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Meet Our Physicians

At the Center for Cancer Care, a service of Gwinnett Medical Center, physician services are provided by the independent practitioners of Suburban Hematology-Oncology Associates, P.C.

We’d like to take this opportunity to introduce you to our doctors:

Dr. Alan FreedmanAllan Freedman, MD
Allan Freedman, MD, earned his medical degree from the University of Vermont and completed post-graduate training at Grady Memorial Hospital. He completed his fellowship in medical oncology and hematology at Emory University Hospital.

Dr. Freedman is board-certified in internal medicine and medical oncology. He is an active member of several professional medical organizations, including the American Society of Clinical Oncology and the Georgia Society of Clinical Oncology, and is a board member of the Georgia Cancer Pain Initiative.


Dr. Christopher HagenstadChristopher Hagenstad, MD
Christopher Hagenstad, MD, earned his medical degree from the Wake Forest University School of Medicine in Winston-Salem, North Carolina. After completing post-graduate training at the Medical College of Virginia, he returned to Wake Forest University and completed a fellowship in medical oncology.

Dr. Hagenstad is board-certified in internal medicine and medical oncology. He is an active member of several professional medical organizations, including the American Society of Clinical Oncology, the Georgia Society of Clinical Oncology and the Georgia Medical Society. Dr. Hagenstad serves as a member of the Cancer Committee at Gwinnett Medical Center.

Dr. Hagenstad is married and has three children. His hobbies include hiking, fly-fishing and golf.


Dr. KrischamacharyMohan Krishnamachary, MD
Mohan Krishnamachary, MD is a dedicated and enthusiastic medical professional that is a board certified Hematologist Oncologist. He joined Suburban Hematology-Oncology after gaining strong ties to the community while practicing in a private oncology practice in Athens Georgia. Dr. Krishnamachary is also board certified in Geriatric Medicine and Internal Medicine. He earned his medical degree from Kakatiya Medical College (India) in 1996, where he practiced as an Internist in private practice until 2001, before traveling to the United States. He completed his Internal Medicine fellowship at the University of Wisconsin in 2007 and later his Hematology-Oncology fellowship at the University of Kansas in 2011. He is an active member of the American Society of Clinical Oncology, American Society of Hematology, American Geriatrics Society and American Medical Association.

Dr. Krishnamachary is married and his wife, a physician herself practices as a Nephrologist. He has two children, a son and daughter. He loves wildlife and enjoys spending his time studying their ecology, especially bears and wolves as he has spent time studying their hibernation habits with scientists from the University of Wisconsin. He is a member of the Timber Wolf Information Network.


Dr. Aldemar Montero MDAldemar Montero, MD
Aldemar Montero, MD, joins Suburban Hematology-Oncology Associates after a four-year residency program in medical oncology and hematology at the National Cancer Institute. He also completed his internship and residency at the University of Connecticut.

He has been published in various leading medical journals. We are excited to have him join our practice and help continue to grow our clinical trials program. He is board-certified in internal medicine, medical oncology and hematology.

Dr. Montero is married with two children. He enjoys playing soccer as well as the violin.


Dr. Kevin PeacockKevin H. Peacock, MD
Medical Director, Gwinnett Breast Program


Kevin H. Peacock, MD, earned his medical degree from the Medical College of Virginia. After completing his medical residency, he did his fellowship in hematology oncology at the Wake Forest University School of Medicine. He stayed on as faculty at Wake Forest for three years following his residency.

Dr. Peacock is board-certified in internal medicine, hematology and medical oncology. He is an active member of both the American Society of Hematology and American Society of Clinical Oncology. Dr. Peacock served as a member of the Wake Forest Hematology/Oncology Fellowship committee for more than two years and previously held the position of Cancer Committee chairman of Rockdale Medical Center.

Dr. Peacock is married and has two children. His hobbies include golf, running and soccer.


Dr. Alexander Saker, Jr.Alexander Saker, Jr., MD
Medical Director, Center for Cancer Care

Alexander Saker, Jr., MD, earned his medical degree from the Medical College of Georgia and completed post-graduate training at the University of South Florida. He completed his fellowship in medical oncology and hematology at the University of South Florida at H. Lee Moffitt Cancer Center and Research Institute as well as Emory University.

