What is the treatment for adenoid cystic carcinoma?

Treatment of Adenoid Cystic Carcinoma

The standard treatment for adenoid cystic carcinoma (ACC) consists of complete surgical resection followed by postoperative radiation therapy, with no routine role for systemic chemotherapy in primary management. 1

Surgical Management

Primary Treatment

• Complete surgical resection is the cornerstone of treatment for ACC
• Aim for negative margins whenever possible, as margin-negative resection significantly improves overall survival (20.1 years vs. 10.3 years) 2
• For major salivary gland ACC:
  • Parotidectomy with appropriate facial nerve management for parotid tumors
  • Complete excision of submandibular or sublingual glands when involved
• For minor salivary gland ACC:
  • Wide local excision with appropriate reconstruction

Neck Management

• Elective neck treatment should be offered for:
  • T3 and T4 tumors
  • High-grade malignancies
  • Clinically positive neck disease 1
• For parotid malignancies, selective neck dissection typically includes levels 2-4 1

Radiation Therapy

• Postoperative radiation therapy should be offered to ALL patients with resected adenoid cystic carcinoma 1

• Indications for postoperative RT include:

  • All cases of ACC (regardless of other factors)
  • High-grade tumors
  • Positive or close margins
  • Perineural invasion (common in ACC)
  • Lymph node metastases
  • Lymphatic or vascular invasion
  • T3-T4 tumors 1

• Target volumes:

  • High-dose target should cover the salivary gland surgical bed and appropriate nodal levels
  • In cases of perineural invasion, the associated nerve(s) may be covered with an elective or intermediate dose to the skull base 1

Management of Recurrent Disease

• For resectable, recurrent locoregional disease without distant metastases:

  • Revision resection with appropriate reconstruction should be offered 1
  • Negative margins at reoperation continue to provide survival benefit 2

• For recurrent disease with distant metastases:

  • Palliative revision surgery may be considered if metastatic disease is not rapidly progressive 1
  • Patients should be evaluated for potential adjuvant therapy after revision surgery 1

Systemic Therapy

• The role of chemotherapy in ACC is limited 3
• No significant survival advantage has been demonstrated with adjuvant chemotherapy at initial diagnosis or at recurrence 2
• For special histological types like adenoid cystic carcinoma in breast cancer, no systemic therapy is recommended due to its low-risk endocrine nonresponsive nature 1

Molecular Considerations and Future Directions

• Recent molecular and genetic studies have identified two distinct ACC subtypes (ACC-I and ACC-II) with different prognoses 4
• Molecular drivers like NOTCH1 are being explored as potential therapeutic targets 4
• These advances may eventually lead to more personalized treatment approaches beyond the current standard of surgery and radiation 5

Important Considerations and Pitfalls

• Long-term follow-up is essential as ACC has an indolent but persistent course with late recurrences
• Despite aggressive local therapy, approximately 40% of patients develop metastatic disease 4
• Perineural invasion is characteristic of ACC and should be specifically evaluated during pathologic examination
• Particle therapy (proton, neutron, carbon ion) may be used but has no proven advantage over conventional photon or electron therapy 1
• For unresectable disease, radiation therapy should be offered as primary treatment 1

The treatment of ACC requires a multidisciplinary approach with careful consideration of the extent of disease, potential for complete resection, and the need for adjuvant therapy. While surgery and radiation remain the mainstays of treatment, ongoing research into the molecular biology of ACC offers hope for more effective targeted therapies in the future.