A study has revealed conclusive results that reduce toxicities for Asian patients with metastatic renal cell carcinoma (mRCC), which is cancer that has spread beyond the kidney. The seven-year study began in 2007. Its findings revolutionized the standard protocol for patient management at National Cancer Centre Singapore (NCCS) with an attenuated-dose regimen of sunitinib for patients with mRCC.

Sunitinib was introduced as a treatment for mRCC in Singapore in early 2005. The US Food and Drug Administration (FDA) approved dosing of sunitinib is 50 mg once daily for 4 weeks, followed by a 2-week break in a 6-week treatment cycle (conventional-dose regimen). 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 Tan Min Han, MD, PhD, visiting consultant, Division of Medical Oncology and member of the GU team, NCCS.

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Oncologists in Singapore, where the Genitourinary (GU) oncology team at NCCS conducted the study, have accepted the new, attenuated treatment regimen for sunitinib. The study was published in Clinical Genitourinary Cancer (2015; doi:10.1016/j.clgc.2014.11.004).

For the patients, the new regimen would mean an estimated 30% reduction in fees because of the lower dosage. The median overall survival was 27.4 months with conventional dosing versus 21.8 months with the attenuated dosage.

NCCS initiated a prospective clinical registry with 127 patients with mRCC receiving attenuated dosing of sunitinib: 37.5 mg once daily for 4 weeks, followed by a 2-week break as treatment protocol in 2007.

Clinical data of patients receiving sunitinib at NCCS from 2005 to 2012 and three other tertiary centers 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% of all patients with mRCC treated over the period.

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

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 health care counterparts.”