the morbidity and mortality rates of colorectal cancer are increasing . in cases of progressive and recurrent colorectal cancer ineligible for radical resection , although the survival time has been prolonged because of the advent of various drugs , a cure is difficult to achieve , and the prognosis of colorectal cancer patients remains poor . in addition , with the increasingly aging population , the number of cancer patients with various comorbidities , such as cerebrovascular disorders and hepatic / renal dysfunction , is also increasing ; consequently , problems associated with the administration of chemotherapy to elderly patients with these conditions are also becoming more common . however , even for these patients , the standard treatment should be considered after their general condition , and therapeutic regimens have been sufficiently examined . in fact , it seems that many patients , including elderly patients with colorectal cancer complicated by membranous nephropathy , such as the patient described herein , can be safely treated by adding sufficient supportive therapy . we experienced a case involving an elderly patient with metastatic colorectal cancer that was detected at the onset of membranous nephropathy and that responded to s-1 and oxaliplatin combination ( sox ) therapy . she presented with general malaise , edematous limbs , and pleural effusion , and was suspected to have a nephrotic syndrome . accordingly , she was referred to our hospital from her local clinic . at her initial visit , the test results showed a total protein level of 5.03 g / dl , albumin level of 2.36 g / dl , a total cholesterol level of 265 mg / dl , a strong positivity for urine protein and a daily urine protein excretion of 1.1 g. after undergoing various detailed examinations at the department of nephrology , she was diagnosed with membranous nephropathy secondary to ascending colon cancer and multiple liver metastases . for the colonic stricture and bleeding , a right hemicolectomy and ileostomy were first performed . after surgery , she was referred to our department for chemotherapy . despite her advanced age and the presence of membranous nephropathy , no bone marrow , hepatic or renal dysfunction was noted , and her general condition was favorable , with a performance status 1 . bevacizumab was not administered owing to proteinuria caused by the membranous nephropathy , and anti - epidermal growth factor receptor drugs could not be administered owing to the presence of a kras g12v mutation . considering the toxicity profiles and the patient 's preference , sox therapy was selected as the primary treatment . the sox regimen consisted of s-1 ( 4060 mg depending on the patient 's body surface area ) given orally twice daily for 2 consecutive weeks and 100 mg / m oxaliplatin ( initiated at a dose reduced by 1 step in consideration of her age and underlying diseases ) administered intravenously on day 1 , followed by a 1-week rest period to comprise a 3-week cycle . on day 3 of the first cycle of sox therapy , high fever , shivering , and anorexia ( grade 3 ) were observed . these symptoms were determined to have resulted from infection along with the metastatic lesions in the liver . consequently , the oral administration of s-1 was suspended , and antibiotic therapy was initiated . the symptoms were relieved by conservative therapy , and the oral administration of s-1 was resumed on day 10 . the course after the resumption of the oral administration of s-1 was uneventful , without any particular problems . because of the adverse events , the dose of oxaliplatin was further reduced ( 75 mg / m ) in the second cycle to allow for a treatment continuation . in the subsequent cycles , although grade 12 peripheral sensory neuropathy caused by oxaliplatin was observed , the tolerability of the treatment was considered good . an abdominal ct performed before the initiation of chemotherapy revealed multiple , relatively large , metastatic lesions in a wide area of the liver as well as left pleural effusion ( fig . another abdominal ct scan at the point of maximum treatment effect ( after the completion of 8 cycles of sox therapy ) revealed a marked reduction in the metastatic lesions in the liver and a decrease in the left pleural effusion ( fig . 2 ) . in accordance with the improved imaging findings , the levels of tumor markers also decreased at this time . the levels of carcinoembryonic antigen and carbohydrate antigen 199 were 467.6 ng / ml and 1,881.0 u / ml , respectively , immediately before the initiation of chemotherapy ; at the completion of 8 cycles of sox therapy , they were reduced to 8.0 ng / ml and 22.7 u / ml , respectively . the treatment response was classified as a partial response . according to the evaluation of the ct images at the completion of 16 cycles , the condition of the patient remains stable , without any apparent sign of progressive disease . the occurrence of membranous nephropathy has been reported in lung , gastric , and colorectal cancers   ( among others ) , and leeaphorn et al .   