1323 Differences in proportion adjuvant chemotherapy are not associated with relative survival for stage II colon cancer patients aged 75 years and older - a EURECCA international comparison

Abstracts significant comorbidity (CIRS-G). Pts were randomized to receive either cetuximab 500mg/m2 q2weeks (arm A) or cetuximab plus capecitabine 1000mg/m2 bid d1−14 q3weeks (arm B). Primary endpoint was PFS at week 12. Secondary endpoints included adverse events, quality of life, response, and overall treatment utility (composite endpoint accounting for efficacy and tolerability of treatment). Results: Planned sample size was 78 pts but the trial was stopped prematurely in Jan 2015 due to slow accrual after the inclusion of 24 pts (arm A, 11; arm B, 13). Pts in arm A and B had a median age of 79 and 80 years (range 71−89), a median IADL score of 6 and 7 (range 3−8), and a median CIRS-G score of 7 (range 1−13), respectively. Results up to week 12 are reported. A median of 6 cetuximab infusions were administered per pt in both arms (median dose 500 mg/m2 ). Cetuximab dose was reduced in 4 pts and discontinued in one pt due to a severe anaphylactic reaction. In arm B, a median of 3 capecitabine cycles were administered per pt with a median daily dose of 1855 mg. Capecitabine was dose reduced due to toxicity in 3 pts and discontinued in one pt due to gastrointestinal toxicity. At week 12, 6 of 11 pts (55%) were free of progression in arm A, and 9 of 13 pts (69%) in arm B. Partial response was observed in one pt (9%) of arm A, and in 4 pts (31%) of arm B. Severe toxicities were observed in 4 pts of each treatment arm. In total, there were 14 G3 toxicities, the most common being acneiform rash (4 events), keratitis, diarrhea, and infections (2 events each). The only G4 toxicity was an anaphylactic reaction during cetuximab administration (arm B). There were 3 deaths, one due to tumor progression in arm A and 2 due to infections in arm B. Conclusions: This trial was specifically designed for vulnerable elderly pts with RAS/BRAF WT mCRC. It proved to be more difficult than expected to conduct such a randomized trial of chemotherapy versus no chemotherapy in the given trial population. Cetuximab treatment appeared tolerable and showed promising activity in this population, particularly when combined with an oral fluoropyrimidine. Updated information on secondary endpoints will be presented at the meeting. No conflict of interest. 1323 POSTER Differences in proportion adjuvant chemotherapy are not associated with relative survival for stage II colon cancer patients aged 75 years and older − a EURECCA international comparison A.J. Breugom1 , E. Bastiaannet1 , P.G. Boelens1 , E. Van Eycken2 , 6 T. Vandendael2 , L.H. Iversen3 , K. O’Brien4 , A. Martling5 , L. Pahlman ˚ , G.J. Liefers1 , H.J.T. Rutten7 , V.E. Lemmens8 , C.J.H. Van de Velde1 . 1 Leiden University Medical Centre, Surgery, Leiden, Netherlands; 2 Belgian Cancer Registry, Research, Brussels, Belgium; 3 Aarhus University Hospital, Surgery, Aarhus, Denmark; 4 National Cancer Registry Ireland, Research, Cork, Ireland; 5 Karolinska Institute, Moleculare Medicine and Surgery, Stockholm, Sweden; 6 Uppsala University, Surgical Sciences, Uppsala, Sweden; 7 Catharina Hospital, Surgery, Eindhoven, Netherlands; 8 Comprehensive Cancer Centre Netherlands, Research, Utrecht, Netherlands Background: The benefits of adjuvant chemotherapy for stage II colon cancer are uncertain, especially for older patients who are often excluded from trials. Moreover, most trials did not demonstrate a survival benefit of adjuvant chemotherapy for stage II disease. Comparative Effectiveness Research could give insight into optimal treatment strategies in geriatric oncology. The aim of this population-based international comparison is to compare adjuvant chemotherapy and relative survival in stage II colon cancer patients aged 75 years and older. Material and Methods: We collected population-based national cohort data (2004–2009) from the Netherlands Cancer Registry, the Swedish Colorectal Cancer Registry, the Danish Colorectal Cancer Group database, the National Cancer Registry Ireland, and the Belgian Cancer Registry. We included all surgically treated patients aged 75 years and older with pathological stage II colon cancer. We calculated differences in the proportion of adjuvant chemotherapy. Relative survival was calculated as the ratio of the observed survival and the expected survival based on the matched general population. All analyses were stratified by stage, and adjusted for gender, year of incidence, tumour localisation, and tumour grade. Results: Overall, 14,557 patients were included; 5626 Dutch patients, 1761 Swedish patients, 2064 Danish patients, 966 Irish patients, and 4140 Belgian patients. For stage IIA colon cancer, the proportion of adjuvant chemotherapy was 0.5% in the Netherlands, compared with 0.9% in Sweden, 2.0% in Denmark, 4.3% in Ireland, and 8.4% in Belgium (adjusted p < 0.001). There was no significant trend in relative survival (ptrend =0.223) with an increasing proportion of adjuvant chemotherapy. With the Netherlands as reference, the adjusted RER was 0.62 (95% CI 0.38–1.01; p = 0.057) for Sweden, 0.86 (95% CI 0.64–1.16; p = 0.334) for

