Topical vitamin C in DMSO shrank squamous cell carcinoma in situ 71%, and 94% of patients avoided surgery (small, no control group)

Topical 30% Ascorbic Acid in Dimethyl Sulfoxide for the Treatment of Cutaneous Squamous Cell Carcinoma In Situ

Preprint October, 2025, https://doi.org/10.1101/2025.10.13.25337920

Patricia Miller, Jon Ward, Michael Morgan, Briant Burke

Summary by Claude - September, 2026

Patients painted a 30% vitamin C (ascorbic acid) solution in DMSO onto early squamous cell skin cancer twice a day. After 12 weeks, a repeat biopsy showed the cancer had cleared in 56% of lesions, and 94% of patients avoided surgery. This is a small open-label, single-arm trial (17 patients, 27 lesions), posted as a preprint that has not been peer-reviewed.

Every lesion was biopsy-confirmed squamous cell carcinoma in situ (SCCIS), which is cancer confined to the top layer of skin. Patients applied 30% (w/v) ascorbic acid in 95% DMSO / 5% water with a small cuticle brush, twice daily for 12 weeks.

Results:

15 of 27 lesions (56%) fully cleared on biopsy
Mean lesion area fell from 1.06 to 0.30 cm² (−71%)
Only 2 lesions (7%) did not respond
Most remaining lesions had downgraded to precancer (actinic-keratosis-type atypia) and were then frozen off with cryotherapy
"No participants reported pain, pruritus, burning, or ulceration during therapy." The only reaction was mild redness.

The same group earlier reported >80% clearance of basal cell carcinoma in 8 weeks with this formula, in a small randomized trial against imiquimod [Burke 2022]. The authors propose that high-dose vitamin C generates hydrogen peroxide, which cancer cells low in the enzyme catalase cannot neutralize. Vitamin D was not measured.

What this does NOT show

That vitamin C caused the benefit: there was no placebo, no DMSO-only group, and no comparison treatment
A lasting cure: follow-up ended at 12 weeks, so there are no recurrence data
How many lesions still contained carcinoma at 12 weeks: only "complete resolution" was counted
That the solution alone avoided surgery: the 94% includes cryotherapy of leftover lesions
Statistical strength: results were analyzed descriptively, and 2 of 19 enrolled patients were lost to follow-up
A matching trial registration: the cited NCT04279535 is the authors' earlier BCC trial. Their SCC registration [NCT05932511] describes an 8-week randomized comparison with imiquimod, which is not reported here.
That treating an undiagnosed spot yourself is safe: every lesion here was biopsied before and after treatment

Basal cell, Squamous cell, and Melanoma make up 99% of all Skin Cancers

Claude AI

Here's the ranking for the US, where the data are best. The top three account for more than 99% of cases. Everything from #4 down is rare, and several of the rarer ones are close enough in rate that their order could shift depending on which registry and years you use.

Rank	Skin cancer	Approx. US new cases/yr	Rate / note	Ref
1	Basal cell carcinoma	~3.6 million	~80% of keratinocyte cancers	[SCF]; [ACS]
2	Cutaneous squamous cell carcinoma (SCC)	~1.8 million	Includes keratoacanthoma and Bowen disease (in situ)	[Moffitt]
3	Melanoma	112,000 invasive + 122,680 in situ (2026 est.)	8,510 deaths est.	[AAD]
4	Merkel cell carcinoma	~3,000	~7 per million, rising with aging population	[Paulson JAAD 2018]
5	Cutaneous T-cell lymphoma (57% mycosis fungoides)	~2,500–3,000	8.55 per million (MF alone 5.42)	[ASCO Post]; [CJON]
6	Dermatofibrosarcoma protuberans	~1,300	~4 per million; peaks age 20–39	[NEJM JW]
7	Primary cutaneous B-cell lymphoma	~1,000	3.1 per million	[Blood 2009]
8	Kaposi sarcoma	~1,000	Was 71% of cutaneous sarcomas in SEER	[Rouhani 2008]
9	Sebaceous carcinoma	~800	3.2 (men) / 1.6 (women) per million	[Frey]
10	Extramammary Paget disease	~400	~1.5 per million (French registry)	[Doubs registry]

Just below the top 10 are atypical fibroxanthoma / pleomorphic dermal sarcoma, microcystic adnexal carcinoma, cutaneous angiosarcoma, and cutaneous leiomyosarcoma.

Caveats

BCC and SCC aren't reported to cancer registries, so their numbers are estimates and probably undercounts. The ~5.4 million keratinocyte cancers a year occur in about 3.3 million people, because many people have more than one tumor [ACS].
For #4–#10, I converted the published per-million rates to US case counts myself (US population ≈ 340 million). Most of those rates come from SEER data that are 10–20 years old, so treat the counts as rough.
The Kaposi sarcoma figure is my estimate; I didn't find a current US count. The ranking is different worldwide: GLOBOCAN 2022 estimated about 35,000 Kaposi cases, mostly in HIV-affected sub-Saharan Africa, which would put it at #4 globally. That global figure is from memory, not checked in this search.
Actinic keratosis is precancerous, so it's not on the list, although it's far more common than anything below #3.

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