P340 - SIGNIFICANCE OF PSOAS MUSCLE MASS INDEX AND ITS RELEVANCE TO ADJUVANT CHEMOTHERAPY IN PATIENTS WITH PATHOLOGICAL STAGE III COLORECTAL CANCER AFTER SURGERY

P340

SIGNIFICANCE OF PSOAS MUSCLE MASS INDEX AND ITS RELEVANCE TO ADJUVANT CHEMOTHERAPY IN PATIENTS WITH PATHOLOGICAL STAGE III COLORECTAL CANCER AFTER SURGERY

K. Shiraishi^1,*, S. Furuya¹, K. Takahashi¹, K. Takiguchi¹, K. Matsuoka¹, Y. Higuchi¹, T. Ozawa¹, R. Saito¹, W. Izumo¹, S. Maruyama¹, K. Shoda¹, Y. Kawaguchi¹, H. Amemiya¹, D. Ichikawa¹

¹First Department of Surgery, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan

Rationale: Sarcopenia, defined as progressive loss of skeletal muscle mass and strength, is associated with poor outcomes such as physical disability and mortality. Adjuvant chemotherapy (AC) after curative R0 resection improves prognosis in patients with pathological stage III (pStage III) colorectal cancer. This study aimed to assess the significance of the psoas muscle mass index (PMI) and its relevance to AC indication.

Methods: We retrospectively analyzed 128 patients with pStage III colorectal cancer who underwent curative surgery between 2007 and 2015. PMI was calculated using the cross-sectional area of the psoas muscle at the L3 level on CT, divided by height squared (cm²/m²). Patients were classified into Low PMI and High PMI groups. We evaluated prognosis and AC rates in both groups, and compared clinical features and outcomes between AC and non-AC patients.

Results: Of 128 patients, 49 were in the Low PMI group and 79 in the High PMI group. The Low PMI group had a higher proportion of females (p=0.035) and more frequent vascular invasion (p=0.012). AC was administered to 40.8% of Low PMI patients and 64.6% of High PMI patients (p=0.009). The 5-year overall survival rate was significantly lower in the Low PMI group (55.5%) compared to the High PMI group (76.4%). Among Low PMI patients, those who received AC had better survival (62.9%) than those who did not (49.6%, p<0.05). Patients with a modified Glasgow Prognostic Score (mGPS) of 0 had a 5-year survival of 76.9%, while those with mGPS 2, reflecting cachexia, had a markedly poor prognosis (26.4%, p<0.001).

Conclusion: Low PMI was associated with worse prognosis and a lower AC administration rate. The efficacy of AC may be limited in sarcopenic patients. Careful consideration is needed when selecting postoperative AC for patients with low muscle mass or systemic inflammation.

Disclosure of Interest: None declared