Colorectal cancer : Aspects of staging, treatment, recurrence and survival

Sammanfattning: Colorectal cancer is the third most common malignancy in the world, and major breakthroughs have been made regarding both surgical and oncological treatment. Still, postoperative complications, such as perineal infections after abdominoperineal resection (APR), are a major cause of morbidity, and distant recurrence rate is nearly 20%. In this thesis, means to improve postoperative infection rates, nodal staging in rectal cancer (and resulting overtreatment through (chemo)radiotherapy), cancer recurrence rates and survival, were investigated. In Paper I, the effects on complication rates, recurrence rates and survival of antibiotics applied locally after an APR, by means of a gentamicin-collagen sponge in the perineal wound, were analysed in a randomized setting. No difference was seen regarding any of the endpoints. The results suggest that local antibiotics can safely be omitted in APRs. Paper II investigated the effects of mechanical bowel preparation (MBP) on cancer recurrence and survival, among colon cancer patients undergoing a colon resection. Data from the Swedish randomized MBP trial were used. After follow-up, no improvement in recurrence rates or overall survival was seen, but cancer-specific survival was improved in the MBP group. In conclusion, MBP might be a prognostic favourable factor for outcome in colon cancer patients. In Paper III, the effect of new national guideline criteria for MRI nodal staging in rectal cancer was assessed, regarding the proportion of clinically positive nodes and staging accuracy, and resulting effects on preoperative (chemo)radiotherapy use. Comparing the two years prior to guideline implementation with the two years after implementation revealed a significant decrease in the proportion clinically positive nodes, but staging accuracy remained low, and (chemo)radiotherapy rates decreased with seemingly no correlation to guidelines. Thus, new guidelines decreased the rate of clinically positive nodes, but nodal accuracy remained poor and nodal staging should perhaps not be a criterion in preoperative treatment decisions. Paper IV investigated the impact of the total mesorectal excision quality, by means of the three Quirke grades, mesorectal (best quality), intramesorectal and muscularis propria (worst quality), on recurrence and survival, and assessed risk factors for intramesorectal or muscularis propria resection. Muscularis propria grade was associated with a higher local recurrence rate, but not with distant recurrence or survival. Several factors were associated with intramesorectal and muscularis propria grade, and more caution is warranted in these patients. In conclusion, this thesis provides insight into treatment choice, and the association of day-to-day treatment details with postoperative complications, recurrence and survival rates, as well as the challenges of nodal staging.