A meta-analysis investigated the effects of palliative chemotherapy in patients with locally advanced or metastatic colorectal cancer. Randomised controlled trials that compared palliative chemotherapy with supportive care were included.
Seven trials that provided individual patient data, totalling 866 patients, were identified. Outcome measures included the length of time until death after starting treatment. The Kaplan-Meier survival curves for the length of time until death for the treatments of palliative chemotherapy and supportive care were presented (figure). The median survival time was estimated to be 8.0 months in the control group and 11.7 months in the chemotherapy group.
KaplanMeier survival curves of overall survival for the chemotherapy and control treatment groups derived from individual patient data from seven randomised controlled trials. The median survival time for each treatment group is the length of time corresponding to the probability of 0.5［1]
Which one of the following best describes the median survival time of 11.7 months for the chemotherapy group?
a) Chemotherapy was delivered for an average of 11.7 months.
b) Half of the patients undergoing chemotherapy were alive at 11.7 months after starting treatment.
c) The probability of surviving 11.7 months or longer after starting treatment was 0.5.
Answer c is the best description of the median survival time for the chemotherapy group.