The study investigated whether doctors or patients could accurately assess the quality of life, anxiety, and depression of cancer patients. Doctors and patients completed the same questionnaires, including the Karnofsky, Spitzer, and Linear Analogue Self Assessment (LASA) scales. Correlations between the scores were poor, indicating that doctors could not accurately determine what patients felt. Further studies showed significant variability in results between different doctors, suggesting that reliable measurement of quality of life should come from patients themselves. Quality of life is a subjective concept, but objective measurement is needed in clinical trials due to the often toxic nature of cancer treatments. Several instruments have been developed to quantify these subjective parameters. However, the study found that doctors' assessments were inconsistent and often explained less than 30% of the variability in patients' scores. The Spitzer and HAD scales showed that individual questions contributed significantly to total scores, suggesting that not all questions were equally useful. The study also found that the Karnofsky scale had greater reproducibility than other scales. However, even this scale showed variability, with only 54% of occasions producing the same score. The results suggest that patients should be the ones to measure their own quality of life, as doctors' assessments are inconsistent and unreliable. The study highlights the need for more reliable and practical instruments to assess quality of life in cancer patients.The study investigated whether doctors or patients could accurately assess the quality of life, anxiety, and depression of cancer patients. Doctors and patients completed the same questionnaires, including the Karnofsky, Spitzer, and Linear Analogue Self Assessment (LASA) scales. Correlations between the scores were poor, indicating that doctors could not accurately determine what patients felt. Further studies showed significant variability in results between different doctors, suggesting that reliable measurement of quality of life should come from patients themselves. Quality of life is a subjective concept, but objective measurement is needed in clinical trials due to the often toxic nature of cancer treatments. Several instruments have been developed to quantify these subjective parameters. However, the study found that doctors' assessments were inconsistent and often explained less than 30% of the variability in patients' scores. The Spitzer and HAD scales showed that individual questions contributed significantly to total scores, suggesting that not all questions were equally useful. The study also found that the Karnofsky scale had greater reproducibility than other scales. However, even this scale showed variability, with only 54% of occasions producing the same score. The results suggest that patients should be the ones to measure their own quality of life, as doctors' assessments are inconsistent and unreliable. The study highlights the need for more reliable and practical instruments to assess quality of life in cancer patients.