Basal Cell Carcinoma (BCC) is the most frequently diagnosed type of skin cancer, arising from the basal cells of the epidermis. While surgery remains common, radiation therapy is a highly effective, non-surgical option often chosen for tumors in cosmetically sensitive areas or for patients who are not surgical candidates. Treatment involves delivering a specific total dose of radiation, which is divided into multiple smaller exposures. This process, known as fractionation, forms the basis of the treatment schedule and determines the final number of sessions a patient will undergo.
The Biological Basis for Fractionation
Fractionation, the strategy of dividing the total radiation dose into smaller daily sessions, is a medical necessity rooted in radiobiology. This approach exploits the biological differences between rapidly dividing cancer cells and slower-dividing healthy tissue. The goal is to maximize the lethal effect on the tumor while minimizing damage to the surrounding normal skin and underlying structures.
Fractionation allows healthy cells time to repair the sublethal damage to their DNA that occurs after each exposure. Normal cells have a greater capacity for this repair than most cancer cells. This “Repair” mechanism is important for protecting tissues that respond slowly to radiation, such as connective tissue and blood vessels near the tumor.
Fractionation also leverages the “Reoxygenation” of the tumor. Cancer cells deep within a tumor are often oxygen-starved (hypoxic), making them less sensitive to radiation. By waiting between doses, blood vessels can temporarily re-establish better oxygen flow, making surviving cancer cells more vulnerable to the next treatment. This differential sensitivity ensures the radiation is most effective at destroying the tumor over time.
Typical Ranges and Treatment Schedules
The number of treatments for basal cell carcinoma varies widely, ranging from as few as four up to 35 sessions, depending on the chosen schedule. Oncologists tailor the treatment based on the specific characteristics of the tumor and the patient’s needs.
Hypofractionated Radiation Therapy
This short course schedule typically involves 4 to 10 treatments. A higher dose of radiation is delivered during each session, shortening the overall treatment duration to about one to two weeks. Common schedules include delivering 35 Gray (Gy) in 5 fractions, or 36.75 Gy in 7 fractions. This approach is frequently used for smaller, more superficial, and less aggressive lesions, offering greater patient convenience.
Conventional Fractionation
This long course schedule involves a greater number of sessions, typically ranging from 20 to 35 treatments. These sessions use a lower daily dose of radiation, often 2 Gy per day, extending the treatment duration over four to seven weeks. A common example is 50 Gy delivered over 25 fractions. This protracted schedule is preferred for larger tumors, those located near sensitive structures, or when aiming for the best long-term cosmetic outcome.
Variables That Determine the Final Number of Sessions
The choice between a short- or long-course schedule is determined by evaluating several medical and anatomical factors. These variables dictate the required total radiation dose and the size of the individual daily dose, which sets the final number of sessions. The fundamental consideration is balancing the need to destroy the cancer completely with the need to protect the surrounding healthy tissue.
Tumor characteristics, including size and depth, are primary factors. Larger or deeper basal cell carcinomas generally require a more protracted schedule with a greater number of fractions to ensure the entire tumor volume receives a sufficient dose while sparing underlying structures. Smaller, more superficial lesions are often well-suited for the shorter, hypofractionated course.
The anatomical location is another major determinant. Lesions near highly sensitive structures, such as the eyes, nose, lips, or ears, often necessitate the conventional, longer course (25 to 35 fractions). This approach uses a smaller daily dose, which is less damaging to adjacent healthy tissues, promoting better cosmetic and functional results. Patient factors, including age and overall health, also play a role, as a shorter course may be preferred for older or frail patients.
The Patient Timeline During Radiation Therapy
Once a schedule is selected, the patient’s timeline involves routine, brief hospital visits, typically scheduled five days a week (Monday through Friday). Each individual radiation session is non-invasive and painless, often lasting only a few minutes once the patient is positioned. The majority of the appointment time is spent on setup and ensuring perfect alignment with the treatment machine.
For a patient on a short course of five treatments, the total time commitment is usually one week. A hypofractionated regimen of 10 treatments is completed in approximately two weeks. Patients receiving a conventional long course of 30 treatments should expect the full commitment to span six weeks. The weekend break between treatment weeks is intentional, allowing normal, healthy cells time to repair and recover before the next sessions begin.