Reduction in cavity density means that you are responding to the treatment and your TB is healing. No significant change means the size of the cavity has`nt reduced much. But this in isolation does not mean any thing. If you are feeling better, have no fever
and have gained weight, it means you are responding to the treatment. Sometimes cavity may not close for a long time or even remain for ever. You should continue your treatment and if required it can be extended for a total of 8 to 9 months. Consult your pulmonologist who can advise you correctly.