RESULTS OF A BREAST-CANCER-SURGERY TRIAL COMPARED WITH OBSERVATIONAL DATA FROM ROUTINE PRACTICE

Background The strength of randomised controlled trials (RCTs) is that they allow investigators to draw reliable inferences about treatment differences; physicians can then make a choice between different optio ns. Their weakness is that they are conducted on a set of patients who cannot be regarded as a random sample from the population that will b e treated outside the trial. Observational data collected in a prospec tive clinical database may provide more realistic estimates. Methods A t the Istituto Nazionale dei Tumori of Milan an RCT was started in 197 3 (MI1) in which Halsted mastectomy was compared with quadrantectomy p lus axillary dissection and radiotherapy (QUART), a breast conserving treatment, for ''early-stage'' primary breast cancer. In addition, a p rospective clinical database was established to collect, in standard f ormat, information on ail women undergoing breast conservation thereaf ter and followed up at the institute. 1760 women were treated with QUA RT, 350 of them being accrued in the years 1973-80 in the context of t he MI1 trial. The remaining 1408 received QUART after the MI1 trial, u p to December, 1984. Results In the years after the trial, the criteri a for use of QUART became more liberal. However, after adjustment for baseline characteristics, out-trial patients fared no worse than trial patients in terms of survival or distant metastasis. Out-trial patien ts did have a slightly higher rate of local recurrence, probably becau se of subtle and multiple changes in the surgical procedures since the time of the trial. Interpretation The results of QUART in out-trial p atients resembled those reported from research settings. In this insta nce, the results of clinical trials did not exaggerate the benefits ob tainable in routine practice.