Experiencias y expectativas sobre la enseñanza del francés

Changes in diagnosis following positron emission tomography/ computed tomography

The discordance of diagnoses following MDCT and then PET/CT can be seen inTable 17. This table shows the MDCT- and PET/CT-based diagnoses among patients with and without PDAC. The numbers of discordant

1.0

0.8

0.6

0.4

Quantitative scale for clinician certainty

0.2

0.0

PrePET PostPET

FIGURE 5 Distribution of perceived diagnostic certainty pre and post PET/CT.

TABLE 16 Brier scores of predicted diagnoses before and after PET/CT

Time point Brier score (PDAC diagnosis) Improvement in Brier score

Before PET/CT 0.218 0.045 (95% CI 0.024 to 0.066),p<0.001

After PET/CT 0.173

TABLE 17 Cross-tabulated diagnoses after MDCT and PET/CT (within-range patients, per protocol) for pancreatic cancer

Diagnosis

Patients with PDAC Patients without PDAC

PET/CT positive PET/CT negative PET/CT positive PET/CT negative

MDCT positive 227 4 54 31

patients (those whose diagnoses differed at each stage) drives the relative sensitivity and specificity of PET/CT compared with MDCT. In each case there was a greater number of cases in which the PET/CT diagnosis was correct than in which the MDCT diagnosis was correct, indicating that PET/CT performs better.

Positron emission tomography/computed tomography changed the diagnosis correctly for both the diagnosis of pancreatic cancer and the diagnosis of not pancreatic cancer in 46 patients (8.3%). PET/CT incorrectly changed the diagnoses in 20 patients (3.6%). Considering the diagnosis of malignancy in general, PET/CT correctly changed the diagnosis in 48 patients (8.7%) and incorrectly changed the diagnosis in 11 patients (2%) (Table 18).

Changes in staging following positron emission tomography/ computed tomography

For the purposes of examining change of stage, patients were grouped into four categories: (a) no tumour/ IA/IB/IIA, (b) IIB, (c) III and (d) IV (for the breakdown of changes in staging according to the groups see

Appendix 3). The accuracy of staging among patients in stages IA/IB/IIA was slightly worse under PET/CT than under MDCT, with more incorrect (eight patients) than correct (six patients) changes. However, the difference was not statistically significant (p=0.79). Significantly more patients with stage IIB were correctly staged by PET/CT than by MDCT, with 22 patients (21%) moving to the correct stage compared with five patients (5%) moving to the wrong stage (p=0.002). PET/CT had no significant effect on the accuracy of staging for patients in stage III. Significantly more patients in staging group IV were changed to the correct stage (27 patients) than moved to an incorrect stage (one patient) (43% vs. 2%;p<0.001). A summary of stage changes is provided inTable 19.

Overall, the effect of PET/CT was to change to the correct staging group significantly more often than to change from the correct group to an incorrect group (p<0.001). However, the majority of the benefit was in correct changes to stage IIB or stage IV.

Changes in planned management

Using the question from the D2 (post-PET/CT scan) form,‘Has the PET/CT scan influenced your planned management of this patient’s disease?’, the PET/CT scan was perceived to have changed the planned management in 250 (45%) patients. The proportion whose management was affected was slightly higher among patients whose final diagnosis was not pancreatic cancer [139 (48%) vs. 111 (43%) with

pancreatic cancer] but the difference was not statistically significant (Table 20).

TABLE 18 Cross-tabulated diagnoses after MDCT and PET/CT (within-range patients, per protocol) for malignancy

Diagnosis

Patients with malignancy Patients without malignancy

PET/CT positive PET/CT negative PET/CT positive PET/CT negative

MDCT positive 369 5 46 42

MDCT negative 6 4 6 72

TABLE 19 Change in stage for four staging categories following PET/CT

Change summary n(%)

Remained correct 221 (56)

Remained incorrect 94 (24)

Changed to correct 56 (14)

Changed from correct to incorrect 14 (4)

Using the questions from the D3 (confirmed diagnosis) form,‘Did the patient follow the course of treatment recommended at D1?’and‘Did the patient follow the course of treatment recommended at D2?’, 70% of patients did not undergo a change in management throughout the studyTable 21). In total, 15% underwent a change in management from either that considered at D1 (pre PET/CT) or that considered at D2 (post PET/CT). A significantly higher proportion of patients (11% vs. 4%;p=0.0002) followed the management plan recommended after PET/CT (and not that recommended after MDCT) than followed the MDCT management plan (and not that recommended after PET/CT).

Clinically important changes resulting from positron emission tomography/ computed tomography

Table 22details the frequency of different types of clinically important management changes. The most common change was changing from resection to no resection, which occurred in 61 patients, representing 11% of all patients and 21% of patients scheduled for some kind of resection after MDCT. Changing from no further investigation to some form of further investigation/clinical follow-up occurred in 58 patients, representing 11% of all patients and 13% of those initially not scheduled for further investigation. In total, 13% of patients not thought to need surgical resection following MDCT were then planned for resection following PET/CT. Changes relating to the commencement or cessation of chemotherapy were less common.

TABLE 20 Influence of PET/CT scan on patients’planned management

Group No,n(%) Yes,n(%) Missing,n(%)

All patients 293 (53) 250 (45) 7 (1)

Patients with pancreatic cancer 148 (57) 111 (43) 2 (1)

Patients without pancreatic cancer 145 (50) 139 (48) 5 (2)

TABLE 21 Management followed at confirmed diagnosis (D3) (N=540)

Management

D2 followed,n(%)

Yes No

D1 followed Yes 376 (70) 23 (4)

No 58 (11) 83 (15)

TABLE 22 Frequencies of clinically important management changesa

D1 change to D2 n(%) As a result of PET/CT,n(%) Clinically significant, n(%) Resection to no resection 61 (21) 58 (20) 58 (20) No resection to resection 34 (13) 19 (7) 19 (7) Chemotherapy to no chemotherapy 8 (10) 1 (1) 1 (1) No chemotherapy to chemotherapy 41 (9) 24 (5) 24 (5)

No further investigation to further investigation 58 (13) 31 (7) 31 (7) PET/CT identified or perceived to have led to

identification of a secondary malignancy

5 (NA) 5 (NA) 5 (NA)

NA, not applicable.

Impact of positron emission tomography/computed tomography