:::, en =i ... Cl) > 0 80 60 40 20 p=0.03 0 0 250 500 750 1000 1250 Overall survival tiITB (days) 170 S 160 p<0.0001 ] ,= 150 &a, 140 T t------- --·• I !j:: _/v-'f---t-- l 110 / 1 100 / LL. 90 80t-1--~--~--.------r---.-- 1 2 3 4 Cycle ··• ·- Respond ing patients -o- Non-responding patients 5 6 260 multicentre setting, adding prospective evaluation of quality of life and lung function end points. In order to make the response rates of the two trials directly comparable, it was important that the measurement criteria used in the two studies were the same.Subsequently, the RECIST criteria have been developed andbecome widely accepted and used in clinical trials. The applica- tion of RECIST criteria could, however, be variably interpreted by different investigators in mesothelioma, and this may lead tounsatisfactory results [3]. We have developed Modified RECISTcriteria that are specifically designed to address the unique growthpattern of pleural malignant me sothelioma. Use of these modified response criteria did not materially alter the response rates in ourtwo previous trials. However, the modified criteria avoided diffi-cult and ambiguous situations that arose in response interpretationin the two previous trials; for example, how to evaluate responsewhen discordance between unidi mensional and bidimensional lesions occurred. Whilst tumour response and progression directly reflect changes in tumour bulk, they are most clinically useful when they relateclosely to other measures of a patient’s condition. Response is asurrogate for patient benefit in the evaluation of new drugs and combinations. Patient benefit in pleural mesothelioma may include an improvement in survival or lung function, and improvement insymptom control or quality of life. Thus, it is important that anyvalid measurement of response should reflect changes in theseparameters. We have demonstrated that these Modified RECISTcriteria successfully distinguish between responders and non-responders for the parameters of survival and change in FVC, thusdemonstrating their validity. Further evaluation of these modified criteria should be per- formed before they can be incorporated routinely into future clin-ical trials. The development of an automated measurement formatmay enhance the speed and reproducibility of the measurements[6] and go some way to overcoming the potential problem of inter-observer variability. We have avoided this issue by using the sameobserver or an audit group to undertake the measurements. Testsof inter-observer variability are important, however, as has beendemonstrated in the assessment of response in lung cancer [7]. Toconfirm the practicality of the criteria they should be applied to agroup of clinicians who lack extensive experience in the measure-ment of mesothelioma in clinical trials. Acknowledgements A.K.N.