A Prospective, Randomized, Multicenter Clinical Study Comparing Adjuvant Radiotherapy Versus Observation in High-risk Localized Adrenocortical Carcinoma After Surgery.

Inclusion Criteria:

* age ≥ 18 years and ≤ 75 years.
* ECOG performance status score ≤ 1, with an expected survival period ≥ 6 months.
* Completion of radical resection for adrenocortical carcinoma (ACC) with curative intent.
* Postoperative pathological diagnosis of adrenocortical carcinoma.
* Pathological stage is localized ACC: ENSAT stage 1-3; where ENSAT stage 3 is defined as any T stage (T1-4) with regional lymph node positivity, or tumor invasion into surrounding tissues/organs or the renal vein/inferior vena cava, but without distant metastasis.
* High-risk factors: Ki-67 index \>10%, ENSAT stage 3, positive resection margin, high pathological grade; the presence of any one of these factors qualifies.
* Postoperative imaging review prior to radiotherapy shows no evidence of residual or metastatic disease.

Exclusion Criteria:

* ENSAT Stage 4 adrenocortical carcinoma.
* Performance status: Karnofsky Performance Status (KPS) score ≤ 70 or Zubrod score \> 2.
* Prior radiotherapy to the abdomen or pelvis.
* Insufficient function of major organs (heart, lung, liver, kidney, bone marrow hematopoiesis) precluding tolerance to radiotherapy.
* Pregnant or lactating women, and subjects of childbearing potential unwilling to use contraception.
* Patients with psychiatric disorders, history of alcoholism or substance abuse, or those unable to provide informed consent.
* Other conditions deemed by the investigator to make the subject unsuitable for participation in this trial, including but not limited to: severe illnesses requiring immediate intervention (including psychiatric disorders), severely abnormal laboratory results, or other social or familial high-risk factors.
* Patients with other concurrent primary cancers; or patients diagnosed with another primary malignancy within the 5 years prior to the study (except for adequately treated carcinoma in situ of the cervix, or skin cancers such as basal cell carcinoma, squamous cell carcinoma, or non-melanomatous skin cancer).