The goal of postoperative radiation therapy is to achieve the death of tumor cell complexes that could remain in the surgical area.
It is known that the most actively proliferating cells are located on the periphery of the tumor, which is well vascularized in contrast to its central parts, and which perish during preoperative irradiation. At the same time, certain hopes are also placed on the reduction of implantation abilities of cells “damaged” by irradiation, which reduces the risk of recurrence of the tumor and its metastases.
Approaches to such a combination treatment option depend on the nature of the surgery. The feasibility of using radiation exposure in patients after trial thoracotomy or other palliative interventions has been proven — when the remaining technically non-removable part of the tumor is confirmed by a morphological study.
After radical resection of the lung, the volume of postoperative irradiation depends on the prevalence and topography of the tumor process, the specificity of the extended or combined surgical intervention performed, and the direction of the local-regional lymphatic outflow pathways.
In organ-partial partial resections of the lung for stage III cancer, the scope of exposure includes paratracheal, tracheobronchial and bifurcation lymph nodes on both sides of the mediastinum, as well as the stump of the distal lobe and the root of the lung. The entire amount of exposure covers 80—% isodose.
In these cases, postoperative radiation therapy complements the oncological radicalism of surgical intervention. This mainly applies to patients with advanced stages of disease development —IIIA and IIIB. It is in the course of performing extended or expanded combined resections of the lung that it is most difficult to fully comply with all the rules of ablastics, regional lymphatic collectors are widely revealed when lymph nodes affected by cancer metastasis are removed. At the same time, the probability of admission to the wound is very high, the area of the mediastinum and the pleural cavity together with the lymph of cancer cell complexes are potential tumor metastases. All this constitutes a well-defined object of exposure during subsequent radiotherapy.
At the same time, in patients with lung cancer with I-II stages of development of the disease, when it is reliably established by detailed morphological research
surgical material — tumors in the lung, intrapulmonary, root and mediastinal lymph nodes — the resection volume most fully meets the requirements of the oncologic ablastics, widely retreating from the site of tumor development, including the nearby and unaffected sections of regional lymphatic collectors. In these cases, there is essentially no application space for additional local exposure. Patients with initial manifestations of tumor growth in the I-II stages of its development postoperative radiation therapy often causes additional trauma, causes both common associated disorders, and damage to local organs and tissues.If partial lung resection is performed in cancer stage I-II, postoperative radiotherapy can lead to severe fibrosis of the remaining lung lobe, negating the functional effect of the operation undertaken.
As our studies have shown, the indications for postoperative radiotherapy in this category of patients can be extremely narrowed without the risk of recurrence of the tumor.
When conducting postoperative irradiation, it should be borne in mind that subclinical metastases can develop in scars, which is facilitated by the following conditions: severe hypoxia and tissue anoxia. This determines the need to bring here higher, often exceeding the tolerance of normal tissues, radiation doses. The time between the operation and the start of radiation therapy contributes to the growth and reproduction of tumor cells, which determines the need for summing up doses that are effective 60– Gy.
When the tumor process spreads to the lymphatic collectors of the lung or mediastinum in patients who have previously undergone combined treatment in the form of preoperative radiation after surgery, it is necessary to additionally carry out postoperative radiation therapy. Then the total doses of pre- and postoperative irradiation of regional metastasis zones are 65 — Gy. Such a variant of the combined treatment of patients with a common blastomatous process in the lung —IIIA and IIIB stages is most justified.
Reasonable from the position of reliable stabilization of reparative processes at the site of operation, the time of onset of postoperative radiotherapy is 3—
weeks after lung resection. When performing non-radical, palliative surgical interventions with
this time, radiation therapy is carried out in full accordance with the principles and approaches developed for such treatment as an independent effect.
Until recently, the use of radiotherapy for small cell carcinoma was limited, since it was believed that local methods of exposure could not be effective with such a high-grade histological type of tumor due to its rapid generalization. In recent years, these views and approaches to the treatment of small cell lung cancer are being revised. There are new data on heterogeneity, polymorphism of its structure. The fact that the introduction of methods of subtotal irradiation of patients with lung cancer has received a definite significance.
In patients with small cell lung cancer, not only the primary tumor, lymph nodes of the lung root on the affected side, bifurcation, tracheobronchial, paratracheal lymph nodes on both sides of the mediastinum, but also paraesophageal, located in the lower mediastinum to the diaphragm should be included in the irradiation zone. The re-formation of fields with a decrease in the amount of irradiation is carried out after a dose of 40 — Gr, and then the zone is exactly
The verified lesion is irradiated to a total dose of 60 Gy. For small cell carcinoma, different dose fractionation schemes are used from the classic 2 Gy 5 fractions per week, the enlarged fractionation of 3–5 Gy daily (mainly with split irradiation courses), before the unconventional fractionation with crushing the enlarged fraction during the day. Total focal doses in the affected area are 60 Gy, and in regional metastasis areas — up to 40 — Gy. When remission is achieved in patients with small cell lung cancer due to the high risk of hematogenous metastasis, it is acceptable to conduct brain irradiation in a total dose of 30 Gy