yes, if it is specified so.
However the disease should be a SPECIFIED DISEASE AS PER SEC 80DDB IT Act, 1961. I feel that Cancer, brain tumour, or diseases like that only be defined as specified disease and not the GENERAL DISEASES.
Also, refer IT rule no.84 for form that should be submitted to the IT department.
Deduction in respect of medical treatment, etc.
80DDB. Where an assessee who is resident in India has, during the previous year, actually paid any amount for the medical treatment of such disease or ailment as may be specified in the rules84 made in this behalf by the Board—
(a) for himself or a dependant, in case the assessee is an individual; or
(b) for any member of a Hindu undivided family, in case the assessee is a Hindu undivided family,
the assessee shall be allowed a deduction of the amount actually paid or a sum of forty thousand rupees, whichever is less, in respect of that previous year in which such amount was actually paid :