reported that colorectal cancer accounted for approximately 11% of cases of malignancies with concurrent membranous nephropathy , making it the fourth most common malignancy following lung cancer , prostate cancer , and hematologic malignancies . although the exact incidence rate of membranous nephropathy in patients with colorectal cancer remains unknown , a report of an aggregate analysis performed in japan in 2012   showed that only 8 ( 1.0% ) of 813 cases of membranous nephropathy were associated with malignancy , and that none of these cases were colorectal cancer . thus , the incidence rate of membranous nephropathy is assumed not to be particularly high in patients with colorectal cancer in japan . in patients with malignancy , it is considered that membranous nephropathy is due to tumor - associated antigens and their antibodies forming immune complexes , which deposit on the glomerular basement membrane . in this case , although we initiated treatment for malignancy with an expectation that this treatment would contribute to relief of the membranous nephropathy , as reported in a previous study , the hematological and urinary findings showed only mild relief . however , there was little evidence of deterioration of renal function or of a trend of fluid retention such as edema . at present , oxaliplatin- or irinotecan - based   therapy , combined with molecular target drugs such as bevacizumab , cetuximab   and panitumumab , is widely and commonly applied to unresectable metastatic colorectal cancer . in our case , owing to concerns over diarrhea caused by irinotecan and the management of an ileal stoma , we considered oxaliplatin - based therapy combined with molecular target drugs as the primary treatment . however , bevacizumab was not administered owing to proteinuria caused by the membranous nephropathy , and , furthermore , anti - epidermal growth factor receptor drugs could not be used due to the presence of a kras mutation . although 5-fluorouracil / folinic acid plus oxaliplatin   and capecitabine plus oxaliplatin therapy   could also be considered valid treatment options , sox therapy was selected for our patient in consideration of her request for a treatment that was associated with a lower toxicity profile , allowed longer intervals between visits , was mainly composed of oral medications at low doses and required shorter durations of infusion . although infection and grade 3 anorexia were observed on day 3 of the first cycle of sox therapy , no serious adverse event was subsequently observed . currently , approximately 1 year after the initiation of treatment , the status of the patient remains at partial response and shows no aggravation . in patients receiving sox therapy combined with bevacizumab as the primary treatment for unresectable metastatic colorectal cancer , it is reported that the response rate is 62.5% , and that the progression - free survival is 11.7 months . despite our patient 's advanced age , an adequate treatment response was achieved with this treatment , and we plan to continue sox therapy unless she develops progressive disease or intolerable adverse events . in conclusion , even elderly patients with metastatic colorectal cancer and concurrent membranous nephropathy may respond to sox therapy administered as the primary treatment . our case suggests that , if the organ functions and general condition permit , aggressive drug therapy should be considered .
the incidence , morbidity , and mortality of colorectal cancer are increasing , largely owing to an increasingly aging population . additionally , along with the increasing age of cancer patients , 
 the number of patients with various comorbidities such as membranous nephropathy is also rising , and problems associated with the administration of chemotherapy to elderly patients with these conditions are becoming more common . 
 herein , we describe a case involving an 80-year - old woman who presented with general malaise , edematous limbs , and pleural effusion . 
 an abdominal ct revealed multiple , relatively large , metastatic lesions in a wide area of the liver and left pleural effusion , and she was accordingly diagnosed with membranous nephropathy secondary to ascending colon cancer and multiple liver metastases . despite her advanced age and the presence of membranous nephropathy , her general condition was favorable and chemotherapy was hence administered . 
 taking the toxicity profiles and the patient 's preference into consideration , s-1 and oxaliplatin ( sox ) therapy was selected , which showed a good tolerability . 
 an abdominal ct after 8 cycles of sox therapy revealed a marked reduction in the metastatic lesions in the liver and a decrease in the left pleural effusion , and the levels of tumor markers also decreased ( partial response ) . at the latest follow - up , after the completion of 16 cycles , the condition of the patient remained stable , without any apparent signs of progressive disease . 
 based on this case , we conclude that , even for elderly patients with systemic complications or comorbid diseases , standard treatments should be considered after their general conditions , and therapeutic regimens have been sufficiently examined .