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Radiation therapy of prostate cancer
Last reviewed: 23.04.2024
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It is believed that the long-term results of radiotherapy for prostate cancer are the same as in surgical treatment, and the quality of life does not suffer from this. Since 1990, the possibilities of radiotherapy have been expanded through the introduction of contact irradiation techniques and volumetric planning. In recent years, the intensity modulation has been increasingly used in specialized centers.
Comparative studies of the effectiveness of radiotherapy (remote or contact) and prostatectomy for localized prostate cancer have not been obtained to date.
The surgeon and the radiologist are involved in the choice of treatment tactics. It should take into account the stage of the disease, Yandex Gleason, PSA level, life expectancy, and the side effects of treatment. The patient should be informed of all information about the diagnosis and the possibilities of treatment. The final decision is made by the patient. As with radical prostatectomy, the Gleason index is considered to be the most important prognostic factor.
[Method of irradiation of prostate cancer
Volumetric planning of irradiation fields is carried out on the basis of CT, performed in the position in which the patient will be irradiated. Isolate the clinical volume (the volume of the tumor), which, together with the surrounding healthy tissues, makes up the therapeutic volume. Multi-petalled collimators automatically attach the desired shape to the irradiation field. Visualization of irradiation fields allows real-time comparison of actual fields with simulation ones and correction of deviations exceeding 5 mm. Volumetric planning helps to increase the dose and, accordingly, the effectiveness of irradiation, without increasing the risk of complications. Modulation of the intensity of irradiation is possible on a linear accelerator equipped with a modern multilobal collimator and a special program: the movement of the collimator flaps uniformly distributes the dose in the irradiation field, creating concave isodose curves. Radiation therapy (regardless of the technique) is planned and conducted by a radiologist, a dosimeter, a physics engineer and a programmer.
Radiation therapy for prostate cancer T 1-2c N 0 M 0
For patients with low oncological risk, T 1-2b Gleason index less than 6, PSA level less than 10 ng / ml) with remote exposure dose is 70-72 Gy, its increase does not improve the results.
At moderate risk (T 2b, PSA level - 10-20 ng / ml or Gleason index - 7), increasing the dose to 76-81 Gy significantly improves 5-year disease-free survival without causing severe late radiation reactions. Randomized trials have shown that in a moderate risk group, an increase in the radiation dose is justified. In one study, the dose rates of 70 and 78 Gy were compared (in conventional and volumetric planning, respectively) in 305 patients with T- 1 tumors and a PSA level of more than 10 ng / ml. With a median follow-up time of 40 months, 5-year recurrence-free survival was 48% and 75%, respectively. In another trial, 393 patients with T1b -2b tumors (in 15% of cases Gleason's index was less than 6, PSA level was less than 15 ng / ml ). In the first group, patients underwent irradiation of the prostate with a proton beam at a dose of 19.8 isoG, followed by irradiation of a larger volume of the gland in a dose of 50.4 Gy. In the second group, the dose of irradiation with a proton beam was increased to 28.8 isoGr. With a median follow-up time of 4 years, 5-year disease-free survival in the first group was significantly higher than in the second. The optimal dose has not yet been determined, but for daily practice it is possible to recommend a dose of 78 Gy.
In a high-risk group (T 2c, Gleason score greater than 7, or PSA level greater than 20 ng / ml), increasing the radiation dose increases the disease-free survival rate, but does not prevent recurrence outside the pelvic floor. According to a randomized trial involving 206 patients (PSA content 10-40 ng / ml, Gleason score - no less than 7 or tumor yield per capsule, median follow-up time 4.5 years), adherence during 6 months of hormone therapy to radiotherapy with volumetric planning significantly improves survival, reduces the risk of death from a tumor and prolongs the time before the start of hormone therapy.
Adjuvant radiation therapy of prostate cancer T 3
The use of adjuvant radiotherapy is more successful in patients with signs of extracapsular germination or with a positive surgical margin than in patients with invasion of seminal vesicles or lymphogenous metastasis. If the tumor goes beyond the capsule of the prostate (pT3), the risk of local recurrence reaches 10-50%. As mentioned above, the risk depends on the level of PSA, the Gleason index, and the presence of tumor cells at the margin of resection. Patients tolerate adjuvant radiotherapy well: occurrence of severe complications from the urinary tract is possible in 3.5% of cases; urinary incontinence and stricture in the zone of anastomosis occur no more often than without irradiation. Five-year recurrence-free survival rate is 12.2% (in the control group - 51.8%).
