SRT: Not a One-Size-Fits-All
Last updated: April 2021
Superficial radiation therapy (SRT) for non-melanoma skin cancers is not a one-size-fits-all treatment. Each patient and each skin cancer are different and require an individualized approach. There is a lot of planning that goes into designing the perfect radiation prescription.
Superficial radiation therapy considerations
As you can imagine, we have to consider what type of skin cancer we are treating. Basal and squamous cell carcinomas are currently the only types of skin cancers approved for treatment using superficial radiation. It doesn’t just stop there. There are sub-categories for these carcinomas, and we have to take into account those characteristics. They can be in situ, mixed, nodular, or of the keratoacanthoma type. These traits influence the amount of energy we will use.
Taking depth and thickness into account
If a lesion grows upward from the skin’s surface, it may require debulking to ensure the radiation can get through the entire tumor. A general rule is the thicker or deeper the skin cancer is, the treatment will need more energy to penetrate it.
Size is a crucial factor
The treatment needs to include the skin cancer and a margin around it to ensure all of the cancerous cells are destroyed. The larger the skin cancer is, the higher the risk of recurrence. A larger area may face more challenges through treatment, possibly requiring breaks in treatment. A delay in treatment will, in turn, require additional treatments and a larger overall dose of radiation.
Location, location, location
Different areas of the body can handle radiation better than others, making the location of the skin cancer one of the essential variables in the treatment. We need to take into consideration what kind of skin we are treating. We evaluate the skin’s thickness, the circulation to the tissue, the underlying tissue, and important structures nearby.
Skin texture and circulation
In these areas, there are so many oil glands, and the circulation to this tissue is excellent. Most noses can take radiation treatments with ease; the fractionation, or how often we treat the area, can be reasonably close together. This can call faster treatment courses with overall lower doses of radiation.
Concerns for healing
When it comes to lower extremities like the shin and ankle, we start to see more inadequate circulation, which is a concern for healing. The lower extremities are also in danger of bumping and bruising. Injuries can cause too much damage at once. These areas require a more conservative approach; we may treat these on a more spaced-out schedule that will require more treatments or larger doses.
Recurring cancers may be treated differently
If the skin cancer is a recurrence, more aggressive treatment is typically needed. Skin cancer that was previously removed via surgery may be treated with radiation. An approach that considers the resilience of skin cancer and the damage caused by previous treatment is a balancing act. If the skin cancer was previously treated by radiation and is a recurrence, most signs will point to using a different technique and not irradiation the same area again. Of course, this is on a case-to-case basis and will vary by patient and physician.
Overall we have to consider the patient’s status as a whole. Is the patient on blood thinners, immunosuppressants, problems with blood pressure, advanced age, disabilities that will affect caring for themself, diabetes, or cardiovascular disease? These do not disqualify anyone from receiving radiation therapy. We need to keep these comorbidities in mind when determining if the prescription to eliminate cancer will be right for the patient.
Making adjustments and modifications
Each one of these factors holds weight when creating a treatment plan. After a plan is finalized and treatment is begun, it still is not set in stone. We can always modify the prescription as we see how the patient and the skin cancer respond. If we notice the patient has an intense reaction, we can back off and move to a more conservative approach. If the opposite occurs, and we see the skin cancer is not responding, we can re-evaluate and opt for a more aggressive strategy.
It's all in the details
Each radiation prescription is planned with the patient in mind. It is never a one-size-fits-all approach. Every detail matters!
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