Storytelling works wonders. Could you gather the stories of patients you have already helped and use these as part of your marketing strategy? Write blogs, get video testimonials from the patients and their families and start a YouTube channel where you can host them with Call To Actions through to find out more/purchase. Are there Facebook groups dedicated to those living with cancer that you could reach out to? Also, think broader in terms of bricks & mortar affiliations – beyond cancer charities, but still targeted are organisations like Hospice and Ronald McDonald House etc who care for the terminally ill from extensive causes including cancer.