Skin Cancer

Photodynamic therapy (PDT)

About Photodynamic therapy

Photodynamic therapy is a safe and effective non-surgical treatment for certain skin lesions. These range from precancerous lesions such as actinic keratosis (sun spots) to low risk skins cancers such as superficial basal cell carcinoma and intraepidermal carcinoma.

PDT utilizes a combination of photosensitizing medication, oxygen and light to produce a photochemical reaction. This combined reaction can selectively destroy cancerous cells while minimizing injury to normal skin cells.

The main advantage of PDT is that it can eradicate the cancerous cell while achieving excellent cosmetic results. This prevents the formation of surgical scars, which are usually inevitable from surgery. This also reduces exposure of you to surgical complications such as infections, wound dehiscence, prolonged discomfort and sensory changes.

Photodynamic therapy
PDT

PDT treatment is a single day procedure. It involves the following steps:

  • A 10-minute session where light-activated cream (Metvix or ALA) is applied to the identified site. Following this, a skin coloured dressing is applied to the area.
  • A 3 hour waiting period (minimum) is required for the light-activated cream to be absorbed. You are free to leave the room but the dressing must remain intact. Nursing staff may offer you paracetamol before starting the illuminating session.
  • Once you have returned to the room, the light-activated cream will be cleaned off. Following this, the area of the skin will be illuminated with a red light. This treatment period usually last about 9 minutes.
  • Subsequent cycle of PDT is dependent on the diagnosis. If treating precancerous lesions such as actinic keratosis/ sunspots, only one cycle is required usually. If treating low-grade skin cancers such as superficial basal cell carcinomas or intraepidermal carcinoma, you may be asked to return in 2 weeks for another cycle of treatment.

Metvix® PDF treatment procedure

After Care
PDT is a safe treatment with minimal after care. Simple analgesia such as paracetamol may be used to help with minor discomfort. Ointments such as Vaseline or white soft paraffin may accelerate skin healing but are not necessary.

PDT for superficial basal cell carcinoma (sBCC) and intraepidermal carcinoma (IEC)
Studies have shown that PDT success rates for selected superficial BCC (sBCC) and intraepidermal carcinoma (IEC/SCC in suti/Bowen’s disease) range between 85 to 90% approximately. Nodular BCC are less responsive to PDT but may be used in appropriate circumstances.

PDT is not suitable for squamous cell carcinoma, high risk BCC (e.g. morpheic), recurrent BCC (lesions which have recurred after previous treatment), thick BCC (lesions greater than 2mm in depth) or melanoma.

A skin biopsy is usually recommended prior to treatment to ascertain the correct diagnosis. This ensures that we are providing the best treatment for you.

PDT for Actinic Keratoses (AK)
Actinic keratoses (sunspots) are pre-cancerous lesions that require ongoing monitoring. However, in situations where they become more advanced, treatment is often recommended. This is because a small percentage of actinic keratosis can progress to squamous cell carcinomas, which are potentially dangerous skin cancers. Squamous cell carcinoma may require surgical excision. Therefore by initiating early treatment, we can stop this progression from sunspots to SCC.

In addition, actinic keratoses are often cosmetically obvious, scaly and irritable. Due to this, treatment are often recommended.

Actinis keratosis usually occur in area of sun damage. Some lesions may be clinically visible while some may not be readily visible (subclinical lesions). Field treatments can be beneficial. These involves the use of topical creams (5-fluorouracil, imiquimod, ingenol mebutate) and PDT.

Follow-Up
Follow-up after PDT is usually 3 months. Subsequent timeframe for clinic review depends on the type of lesion you had therapy for.

Often, if you have developed one skin cancer, there is a higher risk (perhaps 40%) of developing further skin cancers. In view of this, we may ask you to return for yearly review for a few years for regular skin checkup. Sun protection and sun avoidance are also important in preventing further skin cancer development.

Potential
Side Effects

The potential of scaring and side effects are minimized due to the non-invasive and selective nature of the treatment. However, this does not mean side effects do not exist. Within a few days, the exposed skin and skin cancer will scab over and flake away.

Short-term side effects may include:

  • Pain (common): Mild to moderate burning sensation, which can be treated with local anaesthetic if unbearable. The pain is usually much shorter in duration and less severe than surgical excision.
  • Redness (common): Usually lasts for a few weeks. Rarely long lasting.
  • Swelling (common): Usually lasts for several days.
  • Pustules (common): Tiny white pustules are common and not indicative of infection. Usually disappear over several days.
  • Blistering (uncommon).
  • Ulceration (uncommon).
  • Infection (rare).

Medium to long-term side effects may include:

  • Hyperpigmentation (common): Area of skin treated may be darker than the surrounding skin, appearing like an area of dark tan.This may last for several months but usually settles spontaneously.Fading cream can be used to accelerate improvement.
  • Hypopigmentation (uncommon): Area of skin treated may be paler than the surrounding area.
  • Scarring (rare): True permanent scarring is rare. Small biopsy done to diagnose the lesion may leave a tiny scar.

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