KORELASI ANTARA VOLUME TUMOR DAN SKELETAL MUSCLE INDEX (INDEKS SARKOPENIA) PADA PASIEN KARSINOMA REKTUM MELALUI PEMERIKSAAN COMPUTED TOMOGRAPHY

Hendri Tanoyo Kusuma, Dr. dr. Bambang Supriyadi, Sp. Rad., Subsp. MSK (K), MM; dr. Bambang Purwanto Utomo, Sp. Rad., Subsp. Abd (K), M. Med. Ed

2026 | Tesis-Spesialis | S2 Radiologi

Latar Belakang: Karsinoma rektum merupakan salah satu keganasan gastrointestinal dengan morbiditas dan mortalitas tinggi. Volume tumor mencerminkan beban penyakit dan berpotensi menjadi biomarker radiologis, sedangkan skeletal muscle index (SMI) pada computed tomography (CT) merefleksikan status massa otot rangka yang berhubungan dengan sarkopenia. Albumin sebagai protein plasma utama dapat mencerminkan status nutrisi dan inflamasi sistemik, sehingga berpotensi memengaruhi hubungan antara volume tumor dan SMI.

Tujuan: Mengetahui korelasi antara volume tumor dan skeletal muscle index pada pasien karsinoma rektum melalui pemeriksaan computed tomography, serta menilai hubungan tersebut setelah mempertimbangkan albumin sebagai kovariat.

Metode: Penelitian ini merupakan penelitian analitik observasional dengan desain potong lintang retrospektif. Subjek penelitian adalah pasien karsinoma rektum yang menjalani pemeriksaan CT abdomen di RSUP Dr. Sardjito Yogyakarta dan memenuhi kriteria inklusi. Volume tumor diukur melalui metode volumetri pada CT, sedangkan SMI dihitung dari luas otot rangka pada level vertebra L3 yang dinormalisasi terhadap kuadrat tinggi badan. Analisis korelasi dilakukan menggunakan uji Spearman. Analisis multivariat dilakukan menggunakan regresi linear dengan SMI sebagai variabel dependen, volume tumor sebagai variabel independen utama, dan albumin sebagai kovariat

Hasil: Penelitian ini melibatkan 58 subjek. Median volume tumor adalah 113,37 cm³ dengan rentang interkuartil 175,7, sedangkan median SMI adalah 33,8 dengan rentang interkuartil 12,7. Terdapat korelasi negatif bermakna antara volume tumor dan SMI dengan kekuatan sedang (r = -0,320; p = 0,014). Data albumin tersedia pada 46 subjek. Analisis multivariat menunjukkan bahwa model regresi linear bermakna secara statistik (p = 0,008) dengan adjusted R² sebesar 0,164. Albumin menunjukkan arah hubungan positif terhadap SMI dengan kecenderungan mendekati kemaknaan statistik (B = 3,562; ß = 0,299; p = 0,069).

Kesimpulan: Volume tumor memiliki korelasi negatif bermakna dengan SMI pada pasien karsinoma rektum melalui pemeriksaan CT. Pada analisis multivariat, menunjukkan bahwa hubungan antara beban tumor dan status massa otot perlu diinterpretasikan bersama faktor status nutrisi dan inflamasi sistemik pasien, khususnya albumin.

Kata Kunci: karsinoma rektum, volume tumor, skeletal muscle index, sarkopenia, computed tomography, albumin.

Introduction: Rectal carcinoma is a gastrointestinal malignancy associated with high morbidity and mortality. Tumor volume reflects disease burden and may serve as a radiological biomarker, whereas computed tomography (CT)-based skeletal muscle index (SMI) represents skeletal muscle mass and is associated with sarcopenia. Albumin, as the main plasma protein, may reflect nutritional status and systemic inflammation, and therefore may influence the relationship between tumor volume and SMI.

Objective: To evaluate the correlation between tumor volume and skeletal muscle index in patients with rectal carcinoma using computed tomography, and to assess this relationship after considering albumin as a covariate.

Methods: This was an observational analytic study with a retrospective cross-sectional design. The study included patients with rectal carcinoma who underwent abdominal CT examination at Dr. Sardjito General Hospital Yogyakarta and met the inclusion criteria. Tumor volume was measured using CT-based volumetric assessment, while SMI was calculated from the skeletal muscle area at the third lumbar vertebral level normalized by height squared. Correlation analysis was performed using Spearman’s test. Multivariate analysis was performed using linear regression with SMI as the dependent variable, tumor volume as the main independent variable, and albumin as a covariate in subjects with complete albumin data.

Results: A total of 58 subjects were included in this study. The median tumor volume was

113.37 cm³ with an interquartile range of 175.7, while the median SMI was 33.8 with an interquartile range of 12.7. A significant negative correlation was found between tumor volume and SMI with moderate strength (r = -0.320; p = 0.014). Albumin data were available in 46 subjects. Multivariate analysis showed that the linear regression model was statistically significant (p = 0.008), with an adjusted R² of 0.164. Albumin showed a positive association with SMI with a trend toward statistical significance (B = 3.562; ß = 0.299; p = 0.069).

Conclusion: Tumor volume was significantly and negatively correlated with SMI in patients with rectal carcinoma on CT examination. In the multivariate analysis, the relationship between tumor burden and skeletal muscle status should be interpreted in conjunction with the patient’s nutritional status and systemic inflammatory condition, particularly albumin.

Keywords: rectal carcinoma, tumor volume, skeletal muscle index, sarcopenia, computed tomography, albumin

Kata Kunci : karsinoma rektum, volume tumor, skeletal muscle index, sarkopenia, computed tomography, albumin