Dr. Saker is board-certified in internal medicine, medical oncology and hematology. He is an active member of several professional medical organizations, including the American Society of Clinical Oncology, the Georgia Medical Society and the American College of Physicians.

Dr. Saker serves as a member of the Cancer Committee and Blood Utilization Committee at Gwinnett Medical Center. Dr. Saker is married and has three children. He enjoys gardening and softball.


Dr. P. Ravi SarmaP. Ravi Sarma, MD
P. Ravi Sarma, MD, earned his medical degree from Andhra Medical College (India). He completed post-graduate training in Internal Medicine at Cook County Hospital. He completed his fellowship training in hematology and medical oncology at Emory University Hospitals and University of Illinois Hospitals.

Dr. Sarma is board-certified in internal medicine, hematology, medical oncology and geriatric medicine. He is an active member of several professional medical organizations, including the American Society of Clinical Oncology, the Dekalb Medical Center Cancer Committee and the Transfusion Committee at Eastside Medical Center. Dr. Sarma is a founding member of the Georgia Society of Clinical Oncology and a fellow of the American College of Physicians.

Dr. Sarma served as an associate professor of medicine in the Department of Hematology-Oncology at the Emory University School of Medicine until 1995.

Dr. Sarma is married with three children.


Sativr Singh, MDSativr Singh, MD
Sativr Singh, MD, performed a three-year fellowship at East Carolina University. Prior to his fellowship, Dr. Singh was a specialist in internal medicine at Pitt County Memorial Hospital. He also served as the chief of the Department of Internal Medicine at Sampson Regional Medical Center.

Currently, Dr. Singh is board-certified in internal medicine, medical oncology and hematology, and has twice won awards as an outstanding physician in patient satisfaction.

Dr. Singh is married and has two children.


Praveen Sivakumaran, MD

Praveen Sivakumaran, MDDr. Sivakumaran received his medical degree from the Wayne State University School of Medicine in Detroit, Michigan. After medical school, he continued his medical education at Wayne State where he completed his residency in internal medicine.   He then did a fellowship in Transfusion Medicine at Cedars-Sinai Medical Center (Los Angeles, California) before returning to the east coast to complete his fellowship in hematology-oncology at Georgetown University/Medstar Washington Hospital Center in our nation’s capital.

Dr. Sivakumaran is board-certified in hematology and oncology, as well as internal medicine. He is well-versed in treating all types of malignancies and has presented at numerous conferences, including the annual ASCO (American Society of Clinical Oncology) meeting in Chicago, Illinois. He is married and has deep roots in the south, growing up in nearby Florida. His hobbies include basketball and running.


Deb Miller, MD

Deb Miller, MDDr. Miller received her medical degree at the Bowman-Gray School of Medicine at Wake Forrest University.  After medical school, she completed both her residency and fellowship at Vanderbilt University.  She has 21 years of oncology experience and has been with Gwinnett Medical since 2016.  Dr. Miller enjoys spending time with her family, exercising, dancing and cooking. She has a true passion for patient care, the community, and inspiring others.


I-Wen Chang, MD

I-Wen Chang, MD has been in private practice for 10 years in eastern North Carolina prior to joining Suburban Hematology Oncology Associates in 2018. She was also an assistant professor of Internal Medicine at Campbell University Jerry M. Wallace School  of Osteopathic Medicine. 

Dr. Chang earned her medical degree from Wake Forest University School of Medicine in Winston-Salem, North Carolina in 2001. She completed internal medicine residency and then hematology and oncology fellowship at Wake Forest University in 2007. Dr. Chang is board-certified in hematology and medical oncology.

Dr. Chang is a strong believer in clinical trials for cancer treatment. She has earned several awards for clinical trial accrual through NCI Community Oncology Research Program. In addition to general oncology, she has a special interest in lung and breast cancers as well as palliative care with emphasis on symptom management and maintaining quality of life. Dr. Chang is married and has two daughters. She enjoys spending time with her family and hiking.

Languages spoken include English, Mandarin Chinese and Taiwanese.