Physics-based Therapies treatment methods do not involve direct contact with the tumor tissue. These therapies are usually derived of various types of radiation, including, but not limited to, radiation therapy and photodynamic therapy.
Photo Dynamic Therapy (PDT)
PDT is applied to treat extensive, superficial tumors. Its frequently used to treat actinic keratosis. PDT is typically administered in cases where tumors are difficult to access through surgery or in cases where surgical tumor removal would result in unwanted scaring or loss of function. PDT is administered in a targeted manner on the tumor tissue, leaving the surrounding healthy tissue untouched. The affected skin area is first relieved of scabs via the administration of curettage, followed by the application of a photosensitizing substance (e.g. 5-aminolevulinic acid-cream, like by Ameluz®) to the area. The applied substance acts to increase the light sensitivity of the skin, but in particular, it increases the light sensitivity of the tumor cells. After a few hours when the substance has completely settled, the skin area in question is irradiated with red cold light, whereby the skin tumor cells are destroyed specifically. During the radiation part of the procedure, some patients tend to feel slight pain. The results of the treatment, in terms of tumor removal, are comparable to those results achieved via cryotherapy. The wound, as it heals, can develop redness and moistening of the skin, followed by the formation of a scab. The cosmetic result of PDT therapy in comparison to cryotherapy, tends to be more favorable.
In general, radiation therapy may be used during all tumor stages. Gamma, x-ray or electron radiation is used when surgery is a less suitable option. Often, surgery is a less suitable option when tumors appear in unfavorable places, are extensive, or are infiltrative types of tumors, which permeate deeply and widely in the skin. Infiltrative tumors may or may not have an effect on bones.
Radiologically, the most frequently used radiation is weak radiation therapy, administered using x-rays. The radiation damages the tumor cells which eventually die off. The disadvantage of radiation therapies is that healthy tissue surrounding the tumor tissue may also be compromised. However, this healthy skin tissue may be able to resist higher radiation levels than cancer cells, due to physiological factors.
In order to administer the necessary dose of radiation without damaging the patient’s body, the radiation has to be administered during several sessions (up to 5 times in a week). Thus, it is possible that radiation therapy as a treatment option can take several weeks (4-7 weeks).
Brachytherapy with Enclosed Isotopes
Radioactive isotopes have for some time been used as a radiation source for skin cancer treatment. The most common isotopes used are gamma radiation (e.g. Iridium-192, Ir-192). These radiation sources are applied to the tumor tissue and then later removed. Due to both the proximity to the skin and properties of the radiation waves, the treatment successfully destroys the tumor cells.
To protect healthy skin tissue, as well the surrounding staff, these radioactive sources are enclosed and shielded, while only a small area of the skin is irradiated. These shielding mechanisms are called “applicators” and are often bell-shaped. This differs from a different type of brachytherapy, which uses open isotopes, in which a radioactive paste is applied directly over the tumor (click here for further information).
These therapies differ in whether they use Low-Dose-Rate (LDR) or High-Dose-Rate (HDR). The strength of the radioactive radiator deposits correlate with the dose rate (the damage). Thereby, a higher dose rate generates more damage to the skin and tumor tissue than a treatment with a lower rate.
Brachytherapy with Open Isotopes
This form of radiation therapy irradiates a skin area by applying the irradiation source directly over the tumor without coming in contact with the skin.
Brachytherapy with open isotopes applies the irradiation material via a paste near the tumor. Currently, the isotope rhenium (Re-188) is used.
Brachytherapy with open isotopes is suitable for the treatment of superficial tumors, as well as for treating nodular, infiltrated, ulcerated and recurrent tumors. This procedure can also be used to treat tumors that appear on difficult to treat parts of the body. Additionally, tumors that are large in area are good candidates for this treatment.
85-89% of the patients undergoing this treatment need only one application to achieve long-lasting results. Remission is achieved in 98% of the cases after 1 to 3 applications. Application of the therapy takes anywhere between a few minutes to 2 to 3 hours, with the average therapy time lasting 1 hour. The total time of treatment application depends on the size of the tumor.
This treatment is completely painless and without side effects. The irradiation has a therapeutic effect in the tissue to a depth of 2-3 mm. Because of the special form of irradiation (beta irradiation) that Rhenium-188 releases, the healthy tissue deeper than 2-3 mm stays completely intact and unharmed.
The healing process of this therapy takes between 60-180 days and delivers aesthetic results, with little or no cosmetic damage.
Here you can find detailed information about brachytherapy with open isotopes.