Neoadjuvant Radiation Therapy Shows Promise for High-Risk Renal Cell Carcinoma with Vascular Invasion
Key Insights
Neoadjuvant stereotactic ablative radiation therapy (search) (SABR (search)) before surgery achieved a 71.4% relapse-free survival rate at 12 months in patients with renal cell carcinoma (search) and inferior vena cava tumor thrombus (search), exceeding the 55.7% historical rate with surgery alone.
The phase II trial demonstrated zero perioperative mortality compared to the historical 10.8% rate, with acceptable surgical complications and no grade 4 or higher radiation-related adverse events.
Results support further evaluation of neoadjuvant SABR (search) as a strategy to improve oncologic control in this high-risk patient population, with both 1-year overall survival and cancer-specific survival rates reaching 95.2%.
A phase II clinical trial has demonstrated that neoadjuvant stereotactic ablative radiation therapy (search) (SABR (search)) significantly improves outcomes for patients with renal cell carcinoma (search) (RCC) complicated by inferior vena cava tumor thrombus (search) (IVC-TT), a challenging condition affecting up to 10% of RCC patients. The prospective, single-center study showed a 12-month relapse-free survival rate of 71.4%, substantially exceeding the 55.7% historical benchmark achieved with surgery alone.
Trial Design and Patient Population
The single-arm phase II trial (NCT02473536) enrolled 23 patients with newly diagnosed RCC and Mayo level II to IV IVC tumor thrombus between July 2015 and January 2024. Patients received neoadjuvant SABR (search) targeting only the IVC tumor thrombus at doses of either 40 Gy in 5 fractions (54.5% of patients) or 36 Gy in 3 fractions, delivered 4 to 14 days before radical nephrectomy and IVC thrombectomy.
The study population had a median age of 62.5 years, with 54.5% male patients. Most patients presented with level II thrombus (54.5%), followed by level III (36.4%) and level IV (9.1%). Clear cell histology was predominant (90.9%), and the majority had pathological stage pT3b disease (68.2%).
Surgical Outcomes and Safety Profile
Twenty-two patients underwent surgery after one was excluded due to widespread metastatic disease. The perioperative mortality rate was 0%, a significant improvement over the historical rate of 10.8% associated with this complex surgical procedure. Surgical complications graded as Clavien-Dindo III to IV occurred in 13.6% of patients, with a median hospital stay of 4 days.
Intraoperatively, 22.7% of patients experienced thrombus downstaging, and 13.6% required cardiopulmonary bypass and thoracotomy. The median case duration was 217.5 minutes with a median estimated blood loss of 800 mL, and 63.6% of patients required intraoperative transfusion.
Efficacy and Long-term Outcomes
At a median follow-up of 35.2 months, 21 patients were evaluable for efficacy analysis after excluding one patient who died perioperatively from COVID-19 pneumonia. The primary endpoint was met with a 12-month relapse-free survival rate of 71.4% (80% CI, 56.6%-82.0%; P = .087), representing a 16.7% improvement over historical controls.
The median relapse-free survival reached 13.7 months (80% CI, 12.3-37.8 months). Remarkably, both 1-year overall survival and cancer-specific survival rates achieved 95.2%, substantially higher than historical rates of approximately 66%.
Metastatic Patterns and Subsequent Treatment
Pulmonary metastasis developed in 57.1% of patients, while systemic metastasis occurred in 71.4%. Notably, no patients experienced pulmonary embolism during the study period. Subsequent systemic therapy was required in 42.9% of patients.
Biological Effects and Toxicity
Correlative studies revealed that neoadjuvant SABR (search) reduced Ki-67 (search) expression in tumor specimens (P = .038), suggesting decreased proliferative activity following radiation treatment. The safety profile was favorable, with no radiation-related adverse events of grade 4 or higher reported. However, 36.4% of patients experienced perioperative adverse events of grade 3 or higher.
Clinical Implications
Lead study author Lin Lin, MD, a urologic oncology fellow at UT Southwestern, emphasized the importance of timing: "We found a sweet spot because within 2 weeks of radiation not that many changes can be observed in terms of tissue and thrombus. Therefore, we do not anticipate too much of a surgical approach change in this respect."
The results address a significant unmet medical need in RCC management, as patients with IVC tumor thrombus historically face 5-year cancer-specific survival rates ranging from only 25% to 53%. The study authors concluded that these findings "demonstrate promising oncologic efficacy with limited toxicity and support further evaluation of neoadjuvant SABR (search) in this high-risk RCC population."