This petition was rejected

The Government e-Petitions Team gave the following reason:

Petitions need to call on the UK Government or Parliament to take a specific action.

The 1939 Cancer Act does not prevent doctors discussing, investigating or offering cancer treatments. In fact, no UK law or Government policy prevents medical personnel in the UK from discussing or investigating potential cancer treatments, so we're not sure exactly what you'd like the Government or Parliament to do.

Section 4 is the only provision of the Act still in force. It prohibits taking part in “the publication of advertisements containing an offer to treat any person for cancer, or to prescribe any remedy thereof, or to give any advice in connection with the treatment thereof”. It does not prohibit doctors from offering or advising on cancer treatments or alternatives to chemotherapy.

You can read the Government response to a similar petition here:

petition.parliament.uk/petitions/203708

You could start a new petition explaining clearly what you would like the Government or Parliament to do. For example, you could start a new petition asking the UK Government and Parliament to change the laws around advertising of cancer treatments, if that's something you'd like to happen.