Thymus: why do I get sick more often?

Had my regular post-scan oncology appointment today and the professor was happy with the lack of change in my most recent scan. He did his usual poking and prodding and this time I was careful to not overreact and score an extra PET scan.

After steadily improving since April or May, my energy levels seem to have reached a plateau over the last couple of months. I have been sick with colds and the flu a number of times, and they have hung around longer than usual. This has reduced the regularity of my exercise. Of course, by 'exercise', I mean nothing more strenuous than a 30 minute walk! In any case, I found out today that there may be three reasons for the frequency and duration of these illnesses: (a) already being somewhat run down/still recovering in my overall level of health; (b) radiotherapy scarring probably means that my trachea is less effective at thwarting airborne pathogens; and (c) my thymus was also in the field of radiation. The thymus is a gland in the centre of your chest that plays an important role in your immune system. I didn't ask him directly, but it sounds like the latter two effects may be long term.

Although it is months since my first good scan, I have been acknowledging again to myself in recent weeks that I am very much still in recovery mode, physically and emotionally.