Quit PhD due to illness/no support and make a step back and apply to Masters/PhD again Years ago I was diagnosed with leukemia and fortunately I won at that time the battle. Beginning of last year I started a PhD and after 1 year, my old illness was again knocking the doors and I had to stop the PhD asking for a Leave of Absence to start my treatment. 

I've got a LOA but unfortunately, 6 months later and although my treatment works fine, it seems I'll need around 6 months or more to recover and I'm afraid to have a long year gap in my CV. Moreover, there is a total lack of support and communication from my university and academic committee and I was thinking to quit my PhD.

Therefore, and seeing this gap won't help me, I decided to make a step back in my career, apply for a MSc. in a related area of my PhD and later, apply again to other PhD program in a different university.

I understand is a big step back, but it seems I'll need around a year to recover (if everything works fine) and I don't think I'll get a rec. letter from my supervisor. I also need to refresh again my background and be humble about my situation, so I don't think it's really bad. However, I'd like to hear from you suggestions or ideas.

Thanks in advance for reading and all your comments
If you have had a very serious medical problem like cancer, most PhD programs will take you back after you have recovered without much trouble.  If you contact them now and tell them that your recovery is taking longer than anticipated, they will probably tell you to get better and come back when you are ready.  I think withdrawing and moving to a master's program would be a very poor idea, unless you have gotten specifically negative information from your doctoral program, indicating they are unhappy with your extended absence.

You say that there has been a total lack of communication and support from your graduate program, but you may be expecting more than was reasonable or likely.  When a student takes a leave of absence for a medical reason, the faculty and administrators may not follow up very extensively, unless you keep in regular contact with them.  This is not necessarily because they do not care about how you are doing, but because they are trying to respect your privacy.  If you have not shared many details about how you are doing with other students and the faculty, they may feel that your medical status is none of their business.

I have observed that once a student leaves graduate school, for any reason, there is a good likelihood that they will never come back.  This is particularly true for students early in their graduate career.  So your advisor and other faculty members may not be expecting you to come back, particularly if you have not been in touch with them during your cancer treatment.  However, I would guess that they would probably be very happy to hear from you and would welcome you back when you were fully recovered.