S195 Denmark, 0.91 (95% CI 0.65–1.26; p = 0.568) for Ireland, and 0.85 (95% CI 0.70–1.04; p = 0.107) for Belgium. For stage IIB colon cancer, 4.7% Dutch patients, 7.6% Swedish patients, 9.7% Danish patients, 11.8% Irish patients, and 21.9% Belgian patients (adjusted p < 0.001) had adjuvant chemotherapy. We observed no significant trend in relative survival (ptrend =0.280) with an increasing proportion adjuvant chemotherapy. The adjusted RER, with the Netherlands as reference, was 1.09 (95% CI 0.73–1.62; p = 0.691) for Sweden, 0.71 (95% CI 0.50–1.00; p = 0.051) for Denmark, 1.09 (95% CI 0.80–1.48; p = 0.591) for Ireland, and 1.00 (95% CI 0.80–1.25; p = 0.991) for Belgium. Conclusions: The present international comparison shows variation in administered adjuvant chemotherapy for stage II colon cancer patients aged 75 years and older among five European countries. However, we did not observe a significant trend in relative survival with an increasing proportion adjuvant chemotherapy. No conflict of interest. 1324 POSTER EURECCA international comparison of treatment and survival in metastatic rectal cancer for patients over the age of 80 years E. Bastiaannet1 , A. Breugom1 , M. Kiderlen1 , L. Iversen2 , A. Martling3 , R. Johansson4 , H. Ortiz5 , V. Valentini6 , E. Van Eycken7 , T. Vandendael7 , P. Mroczkowski8 , H. Lippert8 , H. Rutten9 , G.J. Liefers1 , V. Lemmens10 , P. Boelens1 , C. Van de Velde1 . 1 LUMC, Surgery, Leiden, Netherlands; 2 Aarhus University Hospital, Surgery, Aarhus, Denmark; 3 Karolinska Institutet, Molecular medicine and Surgery, Stockholm, Sweden; 4 ˚ Sweden; University Hospital Norrlands, Epidemiology, Umea, 5 Universidad Publica de Navarra, Surgery, Pamplona, Spain; 6 Universita` Cattolica S.Cuore, Radiation Oncology Department, Rome, Italy; 7 National Cancer Registry, Research, Brussel, Belgium; 8 University of Magdeburg, Institute for Quality Assurance in Surgical Care, Magdeburg, Germany; 9 Catharine Hospital, Surgery, Eindhoven, Netherlands; 10 Comprehensive Cancer Center Netherlands, Research, Utrecht, Netherlands Introduction. The most appropriate treatment strategy for older patients with metastatic rectal cancer is not clear, as they are mostly excluded for randomized controlled trials (RCTs) which are also harder to perform due to the heterogeneity of the population. Comparative Effectiveness Research, by using country as instrumental variable, could provide clues to the best treatment strategy in geriatric oncology. The aim of this study is to compare treatment strategies and relative survival between seven European countries. Methods: Population-based cohorts (2001–2010) from Denmark, Sweden, Belgium, the Netherlands, Germany, Spain, and Italy were compared sideby-side for neighboring countries on treatment strategy and relative survival for patients of 80 years and older with metastatic rectal cancer at primary diagnosis, adjusted for sex, age and differentiation grade. Relative survival was calculated as the ratio of the survival observed in the cohort and the expected survival based on the matched general population in the specific countries. Results: Overall, 4210 patients with metastatic rectal cancer were included. Treatment strategy in Sweden comprised a higher proportion of surgery than Denmark (60.9% versus 45.3%), but a lower proportion of chemotherapy, both after surgery (0.7% versus 8.1%) and solely chemotherapy (0.8% versus 10.0%). Relative survival rate was lower in Sweden with an adjusted Relative Excess Risk (RER) of 1.4 (95% CI 1.3−1.7); p < 0.001. Treatment strategy in Belgium compared to the Netherlands comprised a higher proportion of surgery (39.8% versus 29.2%) and chemotherapy (44.5% versus 9.5%). Relative survival rate showed a trend towards a higher survival in Belgium with an adjusted RER of 1.1 (95% CI 1.0−1.3); p = 0.06. Treatment strategy in the Netherlands as compared to Germany showed a higher proportion of surgery and chemotherapy (2.8% versus 0.8%) and no differences in relative survival (RER 1.0 (0.9−1.2); p = 0.6). There were no survival differences between Spain and Italy. Conclusion: The current comparison shows a higher survival rate for older patients with metastatic rectal cancer in countries with a higher proportion of chemotherapy in the treatment strategy, which might be due to patient selection. Further detailed analyses of these selection criteria for chemotherapy and adverse events could contribute to specific RCTs, treatment strategy changes and tailored treatment for patients over the age of 80 years with metastatic rectal cancer. No conflict of interest.