[Long-term results of a trial of short-term chemotherapy. French study 6.9.12].
The relapse rate after short course chemotherapy is usually assessed by cases that are available for analysis, with a delay which rarely exceeds 3 years from the time of instituting therapy. This level may be disputed if too many are lost to follow up or non-compliers appearing late. To understand the true failure rate we strove to trace every patient in a trial carried out between 1969 and 1973, consisting of three groups of patients treated with the same chemotherapy: Isoniazid (450 mg/day), Rifampicin (600 mg/day) given every day but for differing durations: 6 months (Group A), 9 months (Group B), 12 months (Group C), with either daily Ethambutol or Streptomycin in addition for the first three months. Amongst the 356 patients in the trial 86 were eliminated for failure to comply with the protocol, either due to a mishap or change of treatment. Amongst the 270 remaining patients, 248 were traced with a mean delay of post-therapy follow up of 101 months for patients still living and of 72 months for patients who had died in the intervening period, but of non-tuberculous disease. In the 242 old patients whose disease could be evaluated, the number of bacteriological relapses was 4/81 (6.2 %) in group A, and 2/85 (2.3 %) in group B and 2/76 (2.6 %) in group C. There was no significant differences between the groups. From these results it is seen that the Isoniazid/Rifampicin combination given daily for 6 months is a powerful combination with few failures. Maintaining such chemotherapy for 12 months does not seem to yield substantial gains. In conclusion nine months of chemotherapy with this regime offers a sufficiently ample guarantee of cure.