SRT: Superficial Radiation Therapy

What is SRT?

  • SRT uses low energies and doses of radiation to treat Squamous Cell Cancer and Basal Cell Cancer just below the skin surface.
  • Due to the low energies (kilovoltage), skin reactions are typically mild and very small.
  • Radiation is site-specific.
  • There is no scarring, cutting, pain, or downtime and the treatments are approximately 15 minutes.  
  • Traditional radiation is the opposite, in which it delivers massive amounts of energy (megavoltage) that penetrate deep into the body which can cause more skin reactions.

What Skin Cancer Treatment Is Right For You?

Candidates of SRT?

  • Does not want surgery.
  • Poor surgical candidate.
  • Wants to stay active/no downtime.
  • Has sun damaged skin/poor circulation.
  • Has a comorbid diagnosis or medication.
  • Reduced functional status/advanced age/frail.
  • Anatomic site impacts mobility/function.
  • Has NMSC of low metastatic potential.

SRT Treatment Protocols

  • cGy stands for Centigray-a unit of measurement that stands for how much radiation is being absorbed by the skin.
  • Common:
    3 days a week for a total of 20 treatments
    260 cGy per treatment.
  • 4 days a week for a total of 20 treatments
    255 cGy per treatment.
    Recommended for tumors larger than 2 cm.
  • 2 days a week for a total of 13 treatments
    380 cGy per treatment.
    Use only if travel challenged (ex: longer distance or in nursing home).
  • Keloids
    3 total treatments at 600 cGy per treatment.
    Patient will need to be treated same day or day after surgery for best results to ensure no regrowth.

Why Do I Need 20 SRT Treatments?

20 treatments are usually necessary because the treatments are Smaller doses, Spread out over time, Allows repair, Allows reassortment, Allows reoxygenation and Allows cellular repopulation.


The first day the patient will come into the treatment room. Consent form is signed agreeing to treatments. Skin care will be discussed. Treatments will be scheduled. Dr. Musick will come into room to review clinical photos and pathology.  He will then outline the clinical lesion including the margin around it. Pictures will then be taken of area marked. Ultrasound will be obtained to get a baseline depth of the lesion to determine the treatment energy. Most simulation days take approximately 30-45 minutes.

Skin Care

Simulation of a Basal Cell Cancer of the left lateral calf

Lesions Deeper Than 2.5mm Need To Be Debulked For Ultrasound.  WD SCC of The Right Lateral Forehead

The SRT-100™ offers a wide range of treatment applicators.
Skin Cancer Applicator Set – 1.5 cm, 2 cm, 2.5 cm, 3 cm, 4 cm, 5 cm diameter at 15 cm SSD
Keloids Applicator Set – 7.3 cm diameter at 15 cm SSD & 10 cm, 12.7 cm diameter at 25 cm SSD, 18×8 at 30cm SSD
Safety Block — Safety X-Ray Port Block
Ease of use — Turn & Lock
Automatic Applicator Sensing and Display




  • Ultrasounds are taken daily to measure the depth of the lesion
  • At first ultrasounds will be close to the same depth until about halfway when skin is inflamed due to radiation.
  • Inflammation will cause the depth of the ultrasound to increase, this is not due to the lesion growing larger
  • Once swelling decreases, around treatment 15, the depth measurement will decrease


Depth on sim day of 2.24mm                                      Depth after 10th treatment of 2.09mm

*Note the black area showing the cancerous tissue. The next US shows the black area decreasing in size and the healthy tissue denoted by the green, yellow, red areas*

Treatment Energy

  • Lesions measuring <1.5 mm treated at 50kV
    50 kV results in penetration at about 3 mm into the tissue.
  • Lesions measuring 1.5- 2.5 mm usually treated at 70 kV.
    70 kV results in penetration at about 4-7 mm into the tissue.
  • Lesions measuring 2.5 mm need to be debulked before treatment.
  • Maximum width- lesion plus margin must be below 10 cm. because the largest applicator is only 10cm.
  • All energies used are less than getting a chest x-ray.


  • Patient is seen 2, 3, or 4 days a week for approximately 15 minutes per lesion.
  • The 15 minutes accounts for set up plus treatment time.
  • Radiation is typically administered in approximately 32-45 seconds depending on dose and energy.
  • Each day an ultrasound will be done to obtain depth of lesion.
  • Shields for concavities, thyroid, eyes, gums, nasal mucosa, cornea, mastoid, and hair bearing areas will be worn to protect the low dose tolerance areas.
  • Treatment itself is painless in which the patient will not see or feel anything during their daily treatment.
  • After every 5th treatment, Dr. Musick will check in with the patient on in the treatment room with any concerns regarding SRT and view the treatment area to check side effects.

Follow Up And Results


  • 2 weeks following the last treatment the patient will come in to the SRT room for a final ultrasound.  This depth measurements will be highly decreased when compared to the simulation day.
  • Dr. Musick will see the patient for a skin check of the treatment area and to answer any patient questions.
  • Even though treatments are complete radiation will continue working for up to four weeks after the patient’s last day.  


  • SRT offers 95% or greater cure rate of BCC and SCC.
  • If the patient experiences a reoccurrence in the same area,  they may not be treated with radiation again.

Why Choose SRT?

  • Same cure rate a Mohs
  • No Downtime
  • No Scarring
  • No Cutting
  • In the hands of a board certified Radiation Therapist
  • Great for areas that do not heal well

I have confidence that this modality will give the patient wonderful results.   

Cost of SRT

Patients generally have some out of pocket cost based on coverage and deductibles. The amounts can vary from very little to several thousand dollars based on the patient’s insurance plan. Commercial insurance generally associated with a deductible and varies greatly. Medicare usually when accompanied with secondary insurance often costs nothing for treatment. If a patient is in question, I can email my SkinCure billing specialist and obtain an estimated out of pocket cost for the patient.

Side Effects

  • Erythema
  • Edema
  • Crusting
  • Ulceration
  • Pruritis
  • Hair loss- Only in the area being treated
  • Hypopigmentation or Hyperpigmentation

Schedule a Consultation

To learn more about SRT, contact Musick Dermatology & Advanced Clinical Spa in Swansea, IL today at (618) 628-2588 to make an appointment,

Musick Dermatology & Advanced Clinical Spa

Monday-Friday 8:00 am- 4:00 pm