Intralesional 5-Fluorouracil (5FU), Topical Calcipotriene Treatment for SCC

Squamous cell carcinoma of the skin is a common form of keratinocyte skin cancer. The majority of cutaneous SCCs occur on the head and neck, more so in men than women, but can occur anywhere squamous cells are found. Squamous cell carcinoma of the skin is usually not life-threatening, though it can be aggressive in some cases, and is normally treated with minor surgery.

Squamous cell carcinoma (SCC) of the lower extremity is a distinct subset of cutaneous squamous cell carcinomas which tend to occur multiply in elderly women. Histopathological studies of lower extremity SCCs reveals that they tend to be well differentiated and have low incidence of perineural and lymphovascular invasion and are also less prone to metastasis. Minor surgery has been the standard of care for this subset of SCC but leads to many complications such as poor wound healing and postoperative infections. Furthermore, a phenomenon called eruptive postoperative SCC can occur, in which cytokines released during wound healing triggering secondary tumor formation in genetically predisposed cells surrounding the original SCC. Given that lower extremity SCCs are less aggressive but more prone to surgical complications when excised, we believe they may be good candidates for localized non-surgical treatment.

5-fluorouracil (5FU) is a well-studied and characterized chemotherapeutic agent that has been used systemically, topically and intralesionally for a variety of malignancies and conditions including many dermatologic abnormalities.

It has been used on and off label topically for the treatment of actinic keratosis, SCC, superficial basal cell carcinoma, extra-mammary Paget's disease confined to the epidermis, Bowen's disease, porokeratosis, and genital warts. Intralesionally it has been used off label for the treatment of keloids, knuckle pads, warts, hypertrophic scars, basal cell carcinoma, and keratoanthoma.

Reports of its use intralesionally in invasive cutaneous SCC, other than in keratoacanthomas, are very limited. We are aware of 3 such reports in the literature. In the largest study to date, 6 weekly intralesional injections of 5FU-epinephrine gel were performed on 23 patients with cutaneous SCC on various body sites, 22 (96%) of whom demonstrated histologically confirmed tumor clearance. This study, however, used a proprietary gel formulation which is not widely available. There are two other case reports of successful treatment of SCC with 6-8 intralesional injections of 5FU at weekly intervals. The three published studies injected 0.6ml to 2.4ml of 5FU, per each weekly session, at concentrations of 30mg/ml to 50mg/ml.

Calcipotriene is a synthetic form of vitamin D. It is FDA approved for the treatment of psoriasis. Calcipotriene binds to vitamin D receptors on skin cells and helps regulate the growth and differentiation of skin cells. It inhibits keratinocyte proliferation (cell growth) and enhances keratinocyte differentiation. Recently it has been shown that calcipotriene acts as topical immune response modulator through induction of thymic stromal lymphoprotein (TSLP) expression. TSLP is an epithelium-derived cytokine and a regulator of allergic inflammation in the skin. It has been shown by Shadmehr Demehri et.al. that TSLP released by barrier-defective skin in mice blocks cancer development by recruiting T cells to mount robust antitumor immunity in the skin. The adaptive immune response mounted by TSLP against cancer can eliminate cancerous lesions in the skin and prevent new lesions from developing.

A recent clinical trial conducted by Demehri showed that participants treated with topical 5FU and topical and topical calcipotriene showed a significant reduction in the number of actinic keratosis (face, scalp, \& upper extremities) vs topical 5FU and vaseline. Furthermore, the cohort treated with 5FU and topical and topical calcipotriene remained SCC-free for more than 1,500 days suggesting the induction of tissue-resident memory T (trm) cells.

The purpose of the study is to evaluate this relatively unexplored approach to the treatment of SCC on the lower extremities and establish a non-surgical therapy to improve outcomes, eliminate the need for surgery and mitigate the occurrence of infections and secondary tumor eruptions.

Topical 5FU is approved for the treatment of superficial basal cell carcinoma smaller than 2cm in diameter and not located on the feet, hands or feet but cannot penetrate deep enough into the skin to be an effective treatment for SCC. For the proposed phase I clinical trial, we propose to increase tumor accessibility by delivering 5FU directly and specifically to the tumor through intralesional injections to kill accessible localized SCC cells.

5FU is currently in clinical use with a well-established safety profile. It is anticipated that intralesional injections of 5FU will enable direct and specific delivery of chemotherapy to the tumor, thereby reducing the potential for systemic toxicity. Further, intralesional injections of-5FU enable tumoral delivery of locally effective concentrations of 5FU using doses that are orders of magnitude below those used currently for the intravenous (IV) treatment of multiple malignancies.

5FU alone may not be enough eliminate all the tumor cells so we also propose to treat a group of patients with intralesional 5FU and 0.005% calcipotriene topical cream. The goal is to develop a synergistic effect and establish an immune response to the 5FU induced apoptotic SCC cells in order to kill off any remaining SCC cells not undergoing apoptosis. Also 5FU alone may not be as effective of a treatment as the combination therapy in the prevention of secondary tumor recurrence. It is hoped that the combination therapy will induce a memory response and reduce the incidence of secondary tumors.

Participants will have at least 1 SCC lesion greater 1cm and less than 2 cm in largest diameter, on their lower extremities. The clinical diagnosis of SCC will be confirmed histologically by a deep shave biopsy of less than half of the lesion. The remainder of the lesion will be used for intralesional injections of 5FU or intralesional 5FU/topical calcipotriene according to the following schema:

In this study, a total of 30 patients will be randomly assigned into 3 groups. Randomization will be conducted using the UPCI randomizer, which is maintained by the Biostatistics Facility of UPCI (https://randomize.upci.pitt.edu/randomizer/home.seam). Group 1: 10 patients will serve as a control group, and will receive neither 5FU injection nor topical calcipotriene. Group 2: 10 patients, will receive a single intralesional injection of 50mg of 5FU in 1ml aqueous injectable solution once a month for 3 months. Group 3: 10 patients will receive intralesional 5FU as administered in the previous group. They will also apply a topical application of 0.005% calcipotriene cream to the same lesion two (2) times daily for four (4) days one (1) day after each of three (3) 5FU injections. At the time of initial consent, a 2 mm punch biopsy of the lesion will be obtained. Half of biopsy will be stored for tissue banking and future study, while the other half will be sent for histological confirmation of SCC. A second 2 mm punch biopsy will be taken at 2 months for mid-point analysis. This will be stored for tissue banking and future study. A month after the last injection (week 12), the lesion will be surgical resected in the non-treated Group 1 to render the participant's disease free. Resection is the current standard of care for these tumors. Participant's in Group 2 and 3 will have a 4mm punch biopsy will be taken to confirm pathologic resolution.

Depending on the results of the confirmational biopsy the following actions will be taken:

1. Negative biopsy - clinical follow-up every 6 months for 2 years
2. Positive biopsy - Mohs surgery 2-4 weeks after in In all groups part of, or all of, the resected tumor and surrounding skin will be stored for tissue banking and future study.

All lesions will be photographed and treatment response will be evaluated 4 weeks after the first 5FU injection prior to excision.