The association between DM and malignant tumors was independently described nearly 100 years ago by two investigators, Kankeleit and Stertz [7]. The incidence of cancer in adult patients with DM is approximately 13–42% [8]. Although its underlying pathogenesis remains unknown, it has been considered as one of the probable reasons why paraneoplastic condition producing bioactive mediators causes immune reactions in the muscle fibers and skin [5, 9]. Patients with DM and malignant disease have reportedly a worse prognosis than patients with idiopathic DM; surgical resection was not possible in many of the patients with cancer because of the advanced stage of their disease [10]. Difficulties in the management of cancer chemotherapy and medication for DM symptoms have also been reported due to severe dysphagia in patients with unresectable metastases [6]. Successful treatment of these malignancies can lead to resolution of paraneoplastic symptoms. Several reports have shown that tumor resection can lead to the resolution of paraneoplastic DM symptoms [11]. In our case, the extent of DM symptoms was associated with the treatment course of rectal cancer, suggesting that we were dealing with a case of paraneoplastic DM caused by rectal cancer.
It has been reported that symptoms also worsen when the malignancy recurred after resection of the primary disease in patients with paraneoplastic DM. However, to date, few reports have described details of recurring disease in the patients with DM accompanied by colorectal cancer. We have therefore investigated recurrent cases of DM accompanied by colorectal cancer to clarify the clinical features of these cases.
A literature search was conducted in April 2016 using the PubMed and Ichushi database to obtain English and Japanese literature describing recurring cases of patients with colorectal cancer and DM; four reports were found [6, 12–14].The keywords used in the search were “dermatomyositis” and “colorectal cancer.” The details of clinicopathological features of these cases, including the present case, are demonstrated in Table 1. There were two men and three women with a mean age of 54 years. Three patients had colon cancer and two had rectal cancer. Two cases had synchronous liver metastases, and hepatic resections were performed after the resection of the primary tumors. Recurrence sites were in the liver in three cases, lung in two cases, and local recurrence in one case (including overlapped case). Four reported cases presented moderately differentiated adenocarcinoma; however, the pathological differences between general colorectal cancers were not determined. The molecular findings for such cases were not described, although one case presented BRAF V600E mutation (case 3). Further investigation is needed to clarify these findings. DM symptoms worsened when cancer recurred in four cases, except in one case that was not described in detail. In the two cases including our case, cancer relapses were detected by exacerbation of DM symptoms, although these were not preceded by cancer relapses in the other two cases. Cancer recurrence occurred within 3 to 7 months after surgery in all cases, except for the case we present here. Systemic chemotherapies were applied in all four cases, and three of the four patients died from disease. Based on these findings, patients with paraneoplastic disease were suggested to have resistance to surgery, although poor prognoses compared with common colorectal cancer could not be determined because of the small sample size. The present case demonstrated good outcomes with resection of metastatic disease and relatively long disease-free survival.
Most patients presented with exacerbating DM symptoms when the colorectal cancer relapsed. It is important to check the exacerbation of DM symptoms, including skin erythema and dysphagia, when following patients with paraneoplastic DM. Few studies reported recurring cases of DM and other cancers. These reports demonstrated the association between DM symptoms and cancer recurrence in patients with ovarian cancer [15], breast cancer [16], and bladder cancer [17], supporting our findings in colorectal cancer. The present report describes a rare case with a good outcome of resecting liver metastases that were detected early by exacerbation of skin symptoms before annual examination in a patient with DM accompanied by rectal cancer.