformal radiation therapy for pediatric patients with low-grade glioma: prospective evaluation of cognitive, endocrine and hearing deficits. J Clin Oncol 27(22):3691-7, August 2009.

Merchant TE. Proton beam therapy in pediatric oncology. Cancer J 15(4):298-305, 2009.

Dolson E, Conklin H, Li C, Xiong X, Merchant TE. Predicting behavioral problems in craniopharyngioma survivors after conformal radiation. Pediatr Blood Cancer 52(7):860-4, 2009.

Wilson CM, Gaber MW, Sabek OM, Zawaski JA, Merchant TE. Radiation-induced astrogliosis and blood-brain barrier damage can be abrogated using anti-TNF treatment. Int J Radiat Oncol Biol Phys74(3):934-41, 2009.

Merchant TE, Li C, Xiong X, Gaber, MW. Cytokine and growth factor responses after radiation therapy for localized ependymoma. Int J Radiat Oncol Biol Phys 74(1):159-67, 2009.

Merchant TE, Li C, Xiong X, Kun LE, Boop FA, Sanford RA. Conformal radiation therapy for pediatric ependymoma. Lancet Oncol 10(3):258-66, 2009.

Last update: January 2016