Mixed-Stage Radiation Oncology Training Within a National Cross-Specialty Oncology Program: Educational Outcomes and Regulatory Implications.

France's national cross-specialty oncology training program (Transversal Specialized Training, FST) includes 6-month rotations in medical oncology and radiation oncology. For selected specialties, a mixed-stage pathway may replace the standard radiation oncology rotation with 3 months in radiation oncology plus 3 months in medical oncology or an oncology-certified parent-specialty service. We explored this alternative pathway's educational outcomes. We conducted an exploratory subgroup analysis of 19 residents who completed mixed-stage FST training within a nationwide FST evaluation cohort (n = 203). Outcomes included satisfaction across nine radiation oncology domains, pedagogical evaluations, organization preferences, perceived adequacy of a 3-month radiation oncology placement, and subsequent oncological engagement. Mixed-stage participants (mean age 30.5 ± 1.6 years; 10 males) were residents in urology (n = 7), dermatology (n = 5), hepato-gastroenterology (n = 3), endocrinology (n = 2), and pulmonology (n = 2). Most completed sequential training (16/19), which was also the preferred organization (17/19). Overall, six residents (31.6%) achieved high general satisfaction, defined as a composite score ≥ 7/10. Satisfaction varied substantially by specialty: both pulmonology residents achieved high satisfaction, whereas no hepato-gastroenterology resident did. Patient communication scored highest (6.47 ± 2.61), while clinical research training was lowest-rated (3.79 ± 2.27). High oncological engagement was reported by 8 of 19 residents. Mixed-stage radiation oncology training showed heterogeneous educational outcomes and variable implementation across specialties. Within the limits of this small exploratory analysis, these findings support prioritizing standardized 6-month radiation oncology rotations, or at minimum strictly auditable criteria when mixed-stage pathways are authorized.