Collaborating with Confidence by Dr. Jared R. Robbins, Dr. J. Brett Mangum and Riley M. Goldsmith

Keys for improving communication between dentists and radiation oncologists

by Dr. Jared R. Robbins, Dr. J. Brett Mangum and Riley Goldsmith

• A pre-radiation exam showed a periapical lesion on tooth #14 at the mesial-buccal root with a “hopeless” long-term prognosis (Fig. 1).
• The periapical radiograph of #14 and a panoramic radiograph would be sent to the radiation oncologist to determine whether the oncologist wanted the dentist to remove the tooth. No further communication was received, and the tooth was not extracted. The patient wanted to save the tooth.
• The chart notes that radiation treatment would likely start in a week.
• The patient presented 1.5 months later with pain and radiation-induced mucositis. Magic mouthwash, Hurricaine spray, and prescription-strength fluoridated toothpaste were recommended. The need to extract tooth #14 was mentioned in the chart, and grade II mobility, recession and furcation involvement were noted during every follow-up care visit, every four months, for one year after radiation. A referral was made to a periodontist for treatment of tooth #14.
• One year after the completion of RT and in conjunction with the advice of the community radiation oncologist, but with no actual reference to the radiation plan, the patient had hyperbaric oxygen therapy (HBO) followed by extraction of tooth #14 and bone graft. After healing, an implant was placed.

Fig.1: Pre-radiation panoramic radiograph, showing a periapical lesion on tooth #14 at the mesial-buccal root with a “hopeless” long-term prognosis.

• Grey is the unit of measure that is used in modern times to denote the amount of radiation that is given.
• 3D conformal is the old technique of radiation delivery which is less conformal than modern techniques; in turn, delivering more radiation to surrounding healthy tissues. This would be considered archaic for most radiation treatment plans today with limited exceptions. This is what was typically thought of as treatment fields.
• Intensity-modulated radiation therapy (IMRT) is a complex radiation technique that limits high doses to surrounding structures through innovative technological advances that utilize complex beam arrangements and automated modulation techniques. (Volumetric arch therapy (VMAT), rapid arc and tomotherapy are newer variations of IMRT.) This technique uses photons/X-rays to target the cancer cells. This is currently the standard of care at most radiation centers. It focuses on treatment volumes and limiting doses to normal structures.
• Intensity-modulated proton therapy (IMPT), or proton therapy, limits exit dose past the target of interest, which spares normal tissue. This is accomplished by using proton (positively charged) rather than photon/X-ray energy sources. This is a newer and much more expensive therapy that is only available at 45 centers in the U.S. Early studies suggest it may help reduce radiation toxicity for HN patients.
• Isodose lines refer to lines used to delineate the dose of radiation to specific locations. They are typically generated by overlaying the radiation treatment plan over a CT scan of the patient. It is viewed like a topographical map with various lines or colors reflecting the dose to that area. These help the RO ensure the tumor coverage and sparing of normal structures (Fig. 2).
• Dose-volume histograms are graphical depictions of what volume of the tumor/target or normal structures receive a specific radiation dose. Through rigorous studies, various doses to specific volumes are associated with a specific outcome. For example, the volume of the mandible that received more than 60 Gy correlates with the risk of osteoradionecrosis, so the radiation oncologist will use metrics, such as less than 15% of the mandible should receive 60 Gy, to try to limit the risks to the patient. These are part of the medical chart and can be reviewed to evaluate the dose to various structures related to dental management and the associated risks (Fig. 2).
• Fraction, in general, refers to the number of treatments for each radiation plan. Thirty fractions means that the patient will come 30 times to the office to receive radiation.

Fig. 2: Dose volume histogram (left) depicts each target/organ-at-risk based on the volume that receives a specific dose. Isodose lines (right) delineates the dose to various anatomic structures using lines to depict the dose overlaid on a CT scan.

Fig. 3: Fields vs volumes: Treatment plans for T2N1 tonsil squamous cell carcinoma. 2D radiation fields (left) 2D field based on plain film imaging and bony anatomy. The initial field is blocked out in yellow, with subsequent shrinking fields of orange and then red as a final boost. Minimal critical structures were spared. IMRT plan (right) shows the delineated tumor volumes covered conformally with high-dose radiation and risk-based coverage of at-risk lymph nodes with sparing of normal organs.

Fig. 4: All radiation plans are unique to the patient’s disease and have varying degrees of risk of toxicity to normal structures based on the treated volume. The early larynx and advanced skin cancer cases have almost no risk of dental complication as the sites of disease are far from nearby organs at risk. However, the two tonsil cases have dramatically different toxicity profiles, despite their shared primary anatomic location because of the differing tumor extent, lymph node involvement, and the treatment volume.

Jared R. Robbins, MD is a radiation oncologist specializing in treating head and neck cancer. He works at Duke University in Durham, NC. He enjoys caring for patients, teaching students and residents, doing research, and collaborating with dentists to improve oral health in cancer patients.



Riley Goldsmith is a fourth year medical student from the University of Arizona College of Medicine-Tucson applying to Radiation Oncology. She graduated from the University of Arizona with a B.S. in physiology and a minor in biochemistry and Spanish. She is the first author of three published manuscripts.





J. Brett Mangum, DDS, practices dentistry in Prescott, Arizona. He earned his dental degree from the University of Michigan, completed an AEGD program, and served in the Navy. He is a fellow of the Academy of General Dentistry and has lectured on dental ethics and oral cancer alongside Robbins.