When we think about our risk of skin cancer, most of us think mainly about the sun and whether we’re wearing sunscreen. Other things can increase skin cancer risk though, including medications. Could you be taking a medication that is increasing your risk?
If you’re on a blood pressure medication called hydrochlorothiazide (HCTZ), then you are!
There are a lot of studies that have been published that show an increased risk of skin cancer with this medication.
What types of skin cancer should we worry about? Well the most highly linked type of skin cancer is what’s called squamous cell carcinoma (SCC). This is the second most common type of skin cancer, and it has a risk of spreading if left untreated. One study out of Denmark published in 2018 with more than 8000 people showed a 4 times the number of this skin cancer if one had been taking HCTZ for about 6 years. Taking for longer or higher doses further increased risk up to 7 times the amount (Pederson et al). Another study in Iceland also showed higher chance of getting this skin cancer. The risk is especially increased if you’re 50 years or older, at least as seen in one study.
Does avoiding the sun or using sun screen help? Not necessarily, at least according to the authors from this Iceland study, as they noted that sun exposure in Iceland is fairly low, and yet increased skin cancer risk was still seen. In other words, even though using sunscreen can help, it doesn’t completely eliminate the risk.
The risk of skin cancer associated with HCTZ is not limited to SCC, however. The Danish study also found increased risk of the most common type of skin cancer, called basal cell carcinoma (BCC). This type of skin cancer does not tend to spread and is very treatable. The risk of BCC ranged from 1.29 if taking it for around 6 years and further increased if taking it for longer.
Another study showed increased risk of lip cancer up to 7x. This is important because cancers on the lip are higher risk of spreading due to the location.
More rare types of skin cancer are also increased with HCTZ exposure. An additional study published in Denmark showed between 2.3 to 3.3 times increased risk of Merkel cell carcinoma. This type of skin cancer related to mechanoreceptors in the skin, and it’s a more deadly type of skin cancer; only 40% tend to survive at 5 years.
Interestingly, we can also develop skin cancer related to our sweat glands — like eccrine glands and apocrine glands — hair follicles and oil glands. HCTZ was also shown to increase the risk of these cancers between 3.6 and 5.6 times. These rare tumors, so called malignant adnexal skin tumors, tend to have slightly better prognosis; they metastasize, or spread, less often, only in 12% of patients, and have a 5 year survival of 73%.
Lastly, what about melanoma? There is not as much evidence suggesting increased risk of melanoma, though at least one study found increased risk (Pottegard et al, citation number 4 in the Pedersen et al article).
Of note, studies looked at whether other blood pressure medications similarly increase risk of skin cancer, and no correlation was noted, with exception of one called furosemide with Merkel cell carcinoma risk.
So how does HCTZ increase skin cancer risk? It’s thought that sunlight causes a change in the molecule that then allows it to make free radicals that damage our DNA. With use over time, the damage from HCTZ builds up and ultimately leads to skin cancer.
Because of the evidence out there, the FDA actually updated their labeling on HCTZ to include increased risk of skin cancer, with recommendation for skin cancer screening. Further, the International Agency of Research on Cancer has named HCTZ as a possible carcinogenic (or cancer causing drug) (per Pedersen et al).
So what should you do with this information if you’re on HCTZ?
- If you don’t have history of skin cancer, realize that by taking HCTZ, it’s increasing your risk of most skin cancers that relate to sun exposure. The longer you take it, the higher your risk will be. Because of this, it’s essential that you use strict photoprotection with sunscreen with at least SPF30 or above, avoid sun during peak hours of 10-2, and wear photo protective clothing and a broad rimmed hat.
- If you do have history of skin cancer, particularly multiple skin cancers, talking to your doctor about changing to a different blood pressure medication is a good idea.
- Even if you stop HCTZ, you still may be at increased risk of skin cancer having been exposed to it in the first place because exposure to the medicine causes build up of mutations over time. This means it’s important to continue routine skin checks with your dermatologist at least once a year.
- Doing your own skin exams once a month watching for possible skin cancers is a good idea. In particular, you want to watch for new growths that are changing, bleeding, or hurting or moles that are changing. These may not necessarily look remarkable — in fact, Merkel cell carcinoma and cancers related to our sweat glands and oil glands often times can be pink or red. If you ever notice a new growth that you are concerned about, make sure to that call your dermatologist to allow for further evaluation.
Until the next time!
References
Pedersen SA et al. Hydrochlorothiazide use and risk of non-melanoma skin cancer: a nationwide case-control study from Denmark. JAAD 2018; 78: 673-81.
Pedersen SA et al. Hydrochlorothiazide use and risk for Merkel cell carcinoma and malignant adnexal skin tumors: a nationwide case-control study. JAAD 2019; 80:460-5.
Adalsteinsson JA. Association between hydrochlorothiazide and the risk of an in situ and invasive squamous cell skin carcinoma and basal cell carcinoma: a population-based case-control study. JAAD 2021; 84: 669-75.