Abstract
There is a need to personalize the treatment for rectal cancer patients. The aim of this study was to analyze therapy response and prognosis after preoperative radiotherapy in rectal cancer patients with mucinous adenocarcinoma compared to those with non-mucinous adenocarcinoma. The study included retrospectively collected data from 433 patients, diagnosed with rectal cancer in the South East health care region in Sweden between 2004 and 2012. Patients with non-mucinous adenocarcinoma that received short-course radiotherapy before surgery had better overall survival, cancer specific survival, and disease-free survival, as well as distant- and local-recurrence-free survival (p = 0.003, p = 0.001, p = 0.002, p = 0.002, and p = 0.033, respectively) compared to the patients that received long-course radiotherapy with concomitant capecitabine. The results were still significant after adjusting for sex, age, stage, differentiation, and chemotherapy in the neoadjuvant and/or adjuvant setting, except for local-recurrence-free survival that was trending towards significance (p = 0.070). In patients with mucinous adenocarcinoma, no difference in survival was seen when comparing patients that had short-course radiotherapy and patients that had long-course radiotherapy. However, none of 18 patients with mucinous adenocarcinoma treated with long-course radiotherapy had local tumor progression, compared to 7% of 67 patients with non-mucinous adenocarcinoma. The results indicate that mucinous adenocarcinoma and non-mucinous adenocarcinoma may respond differently to radiotherapy.
Highlights
Colorectal cancer (CRC) is the third most common cancer and a major cause of cancer mortality worldwide [1]
It has been shown that mucinous adenocarcinoma (MAC), compared to non-mucinous adenocarcinoma (NMAC), is less likely to be resected with negative surgical margins [8,9], more often metastasizes to lymph nodes [10,11], and is more prone to local recurrence [8,9,12] as well as peritoneal carcinomatosis [11,13]
The Stockholm III study showed that there was no significant difference in cumulative incidence of local recurrence in patients with delayed surgery after short-course radiotherapy (SCRT) compared to SCRT with immediate surgery; nor was there a difference in cumulative local recurrence in long-course radiotherapy (LCRT) with delay compared to any of the SCRT regimens
Summary
Colorectal cancer (CRC) is the third most common cancer and a major cause of cancer mortality worldwide [1]. There are several consistent findings concerning differences between colorectal MAC and non-mucinous adenocarcinoma (NMAC). Most notable of these differences are that MAC more often affects female and young patients [3,4], and generally presents at a later stage [3,4,5,6,7]. It has been shown that MAC, compared to NMAC, is less likely to be resected with negative surgical margins [8,9], more often metastasizes to lymph nodes [10,11], and is more prone to local recurrence [8,9,12] as well as peritoneal carcinomatosis [11,13]. Numerous studies have shown conflicting results regarding the prognosis of colorectal MAC compared to NMAC. Report a worse prognosis for rectal MAC [3,14,15,16]
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