Biochemical outcome after curative treatment for localized prostate cancer with external beam radiotherapy: a cross-sectional study

Abstract

Although many patients who receive definitive radiotherapy (RT) for localised prostate cancer (CaP) experience long-term disease-free survival and better quality of life, some also have biochemical progression during follow-up. Oftentimes this implies additional treatment for patients with the accompanying challenges of cumulative treatment side effects, inconvenience and financial toxicity. This study retrospectively assessed the clinicopathological characteristics and biochemical outcomes of patients treated for localised CaP with external beam radiotherapy (EBRT) between 2015 and 2020 at a major cancer treatment centre in Accra, Ghana. Patients' socio-demographic and clinical data were collected from their hospital records and analysed with the Statistical Package for Social Sciences version 26. Biochemical failure (BCF) was defined as an increase in the level of serum prostate-specific antigen (PSA) >2 ng/mL above the nadir after curative therapy based on the Phoenix definition. The mean age was 67.6 years (SD ± 6.2). The majority of the study participants (n = 79, 64.8%) had initial PSA >20 ng/mL, with the highest recorded value of 705 ng/mL. All the patients had biopsy-proven adenocarcinoma of the prostate gland. Some patients received 3-dimensional conformal radiotherapy (3DCRT) on a cobalt-60 teletherapy machine whereas others were treated with either 3DCRT or intensity-modulated radiotherapy (IMRT) on a 6 MV Linac. In all, 13.1% of the patients experienced BCF after receiving EBRT after an average follow-up of 31.3 months. This study demonstrated a low rate of BCF among patients treated with EBRT for localised CaP in Ghana. Strong prognostic factors of biochemical outcome demonstrated in this study were the percentage of cores positive, grade group, and risk stratification. Diarrhaea and desquamation experienced by treated CaP patients were exclusively attributable to EBRT. RT produced a complete resolution of symptoms in some of the patients.

Keywords: androgen deprivation therapy; biochemical recurrence; external beam radiotherapy; intensity-modulated radiotherapy; localised prostate cancer; prostate adenocarcinoma; prostate-specific antigen; radiotherapy; time to biochemical progression.

Figure 1.. Pre-treatment metastatic workup of the study participants. CT = computed tomography, MRI = magnetic resonance imaging, USG = ultrasonography, CXR = chest X-ray. The modalities for pre-treatment workup undertaken by the patients were not mutually exclusive.

Figure 2.. iPSA of patients with localised CaP. PSA = prostate specific antigen, CaP = prostate cancer. For patients with multiple PSA results of different values done prior to starting treatment, the iPSA was taken to be the highest pretreatment PSA value of the patients.

Figure 3.. Risk stratification of patients with localised CaP. CaP = Prostate cancer. The intermediate risk group was divided into the favourable and unfavourable intermediate risk groups. There were no patients in the category of very low risk CaP.

Figure 4.. Comorbidities of patients with localised CaP. HIV: human immunodeficiency virus, CVA: cardiovascular accident. Hypertensives were patients with known hypertensive heart disease whereas ‘asthma’ signifies patients with bronchial asthma. These comorbidities were not mutually exclusive. There were some patients who had more than one of the listed medical conditions simultaneously.

Figure 5.. Patients’ symptoms pre and post EBRT. LUTS = lower urinary tract symptoms, EBRT = external beam radiotherapy. Presenting symptoms were the complaints experienced and expressed by the patients at the time of their presentation at the hospital before receiving treatment. ‘No complaint’ refers to patients who did not present with or complain of any symptoms before starting their treatment.

Figure 6.. ADT received by patients. The figure summarises the hormonal ADT received by the patients. Some received alternate injections of Goserelin (Zoladex, 11.8 mg) and leuprolide 11.25 mg. This was either due to the unavailability of one of the drugs at some point during treatment or due to financial considerations. The cost of Goserelin was about twice that of leuprolide so patients receiving the former who could no longer afford it often switched to the latter. These medications were administered as 3-monthly injections. Some patients also received Bicalutamide (Casodex 50 mg/150 mg).

Figure 7.. Biochemical outcome after EBRT in localised CaP. BPFS = biochemical progression-free survival, BCF = biochemical failure, EBRT = external beam radiotherapy.

Figure 8.. Pattern of time to BCF. BCF – biochemical failure.