Treatment for Pain Associated with Photodynamic Therapy for Skin Cancer

Lesion type, size, location and other pain predictors should be considered for patients who undergo photodynamic therapy.

The use of photodynamic therapy (PDT) to treat non-melanoma skin cancers such as basal cell carcinoma, Bowen’s disease, and actinic keratoses is often associated with stinging and burning sensation of pain during treatment. The authors of the study “Predictors of Pain Associated with Photodynamic Therapy,” published in the May 2011 issue of Acta Dermato Venereologica studied a cohort of patients undergoing PDT to determine the cause and mechanism of the pain they experienced during treatment “in order to better predict the pain and to try to achieve efficacious pain-relieving strategies.”

For the study, 377 patients (197 men and 180 women) underwent a total of 658 PDT sessions. The average age of male and female participants was 72 years and 71 years, respectively. The study included 229 patients with actinic keratoses (AKs), 128 patients with basal cell carcinoma (BCCs) and 35 with Bowen’s disease (BDs). Some patients presented with a combination of these cancers. Researchers assessed pain experienced during PDT by administering a visual analogue scale (VAS) or asking patients to verbally grade their pain on a scale of 0 to 10. They also assessed size of radiation field during treatment, lesion location, size of the treated area, clearance rates, and other factors.

Lesion location was assigned to one of four body areas: face and/or scalp, the trunk, the upper extremities and the lower extremities. Location breakdown was as follows: the face and scalp (44%), trunk (26%), the lower extremities (21%) and the upper extremities (9%).

PDT was performed using “visible red light from light-emitting diodes.” Mean wavelength was 635 nm, with a fluence rate of 80—90 mW/cm2. Treatment irradiation time was 7–10 minutes. Post-treatment follow up “varied between 3 months and 3 years, depending on the patients’ diagnoses.”

The authors reported that mean VAS score for AKs was 6.1 ± 0.14, compared with 4.6 ± 0.15 for patients with BCCs. AKs were “significantly more painful” than BCCs for patients with lesions on the face or scalp, independent of the size of the radiation field used during treatment. Mean VAS score for BDs was 5.0 ± 0.34.

Although “location of the lesions was the weakest predictor of pain,” PDT on the face, scalp, and/or forehead was associated with a high level of pain. PDT on the trunk was generally well tolerated. PDT on the lower extremities was associated with the lowest mean VAS score (4.8 ± 0.21).

The size of the treatment area was strongly associated with patients’ report of pain during PDT and “had the strongest statistical significance” when compared with the diagnoses and the lesion location. The authors reported that “the treatment of large irradiation fields was significantly more painful for AKs and BCCs on the face and/or scalp, when compared with the smaller irradiation fields.”

Infiltration, spinal, or general anesthesia was required in 125 out of 889 treatment areas, with “pain in the treatment area or painful pre-treatment procedures prior to the irradiation” the most common reasons for anesthesia.

In their discussion of these results, the authors wrote that “the size of the treated area is crucial, but the level of pain also depends on the diagnosis and the location that is treated,” with PDT of large AKs on the scalp and face causing the most severe pain. They also found that “AKs are more painful to treat than BCCs, regardless of the size of the irradiation field.” They also concluded that that gender and age “are poor predictors of pain.”

In terms of pain relief for patients undergoing PDT, the authors noted that although “one could consider trying to reduce the pain by simply treating smaller areas separately,” in their experience this is not a feasible solution as “patients prefer one visit with the whole affected area treated at once even though the pain level is much higher.” One potential solution is th use of nerve blocks, which “effectively relieve pain during PDT in these areas,” are easy to perform and well tolerated by the patients.