If after 1 month after the operation the PSA level is below 0.1 ng / ml and the germination of the capsule or seminal vesicles (pT 3 N 0 ) is detected , tumor cells in the margin of resection, adjuvant radiation therapy is indicated. It begins immediately after the normalization of urination and wound healing (after 3-4 weeks). Another option is dynamic observation in combination with irradiation (at a PSA level of more than 0.5 ng / ml). Since the PCA content is more than 1 ng / ml, the effectiveness of radiotherapy significantly decreases. The dose of radiation to the bed of the removed prostate should be at least 64 Gy. Usually, radiation therapy is performed immediately after the operation.
Radiation therapy for tumors T 3-4 N 0 M 0 and T 1-4 N 1 M 0
Unfortunately, despite the successes of early diagnosis, such tumors in Russia are observed more often than in developed countries. In view of the high risk of micrometastasis, not only increased (N 1 ), but also externally unchanged pelvic lymph nodes (N 0 ) should be included in the irradiation field . The isolated use of radiotherapy in such cases is ineffective, therefore, taking into account the hormone-dependent nature of PCa, it is combined with hormone therapy.
A number of studies confirm the advantage of combined treatment: reducing the risk of distant metastasis (due to the destruction of micrometastases), increasing the effect on the primary tumor - a potential source of new metastases (by enhancing apoptosis in the background of irradiation).
Preventive radiation of pelvic lymph nodes
Metastasis in the pelvic lymph nodes worsens the prognosis, however, randomized trials conducted in the 1970s and 1980s did not confirm the effectiveness of their preventive irradiation. Radiation exposure to lymph nodes does not affect the risk of local recurrence and survival. To assess the risk of metastasis to the lymph nodes, Partin's nomograms and a special formula allow;
Risk of metastases (%) = 2/3 PSA + (Gleason index 6) x 10.
Lymph node biopsy during laparoscopy or laparotomy is also possible.
Modulation of radiation intensity
Modulation of the intensity of irradiation makes it possible to increase the dose to 80 Gy with a uniform distribution in the tumor and without additional damage to healthy tissues. The greatest experience in the use of modulation is the Sloan-Kettering Cancer Center in New York: in 1996-2001, 772 patients received radiotherapy in a dose of 81-86.4 Gy. With a median follow-up time of 2 years (6-60 months), the risk of developing a moderate radiation proctitis was 4%, cystitis 15%; three-year disease-free survival in low, medium and high-risk groups - 92, 86 and 81%, respectively. The method allows to increase the irradiation fractions, thereby shortening the treatment time (for example, 70 Gy is supplied with 28 fractions of 2.5 Gy for 5.5 weeks) .
Complications of radiotherapy for prostate cancer
The probability of post-radiation complications depends on the dose chosen, the technique of irradiation, the volume of irradiated tissues and the tolerance (radiosensitivity) of healthy tissues exposed to radiation. Usually, acute adverse reactions (during a 3-month irradiation) and late radiation complications (occur between 1 month and year after exposure). Acute reactions (proctitis, diarrhea, bleeding, dysuric disorders) occur within 2-6 weeks after the end of irradiation.
Before the start of irradiation, patients are necessarily informed of the risk of late radiation complications from the urinary tract and gastrointestinal tract (GIT), as well as erectile dysfunction. In a test of the European Organization for Research and Treatment of Tumors (EOKTS), conducted in 1987-1995, 415 patients (of whom 90% - with tumors T 3-4 ) received radiotherapy at a dose of 70 Gy; late complications were noted in 377 patients (91%). Complications of moderate severity (changes in the urinary tract and gastrointestinal tract, lymphostasis in the lower extremities) were noted in 86 patients (23%): in 72 patients they were moderate, in 10 - severe and in 4 patients (1%) - fatal. In general, despite these deaths, severe late complications were rare - less than 5% of patients.
According to the survey of patients, radiotherapy with volumetric planning and modulation of intensity less likely to cause impotence than surgical treatment. A recent meta-analysis showed that the probability of maintaining an erection one year after the remote radiation therapy, prostatectomy with preservation of the cavernous nerves and the standard operation is respectively 55, 34 and 25%. In the analysis of studies with a follow-up period of more than two years, these indicators decreased to 52, 25 and 25% respectively, i.e. The gap between radiation therapy and surgery has increased.