**Core Concept**
The management of gallbladder adenocarcinoma depends on the tumor's stage and involvement with surrounding tissues. Early-stage tumors limited to the lamina propria are considered to be at low risk for spread and may be effectively treated with simple surgical resection.

**Why the Correct Answer is Right**
Tumors confined to the lamina propria, the innermost layer of the gallbladder wall, have a low potential for lymph node metastasis. Simple cholecystectomy, which involves the removal of the gallbladder, is sufficient for these early-stage cancers. This approach allows for the complete excision of the tumor with minimal morbidity and preserves the surrounding tissues. The lack of lymph node involvement reduces the need for more extensive surgery, such as radical cholecystectomy, which includes the removal of lymph nodes and surrounding tissues.

**Why Each Wrong Option is Incorrect**
**Option B:** Radical cholecystectomy is typically reserved for more advanced tumors that have invaded deeper layers of the gallbladder wall or have involved regional lymph nodes.
**Option C:** Chemotherapy alone is not the preferred treatment for early-stage gallbladder adenocarcinoma, as surgical resection is usually curative in these cases. Chemotherapy may be considered for more advanced disease or in cases where surgical resection is not feasible.
**Option D:** Radiotherapy is not the primary treatment for early-stage gallbladder adenocarcinoma, as it is typically reserved for cases where surgical resection is not possible or for palliative purposes.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the prognosis for gallbladder adenocarcinoma is generally poor, with a 5-year survival rate of around 5-10% for patients with distant metastases. Early detection and treatment are crucial for improving outcomes in these patients.

**✓ Correct Answer: A. Simple cholecystectomy**