What is the recommended treatment for low‑grade serous carcinoma of the ovary?

Treatment of Low-Grade Serous Carcinoma of the Ovary

Primary debulking surgery achieving complete cytoreduction (no macroscopic residual disease) is the cornerstone of treatment for low-grade serous ovarian carcinoma, followed by carboplatin plus paclitaxel chemotherapy, with consideration of bevacizumab addition and maintenance antiestrogen therapy. 1

Treatment Algorithm by Stage

Early-Stage Disease (Stage I-IIA)

Stage IA (fully staged):

• No adjuvant chemotherapy is recommended 1
• This is a Level II evidence, Strength A recommendation with 100% consensus

Stage IB/IC:

• Adjuvant chemotherapy benefit is uncertain and should be discussed individually 1
• If chemotherapy is given, acceptable regimens are:
  • Carboplatin alone (6 cycles) 1
  • Carboplatin/paclitaxel (minimum 3 cycles, up to 6 cycles for serous tumors) 1
• Level III evidence, Strength C recommendation

Stage IC2-IC3 and Stage IIA:

• Adjuvant chemotherapy is recommended 1
• Use platinum-based regimens as above

Advanced-Stage Disease (Stage IIB-IV)

Surgical approach:

• Complete cytoreduction to no visible residual disease is critical due to the inherently low chemosensitivity of low-grade serous carcinoma 1
• Even debulking to <1 cm residual may improve survival when complete cytoreduction is not feasible 1
• This is more important in low-grade serous than high-grade serous due to limited chemotherapy responsiveness

Systemic therapy:

• Carboplatin plus paclitaxel is the standard chemotherapy 1

  • Standard dosing: Paclitaxel 175 mg/m² IV over 3 hours followed by carboplatin AUC 5-6 IV, every 3 weeks for 6 cycles 2

• Addition of bevacizumab should be considered 1

  • Bevacizumab has shown activity in low-grade serous carcinoma in both first-line and recurrent settings 1
  • Level I evidence, Strength B recommendation with 97.4% consensus

Maintenance therapy:

• Maintenance antiestrogen therapy after chemotherapy can be considered 1
  • Options include aromatase inhibitors (anastrozole, letrozole), leuprolide acetate, or tamoxifen 2
  • The majority of low-grade serous carcinomas have high ER and PR expression 1
  • Level IV evidence, Strength C recommendation with 92.1% consensus

Key Clinical Considerations

Why low-grade serous is different: Low-grade serous carcinoma demonstrates significantly lower response rates and less survival benefit from chemotherapy compared to high-grade serous carcinoma, indicating limited chemosensitivity 1. This fundamental difference explains why:

• Surgery is even more critical
• The magnitude of chemotherapy benefit is uncertain 1
• Alternative strategies (hormonal therapy, targeted agents) are being actively investigated

Common pitfall to avoid: Do not treat low-grade serous carcinoma exactly like high-grade serous carcinoma. While carboplatin/paclitaxel remains standard, the emphasis shifts heavily toward achieving complete surgical cytoreduction, and maintenance hormonal therapy becomes a viable option given the high hormone receptor expression 1.

Recurrent Disease

Secondary cytoreductive surgery:

• Should be considered with the aim of no macroscopic residual disease 1
• Level I evidence, Strength B recommendation with 100% consensus
• Significantly increased PFS and OS have been demonstrated after complete secondary cytoreduction 1

Systemic options for recurrence:

• Chemotherapy is an option but the magnitude of benefit is uncertain 1
• Antiestrogen therapy can be considered 1
  • Small retrospective studies suggest therapeutic value in recurrent settings 1
  • Level IV evidence, Strength B recommendation with 97.3% consensus

Emerging targeted therapies:

• MEK inhibitors (trametinib, avutometinib/defactinib) have shown activity in recurrent disease 3, 4, 5
• Bevacizumab has demonstrated activity in recurrent low-grade serous carcinoma 1

Important note on PARP inhibitors: The NCCN Guidelines specifically state that maintenance therapy recommendations (including PARP inhibitors) apply to high-grade serous or grade 2/3 endometrioid cancer types, and whether these are appropriate for low-grade serous has not been studied 6.