Radiation dose >=54 Gy and CA 19--9 response are associated with improved survival for unresectable, non-metastatic pancreatic cancer treated with chemoradiation

ABSTRACT: BACKGROUND: Unresectable pancreatic cancer (UPC) has low survival. With improving staging techniques and systemic therapy, local control in patients without metastatic disease is becoming clinically important. We investigated whether the radiation dose used in chemoradiation (CRT) as definitive treatment for UPC and the CA 19--9 response to therapy have an impact on overall survival (OS). METHODS: From 1997--2009 46 patients were treated with CRT for non-metastatic UPC. Median prescribed RT dose was 54 Gy (range 50.4-59.4 Gy). All patients received concurrent chemotherapy (41: 5-fluorouracil, 5: other) and 24 received adjuvant chemotherapy. RESULTS: 41 patients were inoperable due to T4 disease and 5 patients with T3 disease were medically inoperable. Five patients did not complete CRT due to progressive disease or treatment-related toxicity (median RT dose 43.2 Gy). Overall, 42 patients were dead of disease at the time of last follow-up. The median and 12 month OS were 8.8 months and 35%, respectively. By univariate analysis minimum CA 19--9 post-CRT of <90 U/mL was favorably associated with OS (12.3 versus 8.8 months, p = 0.012). Radiotherapy dose >=54 Gy trended towards improved OS (11.3 versus 6.8 months, p = 0.089). By multivariable analysis a delivered RT dose of >=54 Gy (HR 0.47, p = 0.028) and minimum CA 19--9 post-CRT of <90 U/mL (HR 0.35, p = 0.008) were associated with OS. CONCLUSIONS: CRT as definitive treatment for UPC had low survival. However, our retrospective data suggest that patients treated to >=54 Gy or who experienced a minimum post-CRT CA 19--9 <90 U/mL had improved likelihood of long-term survival.