Gastrointestinal stromal tumor: a method for optimizing the timing of CT scans in the follow-up of cancer patients.
OBJECTIVE
To develop a mathematical model to adjust the timing of computed tomography (CT) scans with the hazard of cancer recurrence in time to facilitate early detection of cancer recurrence.


METHODS
The clinical data were extracted from the randomized Scandinavian Sarcoma Group (SSG) XVIII/Arbeitsgemeinschaft Internistische Onkologie (AIO) trial database. The SSG XVIII/AIO trial was registered (trial no. NCT00116935) and approved by the national or institutional review boards. In the trial, 1- and 3-year durations of adjuvant imatinib mesylate in the treatment of patients with gastrointestinal stromal tumor (GIST) were compared. A nonhomogeneous Poisson model with a piecewise log-constant hazard in time that accounts for the nonlinear pattern of GIST recurrence was applied to tumor site, mitotic count, and recurrence data. The optimal times to obtain follow-up CT scans were computed by modifying the frequency of CT scans with the hazard of tumor recurrence in time. The hazard-adjusted follow-up schedules were compared with the National Comprehensive Cancer Network (NCCN) guidelines of the United States, which suggest imaging with CT at intervals of 3-6 months for 3-5 years and then annually.


RESULTS
Optimized timing of CT scans on the basis of hazard of recurrence resulted in follow-up schedule options where CT is performed more sparsely than in the NCCN guidelines during adjuvant imatinib administration and more frequently, at approximately 3-month intervals, during the first 2 years that follow imatinib discontinuation when the risk of recurrence was the greatest. The number of CT scans could be reduced by a median of 31% (from 13 to nine) compared with the standard schedules within the first 6 years of follow-up without increasing the delay in recurrence detection.


CONCLUSIONS
Detection of GIST recurrence may be enhanced by adjusting the timing of the CT scans with the hazard of recurrence. The method may be applicable to other human tumor types. Online supplemental material is available for this article.
From the Department of Oncology, Helsinki University Central Hospital, Haartmaninkatu 4, PO Box 180, FIN-00029 Helsinki, Finland (H.J.); Sarkomzentrum Berlin-Brandenburg, HELIOS Klinikum Berlin-Buch, Berlin, Germany (P.R.); Department of Oncology, Skåne University Hospital, Lund University, Lund, Sweden (M.E.); Department of Oncology, the Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway (K.S.H.); and Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland (A.V.).
Heikki
H
Joensuu
Peter
P
Reichardt
Mikael
M
Eriksson
Kirsten
K
Sundby Hall
Aki
A
Vehtari
D000328:Adult; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001549:Benzamides / Q000008:administration & dosage / Q000627:therapeutic use; D003131:Combined Modality Therapy; D003287:Contrast Media; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000601:surgery; D006801:Humans; D000068877:Imatinib Mesylate; D008279:Magnetic Resonance Imaging; D008297:Male; D010879:Piperazines / Q000008:administration & dosage / Q000627:therapeutic use; D010919:Placebos; D011446:Prospective Studies; D011743:Pyrimidines / Q000008:administration & dosage / Q000627:therapeutic use; D015996:Survival Rate; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D001549:Benzamides; D003287:Contrast Media; D010879:Piperazines; D010919:Placebos; D011743:Pyrimidines; D000068877:Imatinib Mesylate