Hello and welcome to healthcaremagic. One week is too short a time to get rid of the black spots nevertheless you should at least begin the treatment for the spots. Melacare contains a potent steroid and is not recommended for black spots resulting from acne because if used regularly melacare itself causes acne. Therefore it is not advisable to post acne black spots, It does nt cause cancer either. I would suggest thta you see a dermatologist for a proper consultation. Your dermatologist might ask you to use benzoyl peroxide gel twice daily for your acne activity. Along with that your dermatologist might also add oral antibiotics like doxycycline or azithromycin for faster relief of acne. Regarding post acne black spots you need to use a skin lightening cream e.g either kojic acid or hydroquinone based cream once your acne activity is under control. regards