Nodular bronchiectatic Mycobacterium avium complex pulmonary disease. Natural course on serial computed tomographic scans.

RATIONALE

Existing literature is inconclusive regarding how the nodular bronchiectatic form of Mycobacterium avium complex (MAC) disease will progress without treatment and when treatment initiation should be considered.

OBJECTIVES

To assess the natural course of MAC pulmonary disease by serial thin-section computed tomography (CT).

METHODS

Of 339 patients with nodular bronchiectatic form of MAC disease, we selected 265 untreated patients who had serial CTs (mean observation period, 32 ± 21 mo). Two independent chest radiologists reviewed retrospectively all CT scans for the presence and extent of lung abnormalities (maximal total score, 30).

MEASUREMENTS AND MAIN RESULTS

Of 265 patients, 126 patients (48%) had disease that had progressed and that needed treatment owing to radiologic deterioration or worsening symptoms, and the remaining 139 patients (52%) did not. On multivariate analysis, the presence of cavity (adjusted hazard ratio, 2.06; P = 0.004) and consolidation (adjusted hazard ratio, 1.55; P = 0.019) at initial CT remained as independent factors associated with disease progression and treatment requirement. The presence of cavitary lesions demonstrated the highest positive predictive value (61%) and significant correlation (P = 0.005) with smear positivity. Differences in the extent of each pattern and total CT score in the serial studies were significantly larger (P < 0.05) in patients requiring treatment. The total CT score increased by 2.41 in the treatment-requiring group compared with 0.25 in the group that did not receive treatment.

CONCLUSIONS

Without treatment, about half of patients demonstrate progressive disease on serial CT over a mean follow-up period of 32 months and, thus, required treatment. Patients showing cavities or consolidation on initial CT are more likely to have progressive disease and thus to require treatment eventually.