Date: 25 Jun 2016
Stratification of patients into stage II and III colon cancer according to their risk of disease recurrence allows identification of those who should derive the most benefit from adjuvant chemotherapy and limits overtreatment in patients for whom the toxicities of adjuvant chemotherapy outweigh relatively low absolute benefits.
At present, adjuvant chemotherapy is the standard of care for patients with stage III colon cancer; however, there is a lack of definitive data on how to identify patients with low-risk stage III disease who may not require oxaliplatin-based chemotherapy. Furthermore, although adjuvant chemotherapy is also advocated for patients with high-risk stage II colon cancer, the current criteria to define high-risk features are considered inadequate1,2; among the known prognostic factors for recurrence risk in stage II colon cancer (ie, depth of tumor invasion [T stage], number of nodes examined, mismatch repair [MMR] status, tumor grade, and lymphatic and vascular invasion [LVI] score), only T stage, number of nodes examined, and MMR have substantial clinical evidence to support their use.3,4
The 12-gene Recurrence Score assay (Oncotype DX Colon Recurrence Score assay; Genomic Health Inc., Redwood City, CA) was developed to evaluate recurrence risk in patients with colon cancer independent of currently used prognostic parameters. The test uses reverse transcription–polymerase chain reaction (RT-PCR) with formalin-fixed, paraffin-embedded (FFPE) primary colon tumor tissue specimens. The Recurrence Score result was previously validated in patients who had stage II colon cancer treated with surgery alone5,6 and subsequently validated in patients who had stage II or stage III disease treated with adjuvant chemotherapy.7 The Recurrence Score result has not yet been validated in patients who have stage III colon cancer treated with surgery alone. The SUNRISE study aimed to confirm the prognostic value of the 12-gene Recurrence Score result in a cohort of patients in Japan who had stage II and stage III colon cancer treated with complete resection alone from 2000 to 2005. During this time period, adjuvant chemotherapy was not standard of care in Japan for patients with stage III disease,8 which thus presented an unprecedented opportunity to assess performance of the assay in a population of patients with resected stage III disease who had not received adjuvant chemotherapy. Furthermore, the staging of the disease cohort was performed according to current recommendations,9 because Japanese surgeons routinely conducted a lymph node excision and an assessment in more than 12 lymph nodes during that time. The SUNRISE study also afforded a unique opportunity to validate the Recurrence Score result in an Asian patient population that has not previously been represented in validation studies for the 12-gene assay.
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Department of Biostatistics,
Yokohama City University Graduate School of Medicine
Fukuura 3-9, Kanazawa-ku, Yokohama, Japan 236-0004