Scientists pioneer new drug regimen that reduces toxicities for renal cancer patients

The seven-year study began in 2007 and the findings revolutionized the standard protocol for patient management in NCCS with an attenuated-dose regimen of sunitinib for patients with mRCC.

The new treatment regimen for sunitinib has been accepted by oncologists in Singapore. For the patients, this would mean an estimated 30 per cent reduction in fees because of the lower dosage. The median overall survival rate (OStotal) was 27.4 as compared to 21.8 months among patients receiving the attenuated dosage.

Sunitinib was introduced as a treatment for mRCC in Singapore since early 2005. The U.S. Food and Drug Administration (FDA) approved dosing of sunitinib is 50mg once daily for four weeks, followed by a two-week break in a six-week treatment cycle (conventional-doseregimen). Subsequent findings from 2005 to 2006 show that high toxicities were observed with the conventional dosing, especially in Asians.

"Many of the patients were experiencing severe side effects of grade 3 or higher with the conventional dosing. Our immediate response was to refine the treatment protocol to improve patients' quality of life," explained Dr Tan Min Han, Visiting Consultant, Division of Medical Oncology and member of the GU team, NCCS.

NCCS initiated a prospective clinical registry with 127 mRCC patients receiving attenuated sunitinib dosing of 37.5mg/d/4/2 (37.5mg of sunitinib once daily for four weeks, followed by a two-2 week break) as treatment protocol in 2007. Clinical data of patients receiving sunitinib at NCCS from 2005 to 2012 and three other tertiary centres in Singapore (Johns Hopkins-International Medical Centre, National University Hospital Singapore, and Onco-Care of Gleneagles Medical Centre) from 2005 to 2009 were used for comparison, representing at least 90 percent of all patients with mRCC treated over the period.

The data revealed favourable results between the attenuated dosing regimen compared to the conventional dosing. 59 percent of the participants experienced severe side effects as compared to the previous 85 percent; 24 percent than 58 percent required reduction in dose delays; and 35 percent rather than 70 percent of patients requiring dose reduction during their course of treatment. Both dose delays and reduction are only required when high level of toxicities are observed.

Dr Tan reiterated the importance of the findings, "This is an affirmation to our efforts and we believed that the continuous understanding of real world outcomes will reap greater benefits for our patients. The findings would not be possible without the collaborative nature of our tertiary healthcare counterparts."