Imiquimod for sBCC: Five-year trial shows efficacy, cosmesis

Key Points

"We know imiquimod is effective in sBCC, and existing treatment options aren't that great," says Christopher J. Quirk, M.D., a dermatologist in private practice at Dermatology Specialist Group in Ardross, Western Australia.

If a patient has multiple lesions on the trunk, he says, "Having them all excised, treated with photodynamic therapy (PDT) or curetted can be onerous, especially for patients who live in isolated areas.

Study details

For the 18-center, open-label Food and Drug Administration (FDA) phase 3 study, Dr. Quirk and colleagues recruited a total of 169 adult patients with a primary tumor that was histologically confirmed (by two independent dermatopathologists) to be sBCC. Researchers selected target tumors that had a pre-biopsy area between 0.5 cm² and 2.0 cm² and were located on the limbs, trunk, neck or head.

They performed 3 mm punch biopsies on up to four clinically identified sBCC lesions and, ultimately, chose to target one tumor per patient, usually because the tumor was located in an easy-to-treat area.

For six weeks, each subject applied a match-head-sized drop of imiquimod to the target tumor daily. Throughout the study's duration, a total of 29 patients discontinued treatment for reasons including recurrence of sBCC (14 patients), intercurrent illness, death or failure to complete follow-up visits.

To assess patients' progress, investigators scheduled follow-up visits at the end of treatment, then two, four and six weeks thereafter to ensure continued compliance and assess local skin reactions (LSRs) or other potential adverse events.

Investigators determined the treatment's initial clearance rate of target tumors (12 weeks post-treatment) to be 94 percent. They assessed sustained clearance at three, six, 12, 24, 36, 48 and 60 months after the 12-week visit.

Among patients whose target tumors cleared, researchers estimated sustained clearance rates to be between 99 percent (three months) and 85 percent (60 months).

Of 20 target sBCC recurrences observed over five years of follow-up, investigators confirmed 16 as sBCC. Furthermore, 14 (70 percent) of these 20 tumors occurred during the first two years after treatment. For all 169 subjects, researchers estimated the probability of treatment success (achieving initial clinical clearance and sustaining it five years later) at 80.4 percent.

"The high rate of sustained clearance is pretty impressive," Dr. Quirk tells Dermatology Times.

If a physician biopsies a lesion and sees sBCC under the microscope, he says, "One presumes the whole lesion has the same histology. But in fact, in sBCC, there can develop foci of invasion - which one may not pick up on a 3 mm punch biopsy."

Therefore, Dr. Quirk says that some of the lesions which recurred in the study might have had such foci, "and that's perhaps the reason for the recurrence."

LSRs (other than erythema) generally resolved themselves by the three-month visit. However, erythema took up to two years to resolve. Additionally, 23 subjects experienced a total of 37 reported serious adverse events, but investigators judged all these events to be probably not or not related to the study drug.

"Some patients achieved quite a good textural improvement at the end of the study. The skin was smooth and less wrinkled in the treatment site" compared to baseline, Dr. Quirk says. Although some patients weren't entirely pleased that the treatment created patches of hypopigmentation, he adds, "That's still a big improvement over other modalities, and less of a cosmetic nuisance."

Caution

Due to imiquimod's success in treating sBCC, some inexperienced general practitioners might be tempted to use it to treat nonsuperficial BCCs in areas such as the head and neck, or high-recurrence areas such as the nose and ears.

However, attempting to treat such tumors with imiquimod can result in recurrences that require more extensive surgeries than the initial tumors would have, Dr. Quick says.

Disclosure: Dr. Quirk reports no financial interest in 3M or Graceway, which funded the study.