Response

In the CR06 colorectal cancer trial, clinicians assessed the response of the disease twelve weeks from the start of treatment. The results are shown in Table 9.8.

These data can be analysed in a number of ways. For example, we may be interested in the proportion of responders in each treatment group, or we may be interested in the proportion of patients with progressive disease in each treatment group. In both these situations we are considering the data as binary - forming two groups from the large

150 120 100 75 50 25 0

150 120 100 75 50 25 0

Total dose achieved CAP

Dose intensity achieved CAP

Total dose achieved CAP

Total dose achieved Carboplatin

Dose intensity achieved CAP

11

— C

— A

---P

H

Dose intensity achieved carboplatin

Total dose achieved Carboplatin

Dose intensity achieved carboplatin

10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 Percentiles Percentiles

90 100

Fig. 9.3 Total dose and dose intensity curves from the ICON2 trial. Reprinted with permission from Elsevier Science (The Lancet, 1998, 352, 1571-6)

10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 Percentiles Percentiles

90 100

Fig. 9.3 Total dose and dose intensity curves from the ICON2 trial. Reprinted with permission from Elsevier Science (The Lancet, 1998, 352, 1571-6)

Table 9.7 Reasons for not receiving three cycles of chemotherapy in the BA06 bladder cancer trial. Reprinted with permission from Elsevier Science (The Lancet, 1999, 354, 533-40)

Reasons

Number of patients

Renal toxicity/reduced renal function

23

Other toxic effects of chemotherapy 18

Disease progression/death

14

Protocol errors/unspecified

23

Patient refusal

Total

Table 9.8 Response to the three chemotherapy regimens used in the CR06 colorectal cancer trial. Reprinted with permission from Elsevier Science (The Lancet, 2002, 359, 1555-63)

de Gramont (control)

Lokich

raltitrexed

Complete response

4

1

3

Partial response

55

57

43

Stable disease

94

80

86

Progressive disease

60

66

68

Dead at twelve weeks

39

32

50

Total

252

236

250

number of groups available for analysis. To analyse the data in this way we could use methods introduced for binary data in Section 9.3.1. Alternatively we could consider the full data as presented and consider the ordered categories from complete response being the 'best' category to progressive disease being the 'worst' category. Whichever approach is adopted, an important decision to be made is whether the patients who have died by twelve weeks and therefore could not be assessed for response should be included in the analysis. A number of these patients will have died from the toxicity of the treatments, others will have died from progressive disease which has not been catalogued; a very small number may have died from other causes. One can think of many, if not all, these patients as having failed therapy, and thus they could be naturally added to the 'progressive disease' category. This is recommended for analyses of such data. If these data are ignored, then it is entirely possible that inappropriate (biased) conclusions can be reached.

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