A Statistical Approach to Determine the Optimal Duration of Post-Treatment Follow-Up: Application to Metastatic Nonseminomatous Germ Cell Tumors.
The objective of this study was to present a statistical method to define an optimal duration of follow-up for patients in remission after treatment for cancer, for detection of recurrences.



Surveillance duration was estimated using the 2-step approach proposed by Mould et al. Relapse-free interval was modeled using the parametric cure model proposed by Boag. The optimal length of follow-up was then estimated as the minimal elapsed time after which the probability of a patient to relapse and to be cured with success is below a given threshold value. The method is applied to 2 real data sets of patients treated for metastatic non seminomatous germ-cell tumors: T93BP and T93MP.



For the T93BP, cure rate was estimated at 91.3% and proportions of patients who relapsed after 3 and 5 years were estimated at 0.5% and 0.2%. With a probability of success of salvage treatment equal to 80% and 50%, numbers of delayed cases after 5 years were 2 and 1. For T93MP, the proportion of patients who presented relapse after 5 and 10 years were estimated at 5.2% and 2.6%. Considering a probability of salvage treatment equal to 20%, the number of delayed cases after 5 and 10 years were 10 and 5.



Using this methodology, duration of post-therapeutic follow-up might be tailored according to an objective criteria: the number of patients who present relapse after the end of follow-up and who could have been treated with success in case of early detection.
Bureau des Essais Cliniques, Institut Claudius Regaud, Institut Universitaire du Cancer, Toulouse - Oncopole, Toulouse, France; Equipe Méthodologie et Formation, Département de Recherche Clinique, Centre MURAZ, Burkina Faso, France.
Serge M A
SM
Somda
Service d'Oncologie Médicale, Hôpital Saint-Louis, Paris, France.
Stéphane
S
Culine
Département d'Oncologie Médicale, Institut Claudius Regaud, Institut Universitaire du Cancer, Toulouse - Oncopole, Toulouse, France.
Christine
C
Chevreau
Département de Médecine Oncologique, Institut de Cancérologie Gustave Roussy, Villejuif, France.
Karim
K
Fizazi
Toulouse School of Economics, Université Toulouse Capitole, Toulouse, France.
Eve
E
Leconte
Centre Oscar Lambret, Unité de Méthodologie et Biostatistique, Lille, France.
Andrew
A
Kramar
Bureau des Essais Cliniques, Institut Claudius Regaud, Institut Universitaire du Cancer, Toulouse - Oncopole, Toulouse, France. Electronic address: filleron.thomas@iuct-oncopole.fr.
Thomas
T
Filleron
D000293:Adolescent; D000328:Adult; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009362:Neoplasm Metastasis; D009373:Neoplasms, Germ Cell and Embryonal / Q000628:therapy*; D012074:Remission Induction; D013736:Testicular Neoplasms / Q000628:therapy*; D016896:Treatment Outcome; D055815:Young Adult
Cure model; Delayed cases; Log-normal; Salvage treatment; Testis