Friday January 28 2011
The weed needs more testing before it is ready for use
A common weed called “petty spurge” may be a treatment for skin cancer, BBC News has reported. It highlights new research suggesting that the sap from this common garden plant treats non-melanoma skin cancer. This form of skin cancer includes basal cell carcinomas and squamous cell carcinomas, which are the less serious but more common forms of skin cancer. They particularly affect the elderly.
The research studied the effects of an extract from the common garden weed on the non-melanoma skin cancers of 36 patients who were not suitable for (or who refused to have) surgery. The results were positive, with 63% of non-melanoma lesions completely responding by the end of the study.
Further research is now needed to see whether the results can be replicated in a larger group of patients with different types of tumours, and to see how this potential new treatment compares with existing ones for this disease, including surgery, freezing and light therapy (photodynamic therapy).
Where did the story come from?
The study was carried out by researchers from the Mater Radiation Oncology Centre, the Queensland Institute of Medical Research, Griffith Medical Research College and Peplin Biotech Ltd, all in Brisbane, Australia. The study was funded by an Australian Commonwealth Government Industry research and development grant and by Peplin Biotech, who are currently developing and testing the weed extract for market. The researchers state that Peplin Biotech had no role in the design, data collection, analysis, interpretation or writing of the article.
BBC News has reported the results of the study clearly and makes the important distinction between the non-melanoma skin cancers that are being tested here and more serious melanomas, for which surgery is the recommended treatment. The headline of the news article ("Common petty spurge 'could treat' skin cancer") is too broad as it implies that this research is relevant to all skin cancers.
What kind of research was this?
This was a phase I study, which occurs in the early phases of drug testing in humans. It was investigating the potential anti-cancer properties of an extract from the spurge family of plants, Euphorbiaceae. The sap from one of these plants, known as petty spurge in the UK (Euphorbia peplus) has reportedly been used as a home treatment for warts, corns, asthma, catarrh and for skin and other cancers. The researchers wanted to test its use in a scientific setting and, as BBC News reports, “put it through its paces in a proper clinical trial”.
What did the research involve?
The study enrolled outpatients aged over 18 who were attending an Australian oncology centre for the treatment of various non-melanoma skin cancers. These patients had confirmed cases of basal cell carcinoma, intraepidermal carcinomas or squamous cell carcinomas. They had not been successfully treated by previous therapies, had refused to have surgery or were deemed unsuitable for conventional treatment.
The researchers enrolled 36 patients, some with more than one lesion, and researchers applied the extract from the Euphorbia peplus plant to the surface of the lesions once a day for three days using a cotton bud. This extract contained an active ingredient called ingenol mebutate, also known as PEP005. The study treated a total of 48 lesions across the participants. The lesions were covered with a transparent, waterproof dressing between applications.
The participants were examined by an oncologist one, six and 12 months after their treatment for evidence of a positive response or any adverse reactions. Patients who showed a partial response were offered a second course of treatment, while those with a complete response were asked to undergo a biopsy of the treated area to remove some of the local cells for further investigation. The participants were followed up for an average of 15 more months.
There was no control group in this study so the researchers were not able to compare the results of their treatment against a different approach in another group of patients. Instead, they present the results seen in the treated patients in terms of how many achieved a complete response and how many achieved a partial response with treatment. Complete response was defined as the absence of a tumour after clinical investigation.
What were the basic results?
The majority of the studied lesions (28/48) were basal cell carcinomas, while 16 of them were intraepidermal carcinomas and four were squamous cell carcinomas. Assessments by oncologists one month after treatment found that:
- 23/28 (82%) basal cell carcinoma lesions showed a complete response to treatment.
- 15/16 (94%) intraepidermal carcinomas showed complete response.
- 3/4 (75%) squamous cell carcinomas showed complete response.
- 5/28 (18%) of patients with basal cell carcinoma showed a partial response.
The researchers report that at the last follow-up (between two and 31 months for each patient), some patients lesions had returned, although complete response rates were still high:
- 16/28 (57%) of basal cell carcinomas had a complete response.
- 12/16 (75%) of intraepidermal carcinomas had a complete response.
- 2/4 (50%) squamous cell carcinomas had a complete response.
In total, 62.5% of lesions had a complete response to treatment of their non-melanoma skin cancers by their last follow-up.
The patients generally tolerated the treatment well, although some reported short-term pain and irritation of the skin.
How did the researchers interpret the results?
The researchers say that their clinical study affirms the public’s treatment experiences reported with the use of the Euphorbia peplus sap. They say that their results support the need for further clinical development of the PEP005 sap extract for the treatment of these non-melanoma skin cancers.
This phase I study has demonstrated the clinical effects of the Euphorbia peplus extract in patients with non-melanoma skin cancers for whom surgery was either not desirable or appropriate. This is early research that has not yet compared this new treatment with others. It does however form an important step on the pathway to developing PEP500 into an established treatment. The positive results mean that larger, comparative research will follow.
There are two main types of skin cancer: malignant melanomas, which are less common but more serious, and non-melanoma skin cancers, which are very common, especially in older age groups. About three-quarters of non-melanoma skin cancers are basal cell and the remainder are squamous cell carcinoma, both of which are associated with sun exposure. The vast majority of cases are detected early and are not life threatening. Although they are malignant, basal cell cancers hardly ever spread to another part of the body, and while squamous cell may spread to deeper skin tissue it rarely spreads to another part of the body. The picture is somewhat different for melanomas, which spread more frequently. Although survival rates are improving, 80% of deaths from skin cancer are due to melanomas.
The study into this plant extract has shown promising results. Further research will follow and will better demonstrate the exact place of this treatment in the existing armoury against skin cancer. However desirable new treatments are, prevention remains the best approach as sun exposure is the main cause of both malignant melanomas and non-melanoma skin cancers. Excessive sun exposure should be avoided, particularly in people with light eyes, hair or skin, who are at increased risk of sunburn.