Skip to main content
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

Acharya S, Quesada S, Coca K, Richardson C, Hoehn ME, Chiang J, Qaddoumi I, Boop FA, Gajjar A, Merchant TE. Long-term visual acuity outcomes after radiation therapy for sporadic optic pathway glioma. J Neurooncol Aug 14, 2019. doi:10.1007/s11060-019-03264-2. [Epub ahead of print] PubMed PMID: 31414376.

van Iersel L, Xu J, Potter B, Conklin HM, Zhang H, Chemaitilly W, van Santen HM, Merchant TE. Clinical Importance of Free Thyroxine Concentration Decline after Radiotherapy for Pediatric and Adolescent Brain Tumors. J Clin Endocrinol Metab Jun 7. pii: jc.2019-00539, 2019. doi: 10.1210/jc.2019-00539. [Epub ahead of print] PubMed PMID: 31173083.

Conklin HM, Ness KK, Ashford JM, Scoggins MA, Ogg RJ, Han Y, Li Y, Bradley JA, Boop FA, Merchant TE. Cognitive Performance, Aerobic Fitness, Motor Proficiency, and Brain Function Among Children Newly Diagnosed With Craniopharyngioma. J Int Neuropsychol Soc Apr;25(4):413-425, 2019. doi: 10.1017/S1355617718001170. PubMed PMID: 31050329; PubMed Central PMCID: PMC6499492.

Acharya S, Wu S, Ashford JM, Tinkle CL, Lucas JT, Qaddoumi I, Gajjar A, Krasin MJ, Conklin HM, Merchant TE. Association between hippocampal dose and memory in survivors of childhood or adolescent low-grade glioma: a 10-year neurocognitive longitudinal study. Neuro Oncol Apr 12. pii: noz068, 2019. doi: 10.1093/neuonc/noz068. [Epub ahead of print] PubMed PMID: 30977510.

Merchant TE, Bendel AE, Sabin ND, Burger PC, Shaw DW, Chang E, Wu S, Zhou T, Eisenstat DD, Foreman NK, Fuller CE, Anderson ET, Hukin J, Lau CC, Pollack IF, Laningham FH, Lustig RH, Armstrong FD, Handler MH, Williams-Hughes C, Kessel S, Kocak M, Ellison DW, Ramaswamy V. Conformal Radiation Therapy for Pediatric Ependymoma, Chemotherapy for Incompletely Resected Ependymoma, and Observation for Completely Resected, Supratentorial Ependymoma. J Clin Oncol Apr 20;37(12):974-983, 2019. doi: 10.1200/JCO.18.01765. Epub Feb 27, 2019. PubMed PMID: 30811284.

Cherlow JM, Shaw DWW, Margraf LR, Bowers DC, Huang J, Fouladi M, Onar-Thomas A, Zhou T, Pollack IF, Gajjar A, Kessel SK, Cullen PL, McMullen K, Wellons JC, Merchant TE. Conformal Radiation Therapy for Pediatric Patients with Low-Grade Glioma: Results from the Children's Oncology Group Phase 2 Study ACNS0221. Int J Radiat Oncol Biol Phys Mar 15;103(4):861-868, 2019. doi:10.1016/j.ijrobp.2018.11.004. Epub Nov 10, 2018. PubMed PMID: 30419305; PubMed Central PMCID: PMC6548322.


Last update: September 2019