Intermittent breaks from sunitinib therapy are feasible and don’t appear to compromise the agent’s clinical efficacy against metastatic renal cell carcinoma, according to investigators.

One of the greatest challenges in treating this cancer is balancing treatment-related toxicity against efficacy “in a setting … in which patients are largely incurable and thus subjected to chronic therapy,” said Moshe C. Ornstein, MD, and his associates at the Cleveland Clinic Taussig Cancer Institute.

They performed a single-center phase II study that they described as the first prospective trial to assess treatment interruptions whenever tumor burden was reduced by 10% or more, followed by resumption of treatment if tumors then progressed 10% or more. This approach “may result in reduced toxicities, improved quality of life, cost savings, and potentially improved clinical outcomes.”

The study involved 37 adults (median age, 63 years) who were given 50 mg sunitinib once daily for the first 28 days of a 42-day cycle, with dose adjustments allowed to minimize toxicities. Twenty patients (54%) who showed a 10% or greater reduction in tumor burden after four cycles suspended treatment until scans showed a 10% or greater progression, at which point treatment was resumed. These 20 patients were able to take up to 11 treatment breaks (median, 3 breaks per patient), with each break having a median duration of more than 8 weeks (range, 4.7-192.1 weeks).

Seven patients were able to have extended drug holidays lasting 3-43 months, and three have never had to resume sunitinib therapy after their first break. “The overall sum of all the breaks was 1,296.6 weeks, which corresponds to 216 6-week cycles with a median of 9 saved cycles per patient,” Dr. Ornstein and his associates said (J Clin Oncol. 2017 Jan 23. doi: 10.1200/JCO.2016.71.1184 ).

Given that the average wholesale price of sunitinib is $17,811.83 per 28-day cycle, “the 9 cycles saved per patient translates into a median cost saving of $160,302 per patient and $3.85 million overall, not including the cost of toxicity management that may have been incurred without breaks,” they noted.

The median progression-free survival was 22.4 months for the entire study cohort and 37.6 months for the 20 patients who had intermittent therapy.

Patients who showed tumor progression during a treatment break were transitioned back to standard dosing without showing any adverse clinical effects. This suggests that “with close clinical and radiographic monitoring, patients can safely take a therapy break for extended periods of time,” the investigators said.