Stomach cancer, or gastric cancer, is a disease where malignant cells form in the lining of the stomach. Treatment often requires a multi-pronged approach, and radiation therapy is one modality used to target these cells with high-energy beams. This treatment is localized, focusing energy directly on the tumor site and nearby lymph nodes. Radiation works by damaging the cancer cells’ DNA, preventing them from growing and dividing, ultimately leading to their destruction.
Planning the Treatment Course
Before the first radiation dose is delivered, a comprehensive preparation phase known as simulation must be completed. This process maps the exact location of the stomach tumor and the surrounding healthy organs that must be protected. A patient undergoes an imaging scan, typically a specialized computed tomography (CT) or magnetic resonance imaging (MRI) scan, while lying in the treatment position.
During simulation, the clinical team creates custom immobilization devices, such as body molds or casts, to ensure the patient is in the exact same position for every daily treatment. This precision is important because the stomach can shift slightly due to breathing and digestion. Following the simulation, medical physicists and dosimetrists use the scan data to perform detailed calculations of the radiation dose, a process called dosimetry. This planning phase ensures the maximum prescribed dose is delivered to the cancer while sparing nearby tissues, and it can take anywhere from a few days up to three weeks before the first session begins.
Determining the Overall Treatment Timeline
The total length of the radiation course for stomach cancer varies significantly depending on the goal of the treatment. For curative-intent therapy, the radiation is typically delivered in small daily doses called fractions. This approach is usually given five days a week and spans a duration of approximately five to six weeks. The weekends off are deliberately included, allowing healthy cells in the area time to repair themselves from the small daily radiation exposure.
In contrast, when the cancer is advanced, radiation may be used for symptom relief, such as reducing pain or stopping bleeding, which is called palliative treatment. Palliative courses are much shorter, often involving only a few treatments over one or two weeks, as the total required dose is much lower.
What Happens During a Daily Session
While the overall course lasts for many weeks, the time a patient spends receiving the actual radiation beam each day is brief. A typical daily appointment may take between 10 to 30 minutes from the moment the patient enters the treatment room until they leave. The majority of this time is dedicated to ensuring the patient is perfectly positioned on the treatment couch.
Radiation therapists use the markings from the planning session and special verification imaging, like a cone-beam CT scan, performed immediately before the treatment to confirm the tumor’s exact location. The linear accelerator, the machine that delivers the radiation, then moves around the patient to deliver the dose from multiple angles. The actual emission of the radiation beam often lasts just a few minutes, and the patient will not feel anything during this time.
Chemoradiation and Its Impact on Treatment Duration
Radiation therapy for stomach cancer is rarely given alone and is almost always administered alongside chemotherapy, a combined approach called chemoradiation. Chemotherapy drugs, such as fluorouracil, act as radiosensitizers, meaning they make the cancer cells more vulnerable to the effects of the radiation. While the radiation component itself is confined to the five to six-week period, the chemotherapy schedule often dictates the flow of the entire process. The full sequence of care, including chemotherapy cycles that may occur before, during, and after the radiation, can extend the active treatment phase to several months.