AMSTERDAM There has been "very little good quality research" overall on treatments for basal cell carcinoma, according to the latest Cochrane Systematic Review on the topic.
This is particularly hard to fathom since basal cell carcinoma (BCC) is the most common form of cancer in humans and an enormous volume of physician work is devoted to its treatment, Fiona J. Bath-Hextall, Ph.D., the review's lead author, noted at the 11th World Congress on Cancers of the Skin.
The review encompassed 27 published and unpublished randomized controlled trials involving surgical excision, radiotherapy, cryotherapy, photodynamic therapy (PDT), intralesional interferon, the plant-derived mixture of solasodine glycosides known as BEC-5 cream, topical 5-fluorouracil, and imiquimod.
The clear winners in terms of efficacy as reflected in the primary end point adopted for the reviewBCC recurrence rates at 35 yearswere surgery and radiotherapy. And in the sole head-to-head comparative trial of these two therapies, surgery had significantly fewer residual tumors and histologically proven recurrences as well as consistently better cosmetic outcomes than radiotherapy, said Dr. Bath-Hextall of the University of Nottingham (England).
Few of the other therapies have been compared directly with surgery, which is the most widely used form of treatment as well as the one supported by the strongest evidence of efficacy.
Most of the clinical trials involved only BCCs in low-risk locations. Only one focused on high-risk facial BCCs. Moreover, many of the studies didn't make it clear what type of BCC was included. Nor did most trials consider recurrent or morpheic BCCs separately, as is warranted given their lower treatment success rates.
Although the seven PDT trials included in the review collectively indicate that it is a promising modality with cosmetic outcomes significantly better than surgery, PDT also has a relatively high failure rate and is expensive. Longer-term efficacy data are needed before it is appropriate for PDT to enter routine clinical practice, according to the Cochrane reviewers (Cochrane Database Syst. Rev. 2007 Jan. 24;CD003412).
Eight of nine studies on imiquimod for BCCs were industry sponsored. They suggest an 88% success rate for a once-daily 6-week regimen in superficial BCC and a more modest 76% treatment response in nodular BCC with 12 weeks of therapy. An ongoing trial of imiquimod versus surgery should help determine whether the topical therapy is a useful option, the reviewers said.
Dr. Bath-Hextall also presented a first look at a new Cochrane Systematic Review of interventions for prevention of nonmelanoma skin cancers in high-risk groups, namely organ transplant recipients and patients with xeroderma pigmentosa or a history of prior nonmelanoma skin cancers. Ten published randomized studies totalling more than 7,200 participants were identified. Only one focused on xeroderma pigmentosa: The 30-patient trial showed reductions in new actinic keratoses and BCCs during 1 year of topical T4N5, a repair enzyme specific for UV-induced DNA damage.
Several studies demonstrated preventive efficacy for retinoids. One study of a 24-month low-fat diet showed no difference in the rate of nonmelanoma skin cancer in year 1, versus controls, but a trend for fewer tumors in years 25, Dr. Bath-Hextall said at the congress, cosponsored by the Skin Cancer Foundation and Erasmus University, Rotterdam.
One particularly intriguing trial, she continued, involved more than 1,300 patients with a history of nonmelanoma skin cancer who were randomized in double-blind fashion to 10 years of supplemental selenium or placebo. The selenium group showed a nonsignificant increase in skin cancers, but a highly significant 37% reduction in nonskin cancers, including marked reductions in lung, colorectal, and prostate cancer and an adjusted 21% reduction in all-cause mortality (JAMA 1996;276:195763).
Audience members expressed puzzlement at selenium's divergent impacts on skin and internal malignancies. This prompted session chairman Dr. H.A. Martino Neumann, professor of dermatology and venereology at Erasmus, to propose an explanation: Perhaps participation in this study of an oral agent for skin cancer prevention caused some patients to feel a false sense of confidence and become more casual about sun protection.
In the sole head-to-head comparison of surgery and radiotherapy, surgery had fewer residual tumors. DR. BATH-HEXTALL