What is the ruling regarding a Muslim woman going for Umrah with her son and family if her husband is an alcoholic and prevents her out of spite, and she is sick with cancer?

If a woman has not performed the 'Umrat al-Islam (the obligatory 'Umrah), she is permitted to travel to perform it without her husband's permission, and he is not allowed to prevent her. If she has a mahram (unmarriageable kin) with her, there is no objection to her traveling. If she does not have a mahram with her, the more correct view is that she is permitted to travel with a trustworthy group. However, if she has already performed the 'Umrat al-Islam, she is not allowed to travel for a voluntary 'Umrah except with her husband's permission, even if he is a disobedient (fasiq) person, for he has the right of obedience from her.