When a patient starts radiation therapy for breast cancer, she meets with her radiation oncologist and interacts daily with radiation therapists. There is also another vital professional working behind the scenes to ensure their safety and treatment success is the dosimetrist.
“We’re kind of the middleman of the radiation oncology departments,” explains Lori Malenfant, a CAMP dosimetrist with years of experience in the field. “We work with the doctor to understand what their wishes are for each patient, and then we create a plan to make sure the doses are adequate and safe to deliver.”
The Art and Science of Treatment Planning
Dosimetry is where precision medicine meets creative problem-solving. After a patient receives their breast cancer diagnosis and decides on radiation therapy with their oncologist, they come in for a CT scan in a treatment position. From there, the dosimetrist’s work begins.
“The doctor will draw a volume that he wants to treat with a prescription dose,” Lori describes. “Then dosimetrists come up with the best way to treat this patient.”
That “best way” involves meticulous planning and customization. Using the CT scan, dosimetrists contour every organ that radiation could interact with, including the lungs, heart, thyroid, esophagus, and brachial plexus, mapping them slice by slice to track precisely how much radiation each area receives.
Protecting What Matters
For breast cancer patients, particularly those with left-sided tumors, protecting the heart and lungs is paramount. Lori employs several innovative techniques to achieve this, including:
Deep Inspiration Breath Hold (DIBH): Patients who can hold their breath for about 30 seconds during treatment may do this two or three times per session. “The point of that is it will push the heart down and inflate the lung,” Lori explains. “So we’re getting less dose to those normal tissues while still being able to get maximum dose to the breast volume.”
Prone Positioning: Some patients are treated lying on their stomachs, allowing gravity to pull the breast away from the chest wall. “That also reduces heart or lung dose. Gravity works!” she notes.
Angled Fields: Rather than directing radiation straight from the front, which would send high doses through the lung and heart, dosimetrists design angled beams that skim across the top of the lung, minimizing exposure to healthy tissue.
IMRT: Breast or chest-wall treatments with complex anatomy, large breast size, or regional nodal targets may make it difficult to achieve uniform target coverage and normal tissue sparing with 3D conformal techniques. IMRT allows improved dose homogeneity and reduced heart, lung, and contralateral breast exposure, particularly for left-sided, post-mastectomy, or nodal irradiation cases.
Each approach is tailored to the individual. “Every patient is different because body habitus and body shapes vary,” Lori emphasizes. “So every plan is different and customized for the patient specifically.”
The Journey to Dosimetry
Lori’s path to this specialized role reflects a deepening connection with patient care. She started in diagnostic X-ray, where she enjoyed the work but found something missing. “You have a patient, they come in, you see them, you do their exam, and then you never hear what happened to them,” she recalls.
Moving to radiation therapy changed that. Suddenly, she saw patients daily, got to know them, watched them complete treatment, and return for follow-ups. “It’s like you’re all part of a family together,” she says. “You really get to know the person.”
This personal touch and following the patient’s story through were critical for Lori’s transition to dosimetry. As a dosimetrist, while she may not see patients every day, she remains deeply involved in their care, creating the individualized plans that will guide their entire treatment journey.
Safety Through Teamwork
One message Lori wants every patient to know: “When they come, they’re not a number. Everyone gets individual attention, and their plan is customized specifically for them. There is no cookie-cutter in this world.”
The checks and balances in radiation oncology are extensive. Dosimetrists create the plan, physicians review and approve it, physicists verify it’s deliverable, and multiple reviews occur before a single treatment is given.
“It takes a whole team,” Lori stresses. “We would not treat someone if there’s any doubt about being safe.”
Looking Ahead
As technology continues to advance and treatment techniques evolve, continuing education remains essential in the field.
“This field is always changing, and there’s always new treatment or papers or studies being presented to help with better treatment for patients,” Lori notes.
Additionally, autocontouring and AI are developing tools that are streamlining treatment planning by rapidly generating accurate organ and target contours, reducing the manual workload and variability among planners. These tools also accelerate plan optimization and consistency, allowing dosimetrists to focus more on plan quality, with the understanding that all autocontours are reviewed for accuracy.
Her advice for prevention remains straightforward: “Self-checks and screening are definitely important to catch tumors early.”
This is especially important since one in eight women will have breast cancer. Another fact worth knowing: while extremely rare, men can also develop breast cancer.
“It’s not too common at all, but it can happen,” Lori points out. “So men need to do self-exams now and then too.”
The Human Element
“I imagine it’s very hard for patients to come in and have trust in people that they don’t know,” she acknowledges. Knowing that a dedicated team is checking, rechecking, and customizing every aspect of their care, with their best interests at heart, can make the journey a little less daunting.
Behind every radiation treatment is a dosimetrist like Lori, ensuring that each plan delivers the maximum benefit with the minimum risk, one carefully crafted beam at a time.
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