Blood transfusions in prostatectomies
Motivation
Prostate cancer is the most common type of malignant cancer in men. One common treatment option is radical prostatectomy: complete surgical removal of the prostate gland. Unfortunately, the cancer often returns after surgery—in about one quarter of patients, it will recur within five years—so surgeons are interested in understanding factors associated with recurrence and how they can be managed.
One possible factor is the use of blood transfusions during surgery. If the patient loses too much blood during surgery, they will be given a blood transfusion. Most blood transfusions use blood from unrelated donors that matches the recipient’s blood type, but because the blood comes from a different person, it contains different immune cells. It is possible that this suppresses or interferes with the recipient’s immune system, making it more likely the cancer can recur. It is also thought that older blood cells—that is, those that have been in storage for longer before being used in the transfusion—may cause more immune disruption and thus be worse for the patient.
This data comes from an observational study of patients who received blood transfusions during their prostatectomy. The data includes the number of units of blood transfused and the age of the blood used. Patients were tracked for five years to determine if their prostate cancer returned after the surgery, so it is possible to investigate how the age of the transfused blood is associated with recurrence.
Data
Each observation is one patient who had a prostatectomy at the Cleveland Clinic between July 6, 1998 and December 27, 2007, and who had a blood transfusion during their surgery. There are 316 total patients included in this sample.
Data preview
prostatectomy-storage.csv
Variable descriptions
| Variable | Description |
|---|---|
| RBC.Age.Group | Red blood cell storage duration, grouped (1 = less than 13 days, 2 = 13-18 days, 3 = more than 18 days) |
| Median.RBC.Age | Median age of red blood cells transfused (conversion of RBC.Age.Group to days) |
| Age | Patient age (years) |
| AA | 1 if patient is African-American, 0 otherwise |
| FamHx | 1 if patient has family history of prostate cancer |
| PVol | Prostate mass when removed (grams) |
| TVol | Tumor volume (1 = low, 2 = medium, 3 = extensive) |
| T.Stage | Clinical T category, a measure of the stage of cancer, estimated before surgery. 1 = stages T1-T2a, indicating tumor can’t be felt or seen in imaging, or is felt/seen in half of only one side of the prostate. 2 = stages T2b-T3, indicating tumor is felt/seen in more than half of one side, is in both sides, or has spread outside the prostate. |
| bGS | Biopsy Gleason score, discretized. Based on microscopic examination of cells in a biopsy. Low scores means the cells look normal, high scores mean they look abnormal. 0 = score 0-6, 2 = score 7, 3 = score 8-10. |
| BN+ | Bladder neck positive: whether the neck of the bladder, at the edge of the prostate, contained cancerous cells when investigated after surgery. 1 = yes, 0 = no. |
| OrganConfined | 1 if cancer is limited to the prostate gland, 0 if it has spread outside it |
| PreopPSA | Prostate-specific antigen (PSA) levels measured before the surgery; levels are typically higher in people with prostate cancer (ng/mL) |
| PreopTherapy | Whether the patient received cancer treatment prior to surgery (1 = yes, 0 = no) |
| Units | Number of allogeneic units of blood received |
| sGS | Surgical Gleason score, discretized. Same as bGS, but based on examination of the tumor removed in surgery, rather than on cells removed in a biopsy |
| AnyAdjTherapy | Whether the patient received adjuvant therapy after the surgery, i.e., another treatment to prevent recurrence (such as chemotherapy, radiation, or other cancer treatments) |
| AdjRadTherapy | Whether the patient received radiation therapy after surgery to prevent recurrence |
| Recurrence | Whether the prostate cancer recurred (1 = yes, 0 = no) |
| Censor | Whether the study ended before the patient had any recurrence, so their final status is unknown (1 = censored, 0 = not censored) |
| TimeToRecurrence | Time to recurrence of prostate cancer, months |
Questions
- It’s possible that the amount of blood transfused depends on features of the tumor—perhaps more advanced cases required more invasive surgery with greater blood loss, for instance. Conduct an exploratory data analysis to judge the relationship between the units of blood transfused and indicators of the severity of the tumor, such as clinical T category, Gleason score, and tumor volume.
- Explore how tumor severity is related to the risk of recurrence. Conduct an exploratory analysis and then use regression to predict the risk of recurrence. How much more likely is recurrence for patients with a tumor that is advanced at the time of surgery, as measured by clinical T category or surgical Gleason score?
- Analyze the main research question: Is the risk of recurrence related to the age of blood transfused? Is there evidence that older blood is associated with a higher risk of recurrence?
References
Dataset adapted for classroom use by: Amy S. Nowacki, “Blood Storage Dataset”, TSHS Resources Portal (2017). Available at https://www.causeweb.org/tshs/blood-storage/. Released under a CC BY-NC-SA license.
Original study: Cata et al. (2011). “Blood Storage Duration and Biochemical Recurrence of Cancer After Radical Prostatectomy.” Mayo Clinic Proceedings 86 (2), 120-127. https://doi.org/10.4065/mcp.2010.0